when was the last time mount saint helens erupted
Mount St. Helens With the recent volcanic activity starting in 2004, the glacier lobes were pushed aside and upward by the growth of new volcanic domes. The surface of the glacier, once mostly without crevasses, turned into a chaotic jumble of icefalls heavily criss-crossed with crevasses and seracs caused by movement of the crater floor.[15] 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 a slight advance on the western lobe and a more considerable advance on the more shaded eastern lobe. Due to the advance, two lobes of the glacier joined together in late May 2008 and thus the glacier completely surrounds the lava domes.[15][16][17] In addition, since 2004, new glaciers have formed on the crater wall above Crater Glacier feeding rock and ice onto its surface below; there are two rock glaciers to the north of the eastern lobe of Crater Glacier.[18] Crater Glacier is the only known advancing glacier in the contiguous United States.[19]
1980 eruption of Mount St. Helens The May 18, 1980, event was the most deadly and economically destructive volcanic eruption in the history of the United States.[6] Approximately fifty-seven people were killed directly from the blast and 200 houses, 47 bridges, 15 miles (24 km) of railways and 185 miles (298 km) of highway were destroyed; two people were killed indirectly in accidents that resulted from poor visibility, and two more suffered fatal heart attacks from shoveling ash.[29] U.S. President Jimmy Carter surveyed the damage and said it looked more desolate than a moonscape.[30][31] A film crew was dropped by helicopter on Mount St. Helens on May 23 to document the destruction. However, their compasses spun in circles and they quickly became lost.[32] A second eruption occurred the next day (see below), but the crew survived and were rescued two days after that. The eruption ejected more than 1 cubic mile (4.2 km3) of material.[33] A quarter of that volume was fresh lava in the form of ash, pumice and volcanic bombs while the rest was fragmented, older rock.[33] The removal of the north side of the mountain (13% of the cone's volume) reduced Mount St. Helens' height by about 1,280 feet (390 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.[33]
1980 eruption of Mount St. Helens Suddenly, at 8:32 a.m., a magnitude 5.1 earthquake centered directly below the north slope triggered that part of the volcano to slide,[24] approximately 7–20 seconds (about 10 seconds seems most reasonable) after the shock.[6] The landslide, the largest in recorded history, travelled at 110 to 155 miles per hour (177 to 249 km/h) and moved across Spirit Lake's west arm. Part of it hit a 1,150-foot-high (350 m) ridge about 6 miles (10 km) north.[6] 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.[24] 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).[6]
Mount St. Helens Mount St. Helens is most notorious for its major 1980 eruption, the deadliest and most economically destructive volcanic event in the history of the United States.[2] Fifty-seven people were killed; 250 homes, 47 bridges, 15 miles (24 km) of railways, and 185 miles (298 km) of highway were destroyed. A massive debris avalanche triggered by an earthquake measuring 5.1 on the Richter scale caused an eruption[3] that reduced the elevation of the mountain's summit from 9,677 ft (2,950 m) to 8,363 ft (2,549 m), leaving a 1 mile (1.6 km) wide horseshoe-shaped crater.[4] The debris avalanche was up to 0.7 cubic miles (2.9 km3) in volume. The Mount St. Helens National Volcanic Monument was created to preserve the volcano and allow for its aftermath to be scientifically studied.