Volcanic case studies
Mount St Helens 1980
Mount St Helens is on the plate boundary between the Juan de Fuca plate and North American plate. When it erupted it permanently changed the surrounding landscape.
Effects of the eruption
Primary effects Secondary effects
Nuée ardente (hot ash and gas) destroyed forests and logging camps.
63 people were killed, mainly by poisonous gases.
Lahars (mudflows of ash and water) covered an extensive area surrounding the volcano. Ash blocked rivers destroying popular fishing sites and causing flooding. This in turn destroyed crops and livestock.
Flooding destroyed communications such as road and railway bridges.
Sediment carried downstream ruined barge transport on the Columbia River.
Short-term responses and results
• Communications such as roads and bridges were repaired.
• People were rehoused.
Long-term responses and results
• Soil fertility improved due to the ash deposits.
• The volcano is now more carefully monitored.
• Tourism has increased, boosting the local economy.
Case study: Chances Peak, Montserrat, 1995-97 - an LEDC
Before 1995 it had been dormant for over 300 years. In 1995 the volcano began to give off warning signs of an eruption (small earthquakes and eruptions of dust and ash). Once Chances Peak had woken up it then remained active for five years. The most intense eruptions occurred in 1997.
During this time, Montserrat was devastated by pyroclastic flows. Volcanic eruptions and lahars have destroyed large areas of Montserrat. The capital, Plymouth, has been covered in layers of ash and mud. Many homes and buildings have been destroyed, including the only hospital, the airport and many roads.
Short-term responses and results
• Evacuation.
• Abandonment of the capital city.
• The British government gave money for compensation and redevelopment.
• Unemployment rose due to the collapse of the tourist industry.
Long-term responses and results
• An exclusion zone was set up in the
Mount St Helens is on the plate boundary between the Juan de Fuca plate and North American plate. When it erupted it permanently changed the surrounding landscape.
Effects of the eruption
Primary effects Secondary effects
Nuée ardente (hot ash and gas) destroyed forests and logging camps.
63 people were killed, mainly by poisonous gases.
Lahars (mudflows of ash and water) covered an extensive area surrounding the volcano. Ash blocked rivers destroying popular fishing sites and causing flooding. This in turn destroyed crops and livestock.
Flooding destroyed communications such as road and railway bridges.
Sediment carried downstream ruined barge transport on the Columbia River.
Short-term responses and results
• Communications such as roads and bridges were repaired.
• People were rehoused.
Long-term responses and results
• Soil fertility improved due to the ash deposits.
• The volcano is now more carefully monitored.
• Tourism has increased, boosting the local economy.
Case study: Chances Peak, Montserrat, 1995-97 - an LEDC
Before 1995 it had been dormant for over 300 years. In 1995 the volcano began to give off warning signs of an eruption (small earthquakes and eruptions of dust and ash). Once Chances Peak had woken up it then remained active for five years. The most intense eruptions occurred in 1997.
During this time, Montserrat was devastated by pyroclastic flows. Volcanic eruptions and lahars have destroyed large areas of Montserrat. The capital, Plymouth, has been covered in layers of ash and mud. Many homes and buildings have been destroyed, including the only hospital, the airport and many roads.
Short-term responses and results
• Evacuation.
• Abandonment of the capital city.
• The British government gave money for compensation and redevelopment.
• Unemployment rose due to the collapse of the tourist industry.
Long-term responses and results
• An exclusion zone was set up in the