This is Mt. Lassen (Lassen Peak), a prominent volcano and the key scenery in Lassen Volcanic National Park. Lassen Volcano is part of the Cascade Range, a north-south linear chain of active and potentially active volcanoes in America's Pacific Northwest. It extends from northern California to Oregon, Washington State, and into British Columbia, Canada. The Cascade Range formed as a result of tectonic subduction - the offshore Juan de Fuca Plate is diving below the North American Plate. The diving plate causes melting in the mantle. The melt rises and emerges at the surface at volcanic centers. Famous Cascade Range volcanoes include Mt. St. Helens, which had a large eruption in May 1980, Mt. Rainier near Seattle, Mt. Hood, which is the highest peak in Oregon, and Mt. Mazama, which destroyed itself 7,700 years ago in an enormous eruption that produced the modern-day Crater Lake Caldera (also a national park).

Mt. Lassen is a large volcanic dome that developed by lava extruding along the northeastern flanks of a former Cascade Range feature called Brokeoff Volcano (also known as Tehama Volcano). Brokeoff Volcano is an andesitic-dacitic subduction zone stratovolcano (composite volcano). Stratovolcanoes usually have violent, explosive ash eruptions. They tend to erupt igneous materials of intermediate chemistry (between felsic and mafic). Brokeoff Volcano was active from about 4 million years ago, during the Pliocene, to about 400,000 years ago. Only the caldera exists today. Calderas are large holes or depressions left behind after a volcano destroys itself or collapses. The Brokeoff Caldera is an erosional and slow-collapse caldera that formed before about 350,000 years ago.

The Mt. Lassen volcanic dome first started forming in the Late Pleistocene, at about 29 ka. It is principally composed of dacite lava, an extrusive igneous rock that is usually porphyritic-textured. Dacite is between andesite and rhyolite in silica content. Activity through time has ranged from dacite lava extrusion to explosive ash eruptions. Mt. Lassen last experienced eruptive activity in the early 1900s (1914 to 1921).

Locality: Lassen Volcano National Park, northeastern California, USA

The Ijen volcano complex is a group of stratovolcanoes, in East Java, Indonesia. It is inside a larger caldera Ijen, which is about 20 kilometers wide. The Gunung Merapi stratovolcano is the highest point of that complex. The name of this volcano resembles that of a different volcano, Mount Merapi in central Java, also known as Gunung Merapi; there is also a third volcano named Marapi in Sumatra. The name "Merapi" means "fire" in the Indonesian language.

West of Gunung Merapi is the Ijen volcano, which has a one-kilometer-wide turquoise-colored acid crater lake. The lake is the site of a labor-intensive sulfur mining operation, in which sulfur-laden baskets are carried by hand from the crater floor. The work is low-paid and very onerous. Workers earn around $5.50-$8.30 (Rp 50,000 - Rp 75,000) per day and once out of the crater, still need to carry their loads of sulfur chunks about three kilometers to the nearby Pultuding valley to get paid.[1]

Many other post-caldera cones and craters are located within the caldera or along its rim. The largest concentration of post-caldera cones forms an east/west-trending zone across the southern side of the caldera. The active crater at Kawah Ijen has an equivalent radius of 361 metres (1,184 ft), a surface of 0.41 square kilometres (0.16 sq mi). It is 200 metres (660 ft) deep and has a volume of 36 cubic hectometres (29,000 acre·ft).

This is lava from Mt. Lassen (Lassen Peak), a prominent volcano and the key scenery in Lassen Volcanic National Park. Lassen Volcano is part of the Cascade Range, a north-south linear chain of active and potentially active volcanoes in America's Pacific Northwest. It extends from northern California to Oregon, Washington State, and into British Columbia, Canada. The Cascade Range formed as a result of tectonic subduction - the offshore Juan de Fuca Plate is diving below the North American Plate. The diving plate causes melting in the mantle. The melt rises and emerges at the surface at volcanic centers. Famous Cascade Range volcanoes include Mt. St. Helens, which had a large eruption in May 1980, Mt. Rainier near Seattle, Mt. Hood, which is the highest peak in Oregon, and Mt. Mazama, which destroyed itself 7,700 years ago in an enormous eruption that produced the modern-day Crater Lake Caldera (also a national park).

Mt. Lassen is a large volcanic dome that developed by lava extruding along the northeastern flanks of a former Cascade Range feature called Brokeoff Volcano (also known as Tehama Volcano). Brokeoff Volcano is an andesitic-dacitic subduction zone stratovolcano (composite volcano). Stratovolcanoes usually have violent, explosive ash eruptions. They tend to erupt igneous materials of intermediate chemistry (between felsic and mafic). Brokeoff Volcano was active from about 4 million years ago, during the Pliocene, to about 400,000 years ago. Only the caldera exists today. Calderas are large holes or depressions left behind after a volcano destroys itself or collapses. The Brokeoff Caldera is an erosional and slow-collapse caldera that formed before about 350,000 years ago.

The Mt. Lassen volcanic dome first started forming in the Late Pleistocene, at about 29 ka. It is principally composed of dacite lava, an extrusive igneous rock that is usually porphyritic-textured. Dacite is between andesite and rhyolite in silica content. Activity through time has ranged from dacite lava extrusion to explosive ash eruptions. Mt. Lassen last experienced eruptive activity in the early 1900s (1914 to 1921).

The lava boulder shown here is in a volcanic debris flow deposit from 19 and 22 May 1915, when Mt. Lassen last had a significant eruption. The deposit consists of fine sediments, cobbles, and boulders, some of which are quite large. Clasts in the flow deposit include pinkish-reddish porphyritic dacite and gray porphyritic dacite, both of which formed at 27 ka during the Late Pleistocene, early in Mt. Lassen's history. Another clast type in the deposit is black porphyritic dacite, which formed on 14 May 1915. The clast type shown above is lava that formed on 22 May 1915. It consists of banded dacite pumice mixed with andesite. The light-colored streaks are pumice, a frothy-textured, light-weight, extrusive igneous rock. The dark-colored areas are andesite. The rock formed by mixing of two magma types, which resulted in an eruption.

Locality: boulder in Devastated Area, Lassen Volcano National Park, northeastern California, USA

This is Mt. Lassen (Lassen Peak), a prominent volcano and the key scenery in Lassen Volcanic National Park. Lassen Volcano is part of the Cascade Range, a north-south linear chain of active and potentially active volcanoes in America's Pacific Northwest. It extends from northern California to Oregon, Washington State, and into British Columbia, Canada. The Cascade Range formed as a result of tectonic subduction - the offshore Juan de Fuca Plate is diving below the North American Plate. The diving plate causes melting in the mantle. The melt rises and emerges at the surface at volcanic centers. Famous Cascade Range volcanoes include Mt. St. Helens, which had a large eruption in May 1980, Mt. Rainier near Seattle, Mt. Hood, which is the highest peak in Oregon, and Mt. Mazama, which destroyed itself 7,700 years ago in an enormous eruption that produced the modern-day Crater Lake Caldera (also a national park).

Mt. Lassen is a large volcanic dome that developed by lava extruding along the northeastern flanks of a former Cascade Range feature called Brokeoff Volcano (also known as Tehama Volcano). Brokeoff Volcano is an andesitic-dacitic subduction zone stratovolcano (composite volcano). Stratovolcanoes usually have violent, explosive ash eruptions. They tend to erupt igneous materials of intermediate chemistry (between felsic and mafic). Brokeoff Volcano was active from about 4 million years ago, during the Pliocene, to about 400,000 years ago. Only the caldera exists today. Calderas are large holes or depressions left behind after a volcano destroys itself or collapses. The Brokeoff Caldera is an erosional and slow-collapse caldera that formed before about 350,000 years ago.

The Mt. Lassen volcanic dome first started forming in the Late Pleistocene, at about 29 ka. It is principally composed of dacite lava, an extrusive igneous rock that is usually porphyritic-textured. Dacite is between andesite and rhyolite in silica content. Activity through time has ranged from dacite lava extrusion to explosive ash eruptions. Mt. Lassen last experienced eruptive activity in the early 1900s (1914 to 1921).

Locality: Lassen Volcano National Park, northeastern California, USA

One of the most active volcanoes in Southern Kamchatka. It is formed from four (predominantly basaltic) coalescing stratovolcanoes. The crater contains a powerful geothermal field with numerous fumaroles, boiling mud pools/springs. Care is required when visiting this site (should keep away from the direction of the toxic fumes emanating from the fumaroles and any unstable areas).

This is Mt. Lassen (Lassen Peak), a prominent volcano and the key scenery in Lassen Volcanic National Park. Lassen Volcano is part of the Cascade Range, a north-south linear chain of active and potentially active volcanoes in America's Pacific Northwest. It extends from northern California to Oregon, Washington State, and into British Columbia, Canada. The Cascade Range formed as a result of tectonic subduction - the offshore Juan de Fuca Plate is diving below the North American Plate. The diving plate causes melting in the mantle. The melt rises and emerges at the surface at volcanic centers. Famous Cascade Range volcanoes include Mt. St. Helens, which had a large eruption in May 1980, Mt. Rainier near Seattle, Mt. Hood, which is the highest peak in Oregon, and Mt. Mazama, which destroyed itself 7,700 years ago in an enormous eruption that produced the modern-day Crater Lake Caldera (also a national park).

Mt. Lassen is a large volcanic dome that developed by lava extruding along the northeastern flanks of a former Cascade Range feature called Brokeoff Volcano (also known as Tehama Volcano). Brokeoff Volcano is an andesitic-dacitic subduction zone stratovolcano (composite volcano). Stratovolcanoes usually have violent, explosive ash eruptions. They tend to erupt igneous materials of intermediate chemistry (between felsic and mafic). Brokeoff Volcano was active from about 4 million years ago, during the Pliocene, to about 400,000 years ago. Only the caldera exists today. Calderas are large holes or depressions left behind after a volcano destroys itself or collapses. The Brokeoff Caldera is an erosional and slow-collapse caldera that formed before about 350,000 years ago.

The Mt. Lassen volcanic dome first started forming in the Late Pleistocene, at about 29 ka. It is principally composed of dacite lava, an extrusive igneous rock that is usually porphyritic-textured. Dacite is between andesite and rhyolite in silica content. Activity through time has ranged from dacite lava extrusion to explosive ash eruptions. Mt. Lassen last experienced eruptive activity in the early 1900s (1914 to 1921).

Locality: Lassen Volcano National Park, northeastern California, USA

This is a volcanic deposit near Mt. Lassen (Lassen Peak), a prominent volcano and the key scenery in Lassen Volcanic National Park. Lassen Volcano is part of the Cascade Range, a north-south linear chain of active and potentially active volcanoes in America's Pacific Northwest. It extends from northern California to Oregon, Washington State, and into British Columbia, Canada. The Cascade Range formed as a result of tectonic subduction - the offshore Juan de Fuca Plate is diving below the North American Plate. The diving plate causes melting in the mantle. The melt rises and emerges at the surface at volcanic centers. Famous Cascade Range volcanoes include Mt. St. Helens, which had a large eruption in May 1980, Mt. Rainier near Seattle, Mt. Hood, which is the highest peak in Oregon, and Mt. Mazama, which destroyed itself 7,700 years ago in an enormous eruption that produced the modern-day Crater Lake Caldera (also a national park).

