Volcanic hazards

Question 1

Where do Volcanic Hazards usually occur?

Answer 1

Near Plate Margins

• Constructive
• Destructive
• Few volcanoes at hot spots above magma plumes

Question 2

Volcanic Hazards at Constructive Plate Margins?

Answer 2

• Basaltic Lava, hot, low viscosity, flow easily.
• Eruptions are frequent, long lasting, not very violent
• If margin underwater, form Ocean Ridges
• If on land, plates pull apart, Rift Valleys.

Question 3

Volcanic Hazards at Destructive Margins?

Answer 3

• Andesitic and Rhyolitic Lava, cooler, more viscous, flow less frequently.
• Eruptions usually intermittent and short lasting
• At subduction zones, violent volcanic eruptions.

Question 4

Types of Volcanic Hazards?

Answer 4

PRIMARY:

• Pyroclastic flow
• Lava flow
• Volcanic gases
• Pyroclastic and Ash fallout

SECONDARY:

• Mudflows
• Acid Rain

Question 5

Pyroclastic Flow?

Answer 5

Super-heated gas, ash and volcanic rock.

Flow around +80kmh, long way 10-15km

Question 6

Lava Flows?

Answer 6

Speed and distance travelled depend on temperature and viscosity of lava.
Most flows relatively slow, but destroy anything in their path.

Question 7

How is the Magnitude of Volcanoes measured?

Answer 7

Volcanic Explosivity Index

grades volcanoes on a scale of 0-8 based on the amount of material ejected and how high the material is blasted.

Question 8

Primary impacts can be?

Answer 8

Social
Environmental
Economic
Political

Question 9

What are the three main long term responses?

Answer 9

Prevention - Prevent hazard posing a risk
Preparedness - Before eruption to minimise risk and vulnerability
Adaptation - Changing behaviour or surroundings to minimise the risks and maximise benefits of living near a volcano.

Question 10

When did Monserrat erupt?

Answer 10

June - September 1997

Largest eruption 4-5 million m3 of material was released over a 20 minute period.

Question 11

Where is Monserrat located?

Answer 11

Small island in the Caribbean Sea. It is on a destructive plate margin, where the North American plate is being forced under the Caribbean plate.

Question 12

Economic impacts of Monserrat?

Answer 12

• Total loss in value to homes, investment around £1 billion.
• 20+ villages and 2/3s of homes destroyed by pyroclastic flow.
• Lack of tourist income. But now it is on the rise again.
• Schools, hospitals, airport and dock destroyed

Question 13

Social impacts of Monserrat?

Answer 13

• 19 died, several injured
• Hundreds lost their homes
• Fires destroyed many buildings
• Population decline, 8000 of the islands 12 000 inhabitants left.

Question 14

Environmental impacts of Monserrat?

Answer 14

• Large areas covered in volcanic material
• Vegetation and farmland destroyed
• Volcanic ash from eruption has improved soil fertility

Question 15

Short-term responses of Monserrat?

Answer 15

• people evacuated from south to north
• shelters built to house evacuees
• temporary infrastructure built
• UK provided £17 million in emergency aid
• local emergency services provided search and resue support units

Question 16

Long-term responses of Monserrat?

Answer 16

• risk map created and exclusion zone was put in place.
• UK has provided £41 million in long term aid
• Monserrat Volcanic Observatory set up to attempt to predict future eruptions.