Discover and read the best of Twitter Threads about #msh40

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The Cascades run from Northern California up into British Columbia. They’re all fed by the same (very much still-active) geologic priceless.

We monitor the American volcanoes for signs of restlessness.

But in Canada...? Not so much.
I really appreciate all the amazing archival photography, videos, & reports shared on #MSH40, forty years since the last big Cascadia eruption.

But it’s a sharp reminder I live not just on unstable ground, but on young ground. I live not at the foot of mountains, but volcanoes.
On clear days, Mt Baker stands sentinel over Vancouver sunrises.

It’s quiet for now, but depending wind we live within its ashfall radius.

Baker is so close to the border that lahars (superheated mudflows) could snake down river valleys to Abbotsford:…
Read 4 tweets
At 8:32 am Pacific time, May 18, 1980, it happened.

#MountStHelens exploded, producing the largest landslide ever recorded, sending a tower of rock and ash 19 km into the stratosphere, and killing 57.

I've added the Empire State Building to this image for scale.

A thread:
A shallow earthquake caused the entire northern flank of the volcano to slide. The reduced pressure allowed a huge "cryptodome" of hot, pressurised magma inside the volcano to explode—creating a lateral blast that flattened trees for tens of kilometres.
The eruption blasted fragments of volcanic rock and glass, powered by superheated gases, into a huge column (a Plinian eruption) that reached 19 km into the atmosphere; ash blanketed towns 400 km, and some even landed in the Great Plains, 1,500 km away.
Read 8 tweets
Exactly #40YearsAgo Doug Geisler was asleep atop Manastash Ridge Observatory. An astronomy grad student, he’d just logged his first excellent night at the telescope for his PhD thesis.

He was the only person on the summit, ~90 miles from #MountStHelens...

Around this time #40YearsAgo Doug woke up briefly at Manastash Ridge, convinced he’d heard a low boom or distant rumble.

Tired after a night of observing billion-year-old stars, he went back to sleep.

Years later, he told me he dreamed about the end of the world. #MSH40
(it’s hard to say exactly what he heard - it could have been the initial 26 megaton blast or the deafening secondary explosion from the volcano’s superheated material instantly vaporizing nearby bodies of water into steam)

Anyway, back to sleep for the tired astronomer...
Read 17 tweets
May 17, 1980, Mt. St. Helens:

Local property owners threaten to run roadblocks at gunpoint, saying lockdown can't last forever, mountain quieting down, geologists exaggerate

WA Gov relents, allows caravan to Spirit Lake

Second caravan to go morning of May 18th.
Photos show before / after of the lake. Two hours before the May 18th caravan would have arrived, the lakeside houses were first smashed by a nuclear-style blast wave then moments later buried by a 200 foot deep, oven-hot landslide moving more than 100mph
Here's a 2005 article remembering the May 17th "caravan" from a local reporter who went along with the property owners…
Read 6 tweets
40 years ago today, people pushed the state to reopen areas around Mt. St. Helens citing tourism & the economy against advice of scientists. Five days later, the volcano erupted. #msh40
This year, we’re encouraging you to remember the 40th anniversary Mt. St. Helens' eruption inside. The Johnston Ridge Observatory & @WAStatePks visitor center both remain closed. The @MSHInstitute has a huge list of virtual events on its website.…

#msh40 Logo of mt st helens since mt st helens changed our world. 40th anniversary
This @GPNF gallery of high resolution photos of the eruption of Mt. St. Helens available for you to download.…

There's also a list of things to do virtually on the anniversary day of May 18…

#MSH40 A boat on a lake in front of mt st helens, 1980, pre-eruptionMt St Helens explodesDowned trees fill a lake.A car is crushed from downed trees.
Read 3 tweets

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