Hazards

Question 0

State the three main secondary hazards of a volcanic eruption

Answer 0

Lahars, volcanic landslide, tsunami

Question 1

State the three main primary hazards of a volcanic eruption

Answer 1

Lava flows, pyroclastic flows, tephra

Question 2

Are lava flows life threatening?

Answer 2

Rarely

Question 3

T/F

Rebuilding after destruction of lava flows is not possible

Answer 3

True

Rebuilding isn’t possible

Question 4

What are the characteristics of basalt?

Answer 4

Runny and fast flowing

Question 5

What are the characteristics of rhyolite?

Answer 5

Viscous and slow moving

Question 6

What are pyroclastic flows? Are they a threat to humans?

Answer 6

Avalanches of hot ash, pumice, rock fragments and gas

Destroy everything and greatest threat to people - poisonous gases and fast flowing

Question 7

Speeds of pyroclastic flows

Answer 7

100km h

Question 8

What is tephra?

Answer 8

Fragments of volcanic rock that are blasted into the atmosphere by explosive eruptions

Question 9

What are the impacts of tephra

Answer 9

Blankets landