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84-476: Ape Canyon is a gorge along the edge of the Plains of Abraham, on the southeast shoulder of Mount St. Helens in the U.S. state of Washington . The gorge narrows to as close as eight feet (2.5 m) at one point. The name alludes to a legend about a 1924 encounter with "apemen" which was later incorporated into Bigfoot folklore. Ape Canyon was heavily impacted by the 1980 eruption of Mount St. Helens . Adjacent to

168-418: A lava spine nicknamed the "whaleback", which comprised long shafts of solidified magma being extruded by the pressure of magma beneath. These features were fragile and broke down soon after they were 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. Mount St. Helens showed significant activity on March 8, 2005, when

252-407: A magnitude  5.1 earthquake, caused a lateral eruption that reduced the elevation of the mountain's summit from 9,677 to 8,363 ft (2,950 to 2,549 m), leaving a 1 mile (1.6 km) wide horseshoe-shaped crater. The debris avalanche was 0.6 cubic miles (2.5 km ) in volume. The 1980 eruption disrupted terrestrial ecosystems near the volcano. By contrast, aquatic ecosystems in

336-533: A 30-year permit from the U.S. Forest service, the upgrades are projected to cost $ 35 million. As of 2023 , the beginning phases of the project has raised 20% of its projected $ 10 million, including a $ 900,000 donation from a foundation run by the Cowlitz Indian Tribe . After the South Coldwater Slide in 2023, the center was outfitted with exhibits and other facilities as a temporary alternative to

420-400: A 36,000-foot (11,000 m) plume of steam and ash emerged—visible from Seattle . This relatively minor eruption was a release of pressure consistent with ongoing dome building. The release was accompanied by a magnitude 2.5 earthquake. Another feature to emerge from the dome was called the "fin" or "slab". Approximately half the size of a football field, the large, cooled volcanic rock

504-425: A car. The eruption's lateral blast narrowly missed the site as it was deflected by a ridge just west of the meadow. In an interview with KIRO-TV in 1990, a friend called that ridge "the line of death." Windy Ridge is the closest view point accessible to the general public. Beginning in summer 1983, visitors have been able to drive to Windy Ridge, on U.S. Forest Service Road 99, only 4 miles (6.4 km) northeast of

588-685: A combination of weather, elevation, and issues with the terrain, the highway and access to the observatory would be closed until 2026. The USFS and the United States Geological Survey (USGS) disclosed that the site is without electricity and that the observatory may not open until spring 2027. The Coldwater Ridge Visitor Center in the Coldwater Lake area opened in 1993, operated by the Forest Service, but closed in November 2007 due to

672-496: A crater 1.2 to 1.8 miles (2 to 3 km) wide and 2,084 feet (635 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. It destroyed or extensively damaged more than 200 homes, 185 miles (298 km) of highway , and 15 miles (24 km) of railways . Between 1980 and 1986, activity continued at Mount St. Helens, with

756-646: A friend of explorer George Vancouver who surveyed the area in the late 18th century. The volcano is part of the Cascade Volcanic Arc , a segment of the Pacific Ring of Fire . The Mount St. Helens major eruption of May 18, 1980 , remains the deadliest and most economically destructive volcanic event in U.S. history. Fifty-seven people were killed; 200 homes, 47 bridges, 15 miles (24 km) of railways, and 185 miles (298 km) of highway were destroyed. A massive debris avalanche , triggered by

840-407: A gradual extrusion of lava forming a dome in the crater. On January 16, 2008, steam began seeping from a fracture on top of the lava dome. Associated seismic activity was the most noteworthy since 2004. Scientists suspended activities in the crater and the mountain flanks, but the risk of a major eruption was deemed low. By the end of January, the eruption paused; no more lava was being extruded from

924-506: A lack of funding. The grounds were reopened in 2011 for limited use, providing educational programs and events to the public. The center reopened as the Science and Learning Center at Coldwater (SLC) in May 2013, operating as an educational facility and conference center in cooperation with the nonprofit Mount St. Helens Institute. It was open to the public on weekends from 10am to 6pm, though many of

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1008-509: 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, sometimes huge clouds of ash. 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

1092-456: A process known as subduction in geology. As the oceanic slab sinks deeper into the Earth's interior beneath the continental plate, high temperatures and pressures allow water molecules locked in the minerals of solid rock to escape. The supercritical water rises into the pliable mantle above the subducting plate, causing some of the mantle to melt. This newly formed magma ascends upward through

