Volcanjc Hazards

Question 1

Where does volcanic activity occur? (4)

Answer 1

Ocean ridges
Subduction zones
Rift valleys
Hotspots

Question 2

Why is volcanic activity found at ocean ridges

Answer 2

Plates love apart and magma is forced to the surface
It cools and forms new crust
New crust is carried away with sea floor spearing forming volcanos

Question 3

Why is volcanic activity found at subduction zones

Answer 3

Plate melts into magma

Magma is less dense than surroundings to rises up forms volcanos

Question 4

Why is volcanic activity found at rift valleys

Answer 4

Area of crust drops to form rift valleys
crust is thin so starts to split
Magma forces its way to surface

Question 5

Why is volcanic activity found at hotspots

Answer 5

Localised thermal currents occur when plume rises and burns through crust causing a volcano

Question 6

What is the volcanic explosively index

Answer 6

Logarithmic scale 0-8 to measure magnitude of volcano
0 quiet
8 collosal

Question 7

What are the primary impacts of volcanic activity? 4

Answer 7

Tephra
Nuees ardendes
Lava flows
Volcanic gases

Question 8

What are the secondary impacts of volcanic activity

Answer 8

Lahars 
Flooding 
Acid rain 
Tsunamis 
Climatic change

Question 9

When do volcanic evens become hazardous?

Answer 9

When they impact upon people and the environment

Question 10

What is tephra?

Answer 10

Solid material ejected into the atmosphere e.g. Ash

Question 11

What is nuees Ardentes?

Answer 11

Pyrocrastic flows

High velocity flows of mixed gas and tephra

Question 12

Name some volcanic gases?

Answer 12

Carbon dioxide
Carbon monoxide
Sulphur dioxide

Question 13

What are lahars?

Answer 13

Mud flows

Melted snow and ice mixed with ash to form mud

Question 14

How does acid rain occur after volcanic activity?

Answer 14

Sulphur is emitted which combines with atmospheric moisture

Question 15

Name a volcanic event and when it occurs

Answer 15

Monseratt 95-97

Question 16

Primary impacts of your volcanic event

Answer 16

2/3 of island covered in ash
19 people died
50% of population evacuated to the north
Floods as valleys were blocked with ash
Airport and port were closed
Farmland was destroyed
Forest fires were caused as of pyrocrastic flows

Question 17

Secondary responses of event

Answer 17

Airport and port remain closed

Tourist industry suffering
Population dropped from 12000 to 5000
Economy decimated and very high levels of unemployment as the island relied on tourism
Volcanic tourism

Question 18

Primary responses of event

Answer 18

5000 people evacuated to safe zone in. North away from Plymouth

Links with UK provides relief and recovery
Exclusion zone set up in south

Question 19

Secondary responses of event

Answer 19

Volcanic observatory built to monitor volcano
New roads and new airport built
Services in the north expanded
Tourism in the volcano
Out migration , people were granted full residency rights in the U.K.
U.K. Sent 41 million relief aid and a further 75m for long term development

Question 20

Management of event

Answer 20

Residents urged to stay tuned to radio Montserrat

Plymouth and whole of south remains an exclusion zone

Three year development plan by U.K. For reconstruction of houses schools and a new capital

Geologists regularly fly into the most dangerous areas to sample new flow deposits and measure cracks caused by the volcano swelling