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Encyclopedia > 1980 eruption of Mount St. Helens

The 1980 eruption of Mount St. Helens, a volcano located in Washington state, in the United States, was a major volcanic eruption. The eruption was the most significant to occur in the contiguous 48 U.S. states (VEI = 5, 0.3 cu mi, 1.2 km3 of material erupted), in terms of power and volume of material released, since the 1915 eruption of California's Lassen Peak. The eruption was preceded by a two-month series of earthquakes and steam-venting episodes, caused by an injection of magma at shallow depth below the mountain that created a huge bulge and a fracture system on Mount St. Helens' north slope. An earthquake at 8:32 a.m. on May 18, 1980, caused the entire weakened north face to slide away, suddenly exposing the partly molten, gas- and steam-rich rock in the volcano to lower pressure. The rock responded by exploding into a very hot mix of pulverized lava and older rock that sped toward Spirit Lake so fast that it quickly passed the avalanching north face. For the mountain in California, see Mount Saint Helena. ... For the capital city of the United States, see Washington, D.C.. For other uses, see Washington (disambiguation). ... Eruption of Vesuvius in 1822. ... 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      A U.S. state is any one of the fifty subnational entities of... 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. ... This article is about the U.S. state. ... Lassen Peak[1] (also known as Mount Lassen) is the southernmost active volcano in the Cascade Range. ... This article is about the natural seismic phenomenon. ... For other uses, see Steam (disambiguation). ... Magma is molten rock located beneath the surface of the Earth (or any other terrestrial planet), and which often collects in a magma chamber. ... For the mountain in California, see Mount Saint Helena. ... 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). ... For other uses, see Steam (disambiguation). ... This article is about the geological substance. ... Look up lava, Aa, pahoehoe in Wiktionary, the free dictionary. ... Photograph taken on October 4, 1980 Spirit Lake was formerly an attractive lake near Mount St. ...


A volcanic ash column rose high into the atmosphere and deposited ash in 11 U.S. states.[citation needed] At the same time, snow, ice, and several entire glaciers on the mountain melted, forming a series of large lahars (volcanic mudslides) that reached as far as the Columbia River, nearly fifty miles (eighty kilometers) to the south. Less severe outbursts continued into the next day only to be followed by other large but not as destructive eruptions later in 1980. By the time the ash settled, 57 people (including innkeeper Harry Truman and geologist David A. Johnston; a full list is available here: [1]) and thousands of animals were dead. Hundreds of square miles were reduced to wasteland, over a billion U.S. dollars in damage had occurred ($2.74 billion in 2007 dollars[1]), and the face of Mount St. Helens was scarred with a huge crater on its north side. At the time of the eruption, the summit of the volcano was owned by the Burlington Northern Railroad, but afterward the land passed to the United States Forest Service.[2] The area was later preserved, as it was, in the Mount St. Helens National Volcanic Monument. 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. ... Air redirects here. ... Perito Moreno Glacier Patagonia Argentina Aletsch Glacier, Switzerland Icebergs breaking off glaciers at Cape York, Greenland This article is about the geological formation. ... Lahar from a March 1982 eruption of Mount St. ... Mudslide in La Conchita, California A mudslide is a landslide of mud. ... The Columbia River (French: fleuve Columbia) is a river in the Pacific Northwest region of North America. ... 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, 13 1/2 hours before he was killed in the 1980 eruption of Mount St. ... The United States dollar is the official currency of the United States. ... The Burlington Northern Railroad (AAR reporting marks BN) was a United States-based railroad company operating between 1970 and 1995. ... Logo of the U.S. Forest Service. ... Mount St. ...

Mount St. Helens from Monitor Ridge showing the cone of devastation, the huge crater open to the north, the post-eruption lava dome inside and Crater Glacier surrounding the lava dome. The small photo on the left was taken from Spirit Lake before the eruption and the small photo on the right was taken after the eruption from approximately the same place. Spirit Lake can also be seen in the larger image, as well as two other Cascade volcanoes.
Mount St. Helens from Monitor Ridge showing the cone of devastation, the huge crater open to the north, the post-eruption lava dome inside and Crater Glacier surrounding the lava dome. The small photo on the left was taken from Spirit Lake before the eruption and the small photo on the right was taken after the eruption from approximately the same place. Spirit Lake can also be seen in the larger image, as well as two other Cascade volcanoes.

Contents

Download high resolution version (1936x537, 234 KB)St Helens Composite with feathering Adapted from Image:St Helens from Monitor Ridge. ... Download high resolution version (1936x537, 234 KB)St Helens Composite with feathering Adapted from Image:St Helens from Monitor Ridge. ... 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. ...

Buildup to the eruption

Mount St. Helens, May 17, 1980.

Mount St. Helens remained dormant from its last period of activity in the 1840s and 1850s, until March 1980.[3] Several small earthquakes beginning as early as March 15, 1980, indicated that magma may have been moving below the volcano.[4] Then on March 18 at 3:45 p.m. Pacific Standard Time (all times will be in PST), a shallow Richter magnitude 4.2 earthquake (the initial reading was 4.1), centered below the mountain's north flank,[4] signaled the volcano's violent return from 123 years of hibernation.[5] A gradually building earthquake swarm saturated area seismographs and started to climax at about noon on March 25, reaching peak levels in the next two days, including an earthquake registering 4.5 on the Richter scale.[6] A total of 174 shocks of magnitude 2.6 or greater were recorded during those two days.[7] Shocks of magnitude 3.2 or greater occurred at a slightly increasing rate during April and May with five earthquakes of magnitude 4 or above per day in early April, and 8 per day the week before May 18.[5] Initially there was no direct sign of eruption, but small earthquake-induced avalanches of snow and ice were reported from aerial observations. Image File history File links Sthelens1. ... Image File history File links Sthelens1. ... is the 137th day of the year (138th 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 74th day of the year (75th 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 77th day of the year (78th in leap years) in the Gregorian calendar. ... The Pacific Standard Time Zone is a geographic region that keeps time by subtracting eight hours from Coordinated Universal Time (UTC). ... The Richter magnitude test scale (or more correctly local magnitude ML scale) assigns a single number to quantify the size of an earthquake. ... This article is about the natural seismic phenomenon. ... Cleveland Volcano in the Aleutian Islands of Alaska photographed from the International Space Station For other uses, see Volcano (disambiguation). ... Global earthquake epicenters, 1963–1998. ... Seismographs (in Greek seismos = earthquake and graphein = write) are used by seismologists to record seismic waves. ... is the 84th day of the year (85th 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 near Mount Everest. ...


