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(Aerial photo on public signage at Jonsrud Viewpoint in the town of Sandy, Oregon, USA.)
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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.
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Although there was concern for overcast skies as I reached the shore I knew the stratovolcanoes would be above the cloud tops and visible. Clouds were broken though
Southern Yatsugatake Volcanic Group (南八ヶ岳, Minami-Yatsugatake), also known as just Yatsugatake is a volcanic group of inactive volcanoes located on the border of Nagano Prefecture and Yamanashi Prefecture on Honshū in Japan.
The Southern Yatsugatake Volcanic Group is part of the Yatsugatake Mountains. The southern group is defined as the mountains south of the Natsuzawa Pass. The highest peak of the mountains is Mount Aka and the elevation is 2,899 metres.
The southern Yatugatake mountains are steep and have alpine characteristics. The mountains of the Northern Yatsugatake Volcanic Group are gentler and lower.
This volcanic group is listed among the 100 famous mountains in Japan. There the mountains are listed as Yatsugatake. Mount Tateshina is also part of the Yatsugatake mountains, but is listed separately.
These mountains are part of the Yatsugatake-Chūshin Kōgen Quasi-National Park.
The volcanoes are stratovolcanoes that are 1 million to 200,000 years old. The rock is mainly basalt and andesite.
The Ijen volcano complex is a group of stratovolcanoes, in East Java. 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 very, very 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. The lake is recognised as the largest highly acidic crater lake in the world and since it is also a source for the river Banyupahit, resulting in highly acidic and metal-polluted water, it 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. Ijen and its sulfur mining was featured as a topic on the 5th episode of the BBC television documentary Human Planet. In the documentary film War Photographer, journalist James Nachtwey visits Ijen and struggles with noxious fumes while trying to photograph workers. Michael Glawogger film Workingman's Death is about sulfur workers.
earth science, geology, geomorphology, landscape, altiplano, volcano, volcanoes, vulcanology, igneous, volcanic, stratovolcano, composite volcano, avalanche debris, parinacota, pomerape, lauca national park, national park, unesco, man and biosphere reserve, mab, chile, south america
In the center far distance is Glacier Peak Volcano, is the most isolated of the five major stratovolcanoes of the Cascade Volcanic Arc in Washington.
Located in the Glacier Peak Wilderness, the volcano is not easily discernible from any heavily populated area; as a result the volcano is largely understudied and not as much is known about it as other volcanoes in the area.
Since the most recent ice age, it has produced some of largest and most explosive eruptions in the state. The mountain has erupted several times during each of its six episodes in the past 300 years. The volcano formed during the Pleistocene epoch, about 1 million years ago.
(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 morning of 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
Ijen volcano in East Java contains the world's largest acidic volcanic crater lake, called Kawah Ijen, famous for its turquoise color. The active crater measuring 950x600 m is known for its rich sulphur deposits which are being quarried.
The volcano is one of several active stratovolcanoes constructed over the 20 km wide Ijen caldera, the largest caldera in Java.
Eruptions from Ijen are very hazardous because of the risk of the lake draining to form catastrophic lahars.
(Aerial photo on public signage at Jonsrud Viewpoint in the town of Sandy, Oregon, USA.)
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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.
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Info. at:
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 consists of 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.
The watercourse near the bottom of the picture is the Sandy River.
Locality: Mt. Hood Volcano (looking east from the Jonsrud Viewpoint in the town of Sandy), northwestern Oregon, USA
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Info. at:
Scoriaceous lapilli from the uppermost Holocene of Alaska. (collected on 21 August 2023; public domain photo by Darren Tan & provided by the Alaska Volcano Observatory)
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 are volcanic lapilli from an air-fall deposit on Unimak Island. The tephra fragments are from one of Shishaldin's August 2023 explosive eruptions. Most stratovolcanoes erupt andesite and dacite, but these samples are clearly mafic (= dark-colored, silica-poor igneous rocks that are rich in calcium, iron, and magnesium, and dominated by plagioclase feldspar and pyroxene). Analysis by the Alaska Volcano Observatory (AVO) and the United States Geological Survey (USGS) shows that this material is tholeiite / tholeiitic basalt with plagioclase feldspar and olivine.
Locality: Isanotski North seismic station ("ISSN"), Unimak Island, Aleutian Arc, Alaska, USA
Mt. Shasta is the 2nd highest of the Cascade stratovolcanoes, after Mt. Rainier. The south side is less glaciated and multi-hued in color. Mt. Shasta last erupted in the late 1700s.
There is a shivery frisson of the Sublime in the way these stratovolcanoes stand out alone in the haze, like a cloud mirage, at unreal distances.
Like most stratovolcanoes, Mt. Mazama was built of layer upon layer of silicious lava flows and pyroclastics.
On the road to Wellington. Mount Ngauruhoe stealthily blending into the clouds behind it. These stratovolcanoes are full of tricks!
El Tatio is a geyser field located in the Andes Mountains of northern Chile at 4,320 metres (14,170 ft) above mean sea level. Various etymologies have been proposed for the name "El Tatio", which might mean "oven" or "grandfather". It is the third-largest geyser field in the world and the largest in the Southern Hemisphere.
