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Encyclopedia > Mount St. Helens
Mount St. Helens

3,000 ft (1 km) steam plume on May 19, 1982
Elevation 8,365 feet (2,550 m)
Location Washington, USA
Range Cascade Range
Prominence 4,605 feet (1,404 m)
Coordinates 46°12′00.17″N 122°11′21.13″W / 46.2000472, -122.1892028Coordinates: 46°12′00.17″N 122°11′21.13″W / 46.2000472, -122.1892028
Topo map USGS Mount St. Helens
Type Active stratovolcano
Volcanic arc/belt Cascade Volcanic Arc
Age of rock < 40,000 yrs
Last eruption 2004–2008 (ongoing)
First ascent 1853 by Thomas J. Dryer
Easiest route Hike via south slope of volcano (closest area near eruption site)

Mount St. Helens is an active stratovolcano located in Skamania County, Washington, in the Pacific Northwest region of the United States. It is 96 miles (154 km) south of Seattle and 53 miles (85 km) northeast of Portland, Oregon. Mount St. Helens takes its English name from the British diplomat Lord St Helens, a friend of explorer George Vancouver who made a survey of the area in the late 18th century. The mountain is located in the Cascade Range and is part of the Cascade Volcanic Arc, a segment of the Pacific Ring of Fire that includes over 160 active volcanoes. This volcano is well known for its ash explosions and pyroclastic flows. For the volcano in Washington state, USA see Mount St. ... is the 139th day of the year (140th in leap years) in the Gregorian calendar. ... Year 1982 (MCMLXXXII) was a common year starting on Friday (link displays the 1982 Gregorian calendar). ... A topographical summit is a point on a surface which is higher in elevation than all points immediately adjacent to it. ... For the capital city of the United States, see Washington, D.C.. For other uses, see Washington (disambiguation). ... For exotic financial options, see Mountain range (options). ... “Cascades” redirects here. ... In topography, prominence, also known as autonomous height, relative height or shoulder drop (in America) or prime factor (in Europe), is a concept used in the categorization of hills and mountains, also known as peaks. ... Map of Earth showing lines of latitude (horizontally) and longitude (vertically), Eckert VI projection; large version (pdf, 1. ... Map of Earth showing lines of latitude (horizontally) and longitude (vertically), Eckert VI projection; large version (pdf, 1. ... // Topographic maps are a variety of maps characterized by large-scale detail and quantitative representation of relief, usually using contour lines in modern mapping, but historically using a variety of methods. ... The United States Geological Survey (USGS) is a scientific agency of the United States government. ... Mountains can be characterized in several ways. ... A cutaway diagram of a stratovolcano Mount St. ... Mariana Islands, an oceanic island arc Cascade Volcanic Arc, a continental volcanic arc A volcanic arc is a chain of volcanic islands or mountains formed by plate tectonics as an oceanic tectonic plate subducts under another tectonic plate and produces magma. ... A volcanic belt is a district of volcanoes, located in a certain area. ... There are very few or no other articles that link to this one. ... Diagram of geological time scale. ... Cleveland Volcano in the Aleutian Islands of Alaska photographed from the International Space Station For other uses, see Volcano (disambiguation). ... In climbing, a first ascent (FA) is the first climb to reach the top of a mountain, or the first to follow a particular climbing route. ... Thomas Jefferson Dryer (1808-1879) born in 1808. ... Southern and northern Mount Everest climbing routes as seen from the International Space Station. ... A cutaway diagram of a stratovolcano Mount St. ... Skamania County is a county located in the state of Washington. ... For the capital city of the United States, see Washington, D.C.. For other uses, see Washington (disambiguation). ... The Pacific Northwest from space The Pacific Northwest, abbreviated PNW, or PacNW is a region in the northwest of North America. ... Seattle redirects here. ... Nickname: Location of Portland in Multnomah County and the state of Oregon Coordinates: , Country State Counties Multnomah, Washington, Clackamas Incorporated February 8, 1851 Government  - Type Commission  - Mayor Tom Potter[1]  - Commissioners Sam Adams Randy Leonard Dan Saltzman Erik Sten  - Auditor Gary Blackmer Area  - City 145. ... The English language is a West Germanic language that originates in England. ... Alleyne Fitzherbert, 1st Baron St Helens (born Derby 1 March 1753, died London 19 February 1839)[2] was a British diplomat and a friend of explorer George Vancouver, who named Mount St. ... Captain George Vancouver RN (June 22, 1757 – May 12, 1798) was an officer of the British Royal Navy, best known for his exploration of North America, including the Pacific coast along the modern day Canadian province of British Columbia and the American states of Alaska, Washington and Oregon. ... “Cascades” redirects here. ... There are very few or no other articles that link to this one. ... “The Ring of Fire” redirects here. ... Cleveland Volcano in the Aleutian Islands of Alaska photographed from the International Space Station For other uses, see Volcano (disambiguation). ... Ash plume from Mt Cleveland, a stratovolcano Diamond Head, a well-known backdrop to Waikiki in Hawaii, is an ash cone that solidified into tuff Volcanic ash consists of very fine rock and mineral particles less than 2 mm in diameter that are ejected from a volcanic vent. ... Pyroclastic flows sweep down the flanks of Mayon Volcano, Philippines, in 1984 A pyroclastic flow (also known as a pyroclastic density current) is a common and devastating result of some volcanic eruptions. ...


Mount St. Helens is most famous for its catastrophic eruption on May 18, 1980,[1] which was the deadliest and most economically destructive volcanic event in the history of the United States. Fifty-seven people were killed; 250 homes, 47 bridges, 15 miles (24 km) of railways, and 185 miles (300 km) of highway were destroyed. The eruption caused a massive debris avalanche, reducing the elevation of the mountain's summit from 9,677 feet (2,950 m) to 8,365 feet (2,550 m) and replacing it with a mile-wide (1.5 km-wide) horseshoe-shaped crater.[2] The debris avalanche was up to 0.7 cubic miles (2.9 km³) in volume. The Mount St. Helens National Volcanic Monument was created to preserve the volcano and allow for its aftermath to be scientifically studied. The 1980 eruption of Mount St. ... is the 138th day of the year (139th in leap years) in the Gregorian calendar. ... Year 1980 (MCMLXXX) was a leap year starting on Tuesday (link displays the 1980 Gregorian calendar). ... A Himalayan avalanche. ... For other uses, see Horseshoe (disambiguation). ... Mount St. ...


As with most other volcanoes in the Cascade Range, Mount St. Helens is a large eruptive cone consisting of lava rock interlayered with ash, pumice, and other deposits. The mountain includes layers of basalt and andesite through which several domes of dacite lava have erupted. The largest of the dacite domes formed the previous summit, and off its northern flank sat the smaller Goat Rocks dome. Both were destroyed in the 1980 eruption. Look up lava, Aa, pahoehoe in Wiktionary, the free dictionary. ... Specimen of highly porous pumice from Teide volcano on Tenerife, Canary Islands. ... For the cities, see Basalt, Colorado and Basalt, Idaho. ... A sample of andesite (dark groundmass) with amygdaloidal vesicules filled with zeolite. ... One of the Mono Craters, an example of a rhyolite dome. ... Grey, red, black, altered white/tan, flow-banded pumice dacite Dacite (IPA: ) is an igneous, volcanic rock with a high iron content. ...

Mount St. Helens the day before the 1980 eruption, which removed much of the northern face of the mountain, leaving a large crater (caldera).
Mt. St. Helens in 2007. Viewed from Johnston Ridge Observatory.
Mt. St. Helens in 2007. Viewed from Johnston Ridge Observatory.

Contents

Image File history File links Sthelens1. ... Image File history File links Sthelens1. ... Satellite image of Santorini. ... Locator map for Mount St. ... Locator map for Mount St. ...

Geographic setting and description

General

The view in 2002 from Climbers Bivouac
The view in 2002 from Climbers Bivouac

Mount St. Helens is 45 miles (72 km) west of Mount Adams, in the western part of the Cascade Range. These "sister and brother" volcanic mountains are approximately 50 miles (80 km) from Mount Rainier, the highest of Cascade volcanoes. Mount Hood, the nearest major volcanic peak in Oregon, is 60 miles (96 km) southeast of Mount St. Helens. Image File history File linksMetadata Download high-resolution version (2048x1536, 529 KB) File links The following pages on the English Wikipedia link to this file (pages on other projects are not listed): Mount St. ... Image File history File linksMetadata Download high-resolution version (2048x1536, 529 KB) File links The following pages on the English Wikipedia link to this file (pages on other projects are not listed): Mount St. ... Mt. ... For other uses, see Mount Rainier (disambiguation). ... This article is about the tallest mountain in Oregon. ... This article is about the U.S. state. ...


Mount St. Helens is geologically young compared to the other major Cascade volcanoes. It formed only within the past 40,000 years, and the pre-1980 summit cone began rising about 2,200 years ago.[3] The volcano is considered the most active in the Cascades within the Holocene epoch (the last 10,000 or so years).[4] The Holocene epoch is a geological period, which began approximately 11,550 calendar years BP (about 9600 BC) and continues to the present. ...

A view of St. Helens and the nearby area from space.
A view of St. Helens and the nearby area from space.

Prior to the 1980 eruption, Mount St. Helens was the fifth-highest peak in Washington. It stood out prominently from surrounding hills because of the symmetry and extensive snow and ice cover of the pre-1980 summit cone, earning it the nickname "Fuji-san of America" ("Mount Fuji of America").[5] The peak rose more than 5,000 feet (1,525 m) above its base, where the lower flanks merge with adjacent ridges. The mountain is six miles (9.6 km) across at its base, which is at an altitude of 4,400 feet (1,340 m) on the northeastern side and 4,000 feet (1,220 m) elsewhere. At the pre-eruption tree line, the width of the cone was four miles (6.4 km). Image File history File links St_Helens_and_nearby_area_from_space. ... Image File history File links St_Helens_and_nearby_area_from_space. ... Mount Fuji Mount Fuji , IPA: )   is the highest mountain in Japan at 3,776 m (12,388 ft). ... In this view of an alpine tree-line, the distant line looks particularly sharp. ...


Streams that originate on the volcano enter three main river systems: the Toutle River on the north and northwest, the Kalama River on the west, and the Lewis River on the south and east. The streams are fed by abundant rain and snow. The average annual rainfall is 140 inches (3.6 m), and the snowpack on the mountain's upper slopes can reach 16 feet (4.9 m).[6] The Lewis River is impounded by three dams for hydroelectric power generation. The southern and eastern sides of the volcano drain into an upstream impoundment, the Swift Reservoir, which is directly south of the volcano's peak. Butchers Creek, Omeo, Victoria A stream, brook, beck, burn or creek, is a body of water with a detectable current, confined within a bed and banks. ... The Toutle River is a river in southwest Washington State, in the Pacific Northwest region of the United States. ... The Lewis River is a tributary of the Columbia River, approximately 95 mi (153 km), in southwestern Washington in the United States It drains part of the Cascade Range north of the Columbia River. ... This article is about structures for water impoundment. ... Hydroelectric dam diagram The waters of Llyn Stwlan, the upper reservoir of the Ffestiniog Pumped-Storage Scheme in north Wales, can just be glimpsed on the right. ...

Phreatic eruption at the summit of Mount St. Helens, Washington in the spring of 1980.
Phreatic eruption at the summit of Mount St. Helens, Washington in the spring of 1980.

Although Mount St. Helens is in Skamania County, Washington, the best access routes to the mountain run through Cowlitz County to the west. State Route 504, locally known as the Spirit Lake Memorial Highway, connects with the heavily traveled Interstate 5 at Exit 49, 34 miles (55 km) to the west of the mountain. That major north-south highway skirts the low-lying cities of Castle Rock, Longview and Kelso along the Cowlitz River, and passes through the Vancouver, Washington-Portland, Oregon metropolitan area less than 50 miles (80 km) to the southwest. The community nearest the volcano is Cougar, Washington, in the Lewis River valley 11 miles (18 km) south-southwest of the peak. Gifford Pinchot National Forest surrounds Mount St. Helens. Phreatic eruption at the summit of Mount St. ... Phreatic eruption at the summit of Mount St. ... Cowlitz County is a county located in the state of Washington. ... State Route 504 (also known as the Spirit Lake Memorial Highway), is a highway that runs east from Castle Rock, Washington for 52 miles to its present terminus at Johnston Ridge Observatory at the northern base of Mount St. ... Interstate 5 (abbreviated I-5) is the westernmost interstate highway in the continental United States. ... For other uses, see Highway (disambiguation). ... Castle Rock is a city located in Cowlitz County, Washington. ... Longview is a city in Cowlitz County, Washington, United States. ... Kelso is a city in Cowlitz County, Washington, United States. ... The Cowlitz River is a river in the state of Washington in the United States, a tributary of the Columbia River. ... For other uses, see Vancouver (disambiguation). ... Nickname: Location of Portland in Multnomah County and the state of Oregon Coordinates: , Country State Counties Multnomah, Washington, Clackamas Incorporated February 8, 1851 Government  - Type Commission  - Mayor Tom Potter[1]  - Commissioners Sam Adams Randy Leonard Dan Saltzman Erik Sten  - Auditor Gary Blackmer Area  - City 145. ... This article does not cite any references or sources. ... Cougar is a town in Cowlitz County, Washington. ... Gifford Pinchot National Forest is a national forest located in southwestern Washington. ...


Crater Glacier and other new rock glaciers

Main article: Crater Glacier

During the winter of 1980–1981, a new glacier appeared. Now officially named Crater Glacier, it was formerly known as the Tulutson Glacier. Shadowed by the crater walls and fed by heavy snowfall and repeated snow avalanches, it grew rapidly (46 feet or 14 m/year in thickness). By 2004, it covered about 0.36 square mile (0.93 km²), and was divided by the dome into a western and eastern lobe. Typically, by late summer, the glacier looks dark from rockfall from the crater walls and ash from eruptions. As of 2006, the ice had an average thickness of 328 feet (100 m) and a maximum of 656 feet (200 m), nearly as deep as the much older and larger Carbon Glacier of Mount Rainier. The ice is all post–1980, making the glacier very young geologically. However, the volume of the new glacier is about the same as all the pre–1980 glaciers combined.[7][8][9][10][11] The Crater Glacier[1] (also known as Tulutson Glacier) is a geologically extremely young glacier that is located on Mount Saint Helens, in the U.S. state of Washington. ... Perito Moreno Glacier Patagonia Argentina Aletsch Glacier, Switzerland Icebergs breaking off glaciers at Cape York, Greenland This article is about the geological formation. ... The Crater Glacier[1] (also known as Tulutson Glacier) is a geologically extremely young glacier that is located on Mount Saint Helens, in the U.S. state of Washington. ... Carbon Glacier is an album by Laura Veirs, released in 2004. ...


With the recent volcanic activity starting in 2004, the glacier lobes were pushed aside and upward by the growth of new volcanic domes. The surface of the glacier, once mostly uncrevassed, turned into a chaotic jumble of icefalls heavily criss-crossed with crevasses and seracs caused by movement of the crater floor.[12] The new domes have almost separated the Crater Glacier into an eastern and western lobe. Despite the ongoing volcanic activity, the termini of the glacier have still advanced, with a slight advance on the western lobe and a more considerable advance on the more shaded eastern lobe. Due to the advance, two lobes of the glacier joined together in late-May 2008 and thus the glacier completely surrounds the lava domes.[12][13][14] In addition, since 2004, new glaciers have formed on the crater wall above Crater Glacier feeding rock and ice onto its surface below; there are two rock glaciers to the north of the eastern lobe of Crater Glacier.[15] An icefall is a phenomenon found in some glaciers. ... Measuring snowpack in a crevasse on the Easton Glacier, North Cascades, USA A crevasse is a crack or fissure in a glacier or snow field. ... Seracs in firn at 10000 on the Winthrop Glacier of Mount Rainier in Washington, USA A serac (originally from Swiss French sérac, a crumbly white cheese) is a steep ridge or pillar of ice formed between two crevasses of a glacier. ...


Human history

Importance to Native Americans

Traces of ancient campsites have been found in the Gifford Pinchot National Forest, which surrounds the monument. Dating of these sites reveals that people have lived in this area for at least 6,500 years.[16] Throughout human history, Mount St. Helens eruptions have had a dramatic effect on the lives of local inhabitants. Work by archaeologists has shown that a massive eruption 3,500 years ago buried native settlements with a thick layer of pumice. As a result, people abandoned the area for nearly 2,000 years.[16] Later, members of the Cowlitz, Taidnapam, Klickitat, Upper Chinook, and Yakama tribes moved seasonally over the land, harvesting huckleberries and hunting salmon, elk, and deer.[16] Gifford Pinchot National Forest is a national forest located in southwestern Washington. ... Specimen of highly porous pumice from Teide volcano on Tenerife, Canary Islands. ... Cowlitz is a group of Native American peoples from what is now western Washington state in the United States. ... Cowlitz is a group of Native American peoples from what is now western Washington state in the United States. ... The Klickitat (also spelled Klikitat) are a Native American tribe of the Pacific Northwest. ... This article or section does not cite its references or sources. ... The Confederated Tribes and Bands of the Yakama Nation, or simply Yakama Nation (formerly Yakima), is a Native American group with nearly 9,000 enrolled members, living in Washington state. ... For other uses of the word Huckleberry, see Huckleberry Finn and Huckleberry Hound. ... For other uses, see Salmon (disambiguation). ... For other uses, see Elk (disambiguation). ... This article is about the ruminant animal. ...