At 12:36 p.m. on March 27, at least one but possibly two nearly simultaneous phreatic eruptions (exploding groundwater-derived steam) ejected smashed rock from within the old summit crater, excavating a new crater 250 feet (76 m) wide[5] and sending an ash column about 7,000 feet (2,100 m) into the air.[7] By this date, a 16,000-foot (4,900 m) long, east-trending fracture system had also developed across the summit area.[8] This was followed by more earthquake storms and a series of steam explosions that sent ash 10,000 to 11,000 feet (3,000 to 3,400 m) above their vent.[5] Most of this ash fell within 3 to 12 miles (5 to 20 km) from its vent, but some was carried as far as 150 miles (240 km) south to Bend, Oregon, and 285 miles (460 km) east to Spokane, Washington.[9] is the 86th day of the year (87th in leap years) in the Gregorian calendar. ... Phreatic eruption at the summit of Mount St. ... Groundwater is water located beneath the ground surface in soil pore spaces and in the fractures of lithologic formations. ... For other uses, see Steam (disambiguation). ... Craters on Mount Cameroon Perhaps the most conspicuous part of a volcano is the crater, a basin of a roughly circular form within which occurs a vent (or vents) from which magma erupts as gases, lava, and ejecta. ... Bend is a city in Deschutes County, Oregon, United States. ... Spokane redirects here. ...


A second, new crater and a blue flame was observed on March 29.[10][9] The flame was visibly emitted from both craters and was probably created by burning gases. Static electricity generated from ash clouds rolling down the mountain sent out lightning bolts that were up to two miles (3 km) long.[9] Ninety-three separate outbursts were reported on March 30,[9] and increasingly strong harmonic tremors were first detected on April 1, alarming geologists and prompting Governor Dixy Lee Ray to declare a state of emergency on April 3.[11] is the 88th day of the year (89th in leap years) in the Gregorian calendar. ... Static electricity is a class of phenomena involving the net charge present on an object; typically referring to charged object with voltages of sufficient magnitude to produce visible attraction, repulsion, and sparks. ... Not to be confused with lighting. ... is the 89th day of the year (90th in leap years) in the Gregorian calendar. ... Harmonic tremor describes a continuous rhythmic earthquakes in the Earths upper lithosphere that can be detected by a seismograph and is often preceded or accompanied by a volcanic eruptions. ... is the 91st day of the year (92nd in leap years) in the Gregorian calendar. ... Dixy Lee Ray Dixy Lee Ray (September 3, 1914- January 2, 1994) was the seventeenth governor of Washington State, U.S.A. and the first woman to hold that position (for one term, from 1977 until 1981). ... is the 93rd day of the year (94th in leap years) in the Gregorian calendar. ...

USGS photo showing a pre-avalanche eruption on April 10.
USGS photo showing a pre-avalanche eruption on April 10.

By April 7 the combined crater was 1,700 feet (520 m) long, 1,200 feet (365 m) wide and 500 feet (150 m) deep.[12] A USGS team determined in the last week of April that a 1.5-mile (2.4 km) diameter section of St. Helens' north face was displaced out at least 270 feet (82 m).[8] For the rest of April and early May this bulge grew 5 to 6 ft (1.5 to 1.8 m) per day, and by mid-May it extended more than 400 feet (120 m) north.[8] As the bulge moved northward, the summit area behind it progressively sank, forming a complex, down-dropped block called a graben. Geologists announced on April 30 that sliding of the bulge area was the greatest immediate danger and that such a landslide might spark an eruption. These changes in the volcano's shape were related to the overall deformation that increased the volume of the mountain by 0.03 cubic miles (0.1 km³) by mid-May.[13] This volume increase presumably corresponded to the volume of magma that pushed into the volcano and deformed its surface. Because the intruded magma remained below ground and was not directly visible, it was called a cryptodome, in contrast to a true lava dome exposed at the surface. is the 100th day of the year (101st in leap years) in the Gregorian calendar. ... April 7 is the 97th day of the year in the Gregorian calendar (98th in leap years). ... The United States Geological Survey (USGS) is a scientific agency of the United States government. ... USGS image A graben is a depressed block of land bordered by parallel faults. ... is the 120th day of the year (121st in leap years) in the Gregorian calendar. ... This article is about geological phenomenon. ... There are very few or no other articles that link to this one. ... One of the Mono Craters, an example of a rhyolite dome. ...

Photo showing the bulge on April 27.
Photo showing the bulge on April 27.

On May 7, eruptions similar to those in March and April resumed, and over the next days the bulge approached its maximum size.[14] All activity had been confined to the 350-year-old summit dome and did not involve any new magma. A total of about 10,000 earthquakes were recorded prior to the May 18 event, with most concentrated in a small zone less than 1.6 miles (2.6 km) directly below the bulge.[13] Visible eruptions ceased on May 16, reducing public interest and consequently the number of spectators in the area.[15] Mounting public pressure then forced officials to allow 50 carloads of property owners to enter the danger zone on May 17 to gather whatever property they could carry.[15] Another trip was scheduled for 10 a.m. the next morning.[15] Since that was Sunday, more than 300 loggers would not be working in the area. By the time of the climactic eruption, dacite magma intruding into the volcano had forced the north flank outward nearly 500 feet (150 m) and heated the volcano's groundwater system, causing many steam-driven explosions (phreatic eruptions). is the 117th day of the year (118th in leap years) in the Gregorian calendar. ... is the 127th day of the year (128th in leap years) in the Gregorian calendar. ... Magma is molten rock located beneath the surface of the Earth (or any other terrestrial planet), and which often collects in a magma chamber. ... is the 138th day of the year (139th in leap years) in the Gregorian calendar. ... is the 136th day of the year (137th in leap years) in the Gregorian calendar. ... is the 137th day of the year (138th in leap years) in the Gregorian calendar. ... Grey, red, black, altered white/tan, flow-banded pumice dacite Dacite (IPA: ) is an igneous, volcanic rock with a high iron content. ... Groundwater is water located beneath the ground surface in soil pore spaces and in the fractures of lithologic formations. ...


North face slides away

Sequence of events on May 18.

At 7 a.m. on May 18, USGS volcanologist David A. Johnston, who had Saturday night duty at an observation post about 6 miles (10 km) north of the mountain, radioed in the results of some laser-beam measurements he had made moments earlier.[2] Mount St. Helens' activity that day did not show any change from the pattern of the preceding month. The rate of bulge movement, sulfur dioxide emission, and ground temperature readings did not reveal any unusual changes that might have indicated a catastrophic eruption. Mount St. ... Mount St. ... is the 138th day of the year (139th in leap years) in the Gregorian calendar. ... is the 138th day of the year (139th in leap years) in the Gregorian calendar. ... Volcanology (also spelled vulcanology) is the study of volcanoes, lava, magma, and related geological phenomena. ... For other uses, see Laser (disambiguation). ... Sulfur dioxide (or Sulphur dioxide) has the chemical formula SO2. ...

North Fork Toutle River valley filled with landslide deposits.
North Fork Toutle River valley filled with landslide deposits.