Mt. Lassen is a large volcanic dome that developed by lava extruding along the northeastern flanks of a former Cascade Range feature called Brokeoff Volcano (also known as Tehama Volcano). Brokeoff Volcano is an andesitic-dacitic subduction zone stratovolcano (composite volcano). Stratovolcanoes usually have violent, explosive ash eruptions. They tend to erupt igneous materials of intermediate chemistry (between felsic and mafic). Brokeoff Volcano was active from about 4 million years ago, during the Pliocene, to about 400,000 years ago. Only the caldera exists today. Calderas are large holes or depressions left behind after a volcano destroys itself or collapses. The Brokeoff Caldera is an erosional and slow-collapse caldera that formed before about 350,000 years ago.

The Mt. Lassen volcanic dome first started forming in the Late Pleistocene, at about 29 ka. It is principally composed of dacite lava, an extrusive igneous rock that is usually porphyritic-textured. Dacite is between andesite and rhyolite in silica content. Activity through time has ranged from dacite lava extrusion to explosive ash eruptions. Mt. Lassen last experienced eruptive activity in the early 1900s (1914 to 1921).

The boulders and cobbles shown here are in a volcanic debris flow deposit from 19 and 22 May 1915, when Mt. Lassen last had a significant eruption. The deposit consists of fine sediments, cobbles, and boulders, some of which are quite large. Clasts in the flow deposit include pinkish-reddish porphyritic dacite and gray porphyritic dacite, both of which formed at 27 ka during the Late Pleistocene, early in Mt. Lassen's history. Another clast type in the deposit is black porphyritic dacite, which formed on 14 May 1915. Other clast types present include dacite pumice and banded andesite-dacite pumice, both of which formed on 22 May 1915.

Locality: Devastated Area, Lassen Volcano National Park, northeastern California, USA

This is Mt. Lassen (Lassen Peak), a prominent volcano and the key scenery in Lassen Volcanic National Park. Lassen Volcano is part of the Cascade Range, a north-south linear chain of active and potentially active volcanoes in America's Pacific Northwest. It extends from northern California to Oregon, Washington State, and into British Columbia, Canada. The Cascade Range formed as a result of tectonic subduction - the offshore Juan de Fuca Plate is diving below the North American Plate. The diving plate causes melting in the mantle. The melt rises and emerges at the surface at volcanic centers. Famous Cascade Range volcanoes include Mt. St. Helens, which had a large eruption in May 1980, Mt. Rainier near Seattle, Mt. Hood, which is the highest peak in Oregon, and Mt. Mazama, which destroyed itself 7,700 years ago in an enormous eruption that produced the modern-day Crater Lake Caldera (also a national park).

Mt. Lassen is a large volcanic dome that developed by lava extruding along the northeastern flanks of a former Cascade Range feature called Brokeoff Volcano (also known as Tehama Volcano). Brokeoff Volcano is an andesitic-dacitic subduction zone stratovolcano (composite volcano). Stratovolcanoes usually have violent, explosive ash eruptions. They tend to erupt igneous materials of intermediate chemistry (between felsic and mafic). Brokeoff Volcano was active from about 4 million years ago, during the Pliocene, to about 400,000 years ago. Only the caldera exists today. Calderas are large holes or depressions left behind after a volcano destroys itself or collapses. The Brokeoff Caldera is an erosional and slow-collapse caldera that formed before about 350,000 years ago.

The Mt. Lassen volcanic dome first started forming in the Late Pleistocene, at about 29 ka. It is principally composed of dacite lava, an extrusive igneous rock that is usually porphyritic-textured. Dacite is between andesite and rhyolite in silica content. Activity through time has ranged from dacite lava extrusion to explosive ash eruptions. Mt. Lassen last experienced eruptive activity in the early 1900s (1914 to 1921).

Locality: Lassen Volcano National Park, northeastern California, USA

This is a volcanic deposit near Mt. Lassen (Lassen Peak), a prominent volcano and the key scenery in Lassen Volcanic National Park. Lassen Volcano is part of the Cascade Range, a north-south linear chain of active and potentially active volcanoes in America's Pacific Northwest. It extends from northern California to Oregon, Washington State, and into British Columbia, Canada. The Cascade Range formed as a result of tectonic subduction - the offshore Juan de Fuca Plate is diving below the North American Plate. The diving plate causes melting in the mantle. The melt rises and emerges at the surface at volcanic centers. Famous Cascade Range volcanoes include Mt. St. Helens, which had a large eruption in May 1980, Mt. Rainier near Seattle, Mt. Hood, which is the highest peak in Oregon, and Mt. Mazama, which destroyed itself 7,700 years ago in an enormous eruption that produced the modern-day Crater Lake Caldera (also a national park).

Mt. Lassen is a large volcanic dome that developed by lava extruding along the northeastern flanks of a former Cascade Range feature called Brokeoff Volcano (also known as Tehama Volcano). Brokeoff Volcano is an andesitic-dacitic subduction zone stratovolcano (composite volcano). Stratovolcanoes usually have violent, explosive ash eruptions. They tend to erupt igneous materials of intermediate chemistry (between felsic and mafic). Brokeoff Volcano was active from about 4 million years ago, during the Pliocene, to about 400,000 years ago. Only the caldera exists today. Calderas are large holes or depressions left behind after a volcano destroys itself or collapses. The Brokeoff Caldera is an erosional and slow-collapse caldera that formed before about 350,000 years ago.

The Mt. Lassen volcanic dome first started forming in the Late Pleistocene, at about 29 ka. It is principally composed of dacite lava, an extrusive igneous rock that is usually porphyritic-textured. Dacite is between andesite and rhyolite in silica content. Activity through time has ranged from dacite lava extrusion to explosive ash eruptions. Mt. Lassen last experienced eruptive activity in the early 1900s (1914 to 1921).

The scattered boulders shown here are in a volcanic debris flow deposit from 19 and 22 May 1915, when Mt. Lassen last had a significant eruption. The deposit consists of fine sediments, cobbles, and boulders, some of which are quite large. Clasts in the flow deposit include pinkish-reddish porphyritic dacite and gray porphyritic dacite, both of which formed at 27 ka during the Late Pleistocene, early in Mt. Lassen's history. Another clast type in the deposit is black porphyritic dacite, which formed on 14 May 1915. Other clast types present include dacite pumice and banded andesite-dacite pumice, both of which formed on 22 May 1915.

Locality: Devastated Area, Lassen Volcano National Park, northeastern California, USA

The Ijen volcano complex is a group of stratovolcanoes, in East Java, Indonesia. It is inside a larger caldera Ijen, which is about 20 kilometers wide. The Gunung Merapi stratovolcano is the highest point of that complex. The name of this volcano resembles that of a different volcano, Mount Merapi in central Java, also known as Gunung Merapi. The name "Merapi" means "fire" in the Indonesian language. From: wiki.

Java is the world's most densely populated island (population: 136 million). It is home to 60% of Indonesia's population. Much of Indonesian history took place on Java; it was the centre of powerful Hindu-Buddhist empires, Islamic sultanates, the core of the colonial Dutch East Indies, and was at the centre of Indonesia's campaign for independence. The island dominates Indonesian social, political and economic life. More information on wikipedia.

This is Mt. Lassen (Lassen Peak), a prominent volcano and the key scenery in Lassen Volcanic National Park. Lassen Volcano is part of the Cascade Range, a north-south linear chain of active and potentially active volcanoes in America's Pacific Northwest. It extends from northern California to Oregon, Washington State, and into British Columbia, Canada. The Cascade Range formed as a result of tectonic subduction - the offshore Juan de Fuca Plate is diving below the North American Plate. The diving plate causes melting in the mantle. The melt rises and emerges at the surface at volcanic centers. Famous Cascade Range volcanoes include Mt. St. Helens, which had a large eruption in May 1980, Mt. Rainier near Seattle, Mt. Hood, which is the highest peak in Oregon, and Mt. Mazama, which destroyed itself 7,700 years ago in an enormous eruption that produced the modern-day Crater Lake Caldera (also a national park).

Mt. Lassen is a large volcanic dome that developed by lava extruding along the northeastern flanks of a former Cascade Range feature called Brokeoff Volcano (also known as Tehama Volcano). Brokeoff Volcano is an andesitic-dacitic subduction zone stratovolcano (composite volcano). Stratovolcanoes usually have violent, explosive ash eruptions. They tend to erupt igneous materials of intermediate chemistry (between felsic and mafic). Brokeoff Volcano was active from about 4 million years ago, during the Pliocene, to about 400,000 years ago. Only the caldera exists today. Calderas are large holes or depressions left behind after a volcano destroys itself or collapses. The Brokeoff Caldera is an erosional and slow-collapse caldera that formed before about 350,000 years ago.

The Mt. Lassen volcanic dome first started forming in the Late Pleistocene, at about 29 ka. It is principally composed of dacite lava, an extrusive igneous rock that is usually porphyritic-textured. Dacite is between andesite and rhyolite in silica content. Activity through time has ranged from dacite lava extrusion to explosive ash eruptions. Mt. Lassen last experienced eruptive activity in the early 1900s (1914 to 1921).

Locality: Lassen Volcano National Park, northeastern California, USA

This is a volcanic deposit near Mt. Lassen (Lassen Peak), a prominent volcano and the key scenery in Lassen Volcanic National Park. Lassen Volcano is part of the Cascade Range, a north-south linear chain of active and potentially active volcanoes in America's Pacific Northwest. It extends from northern California to Oregon, Washington State, and into British Columbia, Canada. The Cascade Range formed as a result of tectonic subduction - the offshore Juan de Fuca Plate is diving below the North American Plate. The diving plate causes melting in the mantle. The melt rises and emerges at the surface at volcanic centers. Famous Cascade Range volcanoes include Mt. St. Helens, which had a large eruption in May 1980, Mt. Rainier near Seattle, Mt. Hood, which is the highest peak in Oregon, and Mt. Mazama, which destroyed itself 7,700 years ago in an enormous eruption that produced the modern-day Crater Lake Caldera (also a national park).

Mt. Lassen is a large volcanic dome that developed by lava extruding along the northeastern flanks of a former Cascade Range feature called Brokeoff Volcano (also known as Tehama Volcano). Brokeoff Volcano is an andesitic-dacitic subduction zone stratovolcano (composite volcano). Stratovolcanoes usually have violent, explosive ash eruptions. They tend to erupt igneous materials of intermediate chemistry (between felsic and mafic). Brokeoff Volcano was active from about 4 million years ago, during the Pliocene, to about 400,000 years ago. Only the caldera exists today. Calderas are large holes or depressions left behind after a volcano destroys itself or collapses. The Brokeoff Caldera is an erosional and slow-collapse caldera that formed before about 350,000 years ago.

The Mt. Lassen volcanic dome first started forming in the Late Pleistocene, at about 29 ka. It is principally composed of dacite lava, an extrusive igneous rock that is usually porphyritic-textured. Dacite is between andesite and rhyolite in silica content. Activity through time has ranged from dacite lava extrusion to explosive ash eruptions. Mt. Lassen last experienced eruptive activity in the early 1900s (1914 to 1921).

The scattered boulders and cobbles shown here are in a volcanic debris flow deposit from 19 and 22 May 1915, when Mt. Lassen last had a significant eruption. The deposit consists of fine sediments, cobbles, and boulders, some of which are quite large. Clasts in the flow deposit include pinkish-reddish porphyritic dacite and gray porphyritic dacite, both of which formed at 27 ka during the Late Pleistocene, early in Mt. Lassen's history. Another clast type in the deposit is black porphyritic dacite, which formed on 14 May 1915. Other clast types present include dacite pumice and banded andesite-dacite pumice, both of which formed on 22 May 1915.