1176-522: A rifle at one of the animals, he struck it three times, and saw the wounded animal topple off a cliff into an inaccessible canyon. The ape men supposedly returned later to bombard their cabin with large stones and leave giant footprints. The story caused a local sensation, prompting U.S. Forest Service rangers J.H. Huffman and William Welch to investigate. Huffman and Welch descended into the supposedly "inaccessible canyon" but found nothing. They demonstrated how 14 inches (36 cm) long footprints found near

1260-402: 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 in late May 2008 and thus the glacier completely surrounds the lava domes. 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

1344-566: A small hypersthene-homblende dacite dome on the east slope of the volcano, was likely formed around the Sugar Bowl period. Formation of East Dome was preceded by an explosive eruption. Roughly 700 years of dormancy were broken in about 1480, when large amounts of pale gray dacite pumice and ash started to erupt, beginning the Kalama period. The 1480 eruption was several times larger than that of May 18, 1980. In 1482, another large eruption rivaling

1428-447: A theater, a gift shop and outdoor trails. By the end of 1989, the center had hosted more than 1.5 million visitors and in 2007, approximately 300,000 guests were recorded. The 16,000 square feet (1,500 m ) space underwent its first upgrade in 2024, which included artworks, displays, and exhibits expanding on the history and connection of the Cowlitz Indian Tribe to the mountain and surrounding lands. The Johnston Ridge Observatory

1512-543: Is 140 inches (360 cm), and the snowpack on the mountain's upper slopes can reach 16 feet (4.9 m). 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. Although Mount St. Helens is in Skamania County, Washington, access routes to

1596-414: Is 52 miles (84 km) east of Castle Rock, Washington , at the end of Washington State Route 504 , four miles from the mountain. Open daily mid-May through October, exhibits focus on the geologic history of the volcano, eyewitness accounts of the explosion, and the science of monitoring volcanic activity. Two movies and ranger-led programs are available every hour. A half-mile paved trail provides views of

1680-528: Is a popular hiking spot and it is climbed year-round. In 1982, the Mount St. Helens National Volcanic Monument was established by President Ronald Reagan and the U.S. Congress . Mount St. Helens is 34 miles (55 km) west of Mount Adams , in the western part of the Cascade Range. Considered "brother and sister" mountains, the two volcanoes are approximately 50 miles (80 km) from Mount Rainier ,

1764-474: Is an alpine meadow and viewpoint northeast of Mt. St. Helens. It is located on U.S. Forest Service Road 99. Gary Rosenquist camped here with friends on May 17–18, 1980. He started taking his famous eruption photographs from this location. The sequence of eruption photos provide a time-lapse view of the developing eruption . As the lateral blast developed, he and his friends abandoned their campsite fearing for their lives. He continued taking photos as they escaped in

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1848-575: Is at an elevation of 4,400 feet (1,300 m) on the northeastern side and 4,000 feet (1,200 m) elsewhere. At the pre-eruption tree line , the width of the cone was 4 miles (6.4 km). 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

1932-418: 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). St. Helens started its growth in

2016-595: Is considered the most active in the Cascades within the Holocene epoch, which encompasses roughly the last 10,000 years. 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, by some, " Fuji-san of America". Its ice cover just prior to

2100-716: Is likely on branches of the Toutle River , possibly causing destruction in inhabited areas along the I-5 corridor. In its undisturbed state, the slopes of Mount St. Helens lie in the Western Cascades Montane Highlands ecoregion. This ecoregion has abundant precipitation; an average of 93.4 inches (2,373 mm) of precipitation falls each year at Spirit Lake . This precipitation supported dense forest up to 5,200 feet (1,600 m), with western hemlock , Douglas fir , and western redcedar . Above this, this forest

2184-527: The Columbia River from the Far North in search for a suitable area to settle. 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

2268-623: The Pleistocene 37,600 years ago, during the Ape Canyon stage, with dacite and andesite eruptions of hot pumice and ash. Thirty-six thousand years ago a large mudflow cascaded down the volcano; 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 14,000–18,000 years ago during

2352-526: 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. During the winter of 1980–1981, a new glacier appeared. Now officially named Crater Glacier , it

2436-751: The Yn tephra . This eruptive period lasted until about 1600 BC and left 18 inches (46 cm) deep deposits of material 50 miles (80 km) distant in what is now Mount Rainier National Park . Trace deposits have been found as far northeast as Banff National Park in Alberta , and as far southeast as eastern Oregon . All told there may have been up to 2.5 cubic miles (10 km ) of material ejected in this cycle. Some 400 years of dormancy followed. St. Helens came alive again around 1200 BC—the Pine Creek eruptive period. This lasted until about 800 BC and