Suddenly, at 8:32 a.m., a magnitude 5.1 earthquake centred directly below the north slope triggered that part of the mountain to slide,[16] approximately 7–20 seconds (about 10 seconds seems most reasonable) after the shock.[2] One of the largest landslides in recorded history, the slide traveled at 110 to 155 miles per hour (175 to 250 km/h) and moved across Spirit Lake's west arm; part of it hit a 1,150-foot (350 m) high ridge about 6 miles (9.5 km) north.[2] Some of the slide spilled over the ridge, but most of it moved 13 miles (21 km) down the North Fork Toutle River, filling its valley up to 600 feet (180 m) deep with avalanche debris.[16] An area of about 24 square miles (62 km²) was covered, and the total volume of the deposit was about 0.7 cubic miles (2.9 km³).[2] This downstream view of the North Fork Toutle River valley, north and west of St. ... This downstream view of the North Fork Toutle River valley, north and west of St. ... The Toutle River is a river in southwest Washington State, in the Pacific Northwest region of the United States. ...


Most of St. Helens' former north side became a rubble deposit 17 miles (27 km) long, averaging 150 feet (46 m) thick; the slide was thickest at one mile (1.6 km) below Spirit Lake and thinnest at its western margin.[2] All the water in Spirit Lake was temporarily displaced by the landslide, sending 600-foot (180 m) high waves crashing into a ridge north of the lake,[17] adding 295 feet (90 m) of new avalanche debris above the old lakebed, and raising its surface level by about 200 feet (60 m).[2] As the water moved back into its basin, it pulled with it thousands of trees felled by a super-heated wall of volcanic gas and searing ash and rock that overtook the landslide seconds before. Drainage basin. ...


Pyroclastic flows

Initial lateral blast

Computer graphic showing the May 18 landslide (green) being overtaken by the initial pyroclastic flow (red).
Computer graphic showing the May 18 landslide (green) being overtaken by the initial pyroclastic flow (red).

The landslide suddenly exposed the dacite magma in St. Helens' neck to much lower pressure causing the gas-charged, partially molten rock and high-pressure steam above it to explode a few seconds after the slide started. Explosions burst through the trailing part of the landslide, blasting rock debris northward. The resulting blast laterally directed the pyroclastic flow of very hot volcanic gases, ash, and pumice from new lava, and pulverized old rock hugged the ground while initially moving at 220 mph (350 km/h) but quickly accelerating to 670 mph (1080 km/h) (it may have briefly passed the speed of sound).[2][16] Download high resolution version (788x812, 216 KB)These illustrations show the landslide (green) and directed blast (red) that occurred during the first few minutes of the eruption of Mount St. ... Download high resolution version (788x812, 216 KB)These illustrations show the landslide (green) and directed blast (red) that occurred during the first few minutes of the eruption of Mount St. ... is the 138th day of the year (139th in leap years) in the Gregorian calendar. ... Grey, red, black, altered white/tan, flow-banded pumice dacite Dacite (IPA: ) is an igneous, volcanic rock with a high iron content. ... 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. ... Specimen of highly porous pumice from Teide volcano on Tenerife, Canary Islands. ... For other uses, see Speed of sound (disambiguation). ...


Pyroclastic flow material passed up the moving avalanche and spread outward, devastating a fan-shaped area 23 miles (37 km) across and 19 miles (30 km) long.[16] In all, about 230 square miles (600 km²) of forest were knocked down[16] within an 8-mile (13 km) inner-fan area, and extreme heat killed trees miles beyond the blow-down zone. At its vent the lateral blast probably did not last longer than about 30 seconds, but the northward radiating and expanding blast cloud continued for about another minute.


Superheated flow material flashed water in Spirit Lake and North Fork Toutle River to steam, creating a larger, secondary explosion that was heard as far away as British Columbia,[18] Montana, Idaho, and Northern California. Yet many areas closer to the eruption (Portland, Oregon, for example) did not hear the blast. This so-called "quiet zone" extended radially a few tens of miles from the volcano and was created by the complex response of the eruption's sound waves to differences in temperature and air motion of the atmospheric layers and, to a lesser extent, local topography.[2] Motto: Splendor sine occasu (Latin: Splendour without diminishment) Capital Victoria Largest city Vancouver Official languages English (de facto) Government Lieutenant-Governor Steven Point Premier Gordon Campbell (BC Liberal) Federal representation in Canadian Parliament House seats 36 Senate seats 6 Confederation July 20, 1871 (6th province) Area  Ranked 5th Total 944... This article is about the U.S. State. ... -1... Northern California, sometimes referred to as NorCal, is the northern portion of the U.S. state of California. ... 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 376. ... This article is about audible acoustic waves. ... For discussion of land surfaces themselves, see Terrain. ...


Lateral blast result

Everyone in the quiet zone could see the huge ash cloud that was sent skyward from St. Helens' northern foot. The near-supersonic lateral blast, loaded with volcanic debris, caused devastation as far as 19 miles (30 km) from the volcano. The area affected by the blast can be subdivided into three roughly concentric zones:[2]

Felled trees at Johnston Ridge, 2004
Felled trees at Johnston Ridge, 2004
  1. Direct blast zone, the innermost zone, averaged about 8 miles (13 km) in radius, an area in which virtually everything, natural or artificial, was obliterated or carried away.[2] For this reason, this zone also has been called the "tree-removal zone." The flow of the material carried by the blast was not deflected by topographic features in this zone.
  2. Channelized blast zone, an intermediate zone, extended out to distances as far as 19 miles (30 km) from the volcano, an area in which the flow flattened everything in its path and was channeled to some extent by topography.[2] In this zone, the force and direction of the blast are strikingly demonstrated by the parallel alignment of toppled large trees, broken off at the base of the trunk as if they were blades of grass mown by a scythe. This zone was also known as the "tree-down zone."
  3. Seared zone, also called the "standing dead" zone, the outermost fringe of the impacted area, a zone in which trees remained standing but were singed brown by the hot gases of the blast.[2] Later studies indicated that one-third of the 0.045 cubic miles (188,000,000 m³) of material in the flow was new lava, and the rest was fragmented, older rock.[18]
Photographer Reid Blackburn's car after the eruption.
Photographer Reid Blackburn's car after the eruption.

By the time this pyroclastic flow hit its first human victims, it was still as hot as 360 °C (680 °F) and filled with suffocating gas and flying angular material.[18] Most of the 57 people known to have died in that day's eruption succumbed to asphyxiation while several died from burns.[2] Lodge owner Harry Truman was buried under hundreds of feet (tens of meters) of avalanche material. Volcanologist David A. Johnston was one of those killed, as was Reid Blackburn, a National Geographic photographer. A traditional wooden scythe A scythe (IPA: , most likely from Old English siðe, sigði) is an agricultural hand tool for mowing and reaping grass or crops. ... For other uses, see Gas (disambiguation). ... Reid Blackburns (photographer, National Geographic, Vancouver Columbian) car, about 10 miles from Mount St. ... Reid Blackburns (photographer, National Geographic, Vancouver Columbian) car, about 10 miles from Mount St. ... Asphyxia is a condition of severely deficient supply of oxygen to the body. ... 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, 13 1/2 hours before he was killed in the 1980 eruption of Mount St. ... Reid Blackburn (1952-08-11 - 1980-05-18) was a photographer killed in the 1980 volcanic eruption of Mount St. ... The National Geographic Society was founded in the USA on January 27, 1888, by 33 men interested in organizing a society for the increase and diffusion of geographical knowledge. ...