Locality: Devastated Area, Lassen Volcano National Park, northeastern California, USA

The Ijen volcano complex is a group of stratovolcanoes, in East Java, Indonesia. It is inside a larger caldera Ijen, which is about 20 kilometers wide. The Gunung Merapi stratovolcano is the highest point of that complex. The name of this volcano resembles that of a different volcano, Mount Merapi in central Java, also known as Gunung Merapi. The name "Merapi" means "fire" in the Indonesian language. From: wiki.

Java is the world's most densely populated island (population: 136 million). It is home to 60% of Indonesia's population. Much of Indonesian history took place on Java; it was the centre of powerful Hindu-Buddhist empires, Islamic sultanates, the core of the colonial Dutch East Indies, and was at the centre of Indonesia's campaign for independence. The island dominates Indonesian social, political and economic life. More information on wikipedia.

This is lava from Mt. Lassen (Lassen Peak), a prominent volcano and the key scenery in Lassen Volcanic National Park. Lassen Volcano is part of the Cascade Range, a north-south linear chain of active and potentially active volcanoes in America's Pacific Northwest. It extends from northern California to Oregon, Washington State, and into British Columbia, Canada. The Cascade Range formed as a result of tectonic subduction - the offshore Juan de Fuca Plate is diving below the North American Plate. The diving plate causes melting in the mantle. The melt rises and emerges at the surface at volcanic centers. Famous Cascade Range volcanoes include Mt. St. Helens, which had a large eruption in May 1980, Mt. Rainier near Seattle, Mt. Hood, which is the highest peak in Oregon, and Mt. Mazama, which destroyed itself 7,700 years ago in an enormous eruption that produced the modern-day Crater Lake Caldera (also a national park).

Mt. Lassen is a large volcanic dome that developed by lava extruding along the northeastern flanks of a former Cascade Range feature called Brokeoff Volcano (also known as Tehama Volcano). Brokeoff Volcano is an andesitic-dacitic subduction zone stratovolcano (composite volcano). Stratovolcanoes usually have violent, explosive ash eruptions. They tend to erupt igneous materials of intermediate chemistry (between felsic and mafic). Brokeoff Volcano was active from about 4 million years ago, during the Pliocene, to about 400,000 years ago. Only the caldera exists today. Calderas are large holes or depressions left behind after a volcano destroys itself or collapses. The Brokeoff Caldera is an erosional and slow-collapse caldera that formed before about 350,000 years ago.

The Mt. Lassen volcanic dome first started forming in the Late Pleistocene, at about 29 ka. It is principally composed of dacite lava, an extrusive igneous rock that is usually porphyritic-textured. Dacite is between andesite and rhyolite in silica content. Activity through time has ranged from dacite lava extrusion to explosive ash eruptions. Mt. Lassen last experienced eruptive activity in the early 1900s (1914 to 1921).

The lava boulder shown here is in a volcanic debris flow deposit from 19 and 22 May 1915, when Mt. Lassen last had a significant eruption. The deposit consists of fine sediments, cobbles, and boulders, some of which are quite large. Clasts in the flow deposit include pinkish-reddish porphyritic dacite and gray porphyritic dacite, both of which formed at 27 ka during the Late Pleistocene, early in Mt. Lassen's history. Another clast type in the deposit is black porphyritic dacite, shown here, that formed on 14 May 1915. The whitish-colored phenocrysts (click on the photo to zoom in and look around) are plagioclase feldspar.

From park signage:

"After the May 19 avalanche carried hot lava rocks here, the surrounding air temperature rapidly cooled them. As they cooled - from the outside in - some of the rocks fractured inwardly and radially like this one, breaking into pyramid-like shapes. Like a jigsaw puzzle, many of the rock pieces you see here today could easily be reconfigured - solving a hot puzzle of the past."

Locality: boulder in Devastated Area, Lassen Volcano National Park, northeastern California, USA

El grupo indígena que habitaba en esta zona se llamaba cochimíes que significa " gente que vive por la parte norte".

También los llamaron laimones. Los cochimíes era el grupo más numeroso y se extendían desde un poco al norte de Loreto hasta los 33° de latitud norte.

La vestimenta de las mujeres de esta agrupación era con una falda larga que estaba hecha de dos partes formadas por hilos entretejidos de tal manera que caían en forma de tupidas madejas hasta los pies. Se cubrían de los hombros a la cintura con una especie de reboso o mantilla hecha también de hilos sacados de las hojas de palma. Acostumbraban llevar el cabello largo y suelto. En la cabeza lucían unas redes tejidas muy finamente; en el cuello se ponían adornos hechos de figura de nácar, caracolillos, perlas, etc. En las manos y en los tobillos se ponían pulseras y otros colgajos

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The Tres Vírgenes volcanic complex contains the only large stratovolcanoes in Baja California. The roughly 1940-m-high complex rises above the Gulf of California in the east-central part of the peninsula. Three volcanoes, El Viejo, El Azufre, and La Vírgen were constructed along a NE-SW line and are progressively younger to the SW. The youngest volcano, La Vírgen, is an andesitic stratovolcano with numerous dacitic lava domes and lava flows on its flanks. A major plinian explosive eruption from a SW-flank vent took place about 6500 years ago and was followed by effusion of a thick lava flow. An ash plume was reported from Tres Vírgenes volcano by a Spanish Jesuit priest while navigating the Gulf of California in 1746, but no deposits from such a young eruption have been found. A geothermal plant is located at the northern end of the complex near the margin of the Pleistocene El Aguajito caldera.

This is lava from Mt. Lassen (Lassen Peak), a prominent volcano and the key scenery in Lassen Volcanic National Park. Lassen Volcano is part of the Cascade Range, a north-south linear chain of active and potentially active volcanoes in America's Pacific Northwest. It extends from northern California to Oregon, Washington State, and into British Columbia, Canada. The Cascade Range formed as a result of tectonic subduction - the offshore Juan de Fuca Plate is diving below the North American Plate. The diving plate causes melting in the mantle. The melt rises and emerges at the surface at volcanic centers. Famous Cascade Range volcanoes include Mt. St. Helens, which had a large eruption in May 1980, Mt. Rainier near Seattle, Mt. Hood, which is the highest peak in Oregon, and Mt. Mazama, which destroyed itself 7,700 years ago in an enormous eruption that produced the modern-day Crater Lake Caldera (also a national park).

Mt. Lassen is a large volcanic dome that developed by lava extruding along the northeastern flanks of a former Cascade Range feature called Brokeoff Volcano (also known as Tehama Volcano). Brokeoff Volcano is an andesitic-dacitic subduction zone stratovolcano (composite volcano). Stratovolcanoes usually have violent, explosive ash eruptions. They tend to erupt igneous materials of intermediate chemistry (between felsic and mafic). Brokeoff Volcano was active from about 4 million years ago, during the Pliocene, to about 400,000 years ago. Only the caldera exists today. Calderas are large holes or depressions left behind after a volcano destroys itself or collapses. The Brokeoff Caldera is an erosional and slow-collapse caldera that formed before about 350,000 years ago.

The Mt. Lassen volcanic dome first started forming in the Late Pleistocene, at about 29 ka. It is principally composed of dacite lava, an extrusive igneous rock that is usually porphyritic-textured. Dacite is between andesite and rhyolite in silica content. Activity through time has ranged from dacite lava extrusion to explosive ash eruptions. Mt. Lassen last experienced eruptive activity in the early 1900s (1914 to 1921).

The lava boulder shown here is in a volcanic debris flow deposit from 19 and 22 May 1915, when Mt. Lassen last had a significant eruption. The deposit consists of fine sediments, cobbles, and boulders, some of which are quite large. Clasts in the flow deposit include pinkish-reddish porphyritic dacite and gray porphyritic dacite, both of which formed at 27 ka during the Late Pleistocene, early in Mt. Lassen's history. Another clast type in the deposit is black porphyritic dacite, shown here, that formed on 14 May 1915. The whitish-colored phenocrysts (click on the photo to zoom in and look around) are plagioclase feldspar.

Locality: boulder in Devastated Area, Lassen Volcano National Park, northeastern California, USA

This is a volcanic deposit near Mt. Lassen (Lassen Peak), a prominent volcano and the key scenery in Lassen Volcanic National Park. Lassen Volcano is part of the Cascade Range, a north-south linear chain of active and potentially active volcanoes in America's Pacific Northwest. It extends from northern California to Oregon, Washington State, and into British Columbia, Canada. The Cascade Range formed as a result of tectonic subduction - the offshore Juan de Fuca Plate is diving below the North American Plate. The diving plate causes melting in the mantle. The melt rises and emerges at the surface at volcanic centers. Famous Cascade Range volcanoes include Mt. St. Helens, which had a large eruption in May 1980, Mt. Rainier near Seattle, Mt. Hood, which is the highest peak in Oregon, and Mt. Mazama, which destroyed itself 7,700 years ago in an enormous eruption that produced the modern-day Crater Lake Caldera (also a national park).

Mt. Lassen is a large volcanic dome that developed by lava extruding along the northeastern flanks of a former Cascade Range feature called Brokeoff Volcano (also known as Tehama Volcano). Brokeoff Volcano is an andesitic-dacitic subduction zone stratovolcano (composite volcano). Stratovolcanoes usually have violent, explosive ash eruptions. They tend to erupt igneous materials of intermediate chemistry (between felsic and mafic). Brokeoff Volcano was active from about 4 million years ago, during the Pliocene, to about 400,000 years ago. Only the caldera exists today. Calderas are large holes or depressions left behind after a volcano destroys itself or collapses. The Brokeoff Caldera is an erosional and slow-collapse caldera that formed before about 350,000 years ago.

The Mt. Lassen volcanic dome first started forming in the Late Pleistocene, at about 29 ka. It is principally composed of dacite lava, an extrusive igneous rock that is usually porphyritic-textured. Dacite is between andesite and rhyolite in silica content. Activity through time has ranged from dacite lava extrusion to explosive ash eruptions. Mt. Lassen last experienced eruptive activity in the early 1900s (1914 to 1921).

The boulders and cobbles shown here are in a volcanic debris flow deposit from 19 and 22 May 1915, when Mt. Lassen last had a significant eruption. The deposit consists of fine sediments, cobbles, and boulders, some of which are quite large. Clasts in the flow deposit include pinkish-reddish porphyritic dacite and gray porphyritic dacite, both of which formed at 27 ka during the Late Pleistocene, early in Mt. Lassen's history. Another clast type in the deposit is black porphyritic dacite, which formed on 14 May 1915. Other clast types present include dacite pumice and banded andesite-dacite pumice, both of which formed on 22 May 1915.

Locality: Devastated Area, Lassen Volcano National Park, northeastern California, USA

This is lava from Mt. Lassen (Lassen Peak), a prominent volcano and the key scenery in Lassen Volcanic National Park. Lassen Volcano is part of the Cascade Range, a north-south linear chain of active and potentially active volcanoes in America's Pacific Northwest. It extends from northern California to Oregon, Washington State, and into British Columbia, Canada. The Cascade Range formed as a result of tectonic subduction - the offshore Juan de Fuca Plate is diving below the North American Plate. The diving plate causes melting in the mantle. The melt rises and emerges at the surface at volcanic centers. Famous Cascade Range volcanoes include Mt. St. Helens, which had a large eruption in May 1980, Mt. Rainier near Seattle, Mt. Hood, which is the highest peak in Oregon, and Mt. Mazama, which destroyed itself 7,700 years ago in an enormous eruption that produced the modern-day Crater Lake Caldera (also a national park).