El Tatio lies at the western foot of a series of stratovolcanoes, which run along the border between Chile and Bolivia. This series of volcanoes is part of the Central Volcanic Zone, one of several volcanic belts in the Andes, and there are no recorded historical eruptions at the Tatio volcanoes. El Tatio is also part of the Altiplano–Puna volcanic complex (APVC), a system of large calderas and associated ignimbrites, which have been the sources of supereruptions. Some of these calderas may be the source of heat for the El Tatio geothermal system.
El Tatio is a geothermal field with many geysers, hot springs, and associated sinter deposits. These hot springs eventually form the Rio Salado, a major tributary of the Rio Loa, and a major source of arsenic pollution in the river. The vents are sites of populations of extremophile microorganisms and have been studied as analogs for the early Earth and possible past life on Mars.
This walk probably rates as one of the most enjoyable I've done in all my years exploring the Cascades, so mesmerized did I find myself at the northern reach of Loowit's blast zone. In the middle of the day I found myself passing views and features of terrain which I longed for (at least) marginally better light to photograph and so I made the decision to pace myself, stretch my wandering, and "catch things on the way back". Usually I'll bed down in a meadow for a long nap on a journey like this, for the purposes of restoration and letting the sun get down in the sky. This was a unique day of exploring, there was a solemnity about the walk: An abundance of life has returned to the blast zone yet the aftermath of the powerful eruption stands out in stark relief after all these years and that heaviness with regard to the fifty-seven lives lost, remains. On the walk I also found myself pondering just how much the state of mind about this mountain must have changed after May 1980.
Before it erupted, Loowit was arguably one of the most beautiful stratovolcanoes in the world. Certainly, I never knew her in that way for I was a kindergartener back in the Rust Belt on that fateful day. On the other hand, a good friend of mine grew up in a little town south of the mountain and she watched it erupt from the bleachers of a little league field (Loowit was behind left field). Ash covered her family's yard for more than a year!
Looking at pictures from this walk has gotten me to thinking more about the other volcanoes up and down the Cascade Range, imagining them less as static, unchanging features of the landscape. It would be so strange to look out the window tomorrow morning and see that a thousand feet of Mt. Rainier's top had been completely obliterated. "The Mountain", as Rainier is often hushingly referred to by locals, has an indelible psychological influence on everyone who admires it from Seattle. What would happen to the collective psyche of the entire city if part of it just vanished?
This image is a little on the redundant side but it seemed worth sharing for a fuller appreciation of the ripped-open north side of Loowit. The slowly-building dome inside the crater is hazy from windblown ash. These trees gave me the uneasy feeling of being in the cross-hairs of that unimaginable pyroclastic force. I suppose it's a little one-sided of me to share just these monochrome landscapes from the end of summer, when so much of the snow has melted from the mountain. After all, some years even Mt. Rainier can appear shockingly brown and bare after several months of warm weather.
Mount Shasta
Mount Shasta is a volcano that is potentially active and found at the southern end of the Cascade Range in California.
It is the second highest peak located in the Cascades and also at the fifth number with the elevation of 14,179 feet in the entire state.
Undoubtedly, the volume of the Mount Shasta is found to be 85 cubic miles which are responsible for making it the largest stratovolcanoes in the Cascade Volcanic Arc. Well, this is one of the preeminent world’s sacred mountains.
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We are now entering Sunset Crater National Monument, a part of the San Francisco Volcanic Field, just outside of Flagstaff. In the background is THE San Francisco Mountain, which basically was the backyard view from our motel room in Flagstaff. I had no idea what this backyard view was and I certainly had no idea what a composite or stratovolcanoe was.
Glacier Peak is an imposing mountain that is prominent in the North Cascades. At 10,541', it is the most isolated stratovolcanoes in the Cascade volcanic arc.
Glacier Peak.
When it's Mt. Shasta! Ba-dum-bump.
No, but seriously folks, the two also share an impressive lack of and
outstanding characteristics. Actually, the mountain has an estimated
volume of 108 cubic miles, making it the largest stratovolcano by
volume of the Cascades. Though, they say real stratovolcanoes don't
measure that kind of thing.
Lunchspot with a view. Three major stratovolcanoes on horizon, and the rock that can be seen from everywhere as well of course.
This is a picture of Mt. Hekla from a more closer view.
Where the two plates meet, sometimes one moves down, while the other moves upward. As the plate that is moving down is forced deeper, parts of it begin to melt and form magma that rises to the surface, often in explosive eruptions. The plate that rises, tends to create large, classic, cone-shaped volcanoes called stratovolcanoes, such as Mt. Hekla.
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Explain why the eruption happened>
It is most likely that the eruptio happened because the tetonic plates that meet in Iceland and sometimes split apart with terrific results. Sometimes the plated go in different directions, up and down, but sometimes they move in different direction rubbing against one another. When a plate moves down (subduction), being forced deep, part of it begin to melt and form magma that rises to the surface, often in explosive eruptions. Subduction zones tend to create large, classic, cone-shaped volcanoes called stratovolcanoes, such as Mt. Hekla.