Later flows

Subsequent outpourings of pyroclastic material from the breach left by the landslide consisted mainly of new magmatic debris rather than fragments of preexisting volcanic rocks. The resulting deposits formed a fan-like pattern of overlapping sheets, tongues, and lobes. At least 17 separate pyroclastic flows occurred during the May 18 eruption, and their aggregate volume was about 0.05 cubic miles (208,000,000 m³).[2] is the 138th day of the year (139th in leap years) in the Gregorian calendar. ...


The flow deposits were still at about 300 °C to 420 °C (570 °F to 785 °F) two weeks after they erupted.[2] Secondary steam-blast eruptions fed by this heat created pits on the northern margin of the pyroclastic-flow deposits, at the south shore of Spirit Lake, and along the upper part of the North Fork Toutle River. These steam-blast explosions continued sporadically for weeks or months after the emplacement of pyroclastic flows, and at least one occurred about a year later, on May 16, 1981.[2] is the 136th day of the year (137th in leap years) in the Gregorian calendar. ... AUGUST 25 1981 US Marine Sean Vance is Born on the 25th of August {ear nav|1981}} Year 1981 (MCMLXXXI) was a common year starting on Thursday (link displays the 1981 Gregorian calendar). ...


Ash column grows

Photo of the lower part of the May 18 ash column.
Photo of the lower part of the May 18 ash column.

As the avalanche and initial pyroclastic flow were still advancing, a huge ash column grew to a height of 12 miles (19 km) above the expanding crater in less than 10 minutes and spewed tephra into the stratosphere for 10 straight hours.[18] Near the volcano, the swirling ash particles in the atmosphere generated lightning, which in turn started many forest fires. During this time, parts of the mushroom-shaped ash-cloud column collapsed, sending additional pyroclastic flows speeding down St. Helens' flanks. Later, slower flows came directly from the new north-facing crater and consisted of glowing pumice bombs and very hot pumiceous ash. Some of these hot flows covered ice or water which flashed to steam, creating craters up to 65 feet (20 m) in diameter and sending ash as much as 6,500 feet (1980 m) into the air.[19] is the 138th day of the year (139th in leap years) in the Gregorian calendar. ... Tephra refers to air-fall material produced by a volcanic eruption regardless of composition or fragment size. ... This article is about the stratosphere layer; for the hotel in Las Vegas, Nevada, see Stratosphere Las Vegas. ... Not to be confused with lighting. ... Fire in San Bernardino, California Mountains (image taken from the International Space Station) A wildfire, also known as a forest fire, vegetation fire, grass fire, or bushfire (in Australasia), is an uncontrolled fire in wildland often caused by lightning; other common causes are human carelessness and arson. ... The atomic bombing of Nagasaki, Japan on August 9, 1945 A mushroom cloud is a distinctive mushroom-shaped cloud of smoke, flame, or debris resulting from a very large explosion. ...

Map of ash distribution.
Map of ash distribution.

Strong high-altitude wind carried much of this material east-northeasterly from the volcano at an average speed of about 60 mph (100 km/h). By 9:45 a.m. it had reached Yakima, Washington, 90 miles (145 km) away, and by 11:45 a.m. it was over Spokane, Washington.[2] A total of 4 to 5 inches (100 to 130 mm) of ash fell on Yakima, and areas as far east as Spokane were plunged into darkness by noon where visibility was reduced to 10 feet (3 m) and half an inch (13 mm) of ash fell.[18] Continuing east, St. Helens' ash fell in the western part of Yellowstone National Park by 10:15 p.m. and was seen on the ground in Denver, Colorado, the next day.[18] In time ash fall from this eruption was reported as far away as Minnesota and Oklahoma, and some of the ash drifted around the globe within about 2 weeks. Altitude is the elevation of an object from a known level or datum. ... Location of Yakima in Washington Coordinates: , Country State County Yakima Incorporated December 1, 1883 Government  - Mayor Dave Edler Area  - City 20. ... Spokane redirects here. ... Yellowstone redirects here. ... Nickname: Location of Denver in the State of Colorado Location of Colorado in the United States Coordinates: , Country United States State State of Colorado City and County Denver[1] Founded 1858-11-22, as Denver City, K.T.[2] Incorporated 1861-11-07, as Denver City, C.T.[3] Consolidated... Capital Saint Paul Largest city Minneapolis Largest metro area Minneapolis-St. ... For other uses, see Oklahoma (disambiguation). ...


During the nine hours of vigorous eruptive activity, about 540 million tons of ash fell over an area of more than 22,000 square miles (60,000 km²).[2] The total volume of the ash before its compaction by rainfall was about 0.3 cubic miles (1.3 km³).[2] The volume of the uncompacted ash is equivalent to about 0.05 mile³ (208,000,000 m³) of solid rock, or about 7% of the amount of material that slid off in the debris avalanche.[2] By around 5:30 p.m. on May 18, the vertical ash column declined in stature, but less severe outbursts continued through the night and for several days.[20] This article is about precipitation. ... is the 138th day of the year (139th in leap years) in the Gregorian calendar. ...


Mudslides flow downstream

Mudline next to Muddy River from the 1980 lahars.
Mudline next to Muddy River from the 1980 lahars.

The hot, exploding material also broke apart and melted nearly all of the mountain's glaciers along with most of the overlying snow. As in many previous St. Helens' eruptions, this created huge lahars (volcanic mudflows) and muddy floods that affected three of the four stream drainage systems on the mountain,[19] and which started to move as early as 8:50 a.m.[17] Lahars traveled as fast as 90 mph (145 km/h) while still high on the volcano but progressively slowed to about 3 mph (5 km/h) on the flatter and wider parts of rivers.[2] Mudflows from the southern and eastern flanks had the consistency of wet concrete as they raced down Muddy River, Pine Creek, and Smith Creek to their confluence at the Lewis River. Bridges were taken out at the mouth of Pine Creek and the head of Swift Reservoir, which rose 2.6 feet (0.8 m)[19] by noon to accommodate the nearly 18 million cubic yards (13 million m³) of additional water, mud, and debris.[2] Nearly 135 miles (220 kilometers) of river channels surrounding the volcano were affected by the lahars of May 18. ... Nearly 135 miles (220 kilometers) of river channels surrounding the volcano were affected by the lahars of May 18. ... 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. ... Lahar from a March 1982 eruption of Mount St. ... A mudflow or mudslide is the most rapid (up to 80 km/h) and fluid type of downhill mass wasting. ... 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. ...