Indigenous American legends were inspired by the volcano's beauty.
Indigenous American legends were inspired by the volcano's beauty.

US gov PD image from http://vulcan. ... US gov PD image from http://vulcan. ...

Local legends

American Indian lore contains numerous legends to explain the eruptions of Mount St. Helens and other Cascade volcanoes. The most famous of these is the Bridge of the Gods legend told by the Klickitats. In their tale, the chief of all the gods, Tyhee Saghalie and his two sons, Pahto (also called Klickitat) and Wy'east, traveled down the Columbia River from the Far North in search for a suitable area to settle.[17] For other uses, see Native Americans (disambiguation). ... The original Bridge of the Gods was created by the Bonneville Slide, which dammed the Columbia River (see also Columbia River Gorge) in the modern-day Pacific Northwest of the United States in the eighteenth century. ... The Columbia River (French: fleuve Columbia) is a river in the Pacific Northwest region of North America. ...


They came upon an area that is now called The Dalles and thought they had never seen a land so beautiful. The sons quarreled over the land, so to solve the dispute their father shot two arrows from his mighty bow — one to the north and the other to the south. Pahto followed the arrow to the north and settled there while Wy'east did the same for the arrow to the south. Saghalie then built Tanmahawis, the Bridge of the Gods, so his family could meet periodically.[17] Disamb: For the German rock group The Dalles, see The Dalles (band) The Dalles is a city located in Wasco County, Oregon. ...


When the two sons of the Saghalie fell in love with a beautiful maiden named Loowit, she could not choose between them. The two young chiefs fought over her, burying villages and forests in the process. The area was devastated and the earth shook so violently that the huge bridge fell into the river, creating the cascades of the Columbia River Gorge.[18] A cascade is a term for a waterfall, or series of waterfalls, and is applied abstractly to many different concepts involving a series of steps or effects that follow one after the other. ... The Columbia River Gorge is a spectacular canyon of the Columbia River in the Pacific Northwest of the United States. ...


For punishment, Saghalie struck down each of the lovers and transformed them into great mountains where they fell. Wy'east, with his head lifted in pride, became the volcano known today as Mount Hood. Pahto, with his head bent toward his fallen love, was turned into Mount Adams. The fair Loowit became Mount St. Helens, known to the Klickitats as Louwala-Clough, which means "smoking or fire mountain" in their language (the Sahaptin called the mountain Loowit).[19] The Sahaptin people are a Native American people that inhabited territory along the Columbia River. ...


Exploration by Europeans

Royal Navy Commander George Vancouver and the officers of HMS Discovery made the Europeans' first recorded sighting of Mount St. Helens on May 19, 1792, while surveying the northern Pacific Ocean coast. Vancouver named the mountain for British diplomat Alleyne Fitzherbert, 1st Baron St Helens on October 20, 1792,[19] as it came into view when the Discovery passed into the mouth of the Columbia River. This article is about the navy of the United Kingdom. ... Captain George Vancouver RN (June 22, 1757 – May 12, 1798) was an officer of the British Royal Navy, best known for his exploration of North America, including the Pacific coast along the modern day Canadian province of British Columbia and the American states of Alaska, Washington and Oregon. ... HMS Discovery was a Royal Navy ship in which George Vancouver explored the west coast of North America in his 1791-1795 expedition. ... is the 139th day of the year (140th in leap years) in the Gregorian calendar. ... 1792 was a leap year starting on Sunday (see link for calendar). ... Alleyne Fitzherbert, 1st Baron St Helens (born Derby 1 March 1753, died London 19 February 1839)[2] was a British diplomat and a friend of explorer George Vancouver, who named Mount St. ... is the 293rd day of the year (294th in leap years) in the Gregorian calendar. ... 1792 was a leap year starting on Sunday (see link for calendar). ...


Years later, explorers, traders, and missionaries heard reports of an erupting volcano in the area. Geologists and historians determined much later that the eruption took place in 1800, marking the beginning of the 57-year-long Goat Rocks Eruptive Period (see geology section).[20] Alarmed by the "dry snow," the Nespelem tribe of northeastern Washington danced and prayed rather than collecting food and suffered during that winter from starvation.[20]


In late 1805 and early 1806, members of the Lewis and Clark Expedition spotted Mount St. Helens from the Columbia River but did not report either an ongoing eruption or recent evidence of one.[21] They did however report the presence of quicksand and clogged channel conditions at the mouth of the Sandy River near Portland, suggesting an eruption by Mount Hood sometime in the previous decades. Lewis and Clark redirects here. ... This article or section does not adequately cite its references or sources. ... The Sandy River is a tributary of the Columbia River, approxiately 50 mi (80 km) long, in northwestern Oregon in the United States. ... This article is about the tallest mountain in Oregon. ...


European settlement and use of the area

19th century photo of a fur trapper working in the Mount St. Helens area.
19th century photo of a fur trapper working in the Mount St. Helens area.

The area's first non-aboriginal inhabitants were European fur traders and trappers. Most of these men worked for the fur trading enterprise of the British-owned Hudson's Bay Company.[22] In the early 1890s, Ole' Peterson set up housekeeping at Cougar Flats, on the Upper Lewis River.[22] He was a true hermit — preferring to keep to himself, and enjoying the quiet solitude of nature. Image File history File links Fur_trapper_in_Mount_St_Helen_area. ... Image File history File links Fur_trapper_in_Mount_St_Helen_area. ... A fur trapper is a person who is involved the capture of wild mammals for their fur. ... An Alberta fur trader in the 1890s. ... Hbc redirects here. ... For other uses, see Hermit (disambiguation). ...


Also in the early 1890s, a 156-square mile (404 km²) mining district north of Spirit Lake was established. By 1911, over 400 mining claims had been filed.[22] However, the minerals were never found in profitable quantities, and though much effort was spent in attempting to build a road or railroad into the district, by 1911, it was clear that there were no veins of precious minerals rich enough to offset the high transportation costs.[22] Photograph taken on October 4, 1980 Spirit Lake was formerly an attractive lake near Mount St. ...

James Dwight Dana was among the first geologists to view the volcano.
James Dwight Dana was among the first geologists to view the volcano.

The first authenticated eyewitness report of a volcanic eruption was made in March 1835 by Dr. Meredith Gairdner, while working for the Hudson's Bay Company stationed at Fort Vancouver.[23] He sent an account to the Edinburgh New Philosophical Journal, which published his letter in January 1836. James Dwight Dana of Yale University, while sailing with the United States Exploring Expedition, saw the quiescent peak from off the mouth of the Columbia River in 1841. Another member of the expedition later described "cellular basaltic lavas" at the mountain's base.[24] 1904 portrait of James Dwight Dana This image has been released into the public domain by the copyright holder, its copyright has expired, or it is ineligible for copyright. ... 1904 portrait of James Dwight Dana This image has been released into the public domain by the copyright holder, its copyright has expired, or it is ineligible for copyright. ... James Dwight Dana (February 12, 1813 - April 14, 1895) was an American geologist, mineralogist and zoologist. ... Fort Vancouver Fort Vancouver was a 19th century fur trading outpost along the Columbia River that served as the headquarters of the Hudsons Bay Company in the companys Columbia District (known to Americans as the Oregon Country). ... James Dwight Dana (February 12, 1813 - April 14, 1895) was an American geologist, mineralogist and zoologist. ... Yale redirects here. ... The United States Exploring Expedition was an exploring and surveying expedition of the Pacific Ocean (the Southern Seas) conducted by the United States Navy from 1838–1842. ...


In late fall or early winter of 1842, nearby settlers and missionaries witnessed the so-called "Great Eruption." This small-volume outburst created large ash clouds, and mild explosions followed for 15 years.[25] The eruptions of this period were likely phreatic (steam explosions). The Reverend Josiah Parrish in Champoeg, Oregon, witnessed Mount St. Helens in eruption on November 22, 1842. Ash from this eruption may have reached The Dalles, Oregon, 48 miles (80 km) southeast of the volcano.[4] Phreatic eruption at the summit of Mount St. ... For other uses, see Steam (disambiguation). ... Reverend Josiah Lamberson Parrish (1806-1895) was an American missionary in Oregon Country and trustee of the Oregon Institute at its founding. ... Champoeg, Oregon Champoeg, pronounced sham_POO_ee (SAMPA /ʃæm. ... is the 326th day of the year (327th in leap years) in the Gregorian calendar. ... 1842 was a common year starting on Saturday (see link for calendar). ... Location in Oregon Coordinates: County Wasco County Incorporated 1857 Government  - Mayor Robb Van Cleave Area  - City 14. ...

Mount St. Helens erupting at night. Painting by Paul Kane after his 1847 visit to the area.
Mount St. Helens erupting at night. Painting by Paul Kane after his 1847 visit to the area.

In October 1843, future California governor Peter H. Burnett recounted a story of an aboriginal American man who badly burned his foot and leg in lava or hot ash while hunting for deer. The likely apocryphal story went that the injured man sought treatment at Fort Vancouver, but the contemporary fort commissary steward, Napolean McGilvery, disclaimed knowledge of the incident.[26] British lieutenant Henry J. Warre sketched the eruption in 1845, and two years later Canadian painter Paul Kane created watercolors of the gently smoking mountain. Warre's work showed erupting material from a vent about a third of the way down from the summit on the mountain's west or northwest side (possibly at Goat Rocks), and one of Kane's field sketches shows smoke emanating from about the same location.[27] Image File history File links Mount_St_Helens_erupting_at_night_by_Paul_Kane. ... Image File history File links Mount_St_Helens_erupting_at_night_by_Paul_Kane. ... This article is about the painter. ... This article is about the U.S state. ... For the author, see Peter Burnett (author). ... This article is about the painter. ...


On April 17, 1857, the Republican, a Steilacoom, Washington newspaper, reported that "Mount St. Helens, or some other mount to the southward, is seen ... to be in a state of eruption".[28] The lack of a significant ash layer associated with this event indicates that it was a small eruption. This was the first reported volcanic activity since 1854.[28] is the 107th day of the year (108th in leap years) in the Gregorian calendar. ... 1857 was a common year starting on Thursday (see link for calendar). ... Steilacoom is a town located in Pierce County, Washington. ...

Boats in Spirit Lake sometime before the 1980 eruption.
Boats in Spirit Lake sometime before the 1980 eruption.

Before the 1980 eruption, Spirit Lake offered year-round recreational activities. In the summer there was boating, swimming, and camping, while in the winter there was skiing. Image File history File links Boating_in_Spirit_Lake-pre_1980. ... Image File history File links Boating_in_Spirit_Lake-pre_1980. ... Photograph taken on October 4, 1980 Spirit Lake was formerly an attractive lake near Mount St. ... Photograph taken on October 4, 1980 Spirit Lake was formerly an attractive lake near Mount St. ... // Boating, the leisurely activity of traveling by boat typically refers to the recreational use of boats whether power boats, sail boats, or yachts (large vessels), focused on the travel itself, as well as sports activities, such as fishing or waterskiing. ... Swimmer redirects here. ... Car camping is camping in a tent, but nearby the car for easier access and for supply storage. ... Cross-country skiing (skating style) in Einsiedeln, Switzerland. ...


Human impact from the 1980 eruption

Ash from the eruption disrupted life for millions of people. Fifty-seven people died, and the economic cost was US$1 billion.
Ash from the eruption disrupted life for millions of people. Fifty-seven people died, and the economic cost was US$1 billion.

St. Helens catastrophically erupted on May 18, 1980. After many months of lead-up activity, including the growth of a huge bulge on the north part of the mountain, a moderate earthquake caused the entire north flank of the mountain to slide away in the largest landslide in recorded history.[29] The newly-exposed hot and pressurized rock in the volcano responded by producing the largest historic volcanic eruption in the 48 contiguous U.S. states.[29] (See the Geology section for more detail.) The United States dollar is the official currency of the United States. ... is the 138th day of the year (139th in leap years) in the Gregorian calendar. ... Year 1980 (MCMLXXX) was a leap year starting on Tuesday (link displays the 1980 Gregorian calendar). ...


During the lead-up to the 1980 eruption of Mount St. Helens, 83-year-old Harry R. Truman, who had lived near the mountain for 54 years, became famous when he decided not to evacuate before the impending eruption, despite repeated pleas by local authorities. His body was never found after the eruption. Fifty-seven people were killed or never found. Had the eruption occurred one day later, when loggers would have been at work, rather than on a Sunday, the death toll would almost certainly have been much higher.[6] The 1980 eruption of Mount St. ... Harry R. Truman (October 30, 1896 – May 18, 1980) came to brief fame as a well loved, if eccentric resident of Washington who lived near Mount St. ...

David A. Johnston hours before he was killed by the eruption.
David A. Johnston hours before he was killed by the eruption.

Among the victims of the 1980 eruption was 30-year-old volcanologist David A. Johnston, who was stationed on the nearby Coldwater Ridge. Moments before his position was hit by the hot ash cloud, Johnston uttered his famous last words: "Vancouver! Vancouver! This is it!"[30] Johnston's body was never found. Image File history File links MSH80_david_johnston_at_camp_05-17-80_med. ... Image File history File links MSH80_david_johnston_at_camp_05-17-80_med. ... David A. Johnston, 13 1/2 hours before he was killed in the 1980 eruption of Mount St. ... Volcanology (also spelled vulcanology) is the study of volcanoes, lava, magma and related geological phenomena. ... David A. Johnston, 13 1/2 hours before he was killed in the 1980 eruption of Mount St. ...

Mount St. Helens viewed from a regional jet, 7-24-2007
Mount St. Helens viewed from a regional jet, 7-24-2007

U.S. President Jimmy Carter surveyed the damage and said "Someone said this area looked like a moonscape. But the moon looks more like a golf course compared to what's up there."[31] A film crew, led by Seattle filmmaker Otto Seiber, was dropped by helicopter on St. Helens on May 23 to document the destruction. Their compasses, however, spun in circles and they quickly became lost. A second eruption occurred on May 25, but the crew survived and was rescued two days later by National Guard helicopter pilots. Their film, The Eruption of Mount St. Helens, later became a popular documentary. Image File history File links Metadata Size of this preview: 800 × 600 pixelsFull resolution (2048 × 1536 pixel, file size: 949 KB, MIME type: image/jpeg) File historyClick on a date/time to view the file as it appeared at that time. ... Image File history File links Metadata Size of this preview: 800 × 600 pixelsFull resolution (2048 × 1536 pixel, file size: 949 KB, MIME type: image/jpeg) File historyClick on a date/time to view the file as it appeared at that time. ... Federal courts Supreme Court Circuit Courts of Appeal District Courts Elections Presidential elections Midterm elections Political Parties Democratic Republican Third parties State & Local government Governors Legislatures (List) State Courts Local Government Other countries Atlas  US Government Portal      For other uses, see President of the United States (disambiguation). ... For other persons named Jimmy Carter, see Jimmy Carter (disambiguation). ... For other uses, see Helicopter (disambiguation). ... is the 143rd day of the year (144th in leap years) in the Gregorian calendar. ... This article is about the navigational instrument. ... is the 145th day of the year (146th in leap years) in the Gregorian calendar. ... The United States National Guard is a reserve forces component of the United States Army (the Army National Guard) and the United States Air Force (the Air National Guard). ...

Protection and later history

A steam plume rises from the mountain in December 2004.
A steam plume rises from the mountain in December 2004.

In 1982, President Ronald Reagan and the U.S. Congress established the Mount St. Helens National Volcanic Monument, a 110,000 acre (445 km²) area around the mountain and within the Gifford Pinchot National Forest.[32] Download high resolution version (1000x750, 62 KB)Mount St. ... Download high resolution version (1000x750, 62 KB)Mount St. ... Reagan redirects here. ... Congress in Joint Session. ... Mount St. ... Gifford Pinchot National Forest is a national forest located in southwestern Washington. ...


Following the 1980 eruption, the area was left to gradually return to its natural state. In 1987, the National Forest Service reopened the mountain to climbing. It remained open until 2004 when renewed activity caused the closure of the area around the mountain (see Geology section for more detail). The USDA Forest Service, a United States government agency within the United States Department of Agriculture, is under the leadership of the United States Secretary of Agriculture. ... In autumn 2004, Mount St. ...


Most notable was the closure of the Monitor Ridge trail, which previously let up to 100 permitted hikers per day climb to the summit. However, on July 21, 2006, the mountain was again opened to climbers.[33]
is the 202nd day of the year (203rd in leap years) in the Gregorian calendar. ... Year 2006 (MMVI) was a common year starting on Sunday of the Gregorian calendar. ...


Geologic history

Ancestral stages of eruptive activity

The early eruptive stages of Mount St. Helens are known as the "Ape Canyon Stage" (around 40–35,000 years ago), the "Cougar Stage" (ca. 20–18,000 years ago), and the "Swift Creek Stage" (roughly 13–8,000 years ago).[34] The modern period, since about 2500 BCE, is called the "Spirit Lake Stage." Collectively, the pre-Spirit Lake stages are known as the "ancestral stages." The ancestral and modern stages differ primarily in the composition of the erupted lavas; ancestral lavas consisted of a characteristic mixture of dacite and andesite, while modern lava is very diverse (ranging from olivine basalt to andesite and dacite).[35] Image File history File links Cascade_Range-related_plate_tectonics. ... Image File history File links Cascade_Range-related_plate_tectonics. ... The tectonic plates of the world were mapped in the second half of the 20th century. ... “Cascades” redirects here. ... Grey, red, black, altered white/tan, flow-banded pumice dacite Dacite (IPA: ) is an igneous, volcanic rock with a high iron content. ... A sample of andesite (dark groundmass) with amygdaloidal vesicules filled with zeolite. ... The mineral olivine (also called chrysolite and, when gem-quality, peridot) is a magnesium iron silicate with the formula (Mg,Fe)2SiO4. ... For the cities, see Basalt, Colorado and Basalt, Idaho. ...