Mt. Lassen is a large volcanic dome that developed by lava extruding along the northeastern flanks of a former Cascade Range feature called Brokeoff Volcano (also known as Tehama Volcano). Brokeoff Volcano is an andesitic-dacitic subduction zone stratovolcano (composite volcano). Stratovolcanoes usually have violent, explosive ash eruptions. They tend to erupt igneous materials of intermediate chemistry (between felsic and mafic). Brokeoff Volcano was active from about 4 million years ago, during the Pliocene, to about 400,000 years ago. Only the caldera exists today. Calderas are large holes or depressions left behind after a volcano destroys itself or collapses. The Brokeoff Caldera is an erosional and slow-collapse caldera that formed before about 350,000 years ago.

The Mt. Lassen volcanic dome first started forming in the Late Pleistocene, at about 29 ka. It is principally composed of dacite lava, an extrusive igneous rock that is usually porphyritic-textured. Dacite is between andesite and rhyolite in silica content. Activity through time has ranged from dacite lava extrusion to explosive ash eruptions. Mt. Lassen last experienced eruptive activity in the early 1900s (1914 to 1921).

The lava boulder shown here is in a volcanic debris flow deposit from 19 and 22 May 1915, when Mt. Lassen last had a significant eruption. The deposit consists of fine sediments, cobbles, and boulders, some of which are quite large. Clasts in the flow deposit include pinkish-reddish porphyritic dacite and gray porphyritic dacite, both of which formed at 27 ka during the Late Pleistocene, early in Mt. Lassen's history. Another clast type in the deposit is black porphyritic dacite, shown here, that formed on 14 May 1915. The whitish-colored phenocrysts (click on the photo to zoom in and look around) are plagioclase feldspar.

Locality: boulder in Devastated Area, Lassen Volcano National Park, northeastern California, USA

The Ijen volcano complex is a group of stratovolcanoes, in East Java, Indonesia. It is inside a larger caldera Ijen, which is about 20 kilometers wide. The Gunung Merapi stratovolcano is the highest point of that complex. The name of this volcano resembles that of a different volcano, Mount Merapi in central Java, also known as Gunung Merapi. The name "Merapi" means "fire" in the Indonesian language. From: wiki.

Java is the world's most densely populated island (population: 136 million). It is home to 60% of Indonesia's population. Much of Indonesian history took place on Java; it was the centre of powerful Hindu-Buddhist empires, Islamic sultanates, the core of the colonial Dutch East Indies, and was at the centre of Indonesia's campaign for independence. The island dominates Indonesian social, political and economic life. More information on wikipedia.

This is lava from Mt. Lassen (Lassen Peak), a prominent volcano and the key scenery in Lassen Volcanic National Park. Lassen Volcano is part of the Cascade Range, a north-south linear chain of active and potentially active volcanoes in America's Pacific Northwest. It extends from northern California to Oregon, Washington State, and into British Columbia, Canada. The Cascade Range formed as a result of tectonic subduction - the offshore Juan de Fuca Plate is diving below the North American Plate. The diving plate causes melting in the mantle. The melt rises and emerges at the surface at volcanic centers. Famous Cascade Range volcanoes include Mt. St. Helens, which had a large eruption in May 1980, Mt. Rainier near Seattle, Mt. Hood, which is the highest peak in Oregon, and Mt. Mazama, which destroyed itself 7,700 years ago in an enormous eruption that produced the modern-day Crater Lake Caldera (also a national park).

Mt. Lassen is a large volcanic dome that developed by lava extruding along the northeastern flanks of a former Cascade Range feature called Brokeoff Volcano (also known as Tehama Volcano). Brokeoff Volcano is an andesitic-dacitic subduction zone stratovolcano (composite volcano). Stratovolcanoes usually have violent, explosive ash eruptions. They tend to erupt igneous materials of intermediate chemistry (between felsic and mafic). Brokeoff Volcano was active from about 4 million years ago, during the Pliocene, to about 400,000 years ago. Only the caldera exists today. Calderas are large holes or depressions left behind after a volcano destroys itself or collapses. The Brokeoff Caldera is an erosional and slow-collapse caldera that formed before about 350,000 years ago.

The Mt. Lassen volcanic dome first started forming in the Late Pleistocene, at about 29 ka. It is principally composed of dacite lava, an extrusive igneous rock that is usually porphyritic-textured. Dacite is between andesite and rhyolite in silica content. Activity through time has ranged from dacite lava extrusion to explosive ash eruptions. Mt. Lassen last experienced eruptive activity in the early 1900s (1914 to 1921).

The lava boulder shown here is in a volcanic debris flow deposit from 19 and 22 May 1915, when Mt. Lassen last had a significant eruption. The deposit consists of fine sediments, cobbles, and boulders, some of which are quite large. Clasts in the flow deposit include pinkish-reddish porphyritic dacite and gray porphyritic dacite, both of which formed at 27 ka during the Late Pleistocene, early in Mt. Lassen's history. Another clast type in the deposit is black porphyritic dacite, shown here, that formed on 14 May 1915. The whitish-colored phenocrysts (click on the photo to zoom in and look around) are plagioclase feldspar.

From park signage:

"After the May 19 avalanche carried hot lava rocks here, the surrounding air temperature rapidly cooled them. As they cooled - from the outside in - some of the rocks fractured inwardly and radially like this one, breaking into pyramid-like shapes. Like a jigsaw puzzle, many of the rock pieces you see here today could easily be reconfigured - solving a hot puzzle of the past."

Locality: boulder in Devastated Area, Lassen Volcano National Park, northeastern California, USA

This is Mt. Lassen (Lassen Peak), a prominent volcano and the key scenery in Lassen Volcanic National Park. Lassen Volcano is part of the Cascade Range, a north-south linear chain of active and potentially active volcanoes in America's Pacific Northwest. It extends from northern California to Oregon, Washington State, and into British Columbia, Canada. The Cascade Range formed as a result of tectonic subduction - the offshore Juan de Fuca Plate is diving below the North American Plate. The diving plate causes melting in the mantle. The melt rises and emerges at the surface at volcanic centers. Famous Cascade Range volcanoes include Mt. St. Helens, which had a large eruption in May 1980, Mt. Rainier near Seattle, Mt. Hood, which is the highest peak in Oregon, and Mt. Mazama, which destroyed itself 7,700 years ago in an enormous eruption that produced the modern-day Crater Lake Caldera (also a national park).

Mt. Lassen is a large volcanic dome that developed by lava extruding along the northeastern flanks of a former Cascade Range feature called Brokeoff Volcano (also known as Tehama Volcano). Brokeoff Volcano is an andesitic-dacitic subduction zone stratovolcano (composite volcano). Stratovolcanoes usually have violent, explosive ash eruptions. They tend to erupt igneous materials of intermediate chemistry (between felsic and mafic). Brokeoff Volcano was active from about 4 million years ago, during the Pliocene, to about 400,000 years ago. Only the caldera exists today. Calderas are large holes or depressions left behind after a volcano destroys itself or collapses. The Brokeoff Caldera is an erosional and slow-collapse caldera that formed before about 350,000 years ago.

The Mt. Lassen volcanic dome first started forming in the Late Pleistocene, at about 29 ka. It is principally composed of dacite lava, an extrusive igneous rock that is usually porphyritic-textured. Dacite is between andesite and rhyolite in silica content. Activity through time has ranged from dacite lava extrusion to explosive ash eruptions. Mt. Lassen last experienced eruptive activity in the early 1900s (1914 to 1921).

Locality: Lassen Volcano National Park, northeastern California, USA

The Lago de Atitlán is a beautiful lake in the highlands of Guatemala; the water level is at 1562 meters (5,125 ft). The lake basin is volcanic in origin, filling an enormous caldera formed by an eruption 84,000 years ago. It is shaped by deep surrounding escarpments and three stratovolcanoes on its southern flank. Lake Atitlán is the deepest lake in Central America with a maximum depth of about 340 meters (1,120 ft). Its surface area is 130 sq km (50 sq mi).

In view is the Volcán San Pedro (a.k.a. Volcán Las Yeguas) with an altitude of 3020 meters (9,908 ft).

This is a volcanic deposit near Mt. Lassen (Lassen Peak), a prominent volcano and the key scenery in Lassen Volcanic National Park. Lassen Volcano is part of the Cascade Range, a north-south linear chain of active and potentially active volcanoes in America's Pacific Northwest. It extends from northern California to Oregon, Washington State, and into British Columbia, Canada. The Cascade Range formed as a result of tectonic subduction - the offshore Juan de Fuca Plate is diving below the North American Plate. The diving plate causes melting in the mantle. The melt rises and emerges at the surface at volcanic centers. Famous Cascade Range volcanoes include Mt. St. Helens, which had a large eruption in May 1980, Mt. Rainier near Seattle, Mt. Hood, which is the highest peak in Oregon, and Mt. Mazama, which destroyed itself 7,700 years ago in an enormous eruption that produced the modern-day Crater Lake Caldera (also a national park).

Mt. Lassen is a large volcanic dome that developed by lava extruding along the northeastern flanks of a former Cascade Range feature called Brokeoff Volcano (also known as Tehama Volcano). Brokeoff Volcano is an andesitic-dacitic subduction zone stratovolcano (composite volcano). Stratovolcanoes usually have violent, explosive ash eruptions. They tend to erupt igneous materials of intermediate chemistry (between felsic and mafic). Brokeoff Volcano was active from about 4 million years ago, during the Pliocene, to about 400,000 years ago. Only the caldera exists today. Calderas are large holes or depressions left behind after a volcano destroys itself or collapses. The Brokeoff Caldera is an erosional and slow-collapse caldera that formed before about 350,000 years ago.

The Mt. Lassen volcanic dome first started forming in the Late Pleistocene, at about 29 ka. It is principally composed of dacite lava, an extrusive igneous rock that is usually porphyritic-textured. Dacite is between andesite and rhyolite in silica content. Activity through time has ranged from dacite lava extrusion to explosive ash eruptions. Mt. Lassen last experienced eruptive activity in the early 1900s (1914 to 1921).

The scattered boulders and cobbles shown here are in a volcanic debris flow deposit from 19 and 22 May 1915, when Mt. Lassen last had a significant eruption. The deposit consists of fine sediments, cobbles, and boulders, some of which are quite large. Clasts in the flow deposit include pinkish-reddish porphyritic dacite and gray porphyritic dacite, both of which formed at 27 ka during the Late Pleistocene, early in Mt. Lassen's history. Another clast type in the deposit is black porphyritic dacite, which formed on 14 May 1915. Other clast types present include dacite pumice and banded andesite-dacite pumice, both of which formed on 22 May 1915.

Locality: Devastated Area, Lassen Volcano National Park, northeastern California, USA

The Ijen volcano complex is a group of stratovolcanoes, in East Java, Indonesia. It is inside a larger caldera Ijen, which is about 20 kilometers wide. The Gunung Merapi stratovolcano is the highest point of that complex. The name of this volcano resembles that of a different volcano, Mount Merapi in central Java, also known as Gunung Merapi; there is also a third volcano named Marapi in Sumatra. The name "Merapi" means "fire" in the Indonesian language.

West of Gunung Merapi is the Ijen volcano, which has a one-kilometer-wide turquoise-colored acid crater lake. The lake is the site of a labor-intensive sulfur mining operation, in which sulfur-laden baskets are carried by hand from the crater floor. The work is low-paid and very onerous. Workers earn around $5.50-$8.30 (Rp 50,000 - Rp 75,000) per day and once out of the crater, still need to carry their loads of sulfur chunks about three kilometers to the nearby Pultuding valley to get paid.[1]

Many other post-caldera cones and craters are located within the caldera or along its rim. The largest concentration of post-caldera cones forms an east/west-trending zone across the southern side of the caldera. The active crater at Kawah Ijen has an equivalent radius of 361 metres (1,184 ft), a surface of 0.41 square kilometres (0.16 sq mi). It is 200 metres (660 ft) deep and has a volume of 36 cubic hectometres (29,000 acre·ft).

