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