Mount St Helens

Question 1

Primary social impacts

Answer 1

• 57 people died
• David Johnston
• planes grounded

Question 2

Primary environmental impacts

Answer 2

• caused the biggest volcanic landslide in history
• trees were uprooted
• Pyroclastic flow destroyed all with no remains found
• 27km wipeout zone
• ash and debris fell killing wildlife and destroying habitats
• 12% of crops were destroyed

Question 3

Primary economic impacts

Answer 3

• fruit trees were badly effected on top of the 12% of crops around Mt St Helens

Question 4

Primary political impacts

Answer 4

• state of emergency declared

Question 5

Positive impacts

Answer 5

• 2 million tourists
• soil fertility increased
• heat generating geothermal-energy

Question 6

Secondary environmental impacts

Answer 6

• ash clogged air
• 14/32 known small mammals survived
• created lahars
• 7000 big animals were killed
• Toutle river now experience high sedimentation rates
• causing frequent flood events

Question 7

Secondary economic impacts

Answer 7

• Deadliest and most economically destructive volcanic event in the history of the united states.
• over 250 bits of infrastructure was destroyed
• economic cost of $800 million
• second biggest cost was that of the clean up operation- $250 million

Question 8

Secondary social impacts

Answer 8

• over 200 homes, 27 bridges, 185 miles of road and 15 miles of railway was destroyed

Question 9

Nature of hazard

Answer 9

• Destructive subduction plate margin, Juan de Fuca plate beneath North American
• Eruption in 1980 was caused by a lava dome developing from a secondary vent on the side of the volcano
• Eruption started with earthquake of 5 on the Richter scale
• VEI = 5

Question 10

Case study

Answer 10

• Washington state, USA
• Erupted May 18, 1980
• Andesitic lava, lateral blast
• GDP = $16.77 trillion
• State = $311.3 billion
• Stage in DTM = 4
• Active stratovolcano

Question 11

Immediate responses

Answer 11

• Army helicopters mobilised to search and rescue those in the catastrophic blast.
• Rescuing survivors was a priority, followed by emergency treatment in nearby towns.
• Air conditioning systems were cleaned after by clogged with ash and blocked roads were cleared.
• Two million masks were ordered to protect people’s lungs.
• All planes across north america were grounded
• 27km exclusive zone setup
• Camera crews flock to the foot of the volcano
• National Guard issued clean water, emergency food rations and medical supplies
• Ash was cleared from towns such as Yakima within 3 days

Question 12

Long term responses

Answer 12

• Buildings and bridges were rebuilt.
• Drains had to be cleared to prevent flooding. The forest which was damaged had to be replanted by the forest service.
• Roads were rebuilt to allow tourists to visit.
• Mount St. Helens is now a major tourist attraction with many visitor centres.
• Toutle river cleared in following weeks from all debris
• 10 million trees replanted
• Bridges rebuilt with a wider span to avoid blockages from future lahars

Question 13

Management

Answer 13

• United States Geological Survey (USGS) now closely monitor the volcano, Tiltmeters and seismographs monitor magma and lava dome
• Cleat plans have been made to prepare and warn people in the area beyond the immediate blast zone to make them aware of the risks of ash clouds

Question 14

Volcano facts

Answer 14

• Area is subject to frequent earth movements, long history of volcanic activity
• One of the youngest volcanoes in the region - 2500 years old
• Area has been volcanically active for 40,000 years