Volcanjc Hazards Flashcards
Where does volcanic activity occur? (4)
Ocean ridges
Subduction zones
Rift valleys
Hotspots
Why is volcanic activity found at ocean ridges
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
Why is volcanic activity found at subduction zones
Plate melts into magma
Magma is less dense than surroundings to rises up forms volcanos
Why is volcanic activity found at rift valleys
Area of crust drops to form rift valleys
crust is thin so starts to split
Magma forces its way to surface
Why is volcanic activity found at hotspots
Localised thermal currents occur when plume rises and burns through crust causing a volcano
What is the volcanic explosively index
Logarithmic scale 0-8 to measure magnitude of volcano
0 quiet
8 collosal
What are the primary impacts of volcanic activity? 4
Tephra
Nuees ardendes
Lava flows
Volcanic gases
What are the secondary impacts of volcanic activity
Lahars Flooding Acid rain Tsunamis Climatic change
When do volcanic evens become hazardous?
When they impact upon people and the environment
What is tephra?
Solid material ejected into the atmosphere e.g. Ash
What is nuees Ardentes?
Pyrocrastic flows
High velocity flows of mixed gas and tephra
Name some volcanic gases?
Carbon dioxide
Carbon monoxide
Sulphur dioxide
What are lahars?
Mud flows
Melted snow and ice mixed with ash to form mud
How does acid rain occur after volcanic activity?
Sulphur is emitted which combines with atmospheric moisture
Name a volcanic event and when it occurs
Monseratt 95-97
Primary impacts of your volcanic event
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
Secondary responses of event
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
Primary responses of event
5000 people evacuated to safe zone in. North away from Plymouth
Links with UK provides relief and recovery
Exclusion zone set up in south
Secondary responses of event
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
Management of event
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
