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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 (not to be confused with Central Java's Gunung Merapi) is the highest point of that complex.
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. 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 E-W-trending zone across the southern side of the caldera. The active crater at Kawah Ijen has an equivalent radius of 361 meters, a surface of 41 × 106 square meters. It is 200 meters deep and has a volume of 36 × 106 cubic meters
Snæfellsjökull (snow-fell glacier) is a 700,000-year-old glacier-capped stratovolcano in western Iceland. The name of the mountain is actually Snæfell, but it is normally called "Snæfellsjökull" to distinguish it from two other mountains with this name. It is situated on the most western part of the Snæfellsnes peninsula in Iceland. Sometimes it may be seen from the city of Reykjavík over Faxa Bay, at a distance of 120 km.
On clear days, one can see Snæfellsjökull from Iceland’s capital city, Reykjavik, approximately 120 kilometres away over Faxa Bay, making for an impressive sight—and a tick off the bucket list if you can’t make it to travelling across the Peninsula itself. The volcano makes up just a small part of the larger Snæfellsjökull National Park.
Snæfellsjökull has, for centuries, been considered to be one of the world’s ancient power sites, a source of mysticism, energy and mystery for the peninsula’s superstitious population. This likely has something to do with the stratovolcanoes place in the Icelandic sagas; the feature takes a prominent role in Bárðar saga Snæfellsáss, a late 14th-century saga that tells the story of Bárður, half-human-half-troll, who became the “guardian spirit of Snæfellsjökull.”
The mountain is one of the most famous sites of Iceland, primarily due to the novel Journey to the Center of the Earth (1864) by Jules Verne, in which the protagonists find the entrance to a passage leading to the center of the earth on Snæfellsjökull.
The mountain is included in the Snæfellsjökull National Park (Icelandic: Þjóðgarðurinn Snæfellsjökull).
In August 2012 the summit was ice-free for the first time in recorded history.
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The Ijen volcano complex is a group of stratovolcanoes in the Banyuwangi Regency of East Java, Indonesia.
It is inside a larger caldera Ijen, which is about 20 kilometres wide. The Gunung Merapi stratovolcano is the highest point of that complex. The name "Gunung Merapi" means "mountain of fire" in the Indonesian language (api being "fire"); Mount Merapi in central Java and Marapi in Sumatra have the same etymology.
West of Gunung Merapi is the Ijen volcano, which has a one-kilometre-wide turquoise-coloured acidic crater lake. The lake is the site of a labour-intensive sulfur mining operation, in which sulfur-laden baskets are carried by hand from the crater floor. The work is paid well considering the cost of living in the area, but is very onerous. Workers earn around Rp 50,000 - 75,000 ($5.50-$8.30) per day and once out of the crater, still need to carry their loads of sulfur chunks about three kilometers to the nearby Paltuding Valley to get paid.
Many other post-caldera cones and craters are located within the caldera or along its rim. The largest concentration of post-caldera cones run east-west across the southern side of the caldera. The active crater at Kawah Ijen has a diameter of 722 metres (2,369 ft) and a surface area 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).
The lake is recognised as the largest highly acidic crater lake in the world. It is also a source for the river Banyupahit, resulting in highly acidic and metal-enriched river water which has a significant detrimental effect on the downstream river ecosystem. In 2008, explorer George Kourounis took a small rubber boat out onto the acid lake to measure its acidity. The pH of the water in the crater was measured to be 0.5 due to sulfuric acid.
Since National Geographic mentioned the electric-blue flame of Ijen, tourist numbers increased. The phenomenon has occurred for a long time, but beforehand there was no midnight hiking. A two-hour hike is required to reach the rim of the crater, followed by a 45-minute hike down to the bank of the crater. The blue fire is ignited sulphuric gas, which emerges from cracks at temperatures up to 600 degrees Celsius (1,112 degrees Fahrenheit).
The flames can be up to 5 metres (16 feet) high; some of the gas condenses to liquid and is still ignited. It is the largest blue flame area in the world and local people refer to it as 'Blue Fire'.[citation needed]
An active vent at the edge of the lake is a source of elemental sulfur, and supports a mining operation. Escaping volcanic gases are channelled through a network of ceramic pipes, resulting in condensation of molten sulfur. The sulphur, which is deep red in colour when molten, pours slowly from the ends of these pipes and pools on the ground, turning bright yellow as it cools. The miners break the cooled material into large pieces and carry it away in baskets. Miners carry loads ranging from 75 kilograms (165 lb) to 90 kilograms (200 lb), up 300 metres (980 ft) to the crater rim, with a gradient of 45 to 60 degrees and then 3 kilometres (1.86 miles) down the mountain for weighing. Most miners make this journey twice a day. A nearby sugar refinery pays the miners by the weight of sulfur transported; as of September 2010, the typical daily earnings were equivalent to approximately $13 US. The miners often receive insufficient protection while working around the volcano [9] and complain of numerous respiratory afflictions. There are 200 miners, who extract 14 tons per day - about 20 percent of the continuous daily deposit.
Source: Wikipedia
(public domain photo taken by Lauren Flynn & provided by the Alaska Volcano Observatory)
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Great Sitkin Volcano is a subduction zone stratovolcano on Great Sitkin Island (= part of the Andreanof Islands) in the Aleutian Islands of Alaska. The volcano consists of lava flows (andesite, basaltic andesite, and basalt), volcanic tuffs, and lahar deposits. Seen here is a photo of its 25 May 2021 eruption, which was relatively small, short-duration, and the most recent explosive event. In late July 2021, Great Sitkin started a slow effusive (lava flow) eruption, which is ongoing as of late 2023.
The Aleutian Arc is a subduction zone formed as the Pacific Plate dives underneath the North American Plate (this area is sometimes called the Bering Plate). The diving plate in subduction zones releases water at depth, which causes partial melting of overlying mantle rocks. The low-density melt rises and eventually reaches the surface, forming volcanoes. All subduction zones have volcanoes and frequent seismicity. Volcanoes in such settings tend to have explosive ash eruptions. Rocks and tephra deposits at subduction zone volcanoes are usually intermediate in composition - typically andesitic to dacitic.
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Info. at:
en.wikipedia.org/wiki/Great_Sitkin_Island
and
avo.alaska.edu/volcanoes/volcinfo.php?volcname=Great%20Si...
and
The Ijen volcano complex is a group of stratovolcanoes in the Banyuwangi Regency of East Java, Indonesia. It is inside a larger caldera Ijen, which is about 20 kilometers wide. 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 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.