This is a volcanic deposit near Mt. Lassen (Lassen Peak), a prominent volcano and the key scenery in Lassen Volcanic National Park. Lassen Volcano is part of the Cascade Range, a north-south linear chain of active and potentially active volcanoes in America's Pacific Northwest. It extends from northern California to Oregon, Washington State, and into British Columbia, Canada. The Cascade Range formed as a result of tectonic subduction - the offshore Juan de Fuca Plate is diving below the North American Plate. The diving plate causes melting in the mantle. The melt rises and emerges at the surface at volcanic centers. Famous Cascade Range volcanoes include Mt. St. Helens, which had a large eruption in May 1980, Mt. Rainier near Seattle, Mt. Hood, which is the highest peak in Oregon, and Mt. Mazama, which destroyed itself 7,700 years ago in an enormous eruption that produced the modern-day Crater Lake Caldera (also a national park).

Mt. Lassen is a large volcanic dome that developed by lava extruding along the northeastern flanks of a former Cascade Range feature called Brokeoff Volcano (also known as Tehama Volcano). Brokeoff Volcano is an andesitic-dacitic subduction zone stratovolcano (composite volcano). Stratovolcanoes usually have violent, explosive ash eruptions. They tend to erupt igneous materials of intermediate chemistry (between felsic and mafic). Brokeoff Volcano was active from about 4 million years ago, during the Pliocene, to about 400,000 years ago. Only the caldera exists today. Calderas are large holes or depressions left behind after a volcano destroys itself or collapses. The Brokeoff Caldera is an erosional and slow-collapse caldera that formed before about 350,000 years ago.

The Mt. Lassen volcanic dome first started forming in the Late Pleistocene, at about 29 ka. It is principally composed of dacite lava, an extrusive igneous rock that is usually porphyritic-textured. Dacite is between andesite and rhyolite in silica content. Activity through time has ranged from dacite lava extrusion to explosive ash eruptions. Mt. Lassen last experienced eruptive activity in the early 1900s (1914 to 1921).

The boulders shown here are in a volcanic debris flow deposit from 19 and 22 May 1915, when Mt. Lassen last had a significant eruption. The deposit consists of fine sediments, cobbles, and boulders, some of which are quite large. Clasts in the flow deposit include pinkish-reddish porphyritic dacite and gray porphyritic dacite, both of which formed at 27 ka during the Late Pleistocene, early in Mt. Lassen's history. Another clast type in the deposit is black porphyritic dacite, which formed on 14 May 1915. Other clast types present include dacite pumice and banded andesite-dacite pumice, both of which formed on 22 May 1915.

Locality: Devastated Area, Lassen Volcano National Park, northeastern California, USA

This is lava from Mt. Lassen (Lassen Peak), a prominent volcano and the key scenery in Lassen Volcanic National Park. Lassen Volcano is part of the Cascade Range, a north-south linear chain of active and potentially active volcanoes in America's Pacific Northwest. It extends from northern California to Oregon, Washington State, and into British Columbia, Canada. The Cascade Range formed as a result of tectonic subduction - the offshore Juan de Fuca Plate is diving below the North American Plate. The diving plate causes melting in the mantle. The melt rises and emerges at the surface at volcanic centers. Famous Cascade Range volcanoes include Mt. St. Helens, which had a large eruption in May 1980, Mt. Rainier near Seattle, Mt. Hood, which is the highest peak in Oregon, and Mt. Mazama, which destroyed itself 7,700 years ago in an enormous eruption that produced the modern-day Crater Lake Caldera (also a national park).

Mt. Lassen is a large volcanic dome that developed by lava extruding along the northeastern flanks of a former Cascade Range feature called Brokeoff Volcano (also known as Tehama Volcano). Brokeoff Volcano is an andesitic-dacitic subduction zone stratovolcano (composite volcano). Stratovolcanoes usually have violent, explosive ash eruptions. They tend to erupt igneous materials of intermediate chemistry (between felsic and mafic). Brokeoff Volcano was active from about 4 million years ago, during the Pliocene, to about 400,000 years ago. Only the caldera exists today. Calderas are large holes or depressions left behind after a volcano destroys itself or collapses. The Brokeoff Caldera is an erosional and slow-collapse caldera that formed before about 350,000 years ago.

The Mt. Lassen volcanic dome first started forming in the Late Pleistocene, at about 29 ka. It is principally composed of dacite lava, an extrusive igneous rock that is usually porphyritic-textured. Dacite is between andesite and rhyolite in silica content. Activity through time has ranged from dacite lava extrusion to explosive ash eruptions. Mt. Lassen last experienced eruptive activity in the early 1900s (1914 to 1921).

The lava boulder shown here is in a volcanic debris flow deposit from 19 and 22 May 1915, when Mt. Lassen last had a significant eruption. The deposit consists of fine sediments, cobbles, and boulders, some of which are quite large. Clasts in the flow deposit include pinkish-reddish porphyritic dacite and gray porphyritic dacite, both of which formed at 27 ka during the Late Pleistocene, early in Mt. Lassen's history. Another clast type in the deposit is black porphyritic dacite, shown here, that formed on 14 May 1915. The whitish-colored phenocrysts (click on the photo to zoom in and look around) are plagioclase feldspar.

From park signage:

"After the May 19 avalanche carried hot lava rocks here, the surrounding air temperature rapidly cooled them. As they cooled - from the outside in - some of the rocks fractured inwardly and radially like this one, breaking into pyramid-like shapes. Like a jigsaw puzzle, many of the rock pieces you see here today could easily be reconfigured - solving a hot puzzle of the past."

Locality: boulder in Devastated Area, Lassen Volcano National Park, northeastern California, USA

The Ijen volcano complex is a group of stratovolcanoes, in East Java, Indonesia. It is inside a larger caldera Ijen, which is about 20 kilometers wide. The Gunung Merapi stratovolcano is the highest point of that complex. The name of this volcano resembles that of a different volcano, Mount Merapi in central Java, also known as Gunung Merapi. The name "Merapi" means "fire" in the Indonesian language. From: wiki.

Java is the world's most densely populated island (population: 136 million). It is home to 60% of Indonesia's population. Much of Indonesian history took place on Java; it was the centre of powerful Hindu-Buddhist empires, Islamic sultanates, the core of the colonial Dutch East Indies, and was at the centre of Indonesia's campaign for independence. The island dominates Indonesian social, political and economic life. More information on wikipedia.

This is lava from Mt. Lassen (Lassen Peak), a prominent volcano and the key scenery in Lassen Volcanic National Park. Lassen Volcano is part of the Cascade Range, a north-south linear chain of active and potentially active volcanoes in America's Pacific Northwest. It extends from northern California to Oregon, Washington State, and into British Columbia, Canada. The Cascade Range formed as a result of tectonic subduction - the offshore Juan de Fuca Plate is diving below the North American Plate. The diving plate causes melting in the mantle. The melt rises and emerges at the surface at volcanic centers. Famous Cascade Range volcanoes include Mt. St. Helens, which had a large eruption in May 1980, Mt. Rainier near Seattle, Mt. Hood, which is the highest peak in Oregon, and Mt. Mazama, which destroyed itself 7,700 years ago in an enormous eruption that produced the modern-day Crater Lake Caldera (also a national park).

Mt. Lassen is a large volcanic dome that developed by lava extruding along the northeastern flanks of a former Cascade Range feature called Brokeoff Volcano (also known as Tehama Volcano). Brokeoff Volcano is an andesitic-dacitic subduction zone stratovolcano (composite volcano). Stratovolcanoes usually have violent, explosive ash eruptions. They tend to erupt igneous materials of intermediate chemistry (between felsic and mafic). Brokeoff Volcano was active from about 4 million years ago, during the Pliocene, to about 400,000 years ago. Only the caldera exists today. Calderas are large holes or depressions left behind after a volcano destroys itself or collapses. The Brokeoff Caldera is an erosional and slow-collapse caldera that formed before about 350,000 years ago.

The Mt. Lassen volcanic dome first started forming in the Late Pleistocene, at about 29 ka. It is principally composed of dacite lava, an extrusive igneous rock that is usually porphyritic-textured. Dacite is between andesite and rhyolite in silica content. Activity through time has ranged from dacite lava extrusion to explosive ash eruptions. Mt. Lassen last experienced eruptive activity in the early 1900s (1914 to 1921).

The lava boulder shown here is in a volcanic debris flow deposit from 19 and 22 May 1915, when Mt. Lassen last had a significant eruption. The deposit consists of fine sediments, cobbles, and boulders, some of which are quite large. Clasts in the flow deposit include pinkish-reddish porphyritic dacite and gray porphyritic dacite, both of which formed at 27 ka during the Late Pleistocene, early in Mt. Lassen's history. Another clast type in the deposit is black porphyritic dacite, shown here, that formed on 14 May 1915. The whitish-colored phenocrysts (click on the photo to zoom in and look around) are plagioclase feldspar.

Locality: boulder in Devastated Area, Lassen Volcano National Park, northeastern California, USA

This is Mt. Lassen (Lassen Peak), a prominent volcano and the key scenery in Lassen Volcanic National Park. Lassen Volcano is part of the Cascade Range, a north-south linear chain of active and potentially active volcanoes in America's Pacific Northwest. It extends from northern California to Oregon, Washington State, and into British Columbia, Canada. The Cascade Range formed as a result of tectonic subduction - the offshore Juan de Fuca Plate is diving below the North American Plate. The diving plate causes melting in the mantle. The melt rises and emerges at the surface at volcanic centers. Famous Cascade Range volcanoes include Mt. St. Helens, which had a large eruption in May 1980, Mt. Rainier near Seattle, Mt. Hood, which is the highest peak in Oregon, and Mt. Mazama, which destroyed itself 7,700 years ago in an enormous eruption that produced the modern-day Crater Lake Caldera (also a national park).

Mt. Lassen is a large volcanic dome that developed by lava extruding along the northeastern flanks of a former Cascade Range feature called Brokeoff Volcano (also known as Tehama Volcano). Brokeoff Volcano is an andesitic-dacitic subduction zone stratovolcano (composite volcano). Stratovolcanoes usually have violent, explosive ash eruptions. They tend to erupt igneous materials of intermediate chemistry (between felsic and mafic). Brokeoff Volcano was active from about 4 million years ago, during the Pliocene, to about 400,000 years ago. Only the caldera exists today. Calderas are large holes or depressions left behind after a volcano destroys itself or collapses. The Brokeoff Caldera is an erosional and slow-collapse caldera that formed before about 350,000 years ago.

The Mt. Lassen volcanic dome first started forming in the Late Pleistocene, at about 29 ka. It is principally composed of dacite lava, an extrusive igneous rock that is usually porphyritic-textured. Dacite is between andesite and rhyolite in silica content. Activity through time has ranged from dacite lava extrusion to explosive ash eruptions. Mt. Lassen last experienced eruptive activity in the early 1900s (1914 to 1921).

Locality: Lassen Volcano National Park, northeastern California, USA

Mt Hood (11,249') is one of the prominent stratovolcanoes along the Pacific Northwest. Twelve glaciers flow down its flanks. Though dormant, it could erupt again--endangering Portland 50 miles to the west-northwest.

Taken out the window of an airliner en route home from Seattle, 2005, then contrast-enhanced to bring out detail.

