Cascade volcanoes
Map with all coordinates: | Cascade Volcanoes (Cascade Volcanoes) |
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|---|---|
 Mount Rainier from the northeast |
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| Highest peak | Mount Rainier ( 4392 m ) |
| location | British Columbia ( Canada ); California / Oregon / Washington ( USA ) |
| part of | Cascade chain |
| Coordinates | 45 ° 48 ′ N , 121 ° 57 ′ W |
| Age of the rock | Eocene ... Holocene |
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As Cascade volcanoes (Engl. "Cascade Volcanoes" and "Cascade Volcanic Arc" [ Cascade Volcanic Arc ] or "Cascade Arc" [ Cascade arc ]) are a series of volcanoes in a volcanic arc in western North America called ; this arc extends from southwestern British Columbia in Canada through the US states of Washington and Oregon to northern California , an area a good 700 mi (1,127 km) in length. The volcanic arch formed due to subduction along the Cascadia subduction zone . Although the name is derived from the Cascade Range , it is more of a geological grouping than a geographical one; the Cascade Volcanoes extend northward into the Coast Mountains , beyond the Fraser River , which is usually viewed as the northern limit of the actual Cascade Range.
Major cities along the volcanic arc include Portland , Seattle, and Vancouver ; the population of the region is more than 10 million. All of these people are potentially affected by volcanic activity and violent earthquakes in the subduction zone. Because the population in the Pacific Northwest is growing rapidly, the Cascade Volcanoes are among the most dangerous volcanoes because of their eruptive history and potential for future eruptions; they also lie on weak, hydrothermally modified volcanic rock that may be fragile. Consequently, Mount Rainier is one of the Decennial Volcanoes identified by the International Association of Volcanology and Chemistry of the Earth's Interior (IAVCEI) , as it is specifically explored due to the danger it poses to Seattle and Tacoma . Many large, expansive landslides originating from cascading volcanoes have engulfed valleys tens of kilometers from their source. Some of the affected areas are now densely populated.
The Cascade Volcanoes are part of the Pacific Ring of Fire , a ring of volcanoes and neighboring mountains surrounding the Pacific . The cascade volcanoes erupted several times in historical times. The most recent eruptions concerned Lassen Peak from 1914 to 1921 and Mount St. Helens in 1980. They are also the site of the most recent Canadian volcanic eruption about 2,350 years ago on the Mount Meager massif .
geology
The cascade volcanoes include almost 20 large volcanoes among more than 4,000 volcanic vents; There are numerous stratovolcanoes , shield volcanoes , lava domes and cinder and ash cones , as well as a few isolated specimens of rarer volcanic forms such as tabular volcanoes . Volcanism in the arch began about 37 million years ago; however, most of today's cascade volcanoes are less than 2 million years old. Twelve volcanoes reach more than 10,000 ft (approximately 3,000 m) in height, the two highest - Mount Rainier and Mount Shasta - reach more than 14,000 ft (approximately 4,300 m). In terms of volume, the two largest cascade volcanoes are Medicine Lake Volcano and Newberry Volcano with their broad shields, which cover 600 km³ and 450 km³ respectively. The Glacier Peak is the only Cascade volcano exclusively of dacite is.
Over the past 37 million years, the Cascade Arc has created a chain of volcanoes across the entire Pacific Northwest . Several cascade volcanoes are regularly active . The Cascade Volcanoes share some characteristics, but each one has its own unique geological features and history. The Lassen Peak in California, which last erupted in 1917, is the southernmost active volcano in historic times in the bow, while the Mount Meager in British Columbia , which erupted about 2,350 years ago, generally considered the northernmost applies in the chain. A few isolated volcanic centers northwest of Mount Meager massif as the Silverthrone Caldera , which has a circular caldera - complex is about 32 kilometers in diameter, also the product of the Cascadia subduction could be because the igneous rocks andesite , basaltic andesite , dacite and Rhyolite can be found there as well as anywhere else in the subduction zone. There is disagreement about the estimates of plate configuration and subduction rate , but based on chemical data from these volcanoes, they are related to subduction and therefore part of the Cascade Volcano Arc. The Cascade Volcano Arc appears to be segmented, with the central part being the most active while the northern part is the least active.