The active crater at Kawah Ijen has a diameter of 722 metres (2,369 ft) and a surface area 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).
The lake is recognised as the largest highly acidic crater lake in the world.
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 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).
View of Gorely Volcano. Gorely is a volcano located in the southern part of Kamchatka Peninsula, Russia. It consists of five overlapping stratovolcanoes and is one of the most active in southern Kamchatka. Gorely is a large, long-lived shield-type volcano that is currently in an eruptive phase.
The Kamchatka River and the surrounding central side valley are flanked by large volcanic belts containing around 160 volcanoes, 29 of them still active. The peninsula has a high density of volcanoes and associated volcanic phenomena, with 19 active volcanoes included in the six UNESCO World Heritage List sites in the Volcanoes of Kamchatka group, most of them on the Kamchatka Peninsula, the most volcanic area of the Eurasian continent, with many active cones. The Kamchatka Peninsula is also known as the "land of fire and ice".
(public domain photo by Brian Reedy & provided by the Alaska Volcano Observatory)
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Shishaldin Volcano is a subduction zone stratovolcano on Unimak Island in the Aleutian Islands of Alaska. Minor lava eruptions in the summit crater started on 12 July 2023. Thirteen episodes of subsequent explosive ash eruptions took place on 14 July, 15 July, 18 July, 22-23 July, 25-26 July, 4 August, 14-15 August, 25 August, 5 September, 15 September, 24 to 25 September, 3 October, and 2-3 November 2023. This is an oblique aerial view of Shishaldin with a steam plume on 25 November 2023.
The Aleutian Arc is a subduction zone formed as the Pacific Plate dives underneath the North American Plate (this area is sometimes called the Bering Plate). The diving plate in subduction zones releases water at depth, which causes partial melting of overlying mantle rocks. The low-density melt rises and eventually reaches the surface, forming volcanoes. All subduction zones have volcanoes and frequent seismicity. Volcanoes in such settings tend to have explosive ash eruptions. Rocks and tephra deposits at subduction zone volcanoes are usually intermediate in composition - typically andesitic to dacitic. Shishaldin's erupted materials in 2023 have been mafic (basaltic).
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Info. at:
en.wikipedia.org/wiki/Mount_Shishaldin
and
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. 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).
Photo © Tristan Savatier - All Rights Reserved - License this photo on www.loupiote.com/7001689042
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Gunung Sundoro (left) and Gunung Sumbing (right) are two of the many volcanoes on Java Island (Indonesia)
For more information about those volcanoes, read en.wikipedia.org/wiki/Sundoro and en.wikipedia.org/wiki/Sumbing
If you like this photo, follow me on instagram (tristan_sf) and don't hesitate to leave a comment or email me.
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. 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).
Road of the volcanoes - highest pass point at about 4.900 m., viewpoint Mirador de los volcanes - on the road between Arequipa and Chivay
Sabancaya is a 6000m high active stratovolcano in the Andes in southern Peru, located about 100km northwest of Arequipa (2,335m).
It is the most active volcano in Peru and part of a 20 km long north-south chain of 3 large stratovolcanoes.
Nevado Hualca Hualca 6025m, the always most active Sabancaya 6000m, Ampato 6300m.
Mount Drum, a stratovolcano in the Wrangell Mountains, is part of Wrangell-Saint Elias National Park and Preserve.
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.
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).
In 2008, explorer George Kourounis took a small rubber boat out onto the acid lake to measure its acidity. The pH of the water in the crater was measured to be 0.5 due to sulfuric acid
(~6.5 centimeters across at its widest)
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This is a slice from the Erg Chech 002 Meteorite, which was found in May 2020 on sand dunes of the Bir Ben Takoul area, western Algeria, northwestern Africa. It is a stony meteorite, the most common category (the others are irons and stony-irons). The two broad types of stony meteorites are chondrites, which have small rounded structures called chondrules, and achondrites, which have no chondrules - this meteorite is an achondrite. Many specific types of achondrites are known - most are from the Asteroid Belt. Asteroidal achondrites include angrites, aubrites, brachinites, ureilites, lodranites, acapulcoites, howardites, eucrites, diogenites, and the so-called winonaites (which may not be a meteorite type at all). Some planetary achondrites are also known - they come from the Moon (lunaites) or Mars (shergottites, nakhlites, and chassignites). The Erg Chech 002 Meteorites falls into none of these categories. Unclassifiable achondrites are referred to as "ungrouped". I'd prefer establishing names for distinctive types of ungrouped achondrites, but this has not been done.
Erg Chech 002 was originally described as a gabbro with pyroxene megacrysts. Gabbro is a mafic, phaneritic, intrusive igneous rock composed of plagioclase feldspar and pyroxene. Subsequent analysis has shown that Erg Chech 002 is a porphyritic andesite, an intermediate, extrusive igneous rock - in other words, a type of volcanic lava (it could also be from a near-surface intrusion). Andesite lavas and ash deposits are relatively common on Earth - they usually form from eruptions of subduction zone stratovolcanoes. Erg Chech 002 is not an Earth rock, so its lithology indicates the former presence of a differentiated parent body in the early Solar System that had surface volcanism of andesite. No known Solar System bodies have this, so the parent body has been disrupted (if so, probably by one or more impact events) or incorporated into a larger Solar System body.
Uncut and sliced samples of Erg Chech 002 show spectacular translucent green crystals (e.g., see: www.flickr.com/photos/jurvetson/51023828888 and
www.flickr.com/photos/jurvetson/51024557161 and
www.flickr.com/photos/jurvetson/50866150703 ). Prima facie, these look like olivine masses, but they're not. The large greenish-colored crystals and the long, dark blades in Erg Chech 002 are pyroxene phenocrysts (= large crystals in a porphyritic rock) (they've also been characterized as megacrysts and xenocrysts). The brownish-colored areas are iron oxide staining from weathering while on Earth.
The pyroxene content of Erg Chech 002 ranges from orthopyroxene to pigeonite to augite. The plagioclase feldspar component is oligoclase to albite, which are sodium-rich feldspars - this is unusual - most meteorites have calcium-rich feldspar. Minor reported minerals include potassium feldspar, chromite, ilmenite, troilite, cristobalite, tridymite, merrillite, FeNi metal, spinel, and a calcium phosphate mineral.
A dating study found that Erg Chech 002 is 4.565 billion years old.
An impact event ejected this rock from its parent body - shock metamorphism is present.