Glacier and snow melt mixed with tephra on the volcano's northeast slope to create much larger lahars. These mudflows traveled down the north and south forks of the Toutle River and joined at the confluence of the Toutle forks and the Cowlitz River near Castle Rock, Washington, at 1:00 p.m. Ninety minutes after the eruption, the first mudflow had moved 27 river miles (43 km) upstream where observers at Weyerhaeuser's Camp Baker saw a 12-foot (3.7 m) high wall of muddy water and debris pass.[17] Near the confluence of the Toutle's north and south forks at Silver Lake, a record flood stage of 23.5 feet (7.2 m) was recorded.[17] The Cowlitz River is a river in the state of Washington in the United States, a tributary of the Columbia River. ... Castle Rock is a city located in Cowlitz County, Washington. ... Weyerhaeuser is one of the largest pulp and paper companies in the world; the worlds largest private owner of softwood timberland; and the second largest owner in the United States, behind International Paper. ... Flood stage is the point at which the surface of a river, creek, or other body of water has risen to a sufficient level to cause damage. ...


A large but slower-moving mudflow with a mortar-like consistency was mobilized in early afternoon at the head of the Toutle River north fork. By 2:30 p.m. the massive mudflow had destroyed Camp Baker,[17] and in the following hours seven bridges were carried away. Part of the flow backed up for 2.5 miles (4 km) soon after entering the Cowlitz River, but most continued downstream. After traveling 17 miles (27 km) further, an estimated 3.9 million cubic yards (3.0 million m³) of material were injected into the Columbia River, reducing the river's depth by 25 feet (7.6 m) for a four-mile (6 km) stretch.[17] The resulting 13-foot (4 m) river depth temporarily closed the busy channel to ocean-going freighters, costing Portland, Oregon an estimated five million US dollars.[20] Ultimately more than 65 million cubic yards (50 million m³) of sediment were dumped along the lower Cowlitz and Columbia Rivers.[2] The Columbia River (French: fleuve Columbia) is a river in the Pacific Northwest region of North America. ... Animated map exhibiting the worlds oceanic waters. ... Cargo ship or freighter is any sort of ship that carries goods and materials from one port to another. ... 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 376. ... The United States dollar is the official currency of the United States. ...


Aftermath

Map showing 1980 eruption deposits.
Map showing 1980 eruption deposits.

Direct results

The May 18, 1980, event was the most deadly and economically destructive volcanic eruption in the history of the United States.[2] Fifty-seven people were killed and 200 homes, 47 bridges, 15 miles (24 km) of railways and 185 miles (300 km) of highway were destroyed. U.S. President Jimmy Carter surveyed the damage and stated it looked more desolate than a moonscape.[citation needed] A film crew was dropped by helicopter on St. Helens on May 23 to document the destruction. Their compasses, however, span in circles and they quickly became lost.[citation needed] A second eruption occurred the next day (see below), but the crew survived and were rescued two days after that. 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). ... American history redirects here. ... For other persons named Jimmy Carter, see Jimmy Carter (disambiguation). ... This article is about Earths moon. ... is the 143rd day of the year (144th in leap years) in the Gregorian calendar. ... This article is about the navigational instrument. ...


In all, St. Helens released an amount of energy equivalent to 27,000 Hiroshima-sized nuclear weapons and ejected more than 1 cubic mile (4 km³) of material.[21] A quarter of that volume was fresh lava in the form of ash, pumice, and volcanic bombs while the rest was fragmented, older rock.[21] The removal of the north side of the mountain (13% of the cone's volume) reduced St. Helens' height by about 1,313 feet (400 m) and left a crater 1 to 2 miles (2 to 3 km) wide and 2,100 feet (640 m) deep with its north end open in a huge breach.[21] Little Boy was the codename of the atomic bomb which was dropped on Hiroshima, on August 6, 1945 by the 12-man crew of the B-29 Superfortress Enola Gay, piloted by Colonel Paul Tibbets (Tibbets, age 92, died Nov. ... The mushroom cloud of the atomic bombing of Nagasaki, Japan, 1945, rose some 18 kilometers (11 mi) above the hypocenter A nuclear weapon derives its destructive force from nuclear reactions of fusion or fission. ... A cubic mile is an Imperial unit/U.S. customary unit (non-SI non-metric) of volume, used in the United States. ... This article is about the geological substance. ...

St. Helens in September 1980.
St. Helens in September 1980.

More than 4 billion board feet (14.6 km³) of timber was damaged or destroyed, mainly by the lateral blast.[2] At least 25% of the destroyed timber was salvaged after September 1980. Downwind of the volcano, in areas of thick ash accumulation, many agricultural crops, such as wheat, apples, potatoes, and alfalfa, were destroyed. As many as 1,500 elk and 5,000 deer were killed, and an estimated 12 million[2] Chinook and Coho salmon fingerlings died when their hatcheries were destroyed. Another estimated 40,000 young salmon were lost when they swam through turbine blades of hydroelectric generators when reservoir levels were lowered along the Lewis River to accommodate possible mudflows and flood waters.[2] After the May 18, 1980 eruption, Mount St. ... After the May 18, 1980 eruption, Mount St. ... The board foot is a specialized unit of volume for measuring lumber in the United States. ... Timber in storage for later processing at a sawmill Timber is a term used to describe wood, either standing or that has been processed for use—from the time trees are felled, to its end product as a material suitable for industrial use—as structural material for construction or wood... For the Our Gang (Little Rascals) character, see Carl Switzer. ... For other uses, see Elk (disambiguation). ... This article is about the ruminant animal. ... Binomial name (Walbaum, 1792) The Chinook salmon (Oncorhynchus tshawytscha) (derived from Russian чавыча), is a species of anadromous fish in the salmon family. ... Binomial name Oncorhynchus kisutch (Walbaum, 1792) The Coho salmon (Oncorhynchus kisutch, from the Russian кижуч kisutch) is a species of anadromous fish in the salmon family. ... For other uses, see Salmon (disambiguation). ... For other uses, see Salmon (disambiguation). ... A Siemens steam turbine with the case opened. ... 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. ... For other uses, see Lake (disambiguation). ... Flooding near Key West, Florida, United States from Hurricane Wilmas storm surge in October 2005 For other uses, see Flood (disambiguation). ...


Digging out

The ash fall created some temporary but major problems with transportation, sewage disposal, and water treatment systems. Visibility was greatly decreased during the ash fall, closing many highways and roads. Interstate 90 from Seattle to Spokane was closed for a week and a half.[2] Air travel was disrupted for a few days to 2 weeks as several airports in eastern Washington shut down because of ash accumulation and poor visibility. Over a thousand commercial flights were canceled following airport closures.[2] Fine-grained, gritty ash caused substantial problems for internal-combustion engines and other mechanical and electrical equipment. The ash contaminated oil systems and clogged air filters, and scratched moving surfaces. Fine ash caused short circuits in electrical transformers, which in turn caused power blackouts. For the movement of people or objects, see transport. ... Sewage is the mainly liquid waste containing some solids produced by humans which typically consists of washing water, faeces, urine, laundry waste and other material which goes down drains and toilets from households and industry. ... A water treatment plant in northern Portugal. ... Wikimedia Commons has media related to: Interstate 90 Interstate 90 (abbreviated I-90) is the longest interstate highway in the United States at nearly 3,100 miles (5,000 kilometers). ... Seattle redirects here. ... Spokane redirects here. ... An internal combustion engine is an engine that is powered by the expansion of hot combustion products of fuel directly acting within an engine. ... For alternate meanings see Short circuit (disambiguation) A short circuit (sometimes known as simply a short) is a fault whereby electricity moves through a circuit in an unintended path, usually due to a connection forming where none was expected. ... Tree limbs create a short circuit in electrical lines during a storm that spawned two tornados. ...