2520-499: The lava dome, crater , pumice plain, and landslide deposit, with access to hiking trails in the restricted area. The observatory is located near the site of volcanologist David A. Johnston 's camp on the morning of May 18, 1980, and was opened in 1997. On May 14, 2023, access to the observatory was barred due to the 2023 South Coldwater Slide , a landslide that destroyed a bridge on Washington State Route 504 . A team composed of U.S. Forest Service staff and volunteers hiked to

2604-493: The 1980 eruption in volume is known to have occurred. Ash and pumice piled 6 miles (9.7 km) northeast of the volcano to a thickness of 3 feet (0.9 m); 50 miles (80 km) away, the ash was 2 inches (5 cm) deep. Large pyroclastic flows and mudflows subsequently rushed down St. Helens' west flanks and into the Kalama River drainage system. This 150-year period next saw the eruption of less silica -rich lava in

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2688-463: The 1980 eruption included eleven named glaciers: Wishbone, Loowit, Leschi, Forsyth, Nelson, Ape, Shoestring, Swift, Dryer, Toutle, and Talus. Of these eleven, only the Shoestring Glacier revived somewhat post-eruption. The peak rose more than 5,000 feet (1,500 m) above its base, where the lower flanks merge with adjacent ridges. The mountain is 6 miles (9.7 km) across at its base, which

2772-560: The Johnston Ridge Observatory while cleanup and repairs were underway. By 2024, students participating in educational adventures held by the SLC could camp overnight in the building. The Winds of Change Trail #232, a short, barrier-free interpretive trail, departs from the Science and Learning Center. The southern and eastern sides of Mount St. Helens are accessible only by U.S. Forest Service roads. The main roads are: Bear Meadows

2856-782: The Klickitats as Louwala-Clough, which means "smoking or fire mountain" in their language (the Sahaptin call the mountain Loowit). The mountain is also of sacred importance to the Cowlitz and Yakama tribes that also live in the area. They find the area above its tree line to be of exceptional spiritual significance, and the mountain (which they call "Lawetlat'la", roughly translated as "the smoker") features prominently in their creation story, and in some of their songs and rituals. In recognition of its cultural significance, over 12,000 acres (4,900 ha) of

2940-534: The United States' largest slave rebellion . ) The vent was apparently at or near Goat Rocks on the northeast flank. Goat Rocks dome was near 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. On March 20, 1980, Mount St. Helens experienced a magnitude  4.2 earthquake , and on March 27, steam venting started. By

3024-436: The area greatly benefited from the amounts of ash, allowing life to multiply rapidly. Six years after the eruption, most lakes in the area had returned to their normal state. After its 1980 eruption, the volcano experienced continuous volcanic activity until 2008 . Geologists predict that future eruptions will be more destructive, as the configuration of the lava domes requires more pressure to erupt. However, Mount St. Helens

3108-545: The atmosphere. On the Volcanic Explosivity Index scale, the eruption was rated a 5, and categorized as a Plinian eruption . 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 3,900,000 cubic yards (3,000,000 m ) of material

3192-545: The beginning of the 57 year-long Goat Rocks Eruptive Period (see geology section ). Alarmed by the "dry snow", the Nespelem tribe of northeastern Washington supposedly danced and prayed rather than collecting food and suffered during that winter from starvation. Mount St. Helens National Volcanic Monument At dedication ceremonies on May 18, 1983, Max Peterson, head of the USFS, said, "we can take pride in having preserved

3276-492: The building to retrieve scientific items and supplies so that work to observe the volcano, as well as the continuation of services for visitors, could proceed at the Coldwater Science and Learning Center. Another landslide a month later would affect access to Windy Ridge. In early 2024, Washington State Department of Transportation (WSDOT) announced that because of cost and a limited construction schedule for repairs due to

3360-552: The cabin could easily be faked, and concluded the miners probably placed large stones near the cabin themselves to bolster their tale. Despite the story being debunked by the rangers, "people still wanted to believe", and the prospectors' story was repeated and continued to spread in later years, inspiring new theories and claims of new sightings. 46°12′05″N 122°06′24″W  /  46.201358°N 122.106633°W  / 46.201358; -122.106633 Mount St. Helens Mount St. Helens (known as Lawetlat'la to

3444-458: The composition of St. Helens' lava, with the addition of olivine and basalt . 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

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3528-477: 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 1831 eruption is likely what tinted the sun bluish-green in Southampton County, Virginia on the afternoon of August 13—which Nat Turner interpreted as a final signal to launch

3612-667: The continental United States and the third longest (in total mapped length) lava tube in North America at 2.5 miles (4,023 meters). The cave was formed approximately 1,900 years ago, is situated at an average depth of 50 feet below ground, and the air temperature remains a constant 42 degrees throughout the year. Lava tubes are an unusual formation in this region, as volcanoes of the Cascade Range are mostly stratovolcanos and do not typically erupt with pahoehoe (fluid basalt). Two competing mentions of its discovery exist. The cave

3696-468: The countryside with tephra . Swift Creek ended 8,000 years ago. A dormancy of about 4,000 years was broken around 2500 BC 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 BC was the largest known eruption from St. Helens during the Holocene epoch, depositing

3780-502: The crater. From this vantage point overlooking Spirit Lake , people see not only the evidence of a volcano's destruction, but also the remarkable, gradual (but faster than originally predicted) recovery of the land as revegetation proceeds and wildlife returns. Ape Cave is a lava tube located in Gifford Pinchot National Forest just to the south of Mount St. Helens. Its passageway is the longest continuous lava tube in

3864-434: The crust along a path of least resistance, both by way of fractures and faults as well as by melting wall rocks. The addition of melted crust changes the geochemical composition. Some of the melt rises toward the Earth's surface to erupt, forming the Cascade Volcanic Arc above the subduction zone. The magma from the mantle has accumulated in two chambers below the volcano: one approximately 3–7 miles (5–12 km) below

3948-433: The disturbance. These biological legacies highly influence the reestablishment of the post-disturbance ecology. Some species from each trophic level survived the 1980 eruption, which allowed for relatively quick re-establishment of food webs . Larger species saw greater mortality rates, with each of the area's large mammals — mountain goats, elk, deer, black bear and cougars — completely decimated. Eventually, each of

4032-544: The end of April, the north side of the mountain had started to bulge. On May 18, a second earthquake, of magnitude 5.1, triggered a massive collapse of the north face of the mountain. It was the largest known debris avalanche in recorded history. The magma in St. Helens burst forth into a large-scale pyroclastic flow that flattened vegetation and buildings over an area of 230 square miles (600 km ). More than 1.5 million metric tons of sulfur dioxide were released into

4116-534: The eruption and because the eruption did not sterilize the immediate area. More than half of the papers on ecological response to volcanic eruption originated from studies of Mount St. Helens. Perhaps the most important ecological concept originating from the study of Mount St. Helens is the biological legacy . Biological legacies are the survivors of catastrophic disturbance; they can either be alive (e.g., plants that survive ashfall or pyroclastic flow), organic debris, or biotic patterns remaining from before

4200-483: The exhibits were removed, the gift shop, theatre, and some signage remained. The campus was closed during the Covid-19 pandemic , though it was available for educational residential visits, and reopened to weekend visits in 2022 and normal visitation in 2023. A proposed expansion of the SLC would include space for an amphitheater, overnight camping, an outdoor school, improved hiking trails, and timber lodges. Starting from

4284-434: The forest, as the treeline was thought to be moving up the slopes before the eruption. Alpine meadows were uncommon at Mount St. Helens. Mountain goats inhabited higher elevations of the peak, although their population was eliminated by the 1980 eruption. The eruption of Mount St. Helens has been subject to more ecological study than has any other eruption, because research into disturbance commenced immediately after

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4368-471: The form of andesitic ash that formed at least eight alternating light- and dark-colored layers. Blocky andesite lava then flowed from St. Helens' summit crater down the volcano's southeast flank. 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 (~200 m) high at the volcano's summit, which filled and overtopped an explosion crater already at

4452-458: The growth of new volcanic domes. The surface of the glacier, once mostly without crevasses, turned into a chaotic jumble of icefalls heavily criss-crossed with crevasses and seracs caused by movement of the crater floor. The new domes have almost separated the Crater Glacier into an eastern and western lobe. Despite the volcanic activity, the termini of the glacier have still advanced, with