Lava represents the earliest stage in the development of the Cascade-Volcanic Arc, which occurs mainly south of the actual North Cascades , where the uplift of the cascade chain was less and a thicker blanket of volcanic rocks has been preserved. Geologists have not yet identified 35 million year old volcanic rocks with certainty in the North Cascades , but remnants of the internal tube system of the prehistoric arc persist in the form of plutons , which are crystallized magma chambers that once fed the cascade volcanoes. The largest mass of these tubes in the Cascade Arch is the Chilliwack batholith , which makes up much of the northern area in North Cascades National Park and neighboring areas in British Columbia. Individual plutons are between 35 million and 2.5 million years old. The older rocks that were covered by the magma have been altered by the heat.
The older rocks have recrystallized around the plutons of the batholith. This contact metamorphosis created a fine network of intertwined crystals in the old rocks, hardening them in general, making them more resistant to erosion . Where the recrystallization was intense, the rocks took on a new, dense, dark and hard appearance. Many of the rugged peaks in the North Cascades owe their emergence to these processes. These rocks make up some of the giants of the North Cascades such as Mount Shuksan , Mount Redoubt , Mount Challenger and Hozomeen Mountain , all of which were partially formed by the plutons of the nearby or below Chilliwack batholith.
The Garibaldi Volcanic Belt is the northern extension of the Cascade Volcanic Arc. Volcanoes in this huge volcanic field are mostly stratovolcanoes like the rest of the cascade arc, but can also be calderas , cinder and ash cones and small isolated lava masses. The eruption types in the Belt range from effusive to explosive with compositions from basalt to rhyolites . Because of the repeated continental and alpine glaciations, many volcanic deposits reflect complex interactions between magma composition, topography and changing ice configurations. Four volcanoes in the Belt have emerged in connection with seismic activity since 1975 , including Mount Meager, Mount Garibaldi, and Mount Cayley .
The Pemberton Volcanic Belt is an eroded volcanic field north of the Garibaldi Volcanic Belt, which apparently was formed in the Miocene before breaking off the northern end of the Juan de Fuca Plate . The Silverthrone Caldera is the only volcano in the Belt that has emerged in seismic activity since 1975.
The Mount Meager Massif is the least stable volcanic massif in Canada. It has dumped layers of clay and rock in the Pemberton Valley at least three times several meters thick over the past 7,300 years . Recent boreholes in the bottom of the Pemberton Valley encountered debris from a landslide shortly before the last eruption of the volcano, 50 km away, 2,350 years ago. About 1 billion m³ of stones and sand were distributed over the valley. Two previous landslides around 4,450 and 7,300 years ago, respectively, brought debris over at least 32 km from the volcano. Recently, the volcano caused minor landslides about every ten years, including one that killed four geologists near Meager Creek in 1975 . The probability that the Mount Meager massif will cover stable sections of the Pemberton Valley with a landslide is estimated at a period of 2,400 years. There is no evidence of volcanic activity associated with these events. Scientists are warning, however, that the volcano could cause a massive landslide in populated areas without warning.
In the past, Mount Rainier caused the largest debris avalanches and also created mighty lahars due to the presence of large amounts of glacial ice. Its lahars have come all the way to Puget Sound . About 5,000 years ago, a large piece of the volcano slid down; the debris avalanche contributed to the massive Osceola Mudflow , which reached to what is now Tacoma and south of Seattle. This huge avalanche of ice and stones carried away the top 1,600 ft (about 490 m) of the mountain, reducing its height to about 14,100 ft (about 4,300 m). The electron mudflow occurred about 530… 550 years ago, but it was not as powerful as the osceola mudflow.
