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On Sunday, May 18, 1980 at 8:32 a.m., the bulging north flank of Mount St. Helens slid away in a massive landslide -- the largest in recorded history. Seconds later, the uncorked volcano exploded and blasted rocks northward across forest ridges and valleys, destroying everything in its path within minutes.
Nine hours of explosive volcanic activity ensued, altering the landscape, and what we know about volcanoes, forever.
The opening minutes of the eruption claimed the lives of 57 people. Prevailing winds carried 520 million tons of ash eastward across the United States, producing darkness during daylight hours in Spokane, more than 250 miles away, and other communities is its path. Water from melting snow and ice mixed with loose rock debris to form lahars – volcanic mudflows – that poured down river valleys ripping trees from their roots and engulfing roads, bridges and houses.
Thirty years later, excess sediment is still moving down those river drainages most affected by erupted debris on May 18, impressing upon all that hazards can persist long after an eruption is over. The eruption left an indelible effect on the regional economy and lives of citizens in the Pacific Northwest and beyond.
“The spectacular nature of the May 18, 1980 eruption is one of those unforgettable time markers for anyone who lived through the effects of the eruption or saw the images through the media,” said Carolyn Driedger, hydrologist and outreach specialists at the Cascades Volcano Observatory. “Thirty years later, people still want to tell you where they were and what they experienced when Mount St. Helens blew. In the Pacific Northwest and around the world, people awoke to the idea of what it meant to live near an active volcano.”
The eruption of Mount St. Helens -- the most destructive eruption in U.S. history -- was the first large explosive eruption in the United States since the advent of modern volcanology. It was a catalyst for an era of unprecedented scientific discovery, monitoring development and community awareness.
The volcano instantly became, and remains, a volcanologist’s ideal laboratory. Its accessibility has allowed scientists to return to the volcano over and over again to examine new deposits before they eroded away, to test new concepts about how volcanoes work, and to try out new tools. The landslide exposed the inside the mountain affording scientists with an unprecedented opportunity to inspect a volcano’s interior, and learn about its history from the inside out.
“Since the numerous eruptions of Mount St. Helens in the 1980s, volcano monitoring has come a long way,” said Seth Moran, an earthquake specialist at CVO. “In many locations, we’ve essentially gone from having a few instruments placed on a volcano’s flanks to having a broad network of earthquake and deformation monitoring devices feeding us information 24/7. While we’re not able to do this on every volcano, where we can, these instruments have given volcanologists unprecedented access to what’s really happening on a volcano, and help greatly in predicting the nature of future activity.”
Quote from : Wikipedia : Mount St. Helens
Mount St. Helens is an active stratovolcano located in Skamania County, Washington, in the Pacific Northwest region of the United States.
It is 96 miles (154 km) south of Seattle and 50 miles (80 km) northeast of Portland, Oregon. Mount St. Helens takes its English name from the British diplomat Lord St Helens, a friend of explorer George Vancouver who made a survey of the area in the late 18th century.
The volcano is located in the Cascade Range and is part of the Cascade Volcanic Arc, a segment of the Pacific Ring of Fire that includes over 160 active volcanoes.
This volcano is well known for its ash explosions and pyroclastic flows.
Mount St. Helens is most famous for its catastrophic eruption on May 18, 1980, at 8:32 am PDT which was the deadliest and most economically destructive volcanic event in the history of the United States.
Fifty-seven people were killed; 250 homes, 47 bridges, 15 miles (24 km) of railways, and 185 miles (298 km) of highway were destroyed.
The eruption caused a massive debris avalanche, reducing the elevation of the mountain's summit from 9,677 ft (2,950 m) to 8,365 ft (2,550 m) and replacing it with a 1 mile (1.6 km) wide horseshoe-shaped crater.
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.
As with most other volcanoes in the Cascade Range, Mount St. Helens is a large eruptive cone consisting of lava rock interlayered with ash, pumice, and other deposits.
The mountain includes layers of basalt and andesite through which several domes of dacite lava have erupted.
The largest of the dacite domes formed the previous summit, and off its northern flank sat the smaller Goat Rocks dome. Both were destroyed in the 1980 eruption.
Originally posted by LadySkadi
Respect to the Mountain and Mama Nature...