With May 18th approaching fast, my locality once again remembers the 1980 eruption of Mt. St. Helens. This volcanic event had massive ramifications on global flight and climate due to the huge ash cloud. The eruption claimed less than 60 lives due to the efforts of the USGS resisting public urges to reopen the area for recreational activities as they were monitoring the warning signs. A bigger factor in the low death toll was the fact that the volcano erupted laterally, out the northern slope rather than straight upward. This directed the eruption towards miles of forest and wilderness rather than the Portland metro area, home to about 2 million people. But what if the eruption aimed south? In a worse timeline, the lateral eruption aimed directly at Portland, unleashing searing hot glassy ash at the major city and its surrounding suburban sattelite cities. Vancouver, WA, would be eviscerated.
What if Mt. St. Helens "blew the other way"?
- Thread starter Cascadia-97
- Start date
Here is the same map, but with the eruption pattern flipped so that it faces south, rather than north. The explosion is centered on the existing crater, and to scale.
The destruction still happens in wilderness areas. In this scenario, the mud flows would have run down the Lewis River system, which looks to be a series of dam controlled reservoirs, rather than down the Green and Toutle River systems to the north that happened OTL. The town of Woodland Washington, population 6500, is just upstream of where the Lewis River meets the Columbia. In this ATL scenario Woodland is about the same location relative to the mudflows in this scenario that Castle Rock was in relation to the OTL eruption. The USGS site says:
Castle Rock, population 2500, was not harmed by the OTL 1980 eruption, but was in peril from the new geography of Spirit Lake created by the eruption. The Lake was filled by material from the eruption, and there was concern that the natural dam holding back the new lake could collapse and cause a flood downstream. This was enough of a concern that the Army Corps of Engineers drilled a 1.6 mile outflow tunnel through the natural dam to defuse the possible collapse.
Would the reservoirs on the Lewis River contain these ATL mud flows? Or would the dams be overtopped or burst and cause a catastrophic flood on Woodland Washington? I don't know.
In any case, no apocalyptic event would happen to metropolitan Portland, unless the eruption was orders of magnitude stronger.
www.seattletimes.com
The destruction still happens in wilderness areas. In this scenario, the mud flows would have run down the Lewis River system, which looks to be a series of dam controlled reservoirs, rather than down the Green and Toutle River systems to the north that happened OTL. The town of Woodland Washington, population 6500, is just upstream of where the Lewis River meets the Columbia. In this ATL scenario Woodland is about the same location relative to the mudflows in this scenario that Castle Rock was in relation to the OTL eruption. The USGS site says:
Castle Rock, population 2500, was not harmed by the OTL 1980 eruption, but was in peril from the new geography of Spirit Lake created by the eruption. The Lake was filled by material from the eruption, and there was concern that the natural dam holding back the new lake could collapse and cause a flood downstream. This was enough of a concern that the Army Corps of Engineers drilled a 1.6 mile outflow tunnel through the natural dam to defuse the possible collapse.
Would the reservoirs on the Lewis River contain these ATL mud flows? Or would the dams be overtopped or burst and cause a catastrophic flood on Woodland Washington? I don't know.
In any case, no apocalyptic event would happen to metropolitan Portland, unless the eruption was orders of magnitude stronger.
St. Helens sand turns from bane to boon, 35 years after eruption
Volcanic sands from the 1980 blast and landslide keep giving. The massive mound that resulted has fed the small town’s development of parks, trails, baseball diamonds and more.
www.seattletimes.com
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