Mount Fuji and Fog in November Yamanashi-ken, Japan

The Ijen volcano complex is a group of stratovolcanoes, in East Java, Indonesia. It is inside a larger caldera Ijen, which is about 20 kilometers wide. The Gunung Merapi stratovolcano is the highest point of that complex. The name of this volcano resembles that of a different volcano, Mount Merapi in central Java, also known as Gunung Merapi; there is also a third volcano named Marapi in Sumatra. The name "Merapi" means "fire" in the Indonesian language.

West of Gunung Merapi is the Ijen volcano, which has a one-kilometer-wide turquoise-colored acid crater lake. The lake is the site of a labor-intensive sulfur mining operation, in which sulfur-laden baskets are carried by hand from the crater floor. The work is low-paid and very onerous. Workers earn around $5.50-$8.30 (Rp 50,000 - Rp 75,000) per day and once out of the crater, still need to carry their loads of sulfur chunks about three kilometers to the nearby Pultuding valley to get paid.[1]

Many other post-caldera cones and craters are located within the caldera or along its rim. The largest concentration of post-caldera cones forms an east/west-trending zone across the southern side of the caldera. The active crater at Kawah Ijen has an equivalent radius of 361 metres (1,184 ft), a surface of 0.41 square kilometres (0.16 sq mi). It is 200 metres (660 ft) deep and has a volume of 36 cubic hectometres (29,000 acre·ft).

This is Pilot Pinnacle in northern California. It is near Mt. Lassen (Lassen Peak), a prominent volcano and the key scenery in Lassen Volcanic National Park.

Lassen Volcano is part of the Cascade Range, a north-south linear chain of active and potentially active volcanoes in America's Pacific Northwest. It extends from northern California to Oregon, Washington State, and into British Columbia, Canada. The Cascade Range formed as a result of tectonic subduction - the offshore Juan de Fuca Plate is diving below the North American Plate. The diving plate causes melting in the mantle. The melt rises and emerges at the surface at volcanic centers. Famous Cascade Range volcanoes include Mt. St. Helens, which had a large eruption in May 1980, Mt. Rainier near Seattle, Mt. Hood, which is the highest peak in Oregon, and Mt. Mazama, which destroyed itself 7,700 years ago in an enormous eruption that produced the modern-day Crater Lake Caldera (also a national park).

Mt. Lassen (= well off to the right of this photo) is a large volcanic dome that has developed in the remnants of a former Cascade Range feature called Brokeoff Volcano (also known as Tehama Volcano). Brokeoff Volcano is an andesitic-dacitic subduction zone stratovolcano (composite volcano). Stratovolcanoes usually have violent, explosive ash eruptions. They tend to erupt igneous materials of intermediate chemistry (between felsic and mafic). Brokeoff Volcano was active from about 4 million years ago, during the Pliocene, to about 400,000 years ago. Only the caldera exists today.

In the photo, Pilot Pinnacle forms part of the western edge of the Brokeoff Caldera. Calderas are large holes or depressions left behind after a volcano destroys itself or collapses. The Brokeoff Caldera is an erosional and slow-collapse caldera that formed before about 350,000 years ago.

Eruptions still occur in this area. Mt. Lassen last experienced eruptive activity in the early 1900s.

Locality: view from Bumpass Hell Trailhead, just south of Mt. Lassen, Lassen Volcano National Park, northeastern California, USA

(video taken by Hannah Dietterich & provided by the Alaska Volcano Observatory / United States Geological Survey)

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Several Aleutian Arc volcanoes periodically threaten cities and towns in the Anchorage area of southern Alaska, USA. The Aleutian Volcanic Arc consists of dozens of volcanoes, all formed by subduction of the Pacific Plate beneath the North American Plate (the area is sometimes referred to as the "Bering Plate"). Mt. Spurr, in the northeastern Aleutian Volcanic Arc, is a 10-20,000 year old andesitic, subduction zone stratovolcano that formed after the collapse of a Late Pleistocene volcano (“ancestral Spurr Volcano”). Spurr Volcano had explosive ash eruptions in 1953 and 1992.

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Caption from the Alaska Volcano Observatory (AVO):

Video collected during an overflight of the summit of Mount Spurr on December 18, 2024. The lake formed within the ice covered summit crater in late spring 2024. Its green color and floating yellow debris are due to the presence of sulfur.

On October 16, 2024, AVO raised the color code and alert level to YELLOW/ADVISORY, stating: "AVO has observed a gradual increase in volcanic unrest over a period of several months at Mount Spurr, located about 120 km (75 miles) west of Anchorage. GNSS receivers have detected sustained upward and outward ground deformation since March 2024. An increase in seismic activity has also been noted since April (avo.alaska.edu/image/view/196122). Other indications of elevated activity include the development of a small lake in the summit crater in early summer of 2024.

The largest magnitude earthquake detected in this current period of unrest is a M2.3 earthquake on October 6th. This increase in activity was described in detail in an Information Statement (avo.alaska.edu/news/hans/DOI-USGS-AVO-2024-10-09T19:43:26...) that AVO released on October 9th. Analysis of seismic data indicates a subtle increase in the rate and size of earthquakes over the past few weeks. Because this is a notable departure from the normal background seismicity of the volcano, AVO is raising the Aviation Color Code to YELLOW and the Volcano Alert Level to ADVISORY. However, there are no indications that an eruption is imminent. Often this type of seismicity and ground deformation will decline without producing an eruption.

AVO continues to closely monitor activity at Mount Spurr for signals that would indicate that the volcano is moving closer to an eruption. Based on previous eruptions, changes from current activity in the earthquakes, ground deformation, summit lake, and fumaroles would be expected if magma began to move closer to the surface. Therefore, it is very likely that if an eruption were to occur it would be preceded by additional signals that would allow advance warning.

Over the following two weeks, there more than 180 small earthquakes at Mount Spurr. Over the week of November 1st, there were also a few episodes of possible volcanic tremor, which might indicate deep fluid movement. No unusual activity or surface changes were observed in satellite data or webcam views. AVO staff visited on October 24th to conduct pre-winter maintenance on Spurr’s monitoring network and noted that the fumaroles (steam/gas vents) in Spurr summit’s crater were steaming.

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Publications on previous Spurr eruptions:

Wilcox (1953) - Preliminary Report of the Eruption of Mount Spurr Volcano, Alaska, July 9, 1953, and the Ashfall in the Anchorage Area. 25 pp.

Keith (1995) - The 1992 eruptions of Crater Peak Vent, Mount Spurr Volcano, Alaska. U.S. Geological Survey Bulletin 2139. 223 pp.

The Hakkōda Mountains (八甲田山系 Hakkōda-sankei) is a volcanic complex that lies to the south of Aomori in Aomori Prefecture, Japan. The range consists of more than a dozen stratovolcanoes and lava domes arranged into two volcanic groups.[1] The Northern Hakkōda Volcanic Group emerges from the rim of an 8-km wide caldera that dates back to the Pleistocene.[1] The Southern Hakkōda Volcanic Group predates the caldera.[2]

The highest peak in the range is Mount Ōdake, which can be climbed from Sukayu Onsen in about four hours. Heavy snowfall makes Hakkoda a prime destination for backcountry and mountain skiers, and there are two mountain huts for overnight trips. The lower slopes of the mountains are forested interspersed with moorland. Above 1300 meters,[3] the Alpine climate zone starts.

The Hakkōda Mountains, along with Lake Towada and the Oirase Valley make up the Towada-Hachimantai National Park.[3]

en.wikipedia.org/wiki/Hakkōda_Mountains

The Ijen volcano complex is a group of stratovolcanoes, in East Java, Indonesia. It is inside a larger caldera Ijen, which is about 20 kilometers wide. The Gunung Merapi stratovolcano is the highest point of that complex. The name of this volcano resembles that of a different volcano, Mount Merapi in central Java, also known as Gunung Merapi; there is also a third volcano named Marapi in Sumatra. The name "Merapi" means "fire" in the Indonesian language.

West of Gunung Merapi is the Ijen volcano, which has a one-kilometer-wide turquoise-colored acid crater lake. The lake is the site of a labor-intensive sulfur mining operation, in which sulfur-laden baskets are carried by hand from the crater floor. The work is low-paid and very onerous. Workers earn around $5.50-$8.30 (Rp 50,000 - Rp 75,000) per day and once out of the crater, still need to carry their loads of sulfur chunks about three kilometers to the nearby Pultuding valley to get paid.[1]

Many other post-caldera cones and craters are located within the caldera or along its rim. The largest concentration of post-caldera cones forms an east/west-trending zone across the southern side of the caldera. The active crater at Kawah Ijen has an equivalent radius of 361 metres (1,184 ft), a surface of 0.41 square kilometres (0.16 sq mi). It is 200 metres (660 ft) deep and has a volume of 36 cubic hectometres (29,000 acre·ft).

This is Mt. Lassen (Lassen Peak), a prominent volcano and the key scenery in Lassen Volcanic National Park. Lassen Volcano is part of the Cascade Range, a north-south linear chain of active and potentially active volcanoes in America's Pacific Northwest. It extends from northern California to Oregon, Washington State, and into British Columbia, Canada. The Cascade Range formed as a result of tectonic subduction - the offshore Juan de Fuca Plate is diving below the North American Plate. The diving plate causes melting in the mantle. The melt rises and emerges at the surface at volcanic centers. Famous Cascade Range volcanoes include Mt. St. Helens, which had a large eruption in May 1980, Mt. Rainier near Seattle, Mt. Hood, which is the highest peak in Oregon, and Mt. Mazama, which destroyed itself 7,700 years ago in an enormous eruption that produced the modern-day Crater Lake Caldera (also a national park).

Mt. Lassen is a large volcanic dome that developed by lava extruding along the northeastern flanks of a former Cascade Range feature called Brokeoff Volcano (also known as Tehama Volcano). Brokeoff Volcano is an andesitic-dacitic subduction zone stratovolcano (composite volcano). Stratovolcanoes usually have violent, explosive ash eruptions. They tend to erupt igneous materials of intermediate chemistry (between felsic and mafic). Brokeoff Volcano was active from about 4 million years ago, during the Pliocene, to about 400,000 years ago. Only the caldera exists today. Calderas are large holes or depressions left behind after a volcano destroys itself or collapses. The Brokeoff Caldera is an erosional and slow-collapse caldera that formed before about 350,000 years ago.

The Mt. Lassen volcanic dome first started forming in the Late Pleistocene, at about 29 ka. It is principally composed of dacite lava, an extrusive igneous rock that is usually porphyritic-textured. Dacite is between andesite and rhyolite in silica content. Activity through time has ranged from dacite lava extrusion to explosive ash eruptions. Mt. Lassen last experienced eruptive activity in the early 1900s (1914 to 1921).

Locality: Lassen Volcano National Park, northeastern California, USA

Mt. Hood is a subduction zone stratovolcano in northwestern Oregon. It is part of the north-south trending Cascade Range of volcanoes from northern California to southwestern British Columbia. Other famous Cascade volcanoes include Mt. St. Helens, Mt. Rainier, Mt. Shasta, and Mt. Mazama (now Crater Lake Caldera).

Mt. Hood area volcanism started in the Middle Miocene, 8 to 10 million years ago, just after Columbia River Flood Basalt volcanism. Miocene and Pliocene andesites and basalts cap topographic ridges in the Mt. Hood area. During the Late Pliocene (sensu traditio), at 3 to 1.3 million years ago, the Sandy Glacier Volcano occupied the site of the current Mt. Hood. Sandy Glacier Volcano is now mostly buried by the modern Mt. Hood volcanic cone. Mt. Hood itself is less than 730,000 years old - all of its rocks have modern magnetic signatures. Lavas and other eruptive materials are high-silica andesites and low-silica dacites. 70% of the Mt. Hood cone consists of lava flows, while the remaining 30% is volcaniclcastic deposits. The modern cone is less than 300,000 years old. Near the summit of Mt. Hood are lava flows dating to younger than 200,000 years old.