Human history
Indigenous peoples settled the area thousands of years ago and developed their own myths and legends related to the Cascade Volcanoes. According to some of these legends, Mount Baker , Mount Jefferson , Mount Shasta and Mount Garibaldi were used as refuges during a flood . Other stories, such as the saga of the Bridge of the Gods , depicted several cascade peaks such as Mount Hood and Mount Adams as god-like chiefs waging war against each other by throwing fire and stones at each other. The Mount St. Helens with its graceful appearance before 1980 was hosted as a beautiful girl, is why Hood and Adams came into the hair. Among the many stories about Mount Baker, one tells that the volcano used to be married to Mount Rainier and lived near it. She later moved north to her current position due to a marital dispute. The indigenous tribes give the peaks of the high cascades as well as the lower mountains their own names; the best known are Tahoma, the Lushootseed name of Mount Rainier. Mount Cayley and The Black Tusk are known as the "Thunderbird Landing Site " to the Squamish who lived nearby .
Hot springs in the Canadian part of the arch were originally used and revered by the First Nations . The springs at Meager Creek are called Teiq in the Lillooet language and were the farthest up the Lillooet River . The spirit beings / wizards - known as "the Transformers" - reached them on their journey to Lillooet Country ; they were also a "training" place for young Indians where they could gain strength and knowledge. In this area, the chieftain's pipe made of black stone (English "blackstone"), which is an important artifact of the Lillooet, was found in volcanic ash , which probably comes from the eruption of the Mount Meager massif 2,350 years ago.
There are many legends related to the great volcanoes or other peaks or geographic features (many thermal springs, waterfalls, rock towers, etc.). Tales of Tahoma - now Mount Rainier and namesake for the city of Tacoma - allude to grand, hidden caves with sleeping giants, apparitions and other miracles in the volcanoes of Washington. Mount Shasta, California, has long been well known for its associations with everything Lemurian- related, from aliens to elves and - as everywhere in the Cascade Arc - Sasquatch / Bigfoot .
In the spring of 1792, the British navigator George Vancouver reached Puget Sound and began to give English names to the high mountains he saw. Mount Baker was named after Vancouver's third officer, the graceful Mount St. Helens after a famous diplomat, Mount Hood in honor of Samuel Hood, 1st Viscount Hood (an admiral in the Royal Navy ) and the highest peak in the Cascades, Mount Rainier the Admiral Peter Rainier . Vancouver's expedition, however, did not name the mountain range to which these peaks belonged. As maritime trade in the Strait of Georgia and Puget Sound picked up pace from the 1790s, the peaks of Mount Rainier and Mount Baker became trusted by captains and crews (mostly, but not exclusively, British and Americans).
With the exception of the eruption of Lassen Peak in Northern California (1915), the volcanoes in the Cascade Arc were calm for more than a century. On May 18, 1980, the eruption of the little-known Mount St. Helens shook the calm and moved the Cascade Arch into the center of the world's attention. Geologists worried that this eruption might be a sign that the long dormancy of the Cascade Volcanoes was over; reference was made to the period from 1800 ... 1870, when a total of eight of the volcanoes erupted. No other has occurred since the Mount St. Helens eruption, but precautions such as the establishment of the Mount Rainier Volcano Lahar Warning System in Pierce County have been taken.
Cascadia subduction zone
The Cascade Volcanoes were formed by the subduction of the Juan de Fuca Plate, the Explorer Plate and the Gorda Plate (remains of the much larger Farallon Plate ) under the North American Plate along the Cascadia subduction zone . This is a 680 mi (1,090 km) long fault that runs approximately 50 mi (80 km) off the coast of the Pacific Northwest from Northern California to Vancouver Island in British Columbia. The plates move at a speed of more than 10 millimeters per year at a slightly oblique angle.
Because of the large area the fault occupies, the Cascadia Subduction Zone can produce violent earthquakes (magnitude 9.0 or greater) as tensions discharge across the area. When the “closed” zones store energy for an earthquake, the “transition” zone can tear open despite some plasticity. Thermal and deformation studies suggest that the closed zone is completely blocked and can descend about 60 km below the deformation limit. A further dive creates a transition from completely blocked to an aseismic slide.