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Synthesized from info. in:
2020. Meteoritical Bulletin 109.
Yamaguchi et al. (2021) - Petrology and geochemistry of Erg Chech 002, the oldest andesite in the Solar System. 52nd Lunar and Planetary Science Conference, no. 1892.
Chaussidon et al. (2021) - 26 Al chronology of Erg Chech 002, the oldest andesite in the Solar System. 52nd Lunar and Planetary Science Conference, no. 2222.
I'll keep this short:
Rock is a mix of minerals. There are three fundamental kinds of rock: igneous (=magmatic), sedimentary and metamorphic. Magmatic rock comes mainly in two kinds: intrusive (plutonic), which solidifies (crystallises) slowly, deep down, under pressure and still high temperature - and extrusive (effusive, volcanic), which solidifies close to or on the surface. quickly, at near-ambient pressure temperatures. Usually, plutonic rock is composed of large crystals, which need time to form, while volcanic rock will have a fine crystal structure and sometimes no crystal structure at all.
For magmatic rocks there usually are two flavours, chemically equivalent but with very different crystal structures, depending on whether they are plutonic or volcanic. For instance, you will have heard of basalt, which is the volcanic form of a mafic rock, while its plutonic partner is called gabbro.
Magma with a high silica content (i.e., a significant percentage of quartz) is called felsic, while magma with a low or very low silica content is mafic or ultramafic. Oceanic crust tends to be mafic, while continental crust tends to be felsic.
Felsic magma is more likely to be viscous, so when it reaches the surface, it it is more likely to lead to stratovolcanoes, and its higher viscosity may help keep a lid on the melt below, so high pressures can build up, leading to an explosion. Conversely, mafic magma is more likely to be of low viscosity, mostly lacking the mechanical strength to support a high volcanic structure. Therefore, mafic magma usually builds up shield volcanoes.
Note the intentionally vague statements. There are many exceptions to the rules. The magma that led to the formation of the Kaiserstuhl volcanoes in southwest Germany was unusual in being ultramafic and at the same time alkaline (rich in sodium and potassium). It was silica understaturated and at the same time rich in a rather rate (at the surface at least) class of minerals called foids (feldspathoids), which increased its viscosity and allowed it to build a stratovolcano complex, which happened 17-15 million years ago, during the miocene.
Phonolith, shown here in a sample of about 55 mm size, is a volcanic rock, composed of feldspar and foids (nepheline, sanidine, leucite, essexite). The white stuff that looks like dried-up whipped cream is zeolith, which formed in cracks though weathering of foidic material.
I found it in the Hauri quarry, in Bötzingen, Kaiserstuhl, Baden Württemberg, Germany.
Shot with a Canon EOS600D, a Leica Bellows R and a Leica 100mm f/4 Macro-Elmar-R.
Explosive eruption of Mt. Pinatubo on 15 June 1991. (original photo taken by Robert Lapointe; public domain image provided by the United States Geological Survey)
Mt. Pinatubo’s summer 1991 eruption was the largest on Earth since 1912. Pinatubo's big eruption is also famous for having been successfully predicted by American volcanologists. The prediction and subsequent evacuation saved thousands of lives.
Located near the western margin of Luzon Island in the northern Philippines, Mt. Pinatubo is one of several subduction zone stratovolcanoes in the Luzon Volcanic Arc. Published information indicates that Pinatubo is 35,000+ years old and is composed principally of dacitic and andesitic rocks.
The mid-June 1991 eruptions from Pinatubo blanketed ash, pumiceous lapilli, and pumice over the surrounding countryside, including two American military bases (Clark and Subic Bay).
The main eruption started in the middle of the night on 15 June 1991 - the photo shows the eruption in daylight.
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See info. at:
Newhall & Punongbayan (1996) - Fire and Mud, Eruptions and Lahars of Mount Pinatubo, Philippines. Quezon City & Seattle & London. Philippine Institute of Volcanology and Seismology & University of Washington Press. 1126 pp.
(web camera still image provided by the Alaska Volcano Observatory)
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Shishaldin Volcano is a subduction zone stratovolcano on Unimak Island in the Aleutian Islands of Alaska. Minor lava eruptions in the summit crater started on 12 July 2023. Twelve episodes of explosive ash eruptions have occurred since then, on 14 July, 15 July, 18 July, 22-23 July, 25-26 July, 4 August, 14-15 August, 25 August, 5 September, 15 September, 24 to 25 September, and 3 October 2023. Seen here is ash erupting from Shishaldin a little before 8 AM, local time, on 18 July 2023. The Alaska Volcano Observatory reported the ash cloud reached about 30,000 feet high and headed ~southward over the Pacific Ocean.
The Aleutian Arc is a subduction zone formed as the Pacific Plate dives underneath the North American Plate (this area is sometimes called the Bering Plate). The diving plate in subduction zones releases water at depth, which causes partial melting of overlying mantle rocks. The low-density melt rises and eventually reaches the surface, forming volcanoes. All subduction zones have volcanoes and frequent seismicity. Volcanoes in such settings tend to have explosive ash eruptions. Rocks and tephra deposits at subduction zone volcanoes are usually intermediate in composition - typically andesitic to dacitic.
-------------------------------------------
Info. at:
en.wikipedia.org/wiki/Mount_Shishaldin
and
The Ijen volcano complex is a group of stratovolcanoes in the Banyuwangi Regency of East Java, Indonesia. It is inside a larger caldera Ijen, which is about 20 kilometers wide. 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 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.
The active crater at Kawah Ijen has a diameter of 722 metres (2,369 ft) and a surface area 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).
The lake is recognised as the largest highly acidic crater lake in the world.
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.
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).
In 2008, explorer George Kourounis took a small rubber boat out onto the acid lake to measure its acidity. The pH of the water in the crater was measured to be 0.5 due to sulfuric acid
(still image from the Brown Peak web camera on Unimak Island, Alaska)
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Shishaldin Volcano is a subduction zone stratovolcano on Unimak Island in the Aleutian Islands of Alaska. Minor lava eruptions in the summit crater started on 12 July 2023. Thirteen episodes of subsequent explosive ash eruptions took place on 14 July, 15 July, 18 July, 22-23 July, 25-26 July, 4 August, 14-15 August, 25 August, 5 September, 15 September, 24 to 25 September, 3 October, and 2-3 November 2023. Seen here is Shishaldin with a steam plume in the early afternoon of 29 November 2023.
