Volcano Case Studies Flashcards
What kind of volcano is Mount St Helens?
Composite
How was Mount St. Helens formed?
Subduction between Juan de Fuca and North American plates
When was the initial 4.2 magnitude EQ on Mount St. Helens?
20th March
Mount St. Helens 18th may…
5.1 EQ cause north side of volcano to collapse leading to Avalanche which created lahars. Ash eruption for 9 hours
What did the Mount St. Helens eruption create?
1-2 mile wide, 800m deep crater
How many died in Mount St. Helens?
57
Effect Mount St. Helens had on animals…
7000 game animals killed and 12milkion fish from hatcheries killed. 20,000 acres of forest also destroyed causing loss of habitat
How did Mount St. Helens disrupt travel?
185 miles of road, 15 miles of railway destroyed and 2 day airport closure so 1000s flights cancelled
What year was Mount St. Helens eruption?
1980
Secondary impacts of Mount St. Helens?
Lahars covered large area, ash blocked rivers causing flooding
Economic impacts of Mount St. Helens
Agricultural crops destroyed, ash removal cost $2.2M & total cost $1.1B
Immediate responses warning of eruption
Evacuation of those in blast zone and then evacuation of those in exclusion zone
What did USGS scientists use to predict it would erupt soon?
Seismometers, ground surface measurements, Arian infrared surveys and surface temperature measurements
What date did Nevado del Ruiz erupt?
13th november 1985
What kind of volcano is Nevado del Ruiz?
Composite
How did Nevado del Ruiz form?
Due to subduction of Nazca plate below South American plate
What were the warning signs before the main eruption of NdR?
1984 funerole activity and sulphur deposits on summit. 11/09/95 steam erupted
How were lahars, up to 50m wide, on NdR created?
Pyro clastic flow melted snow and glaciers
Main economic impacts of NdR?
3,490 hectares of agricultural land lost. Cost Colombian government $7.7B
Social impacts of NdR
Roads&communications, 2 hospitals, 50 schools & 58 industrial plants destroyed
What did the large lahars do?
Kill 150,000 animals and swept through Armero killing 23,000 people & injuring 5,000
Short term responses to NdR
80,000 doses of tetanus & typhoid vaccines
5-8 helicopters from Colombian military(lahars made rescue on land hard)
Why did NdR receive less aid than it should have?
Mexico City EQ two weeks before so lots of aid/resources already sent there
Long term responses to NdR…
1986 public education campaign on volcano hazards. Red cross civil aged flyers on hazards&evacuations.
Colombia made plans for warning&evacuating. Evacuation route markers painted on buildings
What was done to prepare for NdR eruption?
Little. Hazard warning maps but no key, some errors and poorly distributed
