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The eruption was preceded by a two-month series of earthquakes and steam-venting episodes, caused by an injection of magma at shallow depth below the volcano that created a huge bulge and a fracture system on Mount St. Helens' north slope. An earthquake at 8:32:17 a.m. on May 18, 1980 caused the entire weakened north face to slide away, suddenly exposing the partly molten, gas- and steam-rich rock in the volcano to lower pressure. The rock responded by exploding a hot mix of lava and pulverized older rock toward Spirit Lake so quickly that it overtook the avalanching north face.

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βˆ™ 14y ago
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βˆ™ 14y ago

Mt. St. Helens erupted because the molten lava was producing gases and since there wasn't anywhere for the gas to escape pressure just kept building up until the pressure became to great for the mountain top to hold and it exploded.

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βˆ™ 13y ago

Mt. St. Helens was formed by a series of volcanic eruptions over millions of years.

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Q: How was Mount Saint Helens formed?
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Related questions

How was mount saint helens built?

it was formed not built :) :) :) :)


What plate boundary formed the land features of Mount Saint Helens?

Convergent


Which country is mount saint Helens in?

Mount Saint Helens is located in the United States, specifically in the state of Washington.


Is Mount saint Helens in Washington?

Yes. Mount Saint Helens is located in Washington.


Where is Mount Saint Helens found in?

mount baker,mount rainier and mount hood surround mount saint helens


What olate is mount saint helens situated on?

Mount Saint Helens is situated within the Gifford Pinchot National Forest. The olate that Mount Saint Helens is situated is called the subduction zone.


What volcano is close to mount saint Helens?

Mount Saint Helens is the valcano. It's pretty close to itself.


Is mount Saint Helens east of Mount Rainier?

No. Mount St. Helens is south-southwest of Mount Ranier.


Is mount St Helens in New Hampshire?

No. Mount Saint Helens is in Washington state.


Which mountain erupted in 1980 in Washington US?

Mount St. Helens is a active volcano, in the Washington State.


What did mount saint helens do?

erupted


Is mount saint Helens part of an island chain?

No. Mount Helens is on the mainland of North America.