Volcanic hazards

Question 1

On average how frequently do they occur?

Answer 1

168 in 45 years

Question 2

What is the definition of an extinct volcano?

Answer 2

Has no chance of erupting again

Question 3

What is the definition of a dormant volcano?

Answer 3

Has not erupted in the last 10,000 years but still have the potential to erupt

Question 4

What is the definition of an active volcano?

Answer 4

Has erupted in the last 10,000 years and still have the potential to erupt

Question 5

What is a primary hazard?

Answer 5

An impact directly linked to the volcanic activity in the given location

Question 6

What are the primary hazards from a volcanic eruption?

Answer 6

Lava flows
Pyroclastic flow
Tephra and ballisitc flows
Gas emissions
Earthquakes
Debris avalanches

Question 7

What is the temperature of a lava flow?

Answer 7

800-1200c
Below 800c- forms skin on surface

Question 8

How do lava flows pose a threat to humans?

Answer 8

Low risk to human health due to slow moving nature
High risk of human displacement and disruption due to destructive nature

Question 9

What is the definition of a pyroclastic flow?

Answer 9

A flow of hot gas and volcanic material, high density, travels close to the ground, following topographic lows (valleys)

Question 10

What is the defiition of pyroclastic surge?

Answer 10

A turbulent, low density, high velocity part of a pyroclastic, not constrained by topography

Question 11

What is the distance and speed range of pyroclastic flow?

Answer 11

Km to kms
Low to high speed

Question 12

What are the related hazards to pyroclastic flows and surges?

Answer 12

Poor health (inhilation)
Destruction of infrastructure
Malfunction of machinery
Destruction by fire
Climatic effects

Question 13

What gases are released during a volcanic eruption?

Answer 13

Sulfur dioxide- so2
Carbon dioxide- co2
Hydrogen fluoride- HF

Question 14

Why is sulfur dioxide a hazardous gas?

Answer 14

Causes poor air pollution

Question 15

Why is carbon dioxide a hazardous gas?

Answer 15

Lethal to people and animals (at concentrated levels)
Level of co2 emitted from anthropogenic activity higher than volcanic activity

Question 16

Why is is hydrogen fluoride a hazardous gas?

Answer 16

Death and injury in livestock

Question 17

How are earthquakes primary hazards?

Answer 17

Only when magnitide >5 on Richter scale
Triggers eruptions or landslides that results in eruptions

Question 18

What is the definition of a secondary hazard?

Answer 18

An indirect hazard casued by volcanic activity in a given area

Question 19

What are the secondary hazards from a volcanic eruption?

Answer 19

Lahars (mudflows)
Flooding/Tsunami
Fires
Air pollution
Diseases/Famine
Social effects
Climatic effects

Question 20

How does a lahar form?

Answer 20

When pyroclastic flow meets water e.g. rain, glaciers, river water
The gas rich pyroclastic flow is converted to a fast moving heated mudflow

Question 21

Why are lahars a secondary hazard of an eruption?

Answer 21

One of the most lethal and devestating hazards
Speed up to 200km/h
<100c
Can travel km to 10kms

Question 22

How does a tsunami form?

Answer 22

Eruption triggeres pressure and gravity waves in the atmosphere and tsunami waves in the ocean

Question 23

Why are tsunamis a secondary hazard of an eruption?

Answer 23

Huge economic damage
Damage to infrastructure and agriculture

Question 24

Why are climatic effects a secondary hazard from an eruption?

Answer 24

Ash in the upper atmosphere reduces the amount of radiation reaching the ground
Can reduce temperature worldwide e.g. 0.5 for 10 years

Question 25

Why are social effects (disease and famine) a secondary hazard from an eruption?

Answer 25

One of the greatest killers in less economically developed countries
Without correct aid, famine can be one of the greatest killers
Other primary and secondary hazards leave people homless/destroy their main source of income