Removing and disposing of the ash was a monumental task for some eastern Washington communities. State and federal agencies estimated that over 2.4 million cubic yards (1.8 million m³) of ash — equivalent to about 900,000 tons in weight — were removed from highways and airports in Washington.[2] Ash removal cost $2.2 million and took 10 weeks in Yakima.[2] The need to remove ash quickly from transport routes and civil works dictated the selection of some disposal sites. Some cities used old quarries and existing sanitary landfills; others created dumpsites wherever expedient. To minimize wind reworking of ash dumps, the surfaces of some disposal sites were covered with topsoil and seeded with grass. In Portland, the mayor eventually threatened businesses with fines if they failed to remove the ash from their parking lots.[22] Look up Dump in Wiktionary, the free dictionary. ...


Cost

One of the 200 homes destroyed by the eruption.
One of the 200 homes destroyed by the eruption.

Early estimates of the cost of the eruption ranged from US$2–3 billion.[2] A refined estimate of $1.1 billion ($2.74 billion in 2007 dollars[2]) was determined in a study by the International Trade Commission at the request of the United States Congress.[2] A supplemental appropriation of $951 million for disaster relief was voted by Congress, of which the largest share went to the Small Business Administration, U.S. Army Corps of Engineers, and the Federal Emergency Management Agency.[2] CDC photo from [1] File history Legend: (cur) = this is the current file, (del) = delete this old version, (rev) = revert to this old version. ... CDC photo from [1] File history Legend: (cur) = this is the current file, (del) = delete this old version, (rev) = revert to this old version. ... The United States dollar is the official currency of the United States. ... One thousand million (1,000,000,000) is the natural number following 999,999,999 and preceding 1,000,000,001. ... The United States International Trade Commission is a nonpartisan, quasi-judicial federal indepedent agency that provides trade expertise to both the legislative and executive branches of government, determines the impact of imports on U.S. industries, and directs actions against certain unfair trade practices, such as patent, trademark, and copyright... Type Bicameral Houses Senate House of Representatives President of the Senate President pro tempore Dick Cheney, (R) since January 20, 2001 Robert C. Byrd, (D) since January 4, 2007 Speaker of the House Nancy Pelosi, (D) since January 4, 2007 Members 535 plus 4 Delegates and 1 Resident Commissioner Political... The Small Business Administration (SBA) is a United States government agency that provides support to small businesses. ... United States Army Corps of Engineers logo The United States Army Corps of Engineers, or USACE, is made up of some 34,600 civilian and 650 military men and women. ... FEMA redirects here. ...


There were also indirect and intangible costs of the eruption. Unemployment in the immediate region of Mount St. Helens rose tenfold in the weeks immediately following the eruption, and then returned to nearly normal once timber salvaging and ash-cleanup operations were underway. Only a small percentage of residents left the region because of lost jobs owing to the eruption.[2] Several months after May 18, a few residents reported suffering stress and emotional problems, even though they had coped successfully during the crisis. Counties in the region requested funding for mental health programs to assist such people.[citation needed] CIA figures for world unemployment rates, 2006 Unemployment is the state in which a person is without work, available to work, and is currently seeking work. ... is the 138th day of the year (139th in leap years) in the Gregorian calendar. ... In medical terms, stress is the disruption of homeostasis through physical or psychological stimuli. ... For other uses, see Emotion (disambiguation). ...


Initial public reaction to the May 18 eruption nearly dealt a crippling blow to tourism, an important industry in Washington. Not only was tourism down in the Mount St. Helens–Gifford Pinchot National Forest area, but conventions, meetings, and social gatherings also were canceled or postponed at cities and resorts elsewhere in Washington and neighboring Oregon not affected by the eruption. The adverse effect on tourism and conventioneering, however, proved only temporary. Mount St. Helens, perhaps because of its reawakening, has regained its appeal for tourists. The United States Forest Service and the State of Washington opened visitor centers and provided access for people to view the volcano's devastation.[2] is the 138th day of the year (139th in leap years) in the Gregorian calendar. ... Tourist redirects here. ... Gifford Pinchot National Forest is a national forest located in southwestern Washington. ... This article is about the U.S. state. ... Logo of the U.S. Forest Service. ...


Later eruptions

Further information: 2004 and later volcanic activity of Mount St. Helens

St. Helens produced five more explosive eruptions between May and October 1980. Through early 1990, a total of at least 21 periods of eruptive activity had occurred. The volcano remains active, with smaller, dome-building eruptions continuing into 2008. In autumn 2004, Mount St. ...

Eruption on July 22, 1980.
Eruption on July 22, 1980.

An eruption occurred on May 25, 1980 at 2:30 a.m. that sent an ash column 9 miles (14 km) into the atmosphere.[21] The eruption was preceded by a sudden increase in earthquake activity and occurred during a rain storm. Erratic wind from the storm carried ash from the eruption to the south and west, lightly dusting large parts of western Washington and Oregon. Pyroclastic flows exited the northern breach and covered avalanche debris, lahars, and other pyroclastic flows deposited by the May 18 eruption.[21] is the 203rd day of the year (204th 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 145th day of the year (146th 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 138th day of the year (139th in leap years) in the Gregorian calendar. ...


At 7:05 p.m. on June 12, a plume of ash billowed 2.5 miles (4 km) above the volcano. At 9:09 p.m. a much stronger explosion sent an ash column about 10 miles (16 km) skyward.[23] This event caused the Portland area, previously spared by wind direction, to be thinly coated with ash in the middle of the annual Rose Festival.[24] A dacite dome then oozed into existence on the crater floor, growing to a height of 200 feet (60 m) and a width of 1,200 feet (370 m) within a week.[23] is the 163rd day of the year (164th in leap years) in the Gregorian calendar. ... Grey, red, black, altered white/tan, flow-banded pumice dacite Dacite (IPA: ) is an igneous, volcanic rock with a high iron content. ...


A series of large explosions on July 22 broke more than a month of relative quiet. The July eruptive episode was preceded by several days of measurable expansion of the summit area, heightened earthquake activity, and changed emission rates of sulfur dioxide and carbon dioxide. The first hit at 5:14 p.m. as an ash column shot 10 miles (16 km) and was followed by a faster blast at 6:25 p.m. that pushed the ash column above its previous maximum height in just 7.5 minutes.[23] The final explosion started at 7:01 p.m. and continued for over two hours.[23] When the relatively small amount of ash settled over eastern Washington, the dome built in June was gone.[25] is the 203rd day of the year (204th in leap years) in the Gregorian calendar. ... Sulfur dioxide (or Sulphur dioxide) has the chemical formula SO2. ... Carbon dioxide (chemical formula: ) is a chemical compound composed of two oxygen atoms covalently bonded to a single carbon atom. ...

The growing third dome on October 24, 1980.
The growing third dome on October 24, 1980.

Seismic activity and gas emission steadily increased in early August, and on August 7 at 4:26 p.m., an ash cloud slowly expanded 8 miles (13 km) into the sky.[25] Small pyroclastic flows were sent through the northern breach and weaker outpouring of ash rose from the crater. This continued until 10:32 p.m. when a second large blast sent ash high into the air.[25] A second dacite dome filled this vent a few days later. A new dome started growing on October 18,1980. ... A new dome started growing on October 18,1980. ... is the 297th day of the year (298th 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 219th day of the year (220th in leap years) in the Gregorian calendar. ...


Two months of repose were ended by an eruption lasting from October 16 to October 18. This event obliterated the second dome, sent ash 10 miles (16 km) in the air and created small, red-hot pyroclastic flows.[25] A third dome began to form within 30 minutes after the final explosion on October 18, and within a few days, it was about 900 feet (270 m) wide and 130 feet (40 m) high. In spite of the dome growth next to it, a new glacier formed rapidly inside the crater. is the 289th day of the year (290th in leap years) in the Gregorian calendar. ... is the 291st day of the year (292nd in leap years) in the Gregorian calendar. ... Pyroclastic rocks are formed from lavas which are ejected into the air, as occur in pyroclastic flows or Plinian eruptions. ... is the 291st day of the year (292nd in leap years) in the Gregorian calendar. ... 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. ...


All of the post-1980 eruptions were quiet dome-building events, beginning with the December 27, 1980, to January 3, 1981, episode. By 1987 the third dome had grown to be more than 3,000 feet (900 m) wide and 800 feet (240 m) high.[25] At that rate, assuming additional destructive eruptions do not occur, St. Helens' summit would be restored to its previous height sometime in the mid to late 22nd century. December 27 is the 361st day of the year in the Gregorian calendar (362nd in leap years). ... Year 1980 (MCMLXXX) was a leap year starting on Tuesday (link displays the 1980 Gregorian calendar). ... is the 3rd day of the year in the Gregorian calendar. ... AUGUST 25 1981 US Marine Sean Vance is Born on the 25th of August {ear nav|1981}} Year 1981 (MCMLXXXI) was a common year starting on Thursday (link displays the 1981 Gregorian calendar). ...


Further eruptions occurred over a few months during 1989–1991, and the mountain became active again in late 2004.


Summary table

Eruption Summary

May 18, 1980 Eruption of Mount St. Helens

Volcano Elevation of Summit: Before eruption: 9,677 feet (2,950 m)
After eruption: 8,363 feet (2,549 m)
Total removed: 1,314 feet (401 m)
Crater dimensions: East-West: 1.2 miles (1.9 km)
North-South: 1.8 miles (2.9 km)
Depth: 2,084 feet (635 m)
Crater floor elevation: 6,279 feet (1,914 m)
Eruption Date: May 18, 1980
Time of initial blast: 8:32 a.m. Pacific Daylight Time (UTC-7)
Eruption trigger: A magnitude 5.1 earthquake about 1 mile (1.6 km) beneath the volcano
Landslide /
Debris Avalanche
Area covered: 23 square miles (60 km²)
Volume:
(uncompacted deposits)
0.67 mi³ (2.8 km³)
Depth of deposit: Buried North Fork Toutle River to average depth of 150 feet (46 m) with a maximum depth of 600 feet (183 m)
Velocity: 70 miles per hour (113 km/h) to 150 miles per hour (241 km/h)
Lateral Blast Area covered: 230 square miles (596 km²); reached 17 miles (27 km) northwest of the crater
Volume of deposit:
(uncompacted deposits)
0.046 mi³ (0.19 km³)
Depth of deposit: From about 3 feet (1 m) at volcano to less than 1 inch (2.5 cm) at blast edge
Velocity: At least 300 miles per hour (483 km/h)
Temperature: As high as 660 °F (349 °C)
Energy release: 24 megatons thermal energy (7 by blast, rest through release of heat)
Trees blown down: 4 billion board feet (9.4 million m³) of timber (enough to build about 300,000 two-bedroom homes)
Human fatalities: 57
Lahars Velocity: About 10 miles per hour (16 km/h) to 25 miles per hour (40 km/h) and over 50 miles per hour (80 km/h) on steep flanks of volcano
Damaged: 27 bridges, nearly 200 homes. Blast and lahars destroyed more than 185 miles (298 km) of highways and roads and 15 miles (24 km) of railways.
Effects on Cowlitz River: Reduced carrying capacity at flood stage at Castle Rock from 76,000 ft³/s (2,150 m³/s) to less than 15,000 ft³/s (225 m³/s)
Effects on Columbia River: Reduced channel depth from 40 feet (12 m) to 14 feet (4 m); stranded 31 ships in upstream ports
Eruption Column
And Cloud
Height: Reached about 80,000 feet (24,400 m) in less than 15 minutes
Downwind extent: Spread across U.S. in 3 days; circled Earth in 15 days
Volume of ash:
(based on uncompacted deposits
0.26 mi³ (1 km³)
Ash fall area: Detectable amounts of ash covered 22,000 square miles (57,000 km²)
Ash fall depth: 10 inches (25 cm) at 10 miles (16 km) downwind (ash and pumice)
1 inch (2.5 cm) at 60 miles (97 km) downwind
0.5 inches (1.3 cm) at 300 miles (482.8 km) downwind
Pyroclastic Flows Area covered: 6 square miles (16 km²); reached as far as 5 miles (8 km) north of crater
Volume and depth:
(volume based on uncompacted deposits)
0.029 mi³ (0.12 km³); multiple flows 3 feet (1 m) to 30 feet (9 m) thick; cumulative depth of deposits reached 120 feet (37 m) in places
Velocity: Estimated at 50 miles per hour (80 km/h) to 80 miles per hour (130 km/h)
Temperature: At least 1,300 °F (700 °C)
Other Wildlife: The Washington State Department of Game estimated nearly 7,000 big game animals (deer, elk, and bear) perished as well as all birds and most small mammals. Many burrowing rodents, frogs, salamanders, and crawfish, managed to survive because they were below ground level or water surface when the disaster struck.
Fisheries: The Washington Department of Fisheries estimated that 12 million Chinook and Coho salmon fingerlings were killed when hatcheries were destroyed. Another estimated 40,000 young salmon were lost when forced to swim through turbine blades of hydroelectric generators as reservoir levels along the Lewis River were kept low to accommodate possible mudflows and flooding.
Brantley and Myers, 1997, Mount St. Helens -- From the 1980 Eruption to 1996: USGS Fact Sheet 070–97, accessed 2007-06-05; and Tilling, Topinka, and Swanson, 1990, Eruption of Mount St. Helens - Past, Present, and Future: USGS General Interest Publication, accessed 2007-06-05.
Table compiled by Lyn Topinka, USGS/CVO, 1997

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). ... Year 2007 (MMVII) was a common year starting on Monday of the Gregorian calendar in the 21st century. ... is the 156th day of the year (157th 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 156th day of the year (157th in leap years) in the Gregorian calendar. ...

