Lecture 3 - Volcanic Hazards

Question 1

Primary or Direct hazards - Lava flows

Answer 1

Lava ranges in temperature from 800-1200
Lava flows advance slowly allowing time to escape, but everything in its path will be destroyed.

Question 2

Kileau Lower East Rift Zone

Answer 2

24 injuries
700 Houses destroyed
$800 million in damages

Question 3

What is a pyroclastic flow?

Answer 3

A flow of hot gas and volcanic material ranging from vesiculated, low-density pumice to unvesiculated, dense clasts. Contains 10% of solid by volume.
Tends to follow topographic lows
Laminar flows

Question 4

What is pyroclastic surge?

Answer 4

A turbulent, low-density, high-velocity part of a pyroclastic flow. Not constrained by topography, contains 0.1-1% solids by volume. Turbulent flow.

Question 5

Pyroclastic Activity - Hazards

Answer 5

1. Health hazards
2. Destruction by direct impact
3. Burying sites with hot rock debris
4. Destruction by fire
5. Malfunction of machinery

Question 6

Gas emissions from volcanoes

Answer 6

SO2 - Air pollution, acid rain.
CO2 - At concentrated levels, it is lethal to people and animals.
HF - Can cause death and injury in livestock during ash eruptions if fluorine exceeds 250ppm.

Question 7

What happened in Lake Nyos, Cameroon

Answer 7

• 3000 cattle dead
• 1700 people dead in 6 different villages
  Due to the release of 1.3 x 109m3 of CO2 from a crater lake.

Question 8

What are Mudlows or Lahars?

Answer 8

Fluidized hot mudflows due to pyroclastic flows interacting with severe rain, river water, glacier lakes

Question 9

Eyjafjallajökull eruption, Iceland April 2010

Answer 9

110 million cubic meters of tephra ejected with the plume rising 9km.

Question 10

Impacts of Eyjafjallajökull eruption

Answer 10

• 500 farmers and their families were evacuated
• Thick layers of ash that fell on farms made land difficult to use
• Close of European airspace
• Triggered meltwater floods rushing dow nearby rivers

Question 11

Tonga Eruption

Answer 11

Underwater eruption.
Ash plume rose 30km into the atmosphere.

Question 12

Impacts of Tonga Eruption

Answer 12

• $90.4m damage
• Tsunami across the pacific
• 85% of Tongas agricultural households were affected by crop loss, and damage to reefs.

Question 13

Climatic Effects from eruptions

Answer 13

• Ash in upper atmosphere reduces radiation reaching the ground. Krakatora by 0.5 degrees.
• CFC’s from volcanoes