Unlike nearby Mt. St. Helens, Mt. Hood is much older and has had little explosive activity. Most of Mt. Hood's volcanism has consisted of andesite lava flows and dome-building. Few explosive events have occurred through time here - few tephra deposits have a Mt. Hood source.

Mt. Hood rocks are often porphyritic two-pyroxene andesites, plus a little olivine. There's been little chemical variation in Mt. Hood lavas through time. Because of this, individual lava flows are difficult to date based on lithology - they're all the same. Much of Mt. Hood itself is hydrothermally-altered rocks.

Names are assigned to the various eruptive phases in Mt. Hood's history. The Polallie eruptive phase occurred from 12 to 25 thousand years ago. The Timberline eruptive phase occurred ~1500 years ago. The Old Maid eruptive phase occurred over 200 years ago, often dated to 1780-1801 A.D. Dome building occurred from 1781 to 1793. During that time, periodic, relatively small eruptions occurred.

Because Mt. Hood is a snow-clad volcano, activity results in melting of snow and mobilization of loose materials. Rainstorms could also mobilize loose debris in the area. Mt. Hood lahars have probably formed by both mechanisms.

Locality: Mt. Hood Volcano (looking southwest from The Dalles), northwestern Oregon, USA

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Info. at:

www.usgs.gov/volcanoes/mount-hood

This is Brokeoff Mountain in northern California. It is near Mt. Lassen (Lassen Peak), a prominent volcano and the key scenery in Lassen Volcanic National Park.

Lassen Volcano is part of the Cascade Range, a north-south linear chain of active and potentially active volcanoes in America's Pacific Northwest. It extends from northern California to Oregon, Washington State, and into British Columbia, Canada. The Cascade Range formed as a result of tectonic subduction - the offshore Juan de Fuca Plate is diving below the North American Plate. The diving plate causes melting in the mantle. The melt rises and emerges at the surface at volcanic centers. Famous Cascade Range volcanoes include Mt. St. Helens, which had a large eruption in May 1980, Mt. Rainier near Seattle, Mt. Hood, which is the highest peak in Oregon, and Mt. Mazama, which destroyed itself 7,700 years ago in an enormous eruption that produced the modern-day Crater Lake Caldera (also a national park).

Mt. Lassen (= well off to the right of this photo) is a large volcanic dome that has developed in the remnants of a former Cascade Range feature called Brokeoff Volcano (also known as Tehama Volcano). Brokeoff Volcano is an andesitic-dacitic subduction zone stratovolcano (composite volcano). Stratovolcanoes usually have violent, explosive ash eruptions. They tend to erupt igneous materials of intermediate chemistry (between felsic and mafic). Brokeoff Volcano was active from about 4 million years ago, during the Pliocene, to about 400,000 years ago. Only the caldera exists today.

In the photo, Brokeoff Mountain forms part of the western edge of the Brokeoff Caldera. Calderas are large holes or depressions left behind after a volcano destroys itself or collapses. The Brokeoff Caldera is an erosional and slow-collapse caldera that formed before about 350,000 years ago.

Eruptions still occur in this area. Mt. Lassen last experienced eruptive activity in the early 1900s.

Locality: view from near Sulfur Works, just south of Mt. Lassen, Lassen Volcano National Park, northeastern California, USA

The Ijen volcano complex is a group of stratovolcanoes, in East Java, Indonesia. It is inside a larger caldera Ijen, which is about 20 kilometers wide. The Gunung Merapi stratovolcano is the highest point of that complex. The name of this volcano resembles that of a different volcano, Mount Merapi in central Java, also known as Gunung Merapi; there is also a third volcano named Marapi in Sumatra. The name "Merapi" means "fire" in the Indonesian language.

This is lava from Mt. Lassen (Lassen Peak), a prominent volcano and the key scenery in Lassen Volcanic National Park. Lassen Volcano is part of the Cascade Range, a north-south linear chain of active and potentially active volcanoes in America's Pacific Northwest. It extends from northern California to Oregon, Washington State, and into British Columbia, Canada. The Cascade Range formed as a result of tectonic subduction - the offshore Juan de Fuca Plate is diving below the North American Plate. The diving plate causes melting in the mantle. The melt rises and emerges at the surface at volcanic centers. Famous Cascade Range volcanoes include Mt. St. Helens, which had a large eruption in May 1980, Mt. Rainier near Seattle, Mt. Hood, which is the highest peak in Oregon, and Mt. Mazama, which destroyed itself 7,700 years ago in an enormous eruption that produced the modern-day Crater Lake Caldera (also a national park).

Mt. Lassen is a large volcanic dome that developed by lava extruding along the northeastern flanks of a former Cascade Range feature called Brokeoff Volcano (also known as Tehama Volcano). Brokeoff Volcano is an andesitic-dacitic subduction zone stratovolcano (composite volcano). Stratovolcanoes usually have violent, explosive ash eruptions. They tend to erupt igneous materials of intermediate chemistry (between felsic and mafic). Brokeoff Volcano was active from about 4 million years ago, during the Pliocene, to about 400,000 years ago. Only the caldera exists today. Calderas are large holes or depressions left behind after a volcano destroys itself or collapses. The Brokeoff Caldera is an erosional and slow-collapse caldera that formed before about 350,000 years ago.

The Mt. Lassen volcanic dome first started forming in the Late Pleistocene, at about 29 ka. It is principally composed of dacite lava, an extrusive igneous rock that is usually porphyritic-textured. Dacite is between andesite and rhyolite in silica content. Activity through time has ranged from dacite lava extrusion to explosive ash eruptions. Mt. Lassen last experienced eruptive activity in the early 1900s (1914 to 1921).

The lava boulder shown here is in a volcanic debris flow deposit from 19 and 22 May 1915, when Mt. Lassen last had a significant eruption. The deposit consists of fine sediments, cobbles, and boulders, some of which are quite large. Clasts in the flow deposit include pinkish-reddish porphyritic dacite and gray porphyritic dacite, both of which formed at 27 ka during the Late Pleistocene, early in Mt. Lassen's history. Another clast type in the deposit is black porphyritic dacite, shown here, that formed on 14 May 1915. The whitish-colored phenocrysts (click on the photo to zoom in and look around) are plagioclase feldspar.

Locality: boulder in Devastated Area, Lassen Volcano National Park, northeastern California, USA

This is lava from Mt. Lassen (Lassen Peak), a prominent volcano and the key scenery in Lassen Volcanic National Park. Lassen Volcano is part of the Cascade Range, a north-south linear chain of active and potentially active volcanoes in America's Pacific Northwest. It extends from northern California to Oregon, Washington State, and into British Columbia, Canada. The Cascade Range formed as a result of tectonic subduction - the offshore Juan de Fuca Plate is diving below the North American Plate. The diving plate causes melting in the mantle. The melt rises and emerges at the surface at volcanic centers. Famous Cascade Range volcanoes include Mt. St. Helens, which had a large eruption in May 1980, Mt. Rainier near Seattle, Mt. Hood, which is the highest peak in Oregon, and Mt. Mazama, which destroyed itself 7,700 years ago in an enormous eruption that produced the modern-day Crater Lake Caldera (also a national park).

Mt. Lassen is a large volcanic dome that developed by lava extruding along the northeastern flanks of a former Cascade Range feature called Brokeoff Volcano (also known as Tehama Volcano). Brokeoff Volcano is an andesitic-dacitic subduction zone stratovolcano (composite volcano). Stratovolcanoes usually have violent, explosive ash eruptions. They tend to erupt igneous materials of intermediate chemistry (between felsic and mafic). Brokeoff Volcano was active from about 4 million years ago, during the Pliocene, to about 400,000 years ago. Only the caldera exists today. Calderas are large holes or depressions left behind after a volcano destroys itself or collapses. The Brokeoff Caldera is an erosional and slow-collapse caldera that formed before about 350,000 years ago.

The Mt. Lassen volcanic dome first started forming in the Late Pleistocene, at about 29 ka. It is principally composed of dacite lava, an extrusive igneous rock that is usually porphyritic-textured. Dacite is between andesite and rhyolite in silica content. Activity through time has ranged from dacite lava extrusion to explosive ash eruptions. Mt. Lassen last experienced eruptive activity in the early 1900s (1914 to 1921).

The lava boulder shown here is in a volcanic debris flow deposit from 19 and 22 May 1915, when Mt. Lassen last had a significant eruption. The deposit consists of fine sediments, cobbles, and boulders, some of which are quite large. Clasts in the flow deposit include pinkish-reddish porphyritic dacite and gray porphyritic dacite, both of which formed at 27 ka during the Late Pleistocene, early in Mt. Lassen's history. Another clast type in the deposit is black porphyritic dacite, shown here, that formed on 14 May 1915. The whitish-colored phenocrysts (click on the photo to zoom in and look around) are plagioclase feldspar.

Locality: boulder in Devastated Area, Lassen Volcano National Park, northeastern California, USA

This is lava from Mt. Lassen (Lassen Peak), a prominent volcano and the key scenery in Lassen Volcanic National Park. Lassen Volcano is part of the Cascade Range, a north-south linear chain of active and potentially active volcanoes in America's Pacific Northwest. It extends from northern California to Oregon, Washington State, and into British Columbia, Canada. The Cascade Range formed as a result of tectonic subduction - the offshore Juan de Fuca Plate is diving below the North American Plate. The diving plate causes melting in the mantle. The melt rises and emerges at the surface at volcanic centers. Famous Cascade Range volcanoes include Mt. St. Helens, which had a large eruption in May 1980, Mt. Rainier near Seattle, Mt. Hood, which is the highest peak in Oregon, and Mt. Mazama, which destroyed itself 7,700 years ago in an enormous eruption that produced the modern-day Crater Lake Caldera (also a national park).

Mt. Lassen is a large volcanic dome that developed by lava extruding along the northeastern flanks of a former Cascade Range feature called Brokeoff Volcano (also known as Tehama Volcano). Brokeoff Volcano is an andesitic-dacitic subduction zone stratovolcano (composite volcano). Stratovolcanoes usually have violent, explosive ash eruptions. They tend to erupt igneous materials of intermediate chemistry (between felsic and mafic). Brokeoff Volcano was active from about 4 million years ago, during the Pliocene, to about 400,000 years ago. Only the caldera exists today. Calderas are large holes or depressions left behind after a volcano destroys itself or collapses. The Brokeoff Caldera is an erosional and slow-collapse caldera that formed before about 350,000 years ago.

The Mt. Lassen volcanic dome first started forming in the Late Pleistocene, at about 29 ka. It is principally composed of dacite lava, an extrusive igneous rock that is usually porphyritic-textured. Dacite is between andesite and rhyolite in silica content. Activity through time has ranged from dacite lava extrusion to explosive ash eruptions. Mt. Lassen last experienced eruptive activity in the early 1900s (1914 to 1921).

The lava boulder shown here is in a volcanic debris flow deposit from 19 and 22 May 1915, when Mt. Lassen last had a significant eruption. The deposit consists of fine sediments, cobbles, and boulders, some of which are quite large. Clasts in the flow deposit include pinkish-reddish porphyritic dacite and gray porphyritic dacite, both of which formed at 27 ka during the Late Pleistocene, early in Mt. Lassen's history. Another clast type in the deposit is black porphyritic dacite that formed in 1915.

This boulder is 27 ka pinkish-reddish porphyritic dacite. The whitish-colored phenocrysts (click on the photo to zoom in and look around) are plagioclase feldspar.