4536-503: The highest of the Cascade volcanoes. Mount Hood , the nearest major volcanic peak in Oregon , is 60 miles (100 km) southeast of Mount St. Helens. Mount St. Helens is geologically young compared with the other major Cascade volcanoes. It formed only within the past 40,000 years, and the summit cone present before its 1980 eruption began rising about 2,200 years ago. The volcano

4620-513: The huge bridge fell into the river, creating the cascades of the Columbia River Gorge . For punishment, the chief of the gods 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 beautiful Loowit became Mount St. Helens, known to

4704-423: The ice had an average thickness of 300 feet (100 m) and a maximum of 650 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. From 2004, volcanic activity pushed aside the glacier lobes and upward by

4788-460: The larger mammals migrated back into the area. Without access to adequate forage, many elk starved to death in the winters in the following decades. By 2014, the mountain goat population had grown back to 65 members. In 2015, there were 152. Mountain goats are culturally significant to the Cowlitz Tribe, whose members historically harvested shed tufts of goat wool left behind on the mountain, and

4872-547: The last glacial period of the current ice age . The second eruptive period, the Cougar Stage, started 20,000 years ago and lasted for 2,000 years. 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

4956-604: The lava dome sent an ash plume 2,000 feet (600 m) over the western rim of the crater; the ash plume then rapidly dissipated. 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 did not mention any significant ash plume. The volcano was in continuous eruption from October 2004, but this eruption consisted in large part of

5040-532: The lava dome. On July 10, 2008, it was determined that the eruption had ended, after more than six months of no volcanic activity. Future eruptions of Mount St. Helens will likely be even larger than the 1980 eruption. The current configuration of lava domes in the crater means that much more pressure will be required for the next eruption, and hence the level of destruction will be higher. Significant ashfall may spread over 40,000 square miles (100,000 km ), disrupting transportation. A large lahar flow

5124-660: The local Cowlitz people , and Loowit or Louwala-Clough to the Klickitat ) is an active stratovolcano located in Skamania County, Washington , in the Pacific Northwest region of the United States. It lies 52 miles (83 km) northeast of Portland, Oregon , and 98 miles (158 km) south of Seattle . Mount St. Helens takes its English name from that of the British diplomat Alleyne Fitzherbert, 1st Baron St Helens ,

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5208-411: The monument), opened in 1987 by then- Vice President George H.W. Bush . The center was formerly operated by the U.S. Forest Service and has been operated by Washington State Parks since October 2007. Exhibits include the area's culture and history, and the natural history and geology of the volcano and the eruption, including the recovery of the area's vegetation and animal life. The Center includes

5292-686: The mountain (roughly bounded by the Loowit Trail) have been listed on the National Register of Historic Places . Other area tribal names for the mountain include "nšh'ák'w" ("water coming out") from the Upper Chehalis , and "aka akn" ("snow mountain"), a Kiksht term. Royal Navy Commander George Vancouver and the officers of HMS Discovery made the Europeans' first recorded sighting of Mount St. Helens on 19 May 1792, while surveying

5376-528: The mountain run through Cowlitz County to the west, and Lewis County to the north. State Route 504 , locally known as the Spirit Lake Memorial Highway , connects with Interstate 5 at Exit 49, 34 miles (55 km) to the west of the mountain. That north–south highway skirts the low-lying cities of Castle Rock , Longview and Kelso along the Cowlitz River , and passes through

5460-413: The natural disaster. Beginning in 1983, visitors have been able to drive to Windy Ridge , only 4 miles (6.4 km) northeast of the crater. Mountain climbing to the summit of the volcano has been allowed since 1986 and requires a permit. The Mount St. Helens Visitor Center at Silver Lake, about 30 miles (48 km) west of Mount St. Helens and five miles (8 km) east of Interstate 5 (outside

5544-663: The north of the eastern lobe of Crater Glacier. Mount St. Helens has an alpine tundra climate ( ET ). Mount St. Helens is part of the Cascades Volcanic Province , an arc-shaped band extending from southwestern British Columbia to Northern California , roughly parallel to the Pacific coastline. Beneath the Cascade Volcanic Province, a dense oceanic plate sinks beneath the North American Plate ;

5628-546: The northern Pacific Ocean coast. Vancouver named the mountain for British diplomat Alleyne Fitzherbert, 1st Baron St Helens on 20 October 1792, as it came into view when the Discovery passed into the mouth of the Columbia River. 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

5712-506: The same for the arrow to the south. The chief of the gods then built the Bridge of the Gods, so his family could meet periodically. When the two sons of the chief of the gods 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