The Aleutian Arc is a subduction zone formed as the Pacific Plate dives underneath the North American Plate (this area is sometimes called the Bering Plate). The diving plate in subduction zones releases water at depth, which causes partial melting of overlying mantle rocks. The low-density melt rises and eventually reaches the surface, forming volcanoes. All subduction zones have volcanoes and frequent seismicity. Volcanoes in such settings tend to have explosive ash eruptions. Rocks and tephra deposits at subduction zone volcanoes are usually intermediate in composition - typically andesitic to dacitic. Shishaldin's erupted materials in 2023 have been mafic (basaltic).
-------------------------------------------
Info. at:
en.wikipedia.org/wiki/Mount_Shishaldin
and
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).
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.
Explosive eruption of Mt. Pinatubo on 12 June 1991. (original photo taken by R.S. Culbreth; public domain image provided by the United States Geological Survey)
Mt. Pinatubo’s summer 1991 eruption was the largest on Earth since 1912. Pinatubo's big eruption is also famous for having been successfully predicted by American volcanologists. The prediction and subsequent evacuation saved thousands of lives.
Located near the western margin of Luzon Island in the northern Philippines, Mt. Pinatubo is one of several subduction zone stratovolcanoes in the Luzon Volcanic Arc. Published information indicates that Pinatubo is 35,000+ years old and is composed principally of dacitic and andesitic rocks.
The mid-June 1991 eruptions from Pinatubo blanketed ash, pumiceous lapilli, and pumice over the surrounding countryside, including two American military bases (Clark and Subic Bay).
The "appetizer-scale eruption" seen here occurred on 12 June 1991, a few days before the main eruption, which occurred in the middle of the night.
-------------------
See info. at:
Newhall & Punongbayan (1996) - Fire and Mud, Eruptions and Lahars of Mount Pinatubo, Philippines. Quezon City & Seattle & London. Philippine Institute of Volcanology and Seismology & University of Washington Press. 1126 pp.
Editor's Note: This is a detail of Laguna Verde, cropped from this full-sized image: www.flickr.com/photos/28634332@N05/4968627080/
This photograph, featuring a landscape in the central Andes mountains near the Chile/Argentina border dominated by numerous volcanoes and associated landforms, was photographed by an Expedition 24 crew member on the International Space Station. Layers of older sedimentary rocks are visible to the southeast (upper right). Many of the volcanic cones show grooves eroded by water to form gullies. Such erosion has occurred since the host volcano was built up, indicating that most volcanoes in this view have been inactive for centuries or millennia. A few volcanoes exhibit much less erosion, and even show tongues of recent, dark lava flows (top left). According to scientists, two of these volcanoes, Cerro el Condor and Peinado have likely erupted within approximately the last 12,000 years (the Holocene Epoch). Also visible in the image is the world's highest active volcano, Nevado Ojos del Salado, with a summit at 6,887 meters above sea level. The most recent confirmed eruption of this volcano has been dated to 700 (approximately 300 years), but minor eruptive activity may have occurred as recently as 1993. Stratovolcanoes such as Cerro el Condor, Peinado, and Nevado Ojos del Salado are formed partly by buildup of lava flows and partly by buildup of explosively vented material dropping back down onto the surface. One type of material associated with explosive eruptions is welded tuff, which is formed by molten and fragmented rock that accumulates on the ground and later solidifies. A large tuff sheet is visible at top left. Formed very rapidly, these sheets have been termed "instant landscapes." So active has the Andean volcanic system been that the origin of many of the tuffs in the Andes cannot be pinpointed since source vents have been overprinted by subsequent volcanic events. The volcanic landscape also shows that the erosive work of rivers—and glaciers repeatedly in the recent past—is slower than the opposite processes of the upward building of the volcanoes. The bright blue, nearly 7-kilometer-long lake near the center of the image is known as Laguna Verde. This and other less obvious lakes indicate that water (snowmelt or direct precipitation) is unable to reach the sea, but is rather impounded in the depressions between the volcanic edifices.
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The Ijen volcano complex is a group of stratovolcanoes in the Banyuwangi Regency of East Java, Indonesia. It is inside a larger caldera Ijen, which is about 20 kilometers wide. 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 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.
The active crater at Kawah Ijen has a diameter of 722 metres (2,369 ft) and a surface area 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).
The lake is recognised as the largest highly acidic crater lake in the world.
The North Cascades are a section of the Cascade Range of western North America. They span the border between the Canadian province of British Columbia and the U.S. state of Washington and are officially named in the U.S. and Canada as the Cascade Mountains. The portion in Canada is known to Americans as the Canadian Cascades, a designation that also includes the mountains above the east bank of the Fraser Canyon as far north as the town of Lytton, at the confluence of the Thompson and Fraser Rivers.
They are predominantly non-volcanic, but include the stratovolcanoes Mount Baker, Glacier Peak and Coquihalla Mountain, which are part of the Cascade Volcanic Arc.
Washington, United States
Boat ride from San Pedro La Laguna to Panajachel.
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).
Docks where public boats take passengers across the lake.
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).
ISS030-E-162344 (15 March 2012) --- Ice floes along the Kamchatka coastline are featured in this image photographed by an Expedition 30 crew member on the International Space Station. The vantage point from orbit frequently affords the opportunity to observe processes that are impossible to see on the ground – or in this case the northeastern Pacific Ocean. The winter season blankets the Kamchatka Peninsula of Russia in snow, but significant amounts of sea ice can also form and collect along the coastline. As ice floes grind against each other, they produce smaller floes that can be moved by wind and water currents acting along the coastline. The irregular southeastern coastline of Kamchatka helps to produce large circular eddy currents from the main southwestward-flowing Kamchatka current. Three such eddies are clearly highlighted by surface ice floe patterns at center. The ice patterns are very difficult (and dangerous) to navigate in an ocean vessel – while the floes may look thin and delicate from the space station vantage point, even the smaller ice chunks are likely several meters across. White clouds at top right are distinguished from the sea ice and snow cover in the image by their high brightness and discontinuous nature. The Kamchatka Peninsula also hosts many currently and historically active stratovolcanoes. Kliuchevskoi Volcano, the highest in Kamchatka (summit elevation 4,835 meters) and one of the most active, had its most recent confirmed eruption in June of 2011, while Karymsky Volcano to the south likely produced ash plumes days before this image was taken; the snow cover near the volcano to the south and east of the summit is darkened, probably due to a cover of fresh ash, or melted away altogether (bottom center). In contrast, Kronotsky Volcano – a “textbook” symmetrical cone-shaped stratovolcano – last erupted in 1923.
