Mt. St. Helens

david johnston

-felt scientists must do what is necessary (including taking risks) to help protect the public from natural disasters -his work convinced authorities to close Mt. St. Helens to the public before the 1980 eruption -died in eruption

within _____ seconds the volcanoes northern slope collapses and the largest ______ in history occurs

10 landslide

Casualties from the eruption happened all the way out to what distance from the volcano?

13 miles

How much of the total height (in feet) of Mt. St. Helens was blasted away by the eruption?

1300

landslide took _____ of summit

1300 feet

for how many miles did ash incinerate trees

200 square miles

what mag earthquake

5.1

The video stated that the bed of Spirit Lake was lifted more than 200 vertical feet. What is the most likely explanation for this observation?

Volcanic ash and debris from the eruption filled the bottom of the lake thus displacing a large volume of water.

scientists began surveying what in the area of impact by the eruption almost immediately

biology and geology

_____ from many species dissapeared

birds deer elk insects

area of destruction name

blast (blowdown) zone

The north slope of Mt. St. Helens is also known as the ____________________?

blast zone

Mt. St. Helens is a volcano located in what mountain range?

cascades

pumice plane is directly below the

crater

What caused the landslide that preceded the eruption of Mt. St. Helens?

earthquake

what causes a landslide

earthquake

it erupted ______ bc it has a _____ silica content

explosively; high

_______ began to recover almost immediately; some communities began to _______ only a year after the eruption

flora and fauna thrive

Biodiversity _____ after the eruption

increased

why is the landslide important to understanding the events of this eruption

large pressure drop bc huge mountain is removed off magma chamber which made gas release pressure drives volcanic eruptions

virtually all ____ is extinguished; ___ people are dead- some are up to ____ miles away in areas considered safe

life 57 13

if magma is flowing easily, silica content is probably

low

eruption date

may 18, 1980

example of a volcano getting a caldera

mt pelée

geologists gained valuable insights about the ______ the led up to eruptions like Mt. St. Helens as well as a better understanding of the _____ of volcanic eruptions

precursors power

near the crater, ash and rocks from land slide litter northern slope of mountain... called

pumice plane

_____ races over surrounding countryside

pyroclastic flow

eruption was so powerful it altered the ____ of the mountain: _____ to _____

shape typical cone shape (stratovolcano) gaping wide hole on top

aftermath of eruption: similarities and differences between the 2 images

similarities: lahars follow the rivers differences: rainier is much taller and has many more and larger towns

4 miles below the sumit a large _____ is choked with debris affect on it

spirit lake avalance lifted its bed more than 200 ft