St. Helens started its growth in the Pleistocene 37,600 years ago, during the Ape Canyon stage, with dacite and andesite eruptions of hot pumice and ash.[35] 36,000 years ago a large mudflow cascaded down the volcano;[35] mudflows were significant forces in all of St. Helens' eruptive cycles. The Ape Canyon eruptive period ended around 35,000 years ago and was followed by 17,000 years of relative quiet. Parts of this ancestral cone were fragmented and transported by glaciers 14,000 to 18,000 years ago during the last glacial period of the current ice age.[35] The Pleistocene epoch (IPA: ) on the geologic timescale is the period from 1,808,000 to 11,550 years BP. The Pleistocene epoch had been intended to cover the worlds recent period of repeated glaciations. ... Lahar from a March 1982 eruption of Mount St. ... Perito Moreno Glacier Patagonia Argentina Aletsch Glacier, Switzerland Icebergs breaking off glaciers at Cape York, Greenland This article is about the geological formation. ... Variations in CO2, temperature and dust from the Vostok ice core over the last 400 000 years For the animated movie, see Ice Age (movie). ...


The second eruptive period, the Cougar Stage, started 20,000 years ago and lasted for 2,000 years.[35] Pyroclastic flows of hot pumice and ash along with dome growth occurred during this period. Another 5,000 years of dormancy followed, only to be upset by the beginning of the Swift Creek eruptive period, typified by pyroclastic flows, dome growth and blanketing of the countryside with tephra. Swift Creek ended 8,000 years ago. Pyroclastic flows sweep down the flanks of Mayon Volcano, Philippines, in 1984 A pyroclastic flow (also known as a pyroclastic density current) is a common and devastating result of some volcanic eruptions. ... One of the Mono Craters, an example of a rhyolite dome. ... Tephra refers to air-fall material produced by a volcanic eruption regardless of composition or fragment size. ...


Smith Creek and Pine Creek eruptive periods

A dormancy of about 4,000 years was broken around 2500 BCE with the start of the Smith Creek eruptive period, when eruptions of large amounts of ash and yellowish-brown pumice covered thousands of square miles. An eruption in 1900 BCE was the largest known eruption from St. Helens during the Holocene epoch, judged by the volume of one of the tephra layers from that period. This eruptive period lasted until about 1600 BCE and left 18-in (46-cm) deep deposits of material 50 miles (80 km) distant in what is now Mt. Rainier National Park. Trace deposits have been found as far northeast as Banff National Park in Alberta, and as far southeast as eastern Oregon.[36] All told there may have been up to 2.5 cubic miles (10 km³) of material ejected in this cycle.[36] Some 400 years of dormancy followed. The Holocene epoch is a geological period, which began approximately 11,550 calendar years BP (about 9600 BC) and continues to the present. ... Mount Rainier National Park is a United States National Park located in southeast Pierce County, Washington. ... Moraine Lake, and the Valley of the Ten Peaks Banff National Park is Canadas oldest national park, established in 1885, in the Canadian Rockies. ... For other uses, see Alberta (disambiguation). ... This article is about the U.S. state. ...


St. Helens came alive again around 1200 BCE — the Pine Creek eruptive period.[36] This lasted until about 800 BCE and was characterized by smaller-volume eruptions. Numerous dense, nearly red hot pyroclastic flows sped down St. Helens' flanks and came to rest in nearby valleys. A large mudflow partly filled 40 miles (65 km) of the Lewis River valley sometime between 1000 BCE and 500 BCE.


Castle Creek and Sugar Bowl eruptive periods

The next eruptive period, the Castle Creek period, began about 400 BCE, and is characterized by a change in composition of St. Helens' lava, with the addition of olivine and basalt.[37] The pre-1980 summit cone started to form during the Castle Creek period. Significant lava flows in addition to the previously much more common fragmented and pulverized lavas and rocks (tephra) distinguished this period. Large lava flows of andesite and basalt covered parts of the mountain, including one around the year 100 CE that traveled all the way into the Lewis and Kalama river valleys.[37] Others, such as Cave Basalt (known for its system of lava tubes), flowed up to 9 miles (15 km) from their vents.[37] During the first century, mudflows moved 30 miles (50 km) down the Toutle and Kalama river valleys and may have reached the Columbia River. Another 400 years of dormancy ensued. The mineral olivine (also called chrysolite and, when gem-quality, peridot) is a magnesium iron silicate with the formula (Mg,Fe)2SiO4. ... For the cities, see Basalt, Colorado and Basalt, Idaho. ... Tephra refers to air-fall material produced by a volcanic eruption regardless of composition or fragment size. ... Thurston Lava Tube in Hawaii Volcanoes National Park. ... The Columbia River (French: fleuve Columbia) is a river in the Pacific Northwest region of North America. ... Dormancy is a arrested plant growth. ...


The Sugar Bowl eruptive period was short and markedly different from other periods in Mount St. Helens history. It produced the only unequivocal laterally directed blast known from Mount St. Helens before the 1980 eruptions.[38] During Sugar Bowl time, the volcano first erupted quietly to produce a dome, then erupted violently at least twice producing a small volume of tephra, directed-blast deposits, pyroclastic flows, and lahars.[38]


Kalama and Goat Rocks eruptive periods

The symmetrical appearance of St. Helens prior to the 1980 eruption earned it the nickname "Mount Fuji of America". The once-familiar shape was formed out of the Kalama and Goat Rocks eruptive periods.
The symmetrical appearance of St. Helens prior to the 1980 eruption earned it the nickname "Mount Fuji of America". The once-familiar shape was formed out of the Kalama and Goat Rocks eruptive periods.

Roughly 700 years of dormancy were broken about 1480, when large amounts of pale gray dacite pumice and ash started to erupt, beginning the Kalama period. The eruption in 1480 was several times larger than the May 18, 1980 eruption.[38] In 1482, another large eruption rivaling the 1980 eruption in volume is known to have occurred.[38] Ash and pumice piled six miles (9.5 km) northeast of the volcano to a thickness of three feet (1 m); 50 miles (80 km) away, the ash was two inches (5 cm) deep. Large pyroclastic flows and mudflows subsequently rushed down St. Helens' west flanks and into the Kalama River drainage system. Image File history File links 1890_Clohessy_and_Strengele_engraving_of_Mount_St_Helens. ... Image File history File links 1890_Clohessy_and_Strengele_engraving_of_Mount_St_Helens. ... Mount Fuji Mount Fuji , IPA: )   is the highest mountain in Japan at 3,776 m (12,388 ft). ... is the 138th day of the year (139th in leap years) in the Gregorian calendar. ... Year 1980 (MCMLXXX) was a leap year starting on Tuesday (link displays the 1980 Gregorian calendar). ...


This 150-year period next saw the eruption of less silica-rich lava in the form of andesitic ash that formed at least eight alternating light- and dark-colored layers.[37] Blocky andesite lava then flowed from St. Helens' summit crater down the volcano's southeast flank.[37] Later, pyroclastic flows raced down over the andesite lava and into the Kalama River valley. It ended with the emplacement of a dacite dome several hundred feet (~100 m) high at the volcano's summit, which filled and overtopped an explosion crater already at the summit.[20] Large parts of the dome's sides broke away and mantled parts of the volcano's cone with talus. Lateral explosions excavated a notch in the southeast crater wall. St. Helens reached its greatest height and achieved its highly symmetrical form by the time the Kalama eruptive cycle ended, about 1647.[20] 150 years of quiet returned to the volcano. The chemical compound silicon dioxide, also known as silica, is the oxide of silicon, chemical formula SiO2. ... Andesite is an igneous, volcanic (extrusive) rock, of intermediate composition, with aphanitic to porphyritic texture. ... Scree or detritic cone is a term given to broken rock that appears at the bottom of crags, mountain cliffs or valley shoulders. ...