This satellite image shows 91 small earthquakes that occurred at Mt. St. Helens in Washington State from 16 January to 12 February 2022. The largest event was magnitude +2.0 and the smallest was magnitude -0.6. Hypocenters ranged from the near-surface to 12.4 kilometers deep.
Mt. St. Helens is a subduction zone stratovolcano in southwestern Washington State. It is part of a north-south trending chain of volcanoes from southwestern British Columbia to northern California called the Cascade Range. Other notable Cascade volcanoes include Mt. Hood, Mt. Rainier, Mt. Shasta, and Mt. Mazama (now Crater Lake Caldera).
Mt. St. Helens is the most active Cascade Range volcano. It is a 40,000 to 50,000 year old, andesitic-dacitic-basaltic volcano that typically has explosive ash eruptions (as do all subduction zone stratovolcanoes). A significant explosive eruption occurred here in 1980 - a northward-directed lateral blast immediately followed an enormous landslide event on the northern face of the volcano. The landslide was triggered by a moderate earthquake at 8:32 AM, Sunday, 18 May 1980. Snow and ice on the mountain melted during the eruption, mixed with ash and other debris, and rushed down nearby river valleys as lahars (volcanic mud flows).
The ash, lapilli, and pumice erupted from Mt. St. Helens in May 1980 was dacite, an intermediate extrusive igneous rock. Most of the air-fall dacite ash fell in Washington State, Oregon, and Idaho, but a minor amount accumulated as far east as Minnesota and Oklahoma. Light dustings of ash were also observed in Ohio.
The 1980 eruption was the largest in recent American history. The volcano was intermittently active until 1986. Minor activity occurred from 1989 to 1991 and from 2004 to 2006.
The area is now a park ("national volcanic monument") and is accessible to tourists. The top third of the mountain was blown away during the 1980 eruption. Much of the landscape is still nonvegetated and covered with gray volcanic tephra.
Location: Mt. St. Helens, northwestern Skamania County, Cascade Range, southwestern Washington State, USA (46˚ 12’ 04” North latitude, 122˚ 11” 18” West longitude)
Editor's Note: This is an archive image from 2007.
Pagan Island, Northern Mariana Islands, is featured in this image photographed by an Expedition 14 crewmember on the International Space Station. According to scientists, the Mariana Islands are part a volcanic island arc -- surface volcanoes formed from magma generation as one tectonic plate is overridden (or subducted) beneath another. In the case of the Mariana Islands, the Pacific Plate is being subducted beneath the Philippine Plate along the famously deep Mariana Trench (more than 11 kilometers below sea level). Pagan Island (right) is comprised of two stratovolcanoes (tall, typically cone-shaped structures formed by layers of dense crystallized lava and less-dense ash and pumice) connected by a narrow isthmus of land. Mount Pagan, the larger of the two volcanoes, forms the northeastern portion of the island and has been the most active historically. The most recent major eruption took place in 1981, but since then numerous steam- and ash-producing events have been observed at the volcano -- the latest reported one occurring between Dec. 5-8, 2006. This image records volcanic activity on Jan. 11, 2007 that produced a thin plume (most probably steam, say NASA scientists, possibly with minor ash content) that extended westwards away from Mount Pagan. The island is sparsely populated, and monitored for volcanic activity by the United States Geological Survey and the Commonwealth of the Mariana Islands.
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Sabancaya is a 6000m high active stratovolcano in the Andes in southern Peru, located about 100km northwest of Arequipa (2,335m).
It is the most active volcano in Peru and part of a 20 km long north-south chain of 3 large stratovolcanoes.
Nevado Hualca Hualca 6025m, the always most active Sabancaya 6000m, Ampato 6300m.
El Misti volcano in Peru is featured in this image photographed by an Expedition 21 crew member on the International Space Station. The symmetric conical shape of El Misti is typical of a stratovolcano -- a type of volcano characterized by interlayered lavas and products of explosive eruptions, such as ash and pyroclastic flow deposits. Stratovolcanoes are usually located on the continental crust above a subducting tectonic plate. Magma feeding the stratovolcanoes of the Andes Mountains -- including 5,822 meter-high El Misti -- is associated with ongoing subduction of the Nazca Plate beneath the South American Plate. El Misti's most recent -- and relatively minor -- eruption occurred in 1985. The city center of Arequipa, Peru lies only 17 kilometers away from the summit of El Misti; the gray urban area is bordered by green agricultural fields (right). With almost one million residents in 2009, it is the second city of Peru in terms of population. Much of the building stone for Arequipa, known locally as sillar, is quarried from nearby pyroclastic flow deposits that are white in color. Arequipa is known as "the White City" because of the prevalence of this building material. The Chili River extends northeastwards from the city center, and flows through a canyon (left) between El Misti volcano and Nevado Chachani to the north.
Image credit: NASA
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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.
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
(public domain photo by Craig Walters & provided by the Alaska Volcano Observatory)
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Shishaldin Volcano is a subduction zone stratovolcano on Unimak Island in the Aleutian Islands of Alaska. Minor lava eruptions in the summit crater started on 12 July 2023. Thirteen episodes of explosive ash eruptions have occurred since then, on 14 July, 15 July, 18 July, 22-23 July, 25-26 July, 4 August, 14-15 August, 25 August, 5 September, 15 September, 25 September, 3 October, and 2-3 November 2023. Seen here is Shishaldin in early November with a prominent white steam plume.
The Aleutian Arc is a subduction zone formed as the Pacific Plate dives underneath the North American Plate (this area is sometimes called the Bering Plate). The diving plate in subduction zones releases water at depth, which causes partial melting of overlying mantle rocks. The low-density melt rises and eventually reaches the surface, forming volcanoes. All subduction zones have volcanoes and frequent seismicity. Volcanoes in such settings tend to have explosive ash eruptions. Rocks and tephra deposits at subduction zone volcanoes are usually intermediate in composition - typically andesitic to dacitic.
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Info. at:
en.wikipedia.org/wiki/Mount_Shishaldin
and
Wrangell St. Elias National Park and Preserve, from the Richardson Highway
13:47 4 July 2015
"Mount Drum is a stratovolcano in the Wrangell Mountains of east-central Alaska in the United States. It is located at the extreme western end of the Wrangells, 18 miles (29 km) west-southwest of Mount Sanford and the same distance west-northwest of Mount Wrangell. It lies just inside the western boundary of Wrangell-Saint Elias National Park and Preserve, and is 25 miles (40 km) east of the Copper River."
