volcanoes and volcanic hazards

Question 1

what are the causes and processes of volcanoes?

Answer 1

When there is a gap in the earth, this leaves space for ash, gas and lava to erupt.
when there is magma, this rises due to pressure and erupts as lava, cooling to form new rock.
there can be eruptions of only gas and ash as well.

Question 2

where are volcanoes located?

Answer 2

normally located along plate boundaries, e.g. the Pacific Ring of Fire
less commonly located in hotspots where Earth’s crust is weaker, e.g. Hawaiian Islands

Question 3

characteristics of a volcano?

Answer 3

1. magma chamber
2. the crater
3. layers of rock and ash
4. secondary vents
5. lava flow
6. ash cloud
7. main vent
8. secondary cone

Question 4

what is pyroclastic flow?
- example

Answer 4

caused by explosive eruptions and crater collapse, it’s made of ash, gas, bombs and lapilli, which move at high speeds (300km/h)
e.g. Pompeii

Question 5

what are lahars/mudflow?
- example

Answer 5

when the rain loosens tephra, causing ash, hot rocks, and lapilli to get into waterways, causing flooding and can flow very fast.
e.g. Mount Pinitabu 1981

Question 6

what is lava flow?

Answer 6

when the lava from the volcano flows slowly, posing little threat to life but can cause fires and travel 100km away from the source.
speed depends on the temperature

Question 7

what is an ash cloud?

Answer 7

rock fragments mix with solidified lava fragments in the air.
can be carried far away from the source (the smaller, the further)
disrupts the function of machinery (water, power, sewage, comms)
damages vehicles and aircraft
causes road and rail blockages
irritant to the skin
toxic/fatal to humans and animals
crop failure
decrease in global temperature
e.g. 2008 Chile, an ash cloud blew 1,000km to Argentina

Question 8

what are the volcanic gases?
- example

Answer 8

includes: carbon dioxide/monoxide, sulfur dioxide and HCL
can cause long-term disease and starvation, and acid rain
toxic to humans and animals causing serious health issues
1700 people were asphyxiated, 1986 Cameroon

Question 9

what is Jokulhaup?
- example

Answer 9

translated to glacial run or burst when the glacier melts due to hot magma, causing extreme flooding.
e.g. in Iceland

Question 10

what is tephra?

Answer 10

the collective term for all the airborne and ground-flowing material from volcanoes, which are classified by size:
- bombs: greater than 64mm diameter
- lapilli: 2-6mm diameter
- ash: under 2mm diameter