The 57-year eruptive period that started in 1800 was named after the Goat Rocks dome, and is the first time that both oral and written records exist.[20] Like the Kalama period, the Goat Rocks period started with an explosion of dacite tephra, followed by an andesite lava flow, and culminated with the emplacement of a dacite dome. The 1800 eruption probably rivalled the 1980 eruption in size, although it did not result in massive destruction of the cone. The ash drifted northeast over central and eastern Washington, northern Idaho, and western Montana. There were at least a dozen reported small eruptions of ash from 1831 to 1857, including a fairly large one in 1842. The vent was apparently at or near Goat Rocks on the northeast flank.[20] Goat Rocks dome was the site of the bulge in the 1980 eruption, and it was obliterated in the major eruption event on May 18, 1980 that destroyed the entire north face and top 1,300 feet (400 m) of the mountain. Grey, red, black, altered white/tan, flow-banded pumice dacite Dacite (IPA: ) is an igneous, volcanic rock with a high iron content. ... Tephra refers to air-fall material produced by a volcanic eruption regardless of composition or fragment size. ... For the capital city of the United States, see Washington, D.C.. For other uses, see Washington (disambiguation). ... -1... This article is about the U.S. State. ... is the 138th day of the year (139th in leap years) in the Gregorian calendar. ... Year 1980 (MCMLXXX) was a leap year starting on Tuesday (link displays the 1980 Gregorian calendar). ...


Modern eruptive period

1980 to 2001 activity

Mount St. Helens erupted on May 18, 1980, at 08:32 a.m. Pacific Daylight Time.
Mount St. Helens erupted on May 18, 1980, at 08:32 a.m. Pacific Daylight Time.

On March 20, 1980, Mount St. Helens experienced a magnitude 4.2 earthquake.[1] Steam venting started on March 27.[39] By the end of April, the north side of the mountain started to bulge.[40] With little warning, a second earthquake of magnitude 5.1 May 18 triggered a massive collapse of the north face of the mountain. It was the largest known debris avalanche in recorded history. The magma inside of St. Helens burst forth into a large-scale pyroclastic flow that flattened vegetation and buildings over 230 square miles (600 km²). On the Volcanic Explosivity Index scale, the eruption was rated a five (a Plinian eruption). The 1980 eruption of Mount St. ... is the 138th day of the year (139th in leap years) in the Gregorian calendar. ... Year 1980 (MCMLXXX) was a leap year starting on Tuesday (link displays the 1980 Gregorian calendar). ... is the 79th day of the year (80th in leap years) in the Gregorian calendar. ... Year 1980 (MCMLXXX) was a leap year starting on Tuesday (link displays the 1980 Gregorian calendar). ... The Richter magnitude scale, or more correctly local magnitude ML scale, assigns a single number to quantify the amount of seismic energy released by an earthquake. ... This article is about the natural seismic phenomenon. ... is the 86th day of the year (87th in leap years) in the Gregorian calendar. ... is the 138th day of the year (139th in leap years) in the Gregorian calendar. ... A Himalayan avalanche. ... Magma is molten rock located beneath the surface of the Earth (or any other terrestrial planet), and which often collects in a magma chamber. ... Pyroclastic flows sweep down the flanks of Mayon Volcano, Philippines, in 1984 A pyroclastic flow (also known as a pyroclastic density current) is a common and devastating result of some volcanic eruptions. ... VEI and ejecta volume correlation The Volcanic Explosivity Index (VEI) was devised by Chris Newhall of the U.S. Geological Survey and Steve Self at the University of Hawaii in 1982 to provide a relative measure of the explosiveness of volcanic eruptions. ... Eruption of Vesuvius in 1822. ...


The collapse of the northern flank of St. Helens mixed with ice, snow, and water to create lahars (volcanic mudflows). The lahars flowed many miles down the Toutle and Cowlitz Rivers, destroying bridges and lumber camps. A total of 3.9 million cubic yards (3.0 million ) of material was transported 17 miles (27 km) south into the Columbia River by the mudflows.[41] Lahar from a March 1982 eruption of Mount St. ... The cubic yard (symbols yd³, cu. ... The cubic metre (symbol m³) is the SI derived unit of volume. ... The Columbia River (French: fleuve Columbia) is a river in the Pacific Northwest region of North America. ...


For more than nine hours, a vigorous plume of ash erupted, eventually reaching 12 to 16 miles (20 to 27 km) above sea level.[42] The plume moved eastward at an average speed of 60 miles per hour (95 km/h), with ash reaching Idaho by noon.-1...


By about 5:30 p.m. on May 18, the vertical ash column declined in stature, and less severe outbursts continued through the night and for the next several days. The St. Helens May 18 eruption released 24 megatons of thermal energy;[43][44] it ejected more than 0.67 cubic miles (2.8 cubic km) of material.[29] The removal of the north side of the mountain reduced St. Helens' height by about 1,300 feet (400 m) and left a crater one to two miles (1.6 to 3.2 km) wide and 0.5 mile (800 m) deep, with its north end open in a huge breach. The eruption killed 57 people, nearly 7,000 big game animals (deer, elk, and bear), and an estimated 12 million fish from a hatchery.[6] It destroyed or extensively damaged over 200 homes, 185 miles (300 km) of highway and 15 miles (24 km) of railways.[6] is the 138th day of the year (139th in leap years) in the Gregorian calendar. ... This article is about the ruminant animal. ... For other uses, see Elk (disambiguation). ... For other uses, see Bear (disambiguation). ... For other uses, see Highway (disambiguation). ... This is the top-level page of WikiProject trains Rail tracks Rail transport refers to the land transport of passengers and goods along railways or railroads. ...

Lava dome growth profile from 1980–1986.
Lava dome growth profile from 1980–1986.

Between 1980 and 1986, activity continued at Mount St. Helens, with a new lava dome forming in the crater. Numerous small explosions and dome-building eruptions occurred. From December 7, 1989 to January 6, 1990, and from November 5, 1990 to February 14, 1991, the mountain erupted with sometimes huge clouds of ash.[45] Image File history File links Mt_st_helens_dome_growth_schematic_80-86. ... Image File history File links Mt_st_helens_dome_growth_schematic_80-86. ... One of the Mono Craters, an example of a rhyolite dome. ... One of the Mono Craters, an example of a rhyolite dome. ... is the 341st day of the year (342nd in leap years) in the Gregorian calendar. ... Year 1989 (MCMLXXXIX) was a common year starting on Sunday (link displays 1989 Gregorian calendar). ... is the 6th day of the year in the Gregorian calendar. ... This article is about the year. ... is the 309th day of the year (310th in leap years) in the Gregorian calendar. ... This article is about the year. ... is the 45th day of the year in the Gregorian calendar. ... Year 1991 (MCMXCI) was a common year starting on Tuesday (link will display full calendar) of the Gregorian Calendar. ...


2004 to present activity

Appearance of the "Whaleback" in February 2005.
Appearance of the "Whaleback" in February 2005.

Magma reached the surface of the volcano about October 11, 2004, resulting in the building of a new lava dome on the existing dome's south side. This new dome continued to grow throughout 2005 and into 2006. Several transient features were observed, such as the "whaleback," which comprised long shafts of solidified magma being extruded by the pressure of magma beneath. These features are fragile and break down soon after they are formed. On July 2, 2005, the tip of the whaleback broke off, causing a rockfall that sent ash and dust several hundred meters into the air. [46] In autumn 2004, Mount St. ... Download high resolution version (3008x2000, 3271 KB)Whaleback feature in Mount Saint Helens new lava dome on February 22, 2005. ... Download high resolution version (3008x2000, 3271 KB)Whaleback feature in Mount Saint Helens new lava dome on February 22, 2005. ... is the 284th day of the year (285th in leap years) in the Gregorian calendar. ... Year 2004 (MMIV) was a leap year starting on Thursday of the Gregorian calendar. ... is the 183rd day of the year (184th in leap years) in the Gregorian calendar. ... Year 2005 (MMV) was a common year starting on Saturday (link displays full calendar) of the Gregorian calendar. ...


Mount St. Helens showed significant activity on March 8, 2005, when a 36,000-foot (11,000 m) plume of steam and ash emerged — visible from Seattle.[47] This relatively minor eruption was a release of pressure consistent with ongoing dome building. The release was accompanied by a magnitude 2.5 earthquake. is the 67th day of the year (68th in leap years) in the Gregorian calendar. ... Year 2005 (MMV) was a common year starting on Saturday (link displays full calendar) of the Gregorian calendar. ... City nickname Emerald City City bird Great Blue Heron City flower Dahlia City mottos The City of Flowers The City of Goodwill City song Seattle, the Peerless City Mayor Greg Nickels County King County Area   - Total   - Land   - Water   - % water 369. ...


Another feature to emerge from the dome is called the "fin" or "slab." Approximately half the size of a football field, the large, cooled volcanic rock was being forced upward as quickly as 6 feet (2 m) per day.[48][49] In mid-June 2006, the slab was crumbling in frequent rockfalls, although it was still being extruded. The height of the dome was 7,550 feet (2,301 m), still below the height reached in July 2005 when the whaleback collapsed.


