T 1.5 - 1.9

Question 1

Physical processes that volcanoes cause

Answer 1

• lava flows
• pyroclastic flows
• ash falls
• gas eruptions
• secondary hazards - lahars, jökulhlaup

Question 2

What are lava flows and how are they caused?

Answer 2

• molten magma on the earths surface is so hot, it flows
• viscosity determined by the amount of silicon dioxide
• buildings can be burnt and covered if it is running
• 1977: lake wall collapsed and lava drained in 1 hr, across 9km, swallowing villages while people were asleep

Question 3

Gas steam emissions from volcanic eruptions:

Answer 3

• h20 vapour: rainfall events, then potentially lahars
• steam escapes though geysers
• so2 forms very fine particles that get into the stratosphere, also causes acid rain which corrodes buildings and affects vegetation
• fluorine gas is poisonous in high conc. and contaminated farmland or water supply

Question 4

What are pyroclastic flows and how are they caused?

Answer 4

• frothing bubbles of molten magma in the vent, burst explosively to eject a dense mixture of hot gases and pyroclastic material, eg glass, pumice, ash
• can reach temperatures of up to a 1000
• move rapidly down side of volcano up to 700km/h
• leave behind volcanic deposits ( can dam rivers)

Question 5

How are ash falls caused and what are they?

Answer 5

• carried into the atmosphere, potentially even trans boundary
• most fall locally, causing roofs to collapse, breathing difficulties for people and animals, bury crops
• disrupts flights paths of planes

Question 6

How are lahars caused and what are they?

Answer 6

• water mixed with volcanic deposits, flowing rapidly along existing valleys
• could be caused by heavy rain, or maybe volcanic ash has has created humid air, condensation, clouds and rain
• very fast (60kmh) carry large amounts of material

Question 7

Impacts of Mountain Nyiracongo eruption

Answer 7

• major eruptions in 1977, 2002, 2021
• 2km wide continuous lava lake
• responsible for 40% of Africa’s volcanic eruptions
• shield volcano
  2002 - 147 killed, 400k evacuated

Question 8

Eykafjallajokull eruption 2010

Answer 8

• single eruption divided into many phases
• 14th April, relatively explosive eruption (4 on VEI)
• situated 200m under glacial ice, where melt water caused two things: rapidly vaporising water, rapid lava cooling created cloud of abrasive glass rich ash
• but deaths = 0

Question 9

Social/ human impacts of Eykafjallajokull eruption

Answer 9

• cancelled sports, music and arts events
• localised health effects around south Iceland due to abrasive ash
• increased regional traffic for land based travel
• cancelled/postponed political events

Question 10

Economic impacts of eykafjallajokull eruption

Answer 10

• European economy lost 5 billion
• African economies lost as much as 65 million
• loss for airlines ($1.1 billion)
• knock on effect from cancelled events (eg, MotoGP in Japan)

Question 11

Regional significance of eykafjallajokull eruption

Answer 11

• ash cloud reached as far as northern Italy, meaning any flights to and from Europe were affected
• increased in land based travel so train prices and road traffic rose
• however reduced air and noise pollution recorded around Europe

Question 12

Global significance of eykafjallajokull eruption

Answer 12

• Japan MotoGP suffering
• Kenyan flower industry lost 2 million
• New Zealand fish farmers still were winners as they could have more domestic demand

Question 13

Land use zoning

Answer 13

• keeping residential and commercial zones away from active dormant volcanoes
• easier with shield volcanoes
• hard because of soi fertility

Question 14

Hazard resistant design

Answer 14

• retrofit buildings
• cross bracing
  but this is expensive on a national scale and requires government legislation

Question 15

Engineering defences

Answer 15

• sea walls and mangroves to absorb wave energy
• back up utility plans for hospitals and police stations
• drain craters to prevent lahars

Question 16

Diversion of lava flows

Answer 16

• spray sea water to solidify lava and create basalt rock to diverse lava flows

Question 17

Remote sensing

Answer 17

• monitor gas emissions
• cloud monitoring
• monitor fault line staring
• tilitometers measure ground deformation

Question 18

Hawaii earthquake facts and figures

Answer 18

• early may 2018
• magnitude 6.9
• 24 fissures
• 2000 people evacuated, with damage to electricity generation
• $800m damage

Question 19

How they become disasters - local variables

Answer 19

• distance from source (waves lose energy longer you go)
• offshore bathymetry (shallow or deep)
• coastal topography and geology
• extent vertical fault displacement

Question 20

Benioff zone

Answer 20

• area with height seismic activity/ slab moving downward
• speed and movement of rock produces earthquake
• locked faults are significant concern
• slab builds tension due to frictional resistance, until they release a huge amount of energy in the form of an earthquake

Question 21

How tectonics could affect landslides

Answer 21

• focal depth (changes MMS)
• change amounts of folding (steeper)
• change lava type
• hydration melting - more explosive andesitic lava

Question 22

Stresses at a plate boundary

Answer 22

• angle of slope
• rainwater/ saturation
• vibration
• earthquakes
• sea/cliff erosion

Question 23

Strengths at a plate boundary

Answer 23

• lubricant layers
• tree vegetation roots
• consolidation of material
• porosity of soil

Question 24

Chile - The Andes 🇨🇱

Answer 24

• convergent plate boundary
• Anzac plate below the South American plate
• major EQ and volcanic eruptions
• EQ can trigger avalanches, rock avalanches and landslides

Question 25

Punta Cola avalanche:

Answer 25

Strength - tree bunds land together giving it resistance | Stress - water doing hydraulic action breaking the land cashing a landslide

Question 26

Characteristics of a shield volcano

Answer 26

- constructive plate boundary - divergence - lower silicates and gas content in magma - continuous eruption - runny, basaltic lava, gentle slope, shorter volcano

Question 27

Characteristics of a composite volcano

Answer 27

- destructive plate boundary - subduction - higher silicates and gas content in magma - longer dormancy, pressure build up - explosive eruption, gas and material - viscous andesitic lava - steep sided tall volcano

Question 28

So overall, how are landslides formed at destructive plate boundary?

Answer 28

- one plate is folded up - steeper gradient - increased gravity in this plate which can increase likelihood of landslides - magma can melt the plate = landslides

Question 29

1.8 overall

Answer 29

Tsunamis form and are shaped by coastal morphology e.g Indian Ocean

Question 30

Keychain for tsunami

Answer 30

• Destructive plate boundary • Subduction zone • Earthquake • Megathrust fault – water displacement • Wave… which is fine until the sea-bed shelves • Then friction drags at the bottom of wave as bed shelves • Wave frequency / amplitude changes and grows before hitting land • Backwash out, swash in (wave crash)