"Standing near the low valley of the Copper River, Mount Drum is notable for its large local relief. For example, its south face rises 6,000 feet (1,830 m) over the head of the Nadina Glacier in only 1.6 miles (2.6 km). Its west slopes rise 9,000 feet (2,743 m) over the tundra in only 10 miles (16 km), and 11,000 feet (3,353 m) over the Copper River in only 25 miles (40 km).[3] These numbers are comparable to better-known stratovolcanoes like Mount Rainier and Mount Shasta. However Mount Drum is somewhat overshadowed by its much higher neighbor Mount Sanford, which is also in Alaska."
- Wikipedia
(looking ~east-southeast) (photo stitch by Mary Ellen St. John)
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Mt. St. Helens is the most active volcano in the Cascade Range, a series of subduction zone stratovolcanoes in a ~north-south line from northern California to Oregon to Washington State to southwestern British Columbia. St. Helens is a 40,000 to 50,000 year old, andesitic-dacitic-basaltic volcano that typically has explosive ash eruptions (as do all subduction zone stratovolcanoes).
The 1980 eruption of Mt. St. Helens was a northward-directed lateral blast that immediately followed an enormous landslide event on the northern face of the volcano. The landslide was triggered by a moderate earthquake at 8:32 AM, Sunday, 18 May 1980. Snow and ice on the mountain melted during the eruption, mixed with ash and other debris, and rushed down nearby river valleys as lahars (volcanic mud flows).
The ash, lapilli, and pumice erupted from Mt. St. Helens in May 1980 was dacite, an intermediate extrusive igneous rock. Most of the air-fall dacite ash fell in Washington State, Oregon, and Idaho, but a minor amount accumulated as far east as Minnesota and Oklahoma. Light dustings of ash were also observed in Ohio.
The 1980 eruption was the largest in recent American history. The volcano was intermittently active until 1986. Minor activity occurred from 1989 to 1991 and from 2004 to 2006.
The area is now a park ("national volcanic monument") and is accessible to tourists. This summer 2012 photo is looking up the Toutle River Valley toward the northwestern face of the volcano. The top third of the mountain was blown away during the 1980 eruption. Much of the landscape is still nonvegetated and covered with gray volcanic tephra.
Location: Mt. St. Helens, northwestern Skamania County, Cascade Range, southwestern Washington State, USA (46˚ 12’ 04” North, 122˚ 11” 18” West)
~*Photography Originally Taken By: www.CrossTrips.Com Under God*~
Mount Shasta (Úytaahkoo , Karuk) or the "White Mountain" in English, a 14,179-foot (4,322 m)[6] stratovolcano, is the second-highest peak in the Cascade Range and the fifth highest peak in California. It is a member in the Cascade Volcanic Arc and is located in Siskiyou County, and has an estimated volume of 108 cubic miles (450 km³), making it the most voluminous stratovolcano of the Cascades.[7]
The mountain and its surrounding area are managed by the U.S. Forest Service, Shasta-Trinity National Forest.
Memorable descriptions
Mount Shasta is not connected to any nearby mountain; it rises abruptly from miles of level ground which encircle it, standing nearly 10,000 feet (3,000 m) above the surrounding area.
The mountain has attracted the attention of poets, authors, and presidents. Shasta was memorably described by the poet Joaquin Miller:
"Lonely as God, and white as a winter moon, Mount Shasta starts up sudden and solitary from the heart of the great black forests of Northern California."[8]
Naturalist and author John Muir said of Shasta:
"When I first caught sight of it over the braided folds of the Sacramento Valley, I was fifty miles away and afoot, alone and weary. Yet all my blood turned to wine, and I have not been weary since."[9]
Theodore Roosevelt said
"I consider the evening twilight on Mt. Shasta one of the grandest sights I have ever witnessed."[10]
Mariners witnessing the ash cloud of the most recent eruption in 1786 sometimes referred to Mount Shasta as the "Lighthouse of the Pacific.
Name
The origin of the name, "Shasta," is not known, but one hypothesis suggests that it derives from the Russian word "chistiy" (чистый), meaning "pure," and given by early Russian explorers in the area. Shastina, the name given to the smaller satellite cone, is the Russian diminutive form of Shasta and is never referred to as "Mount Shastina."
An 1821 survey by Spanish Captain Luis Antonio Arguello made reference to a "high, snow-covered hill" called both "Jesús María" (a name also given to what is now called the Sacramento River) and "Los Quates" ("The Twins"), both of which most likely referred to Mount Shasta. The name "Shasta" also applies to the native inhabitants of the vast area ranging from Mount Shasta to southern Oregon, one tribe of which was called Sǔsti'ka, another possible source of the modern name.
Geology and climate
The mountain consists of four overlapping volcanic cones which have built a complex shape, including the main summit and the prominent satellite cone of 12,330 feet (3,758 m) Shastina, which has a visibly conical form (see image at left). If Shastina were a separate mountain, it would rank as the third-highest peak of the Cascade Range.
Mount Shasta's surface is relatively free of deep glacial erosion except, paradoxically, for its south side where Sargents Ridge[11] runs parallel to the U-shaped Avalanche Gulch. This is the largest glacial valley on the volcano, although it does not presently have a glacier in it (see image below left).
There are seven named glaciers on Shasta, with the four largest (Whitney, Bolam, Hotlum, and Wintun) radiating down from high on the main summit cone to below 10,000 ft (3,000 m) primarily on the north and east sides.[4] The Whitney Glacier is the longest and the Hotlum is the most voluminous glacier in the state of California. Three of the smaller named glaciers occupy cirques near and above 11,000 ft (3,300 m) on the south and southeast sides, including the Watkins, Konwakiton, and Mud Creek Glaciers.
There are many buried glacial scars on the mountain which were originally created in recent glacial periods ("ice ages") of the present Wisconsinian glaciation. Most have since been filled-in with andesite lava, pyroclastic flows, and talus from lava domes. Shastina, by comparison, has a fully intact summit crater indicating that Shastina developed after the last ice age.
About 593,000 years ago andesitic lavas erupted in what is now Mount Shasta's western flank near McBride Spring. Over time an ancestral Shasta stratovolcano was built to large but unknown height; sometime between 300,000 to 360,000 years ago the entire north side of the volcano collapsed, creating an enormous landslide or debris avalanche, 6.5 mile³ (27 km³) in volume. The slide flowed northwestward into Shasta Valley where the Shasta River now cuts through the 28 mile (45 km) long flow.