See also

“Cascades” redirects here. ... The Pacific Northwest region of the United States is still geologically active. ... Seconds From Disaster was a documentary television series that investigates the worst man-made disasters and several natural disasters in modern history, and analyses the causes and events that led up to each disaster. ...

Notes

  1. ^ As given by What is a dollar worth?. Federal Reserve Bank of Minneapolis. Retrieved on 2007-09-25.
  2. ^ a b c d e f g h i j k l m n o p q r s t u v w x y z aa ab ac ad ae af ag ah ai aj ak Tilling, Robert I., Topinka, Lyn and Swanson, Donald A. (1990). Eruptions of Mount St. Helens: Past, Present, and Future. The Climactic Eruption of May 18, 1980. U.S. Geological Survey (Special Interest Publication). Retrieved on 2007-06-03.
  3. ^ Gorney, Cynthia. "The Volcano: Full Theater, Stuck Curtain; Hall Packed for Volcano, But the Curtain Is Stuck", The Washington Post, March 30, 1980. 
  4. ^ a b Mount St. Helens Precursory Activity: March 15–21, 1980. United States Geological Survey (2001). Retrieved on 2007-05-26.
  5. ^ a b c d Harris, Fire Mountains of the West (1988), page 202
  6. ^ Ray, Dewey. "Oregon volcano may be warming up for an eruption", Christian Science Monitor, March 27, 1980. 
  7. ^ a b Mount St. Helens Precursory Activity: March 22–28, 1980. United States Geological Survey. Retrieved on 2007-05-26.
  8. ^ a b c Harris, Fire Mountains of the West (1988), page 204
  9. ^ a b c d Harris, Fire Mountains of the West (1988), page 203
  10. ^ Cascades Volcano Observatory USGS Mount St. Helens Precursory Activity
  11. ^ Mount St. Helens Precursory Activity: March 29–April 4, 1980. United States Geological Survey (2001). Retrieved on 2007-05-26.
  12. ^ Mount St. Helens Precursory Activity: April 5–11, 1980. United States Geological Survey (2001). Retrieved on 2007-05-26.
  13. ^ a b Reawakening and Initial Activity. United States Geological Survey (1997). Retrieved on 2007-05-31.
  14. ^ Mount St. Helens Precursory Activity: May 3–9, 1980. United States Geological Survey (2001). Retrieved on 2007-05-26.
  15. ^ a b c Mount St. Helens Precursory Activity: May 10–17, 1980. United States Geological Survey (2001). Retrieved on 2007-05-26.
  16. ^ a b c d e Harris, Fire Mountains of the West (1988), page 205
  17. ^ a b c d e f Harris, Fire Mountains of the West (1988), page 209
  18. ^ a b c d e f Harris, Fire Mountains of the West (1988), page 206
  19. ^ a b c Harris, Fire Mountains of the West (1988), page 208
  20. ^ a b Harris, Fire Mountains of the West (1988), page 210
  21. ^ a b c d e Harris, Fire Mountains of the West (1988), page 211
  22. ^ Painter, John Jr. The 1980s. The Oregonian, December 31, 1989.
  23. ^ a b c d Harris, Fire Mountains of the West (1988), page 212
  24. ^ He Remembers the Year the Mountain Blew (1980). Retrieved on 2008-01-28.
  25. ^ a b c d e Harris, Fire Mountains of the West (1988), page 213

Year 2007 (MMVII) was a common year starting on Monday of the Gregorian calendar in the 21st century. ... is the 268th day of the year (269th 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. ... -1... is the 89th day of the year (90th in leap years) in the Gregorian calendar. ... Year 1980 (MCMLXXX) was a leap year starting on Tuesday (link displays the 1980 Gregorian calendar). ... Year 2007 (MMVII) was a common year starting on Monday of the Gregorian calendar in the 21st century. ... is the 146th day of the year (147th in leap years) in the Gregorian calendar. ... is the 86th day of the year (87th in leap years) in the Gregorian calendar. ... Year 1980 (MCMLXXX) was a leap year starting on Tuesday (link displays the 1980 Gregorian calendar). ... Year 2007 (MMVII) was a common year starting on Monday of the Gregorian calendar in the 21st century. ... is the 146th day of the year (147th in leap years) in the Gregorian calendar. ... The United States Geological Survey (USGS) is a scientific agency of the United States government. ... Year 2007 (MMVII) was a common year starting on Monday of the Gregorian calendar in the 21st century. ... is the 146th day of the year (147th 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 146th day of the year (147th 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 151st day of the year (152nd 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 146th day of the year (147th 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 146th day of the year (147th in leap years) in the Gregorian calendar. ... October 2, 2004 edition. ... is the 365th day of the year (366th in leap years) in the Gregorian calendar. ... Year 1989 (MCMLXXXIX) was a common year starting on Sunday (link displays 1989 Gregorian calendar). ... 2008 (MMVIII) is the current year, a leap year that started on Tuesday of the Anno Domini (or common era), in accordance with the Gregorian calendar. ... is the 28th day of the year in the Gregorian calendar. ...

References

  • Harris, Stephen L. (1988). Fire Mountains of the West: The Cascade and Mono Lake Volcanoes. Missoula: Mountain Press Publishing Company, Missoula. ISBN 0-87842-220-X
  • Tilling, Robert I., Topinka, Lyn and Swanson, Donald A. (1990). Eruptions of Mount St. Helens: Past, Present, and Future. The Climactic Eruption of May 18, 1980. U.S. Geological Survey. (adapted public domain text)
  • Klimasauskas, Ed (2001-05-01). Mount St. Helens Precursory Activity. United States Geological Survey. Retrieved on 2007-06-05.
  • Topinka, Lyn. Mount St. Helens: A General Slide Set, Cascades Volcano Observatory, U.S. Geological Survey. Retrieved on 2007-05-19

This article is about the year. ... is the 121st day of the year (122nd 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 156th day of the year (157th 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 139th day of the year (140th in leap years) in the Gregorian calendar. ...

External links

  • List of victims
  • List of victims with biographical details
  • Mount St. Helens — a virtual tour
  • USGS: Mount St. Helens 1980 Debris Avalanche Deposit
  • USDA Forest Service: Mount St. Helens VolcanoCam
  • Pre-1980 Eruptive History of Mount St. Helens, Washington
  • Video approximation of the first seconds of the May 18th eruption from Gary Rosenquist's photos

Coordinates: 46°12′01″N, 122°11′12″W Map of Earth showing lines of latitude (horizontally) and longitude (vertically), Eckert VI projection; large version (pdf, 1. ...

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). ... For the mountain in California, see Mount Saint Helena. ... 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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