Volcanic Hazards

Question 1

formation of a volcano

Answer 1

plates subducts
friction causes plate to melt into magma
this is less dense so rises
breaks through crust to form volcano

Question 2

types of volcanic hazard

Answer 2

primary
- lava flow
- gas
- ash fallout
- pyroclastic flow
- tephra

secondary
- lahars
- acid rain

Question 3

pyroclastic flow

Answer 3

explosion of ash, has and volcanic rock that flow down side of volcano

• high speeds - 200m/s
• long way - up to 15km
• little warning

eg Mount Pelee

Question 4

lava flow

Answer 4

flow of Laval from vets
distance depends on
- viscosity
- steepness of volcano

often slower so people can evacuate
but very destructive, cause fires

Question 5

volcanic gases

Answer 5

releases CO2 and sulphur dioxide
into atmosphere

can be harmful to humans and animals if inhaled

eg Mammouth Lakes, California
CO2 released causing suffocation

Question 6

ash fallout

Answer 6

tephra and material ejected in eruptions fall back down
large pieces fall closer

larger can damage buildings and people
smaller particles can travel thousands of kilometres, damage agriculture and hinders transport

eg Eyjafjalllajokull

Question 7

nuees ardentes

Answer 7

dense, rapid moving clouds of hot gases, ash
a type of pyroclastic flow
- denser so doesn’t move as far

eg Mount Pelee

Question 8

tephra

Answer 8

solid material ejected in an eruption
larger pieces fall closer

eg Pompeii

Question 9

lahars

Answer 9

when volcanic material mixes with water from rainfall or ice melt
- moves fast, over 80km/h
- travel far, tens of km

bury or destroy habitats and infrastructure

eg Nevado del Ruiz, Colombia

Question 10

acid rain

Answer 10

volcanic gases can react with water vapour
fall as acid rain
damages ecosystems and can erode metal

Question 11

primary impacts

Answer 11

social
- death
- collapse of infrastructure

environmental
- ecosystems damaged

economic
- businesses destroyed
- agriculture damaged

Question 12

secondary impacts

Answer 12

fires caused by lava
- destroy ecosystems and buildings

lahars
- bury buildings and ecosystems

flooding from ice melts

food shortages due to damage

Question 13

short term responses

Answer 13

evacuation
emergency food supplies

Question 14

long term responses

Answer 14

designed to reduce impacts for future

monitoring
reconstruction - buildings strengthened
barriers to divert flow
preparation

Question 15

volcanic form on constructive margins

Answer 15

plates moving apart

• basaltic lava
• runny, less viscous, lower in silica
• less violent eruptions
• more frequent
• mainly lava

Question 16

volcanic form on destructive margins

Answer 16

plates moving towards

• acidic lava
• vicious, higher in silica
• potentially explosive
• less frequent
• tephra and pyroclastic flow

Question 17

adaptation

Answer 17

buildings strengthened
- reduce risk of collapse under ash

capitalise on opportunities
- farming on fertile soils
- tourism

Question 18

prevention

Answer 18

not possible
but risk can be reduced

• evacuation, using prediction
• land use zoning, not developing in at risk areas

Question 19

mitigation

Answer 19

reduce severity

monitoring
- allows prediction and evacuation

emergency shelters and supplies
- save lives

barriers to divert flows away from populated areas
eg Iceland, 4m walls

Question 20

preparedness

Answer 20

monitoring systems
- allow prediction
- monitor gases and seismic activity

evacuation plans

emergency shelters and supplies

Question 21

distribution

Answer 21

90% as plate boundaries
other caused by magma plumes
- vertical commons or extra hot magma
- rises and breaks through crust

Question 22

magnitude

Answer 22

measured on VEI scale
1-8 on destruction

Criticised, Only measures tephra

Question 23

frequency

Answer 23

depends of type of margin

constructive - more frequent, can be continuous

destructive - less frequent

Question 24

predictability

Answer 24

monitored
gases and seismic activity measured

can be predicted
- allows of evacuation

eg Iceland, 30 minute warning

Question 25

regularity

Answer 25

unpredictable

can erupt regularly
or can be dormant or many years

Question 26

Primary vs secondary impacts

Answer 26

Pyroclastic flow worse primary - hardest to avoid, move fast and far

Secondary worse
Lahars
- Nevada Del Ruiz

Flooding
Tsunamis

Effect climate
- Mount Pinatubo eruption reduced global temperatures by 1c