What remains of the oldest of Shasta's four cones is exposed at Sargents Ridge on the south side of the mountain. Lavas from the Sargents Ridge vent cover the Everitt Hill shield at Shasta's southern foot. The last lavas to erupt from the vent were hornblende-pyroxene andesites with a hornblende dacite dome at its summit. Glacial erosion has since modified its shape.
The next cone to form is exposed south of Shasta's current summit and is called Misery Hill. It was formed 15,000 to 20,000 years ago from pyroxene andesite flows and has since been intruded by a hornblende dacite dome.
Since then the Shastina cone has been built by mostly pyroxene andesite lava flows. Some 9,500 years ago, these flows reached about 6.8 miles (11 km) south and three miles north of the area now occupied by nearby Black Butte (see image at right). The last eruptions formed Shastina's present summit about a hundred years later. But before that, Shastina, along with the then forming Black Butte dacite plug dome complex to the west, created numerous pyroclastic flows that covered 43 mile² (110 km²), including large parts of what is now Mt. Shasta, California and Weed, California. Diller Canyon (400 ft (120 m) deep and quarter-mile (400 m) wide) is an avalanche chute that was probably carved into Shastina's western face by these flows.
The last to form, and the highest cone, the Hotlum Cone, formed about 8,000 years ago. It is named after the Hotlum glacier on its northern face; its longest lava flow, the 500 ft (150 m) thick Military Pass flow, extends 5.5 miles (9 km) down its northwest face. Since the creation of the Hotlum Cone, a dacite dome intruded the cone and now forms the summit. The rock at the 600 ft (180 m) wide summit crater has been extensively hydrothermally altered by sulfurous hot springs and fumaroles there (only a few examples still remain).
In the last 8,000 years, the Hotlum Cone has erupted at least eight or nine times. About 200 years ago the last significant Shasta eruption came from this cone and created a pyroclastic flow, a hot lahar (mudflow), and three cold lahars, which streamed 7.5 miles (12 km) down Shasta's east flank via Ash Creek. A separate hot lahar went 12 miles (19 km) down Mud Creek. This eruption was observed by the explorer La Pérouse, from his ship off the California coast, in 1786.
Climbing and recreation
Mount Shasta sees many climbers annually attempt to make it to the summit. The summer climbing season runs from late April until October, although many attempts are made in the winter. The most popular route is Avalanche Gulch, also known as the John Muir Route. It begins at a Sierra Club cabin known as Horse Camp, at elevation 7,900 feet (2,400 m) on the southwest side of the mountain, near tree line. It involves 6,300 ft (1,900 m) of vertical gain over moraines and snowfields, with some danger from rockfall and a bergschrund.[4] Because Mount Shasta is a very popular mountain for climbers in the summertime, it sees many inexperienced climbers who become in need of rescue. Hiking trails also exist in areas around the base of the mountain.[4]
In winter, Sargents Ridge and Casaval Ridge, to the east and west of Avalanche Gulch[12] respectively, become the most traveled routes, to avoid avalanche danger. Mount Shasta is also a popular destination for backcountry skiing. Many of the climbing routes can be descended by experienced skiers, and there are numerous lower-angled areas around the base of the mountain.
Volcanic hazards
During the last 10,000 years Shasta has erupted an average of every 800 years but in the past 4,500 years the volcano has erupted an average of every 600 years. The last significant eruption on Shasta may have occurred 200 years ago, as noted above.
Mount Shasta can release volcanic ash, pyroclastic flows or dacite and andesite lava. Its deposits can be detected under nearby small towns totaling 20,000 in population. Shasta has an explosive, eruptive history. There are fumaroles on the mountain, which show that Shasta is still alive.
The worst case scenario for an eruption is a large pyroclastic flow, such as what occurred in the 1980 eruption of Mount St. Helens. Since there is ice, such as Whitney Glacier and Mud Creek Glacier, lahars would also result. Ash would probably blow inland, perhaps as far as eastern Nevada. There is a small chance that an eruption could also be bigger resulting in a collapse of the mountain, as happened when Mount Mazama in Oregon collapsed to form what is now called Crater Lake, but this is of much lower probability.
The United States Geological Survey considers Shasta a dormant volcano, which will erupt again. It is impossible to pinpoint the date of next eruption, but it likely will occur within the next several hundred years.
History
The oldest known human habitation in the area dates to about 7,000 years ago, and by about 5,000 years ago, there was substantial human habitation in the surrounding area.
At the time of Euro-American contact in the 1820s, the Native American tribes who lived within view of Mount Shasta included the Shasta, Okwanuchu, Modoc, Achomawi, Atsugewi, Karuk, Klamath, Wintu, and Yana tribes.
The historic eruption of Mount Shasta in 1786 may have been observed by la Perouse, but this is disputed. Although perhaps first seen by Spanish explorers, the first reliably-reported land sighting of Mount Shasta by a European or American was by Peter Skene Ogden (a leader of a Hudson's Bay Company trapping brigade) in 1826. In 1827, the name "Sasty" or "Sastise" was given to nearby Mount McLoughlin by Ogden. (The name was transferred to present-day Mount Shasta in 1841, partly as a result of work by the United States Exploring Expedition).
Beginning in the 1820s, Mount Shasta was a prominent landmark along what became known as the Siskiyou Trail, which runs at Mount Shasta's base. The Siskiyou Trail was located on the track of an ancient trade and travel route of Native American footpaths between California's Central Valley and the Pacific Northwest.
The California Gold Rush brought the first Euro-American settlements into the area in the early 1850s, including at Yreka, California and Upper Soda Springs. The first recorded ascent of Mount Shasta occurred in 1854 (by Elias Pearce), after several earlier failed attempts. In 1856, the first women (Harriette Eddy, Mary Campbell McCloud, and their party) were recorded as reaching the summit.
By the 1860s and 1870s, Shasta was the subject of scientific and literary interest. A book by California pioneer and entrepreneur James Hutchings, titled Scenes of Wonder and Curiosity in California, contained an account of an early summit trip in 1855.[13] The summit was achieved (or nearly achieved) by John Muir, Josiah Whitney, Clarence King, and John Wesley Powell. In 1877, Muir wrote a dramatic popular article about an experience in which he survived an overnight blizzard on Shasta by lying in the hot sulfur springs found near the summit (Muir article).