On October 22, 2006, at 3:13 p.m. PST, a magnitude 3.5 earthquake broke loose Spine 7. The collapse and avalanche of the lava dome sent an ash plume 2,000 feet (610 m) over the western rim of the crater; the ash plume then rapidly dissipated. is the 295th day of the year (296th in leap years) in the Gregorian calendar. ... Year 2006 (MMVI) was a common year starting on Sunday of the Gregorian calendar. ...

The volcano continuously steams as seen here in late 2007.
The volcano continuously steams as seen here in late 2007.

On December 19, 2006, a large white plume of condensing steam was observed, leading some media people to assume there had been a small eruption. However, the Cascades Volcano Observatory of the USGS does not mention any significant ash plume.[50] The volcano has been in continuous eruption since October 2004, but this eruption has in large part consisted of a gradual extrusion of lava forming a dome in the crater. is the 353rd day of the year (354th in leap years) in the Gregorian calendar. ... Year 2006 (MMVI) was a common year starting on Sunday of the Gregorian calendar. ...


On January 16, 2008, steam began seeping from a fracture atop the lava dome. Associated seismic activity is the most noteworthy since 2004. Scientists have suspended activities in the crater and the mountain flanks, but the risk of a major eruption is deemed low.[51] is the 16th day of the year in the Gregorian calendar. ... 2008 (MMVIII) is the current year, a leap year that started on Tuesday of the Common Era (or Anno Domini), in accordance with the Gregorian calendar. ...


See also

The Pacific Northwest region of the United States is still geologically active. ... There are very few or no other articles that link to this one. ... View of Silver Lake from the nature trail at the visitor center, 7-22-2007. ...

Notes

  1. ^ a b Mount St. Helens National Volcanic Monument. USDA Forest Service. (accessed 26 November 2006)
  2. ^ May 18, 1980 Eruption of Mount St. Helens. USDA Forest Service. Retrieved on 2007-08-11.
  3. ^ Mullineaux, The Eruptive History of Mount St. Helens, USGS Professional Paper 1250, page 3
  4. ^ a b USGS Description of Mount St. Helens, USGS.gov (accessed 15 Nov 2006)
  5. ^ Harris, Fire Mountains of the West, 1st edition, page 201
  6. ^ a b c d Tilling et al., Eruptions of Mount St. Helens: Past, Present, and Future, USGS Special Interest Publication, 1990 (accessed 12 Nov 2006)
  7. ^ Brugman, Melinda M.; Austin Post (1981). USGS Circular 850-D: Effects of Volcanism on the Glaciers of Mount St. Helens. Retrieved on 2007-03-07.
  8. ^ Wiggins, Tracy B.; Hansen, Jon D.; Clark, Douglas H. (2002). "Growth and flow of a new glacier in Mt. St. Helens Crater". Abstracts with Programs - Geological Society of America 34 (5): 91. 
  9. ^ Schilling, Steve P.; Paul E. Carrara, Ren A. Thompson, and Eugene Y. Iwatsubo (2004). "Posteruption glacier development within the crater of Mount St. Helens, Washington, USA". Quaternary Research 61 (3): 325–329. Elsevier Science (USA). doi:10.1016/j.yqres.2003.11.002. 
  10. ^ McCandless, Melanie; Plummer, Mitchell; Clark, Douglas (2005). "Predictions of the growth and steady-state form of the Mount St. Helens Crater Glacier using a 2-D glacier model". Abstracts with Programs - Geological Society of America 37 (7): 354. 
  11. ^ Schilling, Steve P.; David W. Ramsey, James A. Messerich, and Ren A. Thompson (2006-08-08). USGS Scientific Investigations Map 2928: Rebuilding Mount St. Helens. Retrieved on 2007-03-07.
  12. ^ a b Volcano Review. US Forest Service. Retrieved on 2008-06-07.
  13. ^ Schilling, Steve (2008-05-30). MSH08_aerial_new_dome_from_north_05-30-08. United States Geological Survey. Retrieved on 2008-06-07. - Glacier is still connected south of the lava dome.
  14. ^ Schilling, Steve (2008-05-30). MSH08_aerial_st_helens_crater_from_north_05-30-08. United States Geological Survey. Retrieved on 2008-06-07. - Glacier arms touch on North end of glacier.
  15. ^ Haugerud, R. A.; Harding, D. J., Mark, L. E.; Zeigler, J., Queija, V., Johnson, S. Y. (2004-12). Lidar measurement of topographic change during the 2004 eruption of Mount St. Helens, WA. Retrieved on 2007-09-26.
  16. ^ a b c Native Americans, USGS (accessed 12 Nov 2006)
  17. ^ a b Archie Satterfield, Country Roads of Washington (Backinprint.com: 2003) ISBN 0-595-26863-3, page 82
  18. ^ The Bridge of the Gods, theoutlaws.com (accessed 26 November 2006)
  19. ^ a b USGS. Volcanoes and History: Cascade Range Volcano Names. Retrieved on 2006-10-20.
  20. ^ a b c d e f Harris, Fire Mountains of the West, 1st edition, page 217
  21. ^ Pringle, Roadside Geology of Mount St. Helens National Volcanic Monument and Vicinity
  22. ^ a b c d Explorers and Settlers, USGS.gov (accessed 12 Nov 2006)
  23. ^ Harris, Fire Mountains of the West, 1st edition, page 219
  24. ^ The Volcanoes of Lewis and Clark, USGS.gov (accessed 15 Nov 2006)
  25. ^ Harris, Fire Mountains of the West, 1st edition, pages 220–221
  26. ^ Harris, Fire Mountains of the West, 1st edition, page 224
  27. ^ Harris, Fire Mountains of the West, 1st edition, page 225, 227
  28. ^ a b Harris, Fire Mountains of the West, 1st edition, page 228
  29. ^ a b c Mount St. Helens – From the 1980 Eruption to 2000, USGS Fact Sheet 036-00 (accessed 12 Nov 2006)
  30. ^ Scott LaFee. "Perish the thought: A life in science sometimes becomes a death, too." SignOnSanDiego.com: December 3, 2003. Retrieved October 26, 2006.
  31. ^ Mount St. Helens: Senator Murray Speaks on the 25th Anniversary of the May 18, 1980 Eruption, Senate.gov (accessed 12 Nov 2006)
  32. ^ Mount St. Helens National Volcanic Monument: General Visitor Information, USDA Forest Service (accessed 12 Nov 2006)
  33. ^ Climbing Mount St. Helens, USDA Forest Service (accessed 12 Nov 2006)
  34. ^ Mount St. Helens - Summary of Volcanic History. USDA Forest Service. (accessed 26 November 2006)
  35. ^ a b c d e Harris, Fire Mountains of the West, 1st edition, page 214
  36. ^ a b c Harris, Fire Mountains of the West, 1st edition, page 215
  37. ^ a b c d e Harris, Fire Mountains of the West, 1st edition, page 216
  38. ^ a b c d Mount St. Helens Eruptive History, USGS.gov (accessed 15 Nov 2006)
  39. ^ Summary of Events Leading Up to the May 18, 1980 Eruption of Mount St. Helens: March 22–28.. USDA Forest Service. Retrieved on 2006-10-28.
  40. ^ Summary of Events Leading Up to the May 18, 1980 Eruption of Mount St. Helens: April 26–May 2.. USDA Forest Service. Retrieved on 2006-10-28.
  41. ^ Harris, Fire Mountains of the West, 1st edition, page 209
  42. ^ Kiver and Harris, Geology of U.S. Parklands, 6th edition, page 149
  43. ^ Mount St. Helens – From the 1980 Eruption to 2000, Fact Sheet 036-00 usgs.gov
  44. ^ Mount St. Helens National Volcanic Monument fs.fed.us, '24 megatons thermal energy'
  45. ^ Bobbie Myers, 1992, Small Explosions Interrupt 3-year Quiescence at Mount St. Helens, Washington: IN: Earthquakes and Volcanoes, v.23, n.2, p.58–73 (accessed 26 November 2006)
  46. ^ see USGS before and after images
  47. ^ Mount St. Helens, Washington, "Plume in the Evening", [[March 8 2005], USGS.gov (accessed 15 Nov 2006)
  48. ^ Northwest NewsChannel8. New slab growing in Mount St. Helens dome. Retrieved on 2006-10-20.
  49. ^ See close-up of the slab.
  50. ^ Cascades Volcano Observatory, vulcan.wr.usgs.gov (accessed 4 January 2007)
  51. ^ Small Quake Report- ap.google.com (accessed 16 January 2008)