Locality: boulder in Devastated Area, Lassen Volcano National Park, northeastern California, USA

The Ijen volcano complex is a group of stratovolcanoes, in East Java, Indonesia. It is inside a larger caldera Ijen, which is about 20 kilometers wide. The Gunung Merapi stratovolcano is the highest point of that complex. The name of this volcano resembles that of a different volcano, Mount Merapi in central Java, also known as Gunung Merapi. The name "Merapi" means "fire" in the Indonesian language. From: wiki.

Java is the world's most densely populated island (population: 136 million). It is home to 60% of Indonesia's population. Much of Indonesian history took place on Java; it was the centre of powerful Hindu-Buddhist empires, Islamic sultanates, the core of the colonial Dutch East Indies, and was at the centre of Indonesia's campaign for independence. The island dominates Indonesian social, political and economic life. More information on wikipedia.

This is lava from Mt. Lassen (Lassen Peak), a prominent volcano and the key scenery in Lassen Volcanic National Park. Lassen Volcano is part of the Cascade Range, a north-south linear chain of active and potentially active volcanoes in America's Pacific Northwest. It extends from northern California to Oregon, Washington State, and into British Columbia, Canada. The Cascade Range formed as a result of tectonic subduction - the offshore Juan de Fuca Plate is diving below the North American Plate. The diving plate causes melting in the mantle. The melt rises and emerges at the surface at volcanic centers. Famous Cascade Range volcanoes include Mt. St. Helens, which had a large eruption in May 1980, Mt. Rainier near Seattle, Mt. Hood, which is the highest peak in Oregon, and Mt. Mazama, which destroyed itself 7,700 years ago in an enormous eruption that produced the modern-day Crater Lake Caldera (also a national park).

Mt. Lassen is a large volcanic dome that developed by lava extruding along the northeastern flanks of a former Cascade Range feature called Brokeoff Volcano (also known as Tehama Volcano). Brokeoff Volcano is an andesitic-dacitic subduction zone stratovolcano (composite volcano). Stratovolcanoes usually have violent, explosive ash eruptions. They tend to erupt igneous materials of intermediate chemistry (between felsic and mafic). Brokeoff Volcano was active from about 4 million years ago, during the Pliocene, to about 400,000 years ago. Only the caldera exists today. Calderas are large holes or depressions left behind after a volcano destroys itself or collapses. The Brokeoff Caldera is an erosional and slow-collapse caldera that formed before about 350,000 years ago.

The Mt. Lassen volcanic dome first started forming in the Late Pleistocene, at about 29 ka. It is principally composed of dacite lava, an extrusive igneous rock that is usually porphyritic-textured. Dacite is between andesite and rhyolite in silica content. Activity through time has ranged from dacite lava extrusion to explosive ash eruptions. Mt. Lassen last experienced eruptive activity in the early 1900s (1914 to 1921).

The lava boulder shown here is in a volcanic debris flow deposit from 19 and 22 May 1915, when Mt. Lassen last had a significant eruption. The deposit consists of fine sediments, cobbles, and boulders, some of which are quite large. Clasts in the flow deposit include pinkish-reddish porphyritic dacite and gray porphyritic dacite, both of which formed at 27 ka during the Late Pleistocene, early in Mt. Lassen's history. Another clast type in the deposit is black porphyritic dacite that formed in 1915.

This boulder is 27 ka pinkish-reddish porphyritic dacite. The whitish-colored phenocrysts (click on the photo to zoom in and look around) are plagioclase feldspar.

Locality: boulder in Devastated Area, Lassen Volcano National Park, northeastern California, USA

Docks where public boats take passengers across the lake. In view are the Volcán Tolimán (right) with an altitude of 3158 meters (10,361 ft) and the Volcán Atitlán (left) with an altitude of 3535 meters (11,598 ft).

The Lago de Atitlán is a beautiful lake in the highlands of Guatemala; the water level is at 1562 meters (5,125 ft). The lake basin is volcanic in origin, filling an enormous caldera formed by an eruption 84,000 years ago. It is shaped by deep surrounding escarpments and three stratovolcanoes on its southern flank. Lake Atitlán is the deepest lake in Central America with a maximum depth of about 340 meters (1,120 ft). Its surface area is 130 sq km (50 sq mi).

Before we look at why the plates moved, we should first take a look at the different types of plates and different types of plate boundaries.

Plates

There are two types of plates, oceanic and continental.

Types of Plate boundaries

-Constructive (divergent) plate boundaries

Constructive plate boundaries move apart from each other. Shield volcanoes are found at constructive plate boundaries and a very good example of constructive plate boundaries is at the Mid-Atlantic Ridge where the North American plate is moving apart from the Eurasian plate.

-Destructive (convergent) plate boundaries

Destructive plate boundaries are found at boundaries of oceanic and continental plates overlapping each other. Since the oceanic plate is heavier, it sinks under the continental plate with the continental plate going up to build up Stratovolcanoes. Mount St. Helens in Washington, Mount Pinatubo in the Philippines and Mount Fuji in Japan are all found at destructive plate boundaries.

-Collision plate boundaries

Collision plate boundaries are found when two continental plates move towards each other to build up mountains. Earthquakes are found at collision plate boundaries. The Himalayas, Appalachian Mountains in the USA are all good examples of the mountains formed at collision plate boundaries.

-Conservative (transform) plate boundaries

Conservative plate boundaries slide past each other, earthquakes are found at those boundaries due to the pressure built from sliding past. The San Andreas Fault is a very good example of conservative plate boundary.

This is a volcanic deposit near Mt. Lassen (Lassen Peak), a prominent volcano and the key scenery in Lassen Volcanic National Park. Lassen Volcano is part of the Cascade Range, a north-south linear chain of active and potentially active volcanoes in America's Pacific Northwest. It extends from northern California to Oregon, Washington State, and into British Columbia, Canada. The Cascade Range formed as a result of tectonic subduction - the offshore Juan de Fuca Plate is diving below the North American Plate. The diving plate causes melting in the mantle. The melt rises and emerges at the surface at volcanic centers. Famous Cascade Range volcanoes include Mt. St. Helens, which had a large eruption in May 1980, Mt. Rainier near Seattle, Mt. Hood, which is the highest peak in Oregon, and Mt. Mazama, which destroyed itself 7,700 years ago in an enormous eruption that produced the modern-day Crater Lake Caldera (also a national park).

Mt. Lassen is a large volcanic dome that developed by lava extruding along the northeastern flanks of a former Cascade Range feature called Brokeoff Volcano (also known as Tehama Volcano). Brokeoff Volcano is an andesitic-dacitic subduction zone stratovolcano (composite volcano). Stratovolcanoes usually have violent, explosive ash eruptions. They tend to erupt igneous materials of intermediate chemistry (between felsic and mafic). Brokeoff Volcano was active from about 4 million years ago, during the Pliocene, to about 400,000 years ago. Only the caldera exists today. Calderas are large holes or depressions left behind after a volcano destroys itself or collapses. The Brokeoff Caldera is an erosional and slow-collapse caldera that formed before about 350,000 years ago.

The Mt. Lassen volcanic dome first started forming in the Late Pleistocene, at about 29 ka. It is principally composed of dacite lava, an extrusive igneous rock that is usually porphyritic-textured. Dacite is between andesite and rhyolite in silica content. Activity through time has ranged from dacite lava extrusion to explosive ash eruptions. Mt. Lassen last experienced eruptive activity in the early 1900s (1914 to 1921).

The boulders and cobbles shown here are in a volcanic debris flow deposit from 19 and 22 May 1915, when Mt. Lassen last had a significant eruption. The deposit consists of fine sediments, cobbles, and boulders, some of which are quite large. Clasts in the flow deposit include pinkish-reddish porphyritic dacite and gray porphyritic dacite, both of which formed at 27 ka during the Late Pleistocene, early in Mt. Lassen's history. Another clast type in the deposit is black porphyritic dacite, which formed on 14 May 1915. Other clast types present include dacite pumice and banded andesite-dacite pumice, both of which formed on 22 May 1915.

Locality: Devastated Area, Lassen Volcano National Park, northeastern California, USA

ISS033-E-006245 (20 Sept. 2012) --- Mount Shasta, California is featured in this image photographed by an Expedition 33 crew member on the International Space Station. The Cascade Range includes many impressive stratovolcanoes along its north-south extent, some active over the past few hundred years. Mount Shasta in northern California is among the largest and most active (over the past 4,000 years) of the volcanoes in the Cascades. The summit peak of the volcanic structure is at an elevation of 4,317 meters above sea level, and is formed by the Hotlum cone -- the location of the most recently recorded (1786) volcanic activity. The summit is high enough to retain snow cover throughout the year, and several small glaciers are present along the upper slopes of Shasta. Immediately to the west of the summit peak, but still on the upper slopes of Shasta, is the Shastina lava dome complex, reaching 3,758 meters above sea level. Two dark lava flows that originated from the Shastina complex and flowed downslope (toward the northwest) are visible in the lower part of this image. These contrast sharply with the surrounding vegetated (green) lower slopes and the barren upper slopes (gray) of Shasta. The Black Butte lava dome complex forms another, isolated hill on the lowermost slopes of Shasta near the town of Weed, CA (right). Geologists have mapped prehistoric pyroclastic flow and mudflow (also known as lahars) deposits from Hotlum cone and the Shastina and Black Butte lava dome complexes to distances of 20 kilometers from the summit of Shasta. As Mount Shasta has erupted within the past 250 years and several communities are within this hazard radius, the United States Geological Survey's California Volcano Observatory actively monitors the volcano for signs of activity.

This is Mt. Lassen (Lassen Peak), a prominent volcano and the key scenery in Lassen Volcanic National Park. Lassen Volcano is part of the Cascade Range, a north-south linear chain of active and potentially active volcanoes in America's Pacific Northwest. It extends from northern California to Oregon, Washington State, and into British Columbia, Canada. The Cascade Range formed as a result of tectonic subduction - the offshore Juan de Fuca Plate is diving below the North American Plate. The diving plate causes melting in the mantle. The melt rises and emerges at the surface at volcanic centers. Famous Cascade Range volcanoes include Mt. St. Helens, which had a large eruption in May 1980, Mt. Rainier near Seattle, Mt. Hood, which is the highest peak in Oregon, and Mt. Mazama, which destroyed itself 7,700 years ago in an enormous eruption that produced the modern-day Crater Lake Caldera (also a national park).

Mt. Lassen is a large volcanic dome that developed by lava extruding along the northeastern flanks of a former Cascade Range feature called Brokeoff Volcano (also known as Tehama Volcano). Brokeoff Volcano is an andesitic-dacitic subduction zone stratovolcano (composite volcano). Stratovolcanoes usually have violent, explosive ash eruptions. They tend to erupt igneous materials of intermediate chemistry (between felsic and mafic). Brokeoff Volcano was active from about 4 million years ago, during the Pliocene, to about 400,000 years ago. Only the caldera exists today. Calderas are large holes or depressions left behind after a volcano destroys itself or collapses. The Brokeoff Caldera is an erosional and slow-collapse caldera that formed before about 350,000 years ago.

The Mt. Lassen volcanic dome first started forming in the Late Pleistocene, at about 29 ka. It is principally composed of dacite lava, an extrusive igneous rock that is usually porphyritic-textured. Dacite is between andesite and rhyolite in silica content. Activity through time has ranged from dacite lava extrusion to explosive ash eruptions. Mt. Lassen last experienced eruptive activity in the early 1900s (1914 to 1921).

Locality: Lassen Volcano National Park, northeastern California, USA