Volcanic Hazards

Question 1

Where would you find a volcano?

Answer 1

Along oceanic ridges.
On or near subduction zones.
Associated with rift valleys.
Over hot spots.

Question 2

What type of volcano would you find at an oceanic ridge?

Answer 2

Gentle sides because of the low viscosity of the basaltic lava, frequent but gentle eruptions (effusive)
E.g. Eyjafjallajokull

Question 3

What type of volcano would you find at a subduction zone?

Answer 3

Andesitic lava - viscous - high silica content

Composite and explosive volcanoes

Question 4

What type of volcano would you find at a hot spot?

Answer 4

Basaltic lava - viscous, slow

Shield volcano

Question 5

How would you measure the magnitude of a volcanic eruption?

Answer 5

The volcanic explosivity index, runs from 0-8

Question 6

What are the primary effects of volcanic eruptions?

Answer 6

Tephra
Pyroclastic flow
Lava flows
Volcanic gases

Question 7

What is tephra?

Answer 7

Solid material of varying grain size from volcanic bombs to ash, ejected into the atmosphere

Question 8

What are pyroclastic flows?

Answer 8

Over 800 degrees Celsius, high velosity flows made up of gas and tephra. Usually hug the ground and flow down the sides of a volcano, with speeds up to 700 km/h

Question 9

What are volcanic gases?

Answer 9

Carbon dioxide, carbon monoxide, hydrogen sulphide, sulphur dioxide and chlorine

Question 10

What are the secondary effects of volcanic eruptions?

Answer 10

Lahars
Flooding
Volcanic landslides
Tsunamis
Acid rain
Climactic change

Question 11

What is a lahar?

Answer 11

Melted snow and ice combined with volcanic ash, forms mud flows that can move down valleys at high speeds.

Question 12

Why do volcanic eruptions cause flooding?

Answer 12

Melted glaciers and ice caps from volcanic eruptions result in serious flooding.

Question 13

What is acid rain?

Answer 13

Volcanoes emit gases that contain sulphur, when this combines with atmospheric moisture it causes acid rain.

Question 14

How is prediction done in terms of managing a volcanic hazard?

Answer 14

Studying previous eruption history and the type of activity produced.
Monitoring land swelling.
Changes in groundwater levels.
Chemical composition of groundwater and gas emissions.
Monitoring seismic activity.

Question 15

How is protection done in terms of managing a volcanic hazard?

Answer 15

Identifying a time when the area should be evacuated.
Digging trenches.
Diverting from the built environment.
Identifying areas at greatest risk and land-use planning
Dropping blocks into the lava stream
Using explosives
Pouring sea water to solidify

Question 16

What landform was 2002 Mt Nyragongo associated with?

Answer 16

The African rift valley

Question 17

What was the risk/vulnrability of 2002 Mt Nyragongo?

Answer 17

Fertile organic soils have encouraged large numbers of people to settle there for agricultural work.
The lava is slow flowing so it was not a large threat to people in the past.
People are very vulnerable to the carbon dioxide coming out of the ground around the volcano

Question 18

What were the major effects of the eruption of 2002 Mt Nyragongo?

Answer 18

Lava flows destroyed at least one third of Goma
The commercial centre was destroyed
Lava covered the northern third of the runway at the airport
Around 150 deaths, mostly from poisonous gases, collapsed buildings and contaminated water
350,000 fled
Lava entered Lake Kivu and contaminated drinking water
Several earthquakes accompanied one 5+ on the richter scale

Question 19

What were the responses to the 2002 eruption of Mt Nyragongo?

Answer 19

UN sent humanitarian aid
Emergency rations
UN set up camps to house people
Cost $15m to provide food, shelter, clean water, sanitation and healthcare

Question 20

What were the effects of the 2010 Eyjafjallajokull eruption?

Answer 20

Huge amounts of ice melted causing floods - 1,000 people had to be evacuated
Large quantities of ash were picked up by the jet stream which was blown towards Europe, resulting in European countries shutting down their air spaces - costing £130m per day for six days

Question 21

What was the risk and vulnerability of the 2010 Eyjafjallajokull eruption?

Answer 21

Little risk to people’s lives because it was very remote.

Major threat was to travel due to the ash.