lecture 11

Question 1

cascade continental arc

Answer 1

stretches from northern california to washington/BC border, been active for half a million years

Question 2

mount st helens history

Answer 2

grown within past 1000 years

smith creek, dormant, pine creek, dormant, castle creek, dormant, sugar bowl, dormant, kalama, goat rocks

Question 3

earthquake swarm

Answer 3

many earthquakes of same size, characteristics of fluid moving below the surface
MT st helens started mid march 1980 which first indicated renewed unrest of volcano

Question 4

18th may 1980 eruption

Answer 4

a Mw 5 earthquake and major ladnslide collapsed into unstable north vlank which released pressure- leading to a lateral blast that blew the north side of mountain out triggering pyroclastic flows which drove formation of verticle plume
(reduction of pressure causes volatiles to form bubbles and drives explosion of volcano)

Question 5

lahars at Mt st helens

Answer 5

exacerbated by ice acp and snow on top

Question 6

victims of MSH

Answer 6

majority were killed by the blast

killed 57 people

Question 7

ash fall out MSH

Answer 7

ash was dispersed over 60,000km highways were closed for 2 weeks and 1,000 flights cancelled

Question 8

mount rainier

Answer 8

set up system of accoustic flow moniters (seismographs) to record shaking of ground in high frequencies and listen to sound of lahar
- data telemertered to a control centre and alarm rasied

Question 9

glacier peak eruption history

Answer 9

15,000: multiple large tephra eruptions, dome collapses, laharas large enough to reach the sea
5,000: multiple small tephra eruptions, dome collapses, lahars enough to reach the sea
4,000-present: dome collapses, laharas x3, small steam eruptions

Question 10

timeline for mount baker eruptions (holocene)

Answer 10

12,000 years ago to present

multiple lava/pyroclastic flows and ash eruptions, collapse, lahar, collapse, lahar, increased steam and heat