Year 2007 (MMVII) was a common year starting on Monday of the Gregorian calendar in the 21st century. ... is the 223rd day of the year (224th in leap years) in the Gregorian calendar. ... Year 2007 (MMVII) was a common year starting on Monday of the Gregorian calendar in the 21st century. ... is the 66th day of the year (67th in leap years) in the Gregorian calendar. ... A digital object identifier (or DOI) is a standard for persistently identifying a piece of intellectual property on a digital network and associating it with related data, the metadata, in a structured extensible way. ... Year 2006 (MMVI) was a common year starting on Sunday of the Gregorian calendar. ... is the 220th day of the year (221st in leap years) in the Gregorian calendar. ... Year 2007 (MMVII) was a common year starting on Monday of the Gregorian calendar in the 21st century. ... is the 66th day of the year (67th in leap years) in the Gregorian calendar. ... The USDA Forest Service, a United States government agency within the United States Department of Agriculture, is under the leadership of the United States Secretary of Agriculture. ... 2008 (MMVIII) is the current year, a leap year that started on Tuesday of the Common Era (or Anno Domini), in accordance with the Gregorian calendar. ... is the 158th day of the year (159th in leap years) in the Gregorian calendar. ... 2008 (MMVIII) is the current year, a leap year that started on Tuesday of the Common Era (or Anno Domini), in accordance with the Gregorian calendar. ... is the 150th day of the year (151st in leap years) in the Gregorian calendar. ... InsertSLUTTY WHORES≤ non-formatted text here{| class=toccolours border=1 cellpadding=4 style=float: right; margin: 0 0 1em 1em; width: 20em; border-collapse: collapse; font-size: 95%; clear: right; |+ United States Geological Survey |- |style= align=center colspan=2| [[Image:USGS logo. ... 2008 (MMVIII) is the current year, a leap year that started on Tuesday of the Common Era (or Anno Domini), in accordance with the Gregorian calendar. ... is the 158th day of the year (159th in leap years) in the Gregorian calendar. ... 2008 (MMVIII) is the current year, a leap year that started on Tuesday of the Common Era (or Anno Domini), in accordance with the Gregorian calendar. ... is the 150th day of the year (151st in leap years) in the Gregorian calendar. ... InsertSLUTTY WHORES≤ non-formatted text here{| class=toccolours border=1 cellpadding=4 style=float: right; margin: 0 0 1em 1em; width: 20em; border-collapse: collapse; font-size: 95%; clear: right; |+ United States Geological Survey |- |style= align=center colspan=2| [[Image:USGS logo. ... 2008 (MMVIII) is the current year, a leap year that started on Tuesday of the Common Era (or Anno Domini), in accordance with the Gregorian calendar. ... is the 158th day of the year (159th in leap years) in the Gregorian calendar. ... Year 2007 (MMVII) was a common year starting on Monday of the Gregorian calendar in the 21st century. ... is the 269th day of the year (270th in leap years) in the Gregorian calendar. ... Year 2006 (MMVI) was a common year starting on Sunday of the Gregorian calendar. ... is the 293rd day of the year (294th in leap years) in the Gregorian calendar. ... Year 2006 (MMVI) was a common year starting on Sunday of the Gregorian calendar. ... is the 301st day of the year (302nd in leap years) in the Gregorian calendar. ... Year 2006 (MMVI) was a common year starting on Sunday of the Gregorian calendar. ... is the 301st day of the year (302nd in leap years) in the Gregorian calendar. ... Year 2005 (MMV) was a common year starting on Saturday (link displays full calendar) of the Gregorian calendar. ... Year 2006 (MMVI) was a common year starting on Sunday of the Gregorian calendar. ... is the 293rd day of the year (294th in leap years) in the Gregorian calendar. ...

References

View of the hillside at the Johnston Ridge Observatory, 25 years after the eruption.
View of the hillside at the Johnston Ridge Observatory, 25 years after the eruption.

Image File history File links Download high resolution version (2580x1932, 2643 KB) Mt. ... Image File history File links Download high resolution version (2580x1932, 2643 KB) Mt. ... is the 301st day of the year (302nd in leap years) in the Gregorian calendar. ... Year 2006 (MMVI) was a common year starting on Sunday of the Gregorian calendar. ... is the 301st day of the year (302nd in leap years) in the Gregorian calendar. ... Year 2006 (MMVI) was a common year starting on Sunday of the Gregorian calendar. ... is the 301st day of the year (302nd in leap years) in the Gregorian calendar. ... Year 2006 (MMVI) was a common year starting on Sunday of the Gregorian calendar. ...

External links

Wikimedia Commons has media related to:
InsertSLUTTY WHORES≤ non-formatted text here{| class=toccolours border=1 cellpadding=4 style=float: right; margin: 0 0 1em 1em; width: 20em; border-collapse: collapse; font-size: 95%; clear: right; |+ United States Geological Survey |- |style= align=center colspan=2| [[Image:USGS logo. ... Logo of the U.S. Forest Service. ... InsertSLUTTY WHORES≤ non-formatted text here{| class=toccolours border=1 cellpadding=4 style=float: right; margin: 0 0 1em 1em; width: 20em; border-collapse: collapse; font-size: 95%; clear: right; |+ United States Geological Survey |- |style= align=center colspan=2| [[Image:USGS logo. ... There are very few or no other articles that link to this one. ... Mount Silverthrone is a deeply dissected caldera complex in the Pacific Ranges of the Coast Mountains of British Columbia, located at the northern end of the Garibaldi Volcanic Belt containing rhyolitic, dacitic and andesitic lava domes, lava flows and breccia. ... Plinth Peak is a dormant volcano in British Columbia, Canada. ... Mount Meager (sometimes mistakenly spelled Meagre or Meagher) is a potentially active complex volcano in the Pacific Ranges of the Coast Mountains of British Columbia, Canada, above the west flank of the Lillooet River and just south of the Lillooet Icecap. ... Mount Cayley is a eroded stratovolcano in the Garibaldi Volcanic Belt in southwestern British Columbia, which last erupted during the Pleistocene. ... Mount Garibaldi is a stratovolcano in the British Columbia part of the Cascade Range. ... Image File history File linksMetadata Size of this preview: 800 × 533 pixel Image in higher resolution (1800 × 1200 pixel, file size: 301 KB, MIME type: image/jpeg) Aerial photo of Mount Rainier from the west, taken July 2005 by User:Stan Shebs File links The following pages on the English... Mount Baker (elevation 10,778 feet, 3,285 m) is a glaciated andesitic stratovolcano in the Cascade Volcanic Arc and the Cascades of Washington State in the United States about 30 miles (50km) due east of the city of Bellingham, Whatcom County. ... For the mountain in New Zealand, see Glacier Peak (New Zealand) Glacier Peak (known in the Sauk Indian dialect of Lushootseed as Tda-ko-buh-ba or Takobia [2]) is the most remote of the five major volcanoes in the Cascade Volcanic Belt in Washington. ... For other uses, see Mount Rainier (disambiguation). ... Mt. ... This article is about the tallest mountain in Oregon. ... For other mountains named Mount Jefferson, see Mount Jefferson Mount Jefferson is a possibly extinct stratovolcano in the Cascade Range and is the second-highest mountain in Oregon. ... The Three Sisters are three volcanic peaks of the Cascade Range, located about 15 miles SW from the nearest town of Sisters, Oregon. ... Broken Top is an extinct stratovolcano highly eroded by glaciation. ... Mount Bachelor is a stratovolcano (called Bachelor Butte until the 1980s) built atop a shield volcano in the Cascade Range of central Oregon. ... Map of Newberry Volcano and surroundings Newberry Volcano 7,985 ft (2,434 m) high is a large shield volcano located 40 miles (60 km) east of the Cascade Range and about 20 miles (30 km) southeast of Bend, Oregon. ... Mount Thielsen is a stratovolcano in southern Oregon that has been so deeply eroded by glaciers that there is no summit crater and the upper part of the mountain is more or less a horn. ... Mount Mazama is a destroyed stratovolcano in the Oregon part of the Cascade Volcanic Belt and the Cascade Range. ... A crater lake that simply goes by the name Crater Lake, in Oregon, USA Heaven Lake (Chonji / Tianchi), North Korea / China Cuicocha, Ecuador Lake formed after 1991 eruption of Mount Pinatubo, Philippines Mount Katmai, Alaska, USA Mount Wenchi crater lake, Ethiopia Nemrut, Turkey Volcán Irazú, Costa Rica This page... Mount McLoughlin is a stratovolcano in the southern Oregon part of the Cascade Range. ... Penis Pump juice. ... For the city, see Mount Shasta, California. ... Shastina is the highest satellite cone of Mount Shasta, and one of four overlapping volcanic cones which together form the most voluminous stratovolcano in the Cascade Range. ... Mount Tehama is the name given to a now destroyed volcano in the Cascades, also known as Brokeoff Volcano, centred on the Lassen volcanic center. ... Lassen Peak[1] (also known as Mount Lassen) is the southernmost active volcano in the Cascade Range. ...

 
 

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