Unlike most subduction zones around the world, there is no deep sea channel along the continental margin in the Cascadia subduction zone . Instead, the terranes and accretion wedges were raised and a series of coastal and exotic mountains emerged. A high rate of sedimentation from the three main drains ( Fraser River , Columbia River and Klamath River ) that cross the Cascade Range further obscure the continental margin. However, in line with most subduction zones, the outer continental margin is compressed, similar to a gigantic feather . If the stored energy is suddenly released by a landslide across the fault, the Cascadia subduction zone can create very powerful earthquakes like the one in 1700 , which had a magnitude M w of 8.7-9.2.
Catastrophic outbreaks
- Mount St. Helens eruption in 1980
The eruption of Mount St. Helens in 1980 was one of the most precisely investigated volcanic eruptions in the cascade arc and one of the best investigated at all. It was a Plinian eruption with a volcanic explosive index (VEI) of 5; it was the most significant in the recorded history of the Continental United States . An earthquake on May 18, 1980 at 8:32 a.m. caused the entire weakened northern flank of the mountain to slide. A pillar of ash rose so high into the atmosphere that the ashes could be detected in eleven states. The eruption killed 57 people and thousands of animals ; it also caused $ 1 billion in damage.
- Lassen Peak eruptions 1914–1917
On May 22, 1915, an explosive eruption from Lassen Peak destroyed nearby areas and spread volcanic ash up to 200 mi (approximately 320 km) to the east. A huge column of volcanic ash and gas rose more than 30,000 feet (about 9,100 m) and was visible even in Eureka, California , 150 mi (240 km) west. A pyroclastic current raced down the flank of the volcano, devastating an area of 7.8 square kilometers. This explosion was the most violent in a series of eruptions on Lassen Peak between 1914 and 1917.
- Eruption of the Mount Meager massif approx. 2,350 years ago
The eruption of the Mount Meager massif is the latest volcanic eruption in what is now Canada; the expelled volcanic ash could still be detected in what is now Alberta . The eruption was similar to that of Mt. St. Helens in 1980; the ejected ash column must have reached about 20 km up into the stratosphere . This activity created a series of volcanic deposits emerging along the escarpments of the Lillooet River , known as the Pebble Creek Formation . The eruption was discontinuous and originated from a vent on the northeast side of Plinth Peak . An unusual, massive debris field of melted together vitrophyrical breccia could represent the explosive collapse of a previous lava dome ; the ash was deposited several meters thick around the chimney area.
- Eruption of Mount Mazama about 7,700 years ago
The eruption of Mount Mazama about 7,700 years ago was a violent, catastrophic eruption in what is now the state of Oregon . He began with a large eruption column with pumice -Brocken and volcanic ash that was ejected from a single vent. The eruption was so violent that most of Mount Mazama collapsed and formed a caldera; then there were minor eruptions as the caldera began to fill with water. Eventually Crater Lake was formed within the caldera . Volcanic ash was spread over most of the Pacific Northwest of what is now the United States as well as parts of what is now southern Canada.
- Eruption of Glacier Peak around 13,100 years ago
About 13,000 years ago, Glacier Peak produced an unusually strong sequence of eruptions, the volcanic ash of which can be traced back to Wyoming today.
More outbreaks
- Silverthrone Caldera
Most of the eruptions of the Silverthrone Caldera in the Pacific Ranges occurred during the last Ice Age and were intermittently active during both the Pemberton and Garibaldi stages of volcanism . The caldera is one of the largest among the few calderas in western Canada, it measures about 30 km in length (north-south) and 20 km in width (east-west). The last eruption of Mount Silverthrone struck the ice in Chernaud Creek. The lava was dammed by the ice and formed a cliff with a waterfall . The most recent activity was around 1,000 years ago.
- Mount Garibaldi
The Mount Garibaldi in the Pacific Ranges was last active before about 10,700 ... 9,300 years; activity emanated from a cinder and ash cone called the Opal Cone . It created a 15 km long lava flow with protruding wrinkled ridges. It was unusually long for a silica-rich lava flow.
- Mount Baker
In the middle of the 19th century, Mount Baker erupted for the first time in several thousand years. There is still fumarole activity in Sherman Crater, just south of the volcanic summit; the activity intensified in 1975 and is still energetic. However, an eruption is not expected in the future.