The 1887 completion of the Central Pacific Railroad, built along the line of the Siskiyou Trail between California and Oregon, brought a substantial increase in tourism, lumbering, and population into the area around Mount Shasta. Early resorts and hotels, such as Shasta Springs, grew up along the Siskiyou Trail around Mount Shasta, catering to these early adventuresome tourists and mountaineers.
In the early Twentieth century, the Pacific Highway followed the track of the Siskiyou Trail to the base of Mount Shasta, leading to still more access to the mountain. Today's version of the Siskiyou Trail, Interstate 5, brings thousands of people a year to Mount Shasta.
It was declared a National Natural Landmark in December of 1976.
Religion
The lore of some of the American Indians in the area held that Shasta is inhabited by the spirit chief Skell who descended from heaven to the mountain's summit.
Italian settlers arrived in the early 1900s to work in the mills and as stonemasons, establishing a strong Catholic presence in the area. Many other faiths have been attracted to Shasta over the years -- more than any other Cascade volcano. Mount Shasta City and Dunsmuir, California, small towns near Shasta's western base, are focal points for many of these, which range from a Buddhist monastery (Shasta Abbey, founded by Houn Jiyu-Kennett in 1971) to modern-day Native American rituals. As reported in the documentary In The Light of Reverence, a group of Native Americans from the McCloud River area practice rituals on the mountain. Other surrounding tribes also continue to use the mountain for spiritual practices.[citation needed]
Guy Ballard's I Am Activity (started in the 1930s) and Elizabeth Clare Prophet's Church Universal and Triumphant (started in the 1950s) are probably the best-known among numerous groups to participate in Shasta's spiritual heritage. Some cults hold that races of sentient or spiritual beings generally considered to be Lemurians[citation needed], superior to humans, live in or on Shasta, or visit the mountain.
Mount Shasta City hosts 16 Christian churches. If the membership rolls were combined, they would account for approximately 25 percent of the population.
Cultural references
* Joaquin Miller sets his historical novel, Life Amongst the Modocs,[8] at the base of Mt. Shasta. The poet had spent a number of years as a young man living with and near the Native Americans around Mt. Shasta, and based this work on that time. The first line of the novel is quoted in the first paragraph (above) of this article. Miller also refers to Mt. Shasta repeatedly in his poems and other book-length works, including, for example, Shadows of Shasta.
* Frederick Spencer Oliver's 1894 fantasy novel, A Dweller on Two Planets, is about the Lemurian race. In the novel, Lemurians who traveled to Mount Shasta when their continent sank beneath the Pacific Ocean, are now said to live inside the mountain in a series of tunnels. Several other authors have since expanded on these ideas.[15] [16] People still claim to have encountered Lemurians on Shasta.
* Mt. Shasta was mentioned in the 1963 comedy classic "It's a Mad, Mad, Mad, Mad World" as actress Dorothy Provine searches a map.
* Mt. Shasta is mentioned in Lost Legacy, a speculative fiction short story by Robert A. Heinlein as the home of a group of men who are masters of psychic powers and who decide to teach the world their powers by enlisting Boy Scouts.
* The mountain is also part of a key scene in Ken Grimwood's novel Replay.
* Mt. Shasta inspired singer-songwriter Vienna Teng's song Shasta on her second album Warm Strangers.
* Isaiah Washington's character Dr. Preston Xavier Burke mentioned Mt. Shasta to Dr. Hahn in the Grey's Anatomy episode 17 Seconds (2.25). ("He can climb Mt. Shasta on a Dobutamine drip")
* Mt. Shasta is the subject of a poem ("Mount Shasta, Seen from a Distance," 1852) by John Rollin Ridge (Yellow Bird), the Cherokee author.
* Mt. Shasta is the name of a small family restaurant and lounge located in Michigamme, Michigan. Most noted for being a shooting location for the film Anatomy of a Murder.
(original taken by Rick Hoblitt on 10 March 1998; public domain photo provided by the United States Geological Survey)
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Montserrat is an island in the northern Lesser Antilles Volcanic Arc, which is in the eastern Caribbean. The islands of the Lesser Antilles have a volcanic origin, the result of the North American Plate subducting westward & downward beneath the Caribbean Plate. A significant series of volcanic eruptions decimated the southern half of Montserrat during the 1990s.
The Soufrière Hills Volcano occupies much of the southern half of Montserrat. It is a 31,000+ year old, andesitic, subduction zone stratovolcano. Its current phase of activity began in 1995 and 1996, prompting the evacuation of most of the island’s southern half. A significant ash eruption in summer 1997 destroyed the capital city of Plymouth along the southwestern shore of the island. The eruption was apparently triggered by the injection of basaltic magma into one of the volcano's two magma chambers. Soufrière Hills has erupted intermittently into the 2010s, and the southern part of Montserrat has been off-limits to residents. Many former Plymouth residents have emigrated to Britain.
The photo shows the volcano in 1998 with a new "delta" of land along the island's shoreline. This new lobe of land formed as a series of pyroclastic flows descended from the growing lava dome at the volcano's summit.
Locality: Soufrière Hills Volcano, southern part of the island of Montserrat, Lesser Antilles Volcanic Arc, eastern Caribbean Sea (16° 42' 44.42" North latitude, 62° 10' 35.62" West longitude)
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See info. at:
Explosive eruption of Mt. Pinatubo on 12 June 1991. (original photo taken by Karin Jackson; public domain image provided by the United States Geological Survey)
Mt. Pinatubo’s summer 1991 eruption was the largest on Earth since 1912. Pinatubo's big eruption is also famous for having been successfully predicted by American volcanologists. The prediction and subsequent evacuation saved thousands of lives.
Located near the western margin of Luzon Island in the northern Philippines, Mt. Pinatubo is one of several subduction zone stratovolcanoes in the Luzon Volcanic Arc. Published information indicates that Pinatubo is 35,000+ years old and is composed principally of dacitic and andesitic rocks.
The mid-June 1991 eruptions from Pinatubo blanketed ash, pumiceous lapilli, and pumice over the surrounding countryside, including two American military bases (Clark and Subic Bay).
The "appetizer-scale eruption" seen here occurred on 12 June 1991, a few days before the main eruption, which occurred in the middle of the night.
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See info. at:
Newhall & Punongbayan (1996) - Fire and Mud, Eruptions and Lahars of Mount Pinatubo, Philippines. Quezon City & Seattle & London. Philippine Institute of Volcanology and Seismology & University of Washington Press. 1126 pp.