5796-409: The steep rocky canyon is the present Ape Canyon trail, popular with hikers and mountain bikers. On the south side of the mountain is another feature named Ape Cave . In the summer of 1924, a group of gold prospectors claimed that 7 feet (2.1 m) tall ape-like animals attacked them with boulders. According to their tale, they came across the animals in the wilderness, and when one of the group fired

5880-431: The summit. 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, in about 1647. The volcano remained quiet for the next 150 years. The 57-year eruptive period that started in 1800

5964-495: The surface, the other about 7–25 miles (12–40 km). The lower chamber may be shared with Mount Adams and the Indian Heaven volcanic field. The early eruptive stages of Mount St. Helens are known as the "Ape Canyon Stage" (around 40,000–35,000 years ago), the "Cougar Stage" (ca. 20,000–18,000 years ago), and the "Swift Creek Stage" (roughly 13,000–8,000 years ago). The modern period, since about 2500 BC,

6048-498: The tribe has played a role in monitoring the population, which continues to recover without human intervention. Native American lore contains numerous stories to explain the eruptions of Mount St. Helens and other Cascade volcanoes. The best known of these is the Bridge of the Gods story told by the Klickitat people . In the story, the chief of all the gods and his two sons, Pahto (also called Klickitat) and Wy'east, traveled down

6132-464: The unique episode of natural history for future generations." Since then, many trails, viewpoints, information stations, campgrounds, and picnic areas have been established to accommodate the increasing number of visitors each year. Due to the eruption, the state recognizes the month of May as "Volcano Awareness Month" and events are held at Mount St. Helens, or within the region, to discuss the eruption, safety concerns, and to commemorate lives lost during

6216-405: 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 and ejected more than 0.67 cubic miles (2.79 km ) of material. The removal of the north side of the mountain reduced St. Helens' height by about 1,300 feet (400 m) and left

6300-533: The year 100 BC that traveled all the way into the Lewis and Kalama river valleys. Others, such as Cave Basalt (known for its system of lava tubes ), flowed up to 9 miles (14 km) from their vents. 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 Sugar Bowl eruptive period

6384-480: Was being forced upward as quickly as 6 ft (2 m) per day. 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 (2,300 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

6468-404: 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 (64 km) of the Lewis River valley sometime between 1000 BC and 500 BC. The next eruptive period, the Castle Creek period, began about 400 BC, and is characterized by a change in

6552-416: Was discovered in 1947 by a logger who almost fell into the system while operating a tractor. Another account mentions a discovery around 1951 by Lawrence Johnson, also a logger, when he noticed a tree that "looked wrong." After investigating the tree, he discovered it tilted into a lava tube collapse. A few days later, Johnson brought a group of other people back to the cave, and an individual named Harry Reese

6636-432: Was dominated by Pacific silver fir up to 4,300 feet (1,300 m). Finally, below treeline , the forest consisted of mountain hemlock , Pacific silver fir and Alaska yellow cedar . Large mammals included Roosevelt elk , black-tailed deer , American black bear , and mountain lion . The treeline at Mount St. Helens was unusually low, at about 4,400 feet (1,340 m), the result of prior volcanic disturbance of

6720-493: Was formerly known as the Tulutson Glacier. Shadowed by the crater walls and fed by heavy snowfall and repeated snow avalanches, it grew rapidly (14 feet (4.3 m) per year in thickness). By 2004, it covered about 0.36 square miles (0.93 km ), 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,

6804-451: Was lowered to the floor and became the first known person to explore the interior. The cave system takes its moniker from a local Boy Scout troop, named the Mount St. Helens Apes, who undertook subsequent explorations of the tube after its discovery. Ape Cave is a popular hiking destination with beautiful views of the Mount St. Helens lahar region. Ape Cave Trail No. 239, which runs along

6888-462: Was named after the Goat Rocks dome and is the first period for which both oral and written records exist. As with 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 rivaled the 1980 eruption in size, although it did not result in massive destruction of

6972-423: 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. 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. East Dome,

7056-496: Was transported 17 miles (27 km) south into the Columbia River by the mudflows. For more than nine hours, a vigorous plume of ash erupted, eventually reaching 12 to 16 miles (19 to 26 km) above sea level. The plume moved eastward at an average speed of 60 miles per hour (100 km/h) with ash reaching Idaho by noon. Ashes from the eruption were found on top of cars and roofs the next morning as far away as Edmonton , Alberta, Canada. By about 5:30 p.m. on May 18,

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