- Glacier Peak
The Glacier Peak last erupted in front of 200 ... 300 years from, over the past 4,000 years, about six times.
- Mount Rainier
The Mount Rainier last erupted from 1824 to 1854, but many Witnesses also in 1858, 1870, 1879, 1882 and 1894 eruptive activity. Over the past 4,000 years, Mount Rainier has produced at least four eruptions and many lahars .
- Mount Adams
The Mount Adams was last seen about 1,000 years ago and actively produced during the last few millennia eruptions, the results represent several massive lava flows. The most notable of these were the AG Aiken Lava Bed , the Muddy Fork Lava Flows, and the Takh Takh Lava Flow . One of the most recent lava flows emanated from the South Butte, creating the 4.5 mi (7.2 km) long and 0.5 mi (0.8 km) wide AG Aiken Lava Bed.Thermal anomalies ( hotspots ) and gas emissions ( including hydrogen sulphide ) have occurred especially on the summit plateau since the Great Slide in 1921.
- Mount Hood
The Mount Hood was last active about 200 years ago and produced pyroclastic flows, lahars, and a well-known lava dome near its summit, the Crater rock . Between 1856 and 1865 there were a number of steam explosions on Mount Hood.
- Newberry volcano
There was a lot of volcanic activity on Newberry Volcano , which was last active about 1,300 years ago. Here is one of the largest collections of cinder and ash cones, lava domes, lava flows and fissures in the world.
- Medicine Lake Volcano
The Medicine Lake Volcano collapsed during the past 4,000 years or so eight times and was last active about 1,000 years ago when rhyolite and dacite at Glass Mountain and associated vents near the eastern rim of the caldera were ejected.
- Mount Shasta
The Mount Shasta last erupted in 1786 and was about 4,000 years, the most active volcano in what is now California; it broke out about every 300 years. The 1786 eruption created a pyroclastic current, a lahar, and three cold lahars that drained over Ash Creek on its eastern flank for a distance of about twelve kilometers. Another (hot) lahar flowed 19 km down Mud Creek.
Eruptions in the Cascade Range
Eleven of the thirteen volcanoes in the Cascade Range have erupted at least once in the past 4,000 years, seven of them in the past 200 years. The Cascade Volcanoes generated more than 100 eruptions over the past millennia, many of which were explosive. However, various cascade volcanoes can be dormant ("dormant") for centuries or millennia , which is why the great risk of volcanic activity in the region is not always obvious.
When cascading volcanoes erupt, pyroclastic flows, lava flows, and landslides can devastate areas more than 10 mi (16 km) away; massive mudflows called volcanic ash and debris, lahars, can flood situated below valleys more than 50 mi (km 80). Rain of ash from explosive eruptions can affect human activity hundreds of miles away, and floating clouds of fine ash can cause serious damage to jet-powered aircraft even thousands of miles away.
All known eruptions in historical time (Mount Rainier, Glacier Peak, Mount Baker, Mount Hood, Lassen Peak, and Mount Shasta) occurred in Washington, Oregon, and northern California. The two youngest were those on Lassen Peak from 1914 to 1921 and the one on Mount St. Helens in 1980. Smaller eruptions on Mount St. Helens also occurred recently - as recently as 2006. In contrast, the volcanoes in southern British Columbia and central and southern Oregon are currently dormant. The regions with no new eruptions remain in contact with fracture zones raised by the Gorda Ridge , the Explorer Ridge and the Juan de Fuca Ridge .
The recent volcanic activity in the cascade arc, such as the eruption of Mount St. Helens in 1980, have highlighted the great importance of the cascade volcanoes. One result of the 1980 eruption was a better understanding of the influence of landslides and volcanic development on the evolution of volcanic terrain. A huge piece of the northern flank of Mount St. Helens fell and formed a landscape that was thrown up by the landslide, several kilometers away from the volcano. Pyroclastic currents and lahars moved through the landscape. Something similar happened on Mount Shasta and other cascade volcanoes in prehistoric times.
List of volcanoes
The majority of the very tall volcanoes are in Washington, including four of the highest six; the majority of the next higher peaks are in Oregon. Although Mount Rainier is the tallest, it is not the largest in volume; Mount Shasta in California is the most voluminous, followed by Mount Adams. In terms of eruptive volume, Mount Rainier follows in third place. The following list is sorted by altitude:
See also
- Cascadia subduction zone
- List of volcanoes in the United States
- List of volcanoes in Canada
- Geology of the Pacific Northwest
Individual evidence
- ↑ Global Volcanism Program \ Meager . Smithsonian Institution. Retrieved May 23, 2018.
- ↑ The Cascade Episode . Retrieved October 3, 2007
- ↑ Global Volcanism Program \ Silverthrone . Smithsonian Institution. Retrieved July 15, 2008.
- ^ USGS: Washington State Volcanoes and Volcanics . Retrieved July 16, 2007.
- ↑ Garibaldi volcanic belt . In: Catalog of Canadian volcanoes . Geological Survey of Canada . February 13, 2008. Archived from the original on October 23, 2006. Retrieved on May 10, 2008.
- ↑ Impact of varied slab age and thermal structure on enrichment processes and melting regimes in sub-arc mantle: Example from the Cascadia subduction system . Nathan L., A. Krishna Sinha. Archived from the original on December 19, 2008. Retrieved June 16, 2008.
- ↑ a b Mount Meager . Bivouac.com. Retrieved May 24, 2018.
- ↑ United States Geological Survey: Monitoring Lahars at Mount Rainier , Version dated 2016-05-19
- ↑ Pacific Mountain System - Cascade volcanoes ( Memento of the original from May 31, 2007 in the Internet Archive ) Info: The archive link was automatically inserted and not yet checked. Please check the original and archive link according to the instructions and then remove this notice.
- ↑ a b USGS: Eruptions of Lassen Peak, California, 1914 to 1917
- ↑ a b Catalog of Canadian Volcanoes: Mount Meager ( Memento of the original from June 4, 2011 in the Internet Archive ) Info: The archive link was inserted automatically and has not yet been checked. Please check the original and archive link according to the instructions and then remove this notice. Retrieved July 16, 2007
- ^ A b Volcanology of the 2350 BP Eruption of the Mount Meager Volcanic Complex (PDF). Retrieved July 16, 2007
- ↑ a b c d e f g h i j k Living With Volcanic Risk in the Cascades.Retrieved October 3, 2007
- ^ Charles A. Wood, Jürgen Kienle: Volcanoes of North America: United States and Canada . Cambridge University Press , Cambridge , England 2001, ISBN 978-0-521-43811-7 , OCLC 27910629 .
- ↑ Mount St. Helens, Washington Eruption 2004 to Current.Retrieved October 6, 2007
swell
- Stephen L. Harris: Fire Mountains of the West: The Cascade and Mono Lake Volcanoes (3rd ed.) . Mountain Press Publishing Company, 2005, ISBN 978-0-87842-220-3 , p. 454.
- Charles A. Wood, Jürgen Kienle (eds.): Volcanoes of North America . Cambridge University Press , 1990, ISBN 0-521-43811-X , p. 354.
- Skiing the Cascade Volcanoes - Introduction to the Cascade Volcanoes
- Stephen L. Harris: Fire & Ice: The Cascade Volcanoes . The Mountaineers and Pacific Search Press, Seattle, WA 1980, ISBN 0-89886-009-1 .
Web links
- USGS Cascades Volcano Observatory (English)
- Smithsonian Institution Global Volcanism Program (English)
| British Columbia |
Silverthrone Caldera | Mount Meager | Mount Cayley | Mount Garibaldi |
|
| Washington |
Mount Baker | Glacier Peak | Mount Rainier | Goat Rocks | Mount St. Helens | Mount Adams | Indian Heaven |
|
| Oregon |
Mount Hood | Mount Jefferson | Belknap Crater | Three Sisters | Broken Top | Mount Bachelor | Newberry Volcano | Diamond Peak | Mount Thielsen | Mount Mazama | Yamsay Mountain | Mount McLoughlin |
|
| California |
Medicine Lake Volcano | Mount Shasta | Mount Tehama | Let Peak |
