Volcanic Hazards

Question 1

What shows frequency and predictability of a volcanic eruption?

Answer 1

• volcanoes erupting andesitic lava do so very infrequently

• volcanoes erupting basaltic lava do very frequently/continuously

• vulcanologists measure seismic activity and ground deformations

• changes in CO2 and SO2 signify an imminent eruption

Question 2

Describe pyroclastic flow

Answer 2

• mix of hot rock, lava, ash and gases

• more common with andesitic lava

• often occur at subduction zones

• move at around 200m/s

• can travel large distances

• temperatures of 350C - 1000C

Question 3

What are the impacts of pyroclastic flow?

Answer 3

• knocks down, buried or carries away any object or structure in its path

• extreme temperatures of rocks and gases can ignite fires

• ice and snow melt due to extreme temperatures

• risk of serious burns

• can cause floods and lahars

Question 4

Describe a Nuee Ardente

Answer 4

• Means ‘glowing cloud’

• contain more dense material

• are normally only found 50km from source

Question 5

Describe tephra

Answer 5

• rock fragments ejected during an eruption

• large fragments land close to source

• small fragments (ash) can travel great distance

• ash can cause breathing difficulties, block sunlight and alter temperatures

Question 6

What are tephra and Nuee Ardente impacts?

Answer 6

• damage to crops

• can cause health problems to humans and animals

• endangers aviation and infrastructure

• can interrupt communication equipment

Question 7

Describe mudflows/lahars

Answer 7

• ash and volcanic material mix with water

• commonly occurs in glaciated areas due to rapid melting of ice

• flows at speeds up to 60km/h

• can be highly erosive

• will engulf anything they pass over

Question 8

What are the impacts of mudflows and Nuee Ardente?

Answer 8

• crushes, abrades and buries or carries away anything in it path

• can melt snow and ice

• destroys bridges

• can silt up river causing future flooding events

• can cause flooring

• can trap people in hazardous areas

Question 9

Describe lava flow

Answer 9

• lava flows down the side of a volcano

• low viscosity lava travels at 10km/h and may cover hundreds of kilometres

• slow flow rate allows for evacuation

• will destroy anything it passes over

Question 10

What are the impacts of lava flow?

Answer 10

• knocks over, surrounds, buries or ignites anything in its path

• can trigger a lahar

• can cause water to evaporate immediately create in a molten shower

• can cause methane gas to build (from vegetation), creating explosions.

Question 11

Describe gases and acid rain

Answer 11

• CO2 and SO2 are released upon eruption

• can cause breathing difficulties and harm wildfire

• gas reacts with water vapour creating acid rain

• damages ecosystems and infrastructure

Question 12

What are the impacts of gases and acid rain?

Answer 12

• acid rain can poison water

• gases can cause headaches, dizziness and difficulty breathing as well as irritants

• gases can cause death

• gas can gather in hollows (due to density) creating an unseen hazard

• gases can create aerosols in the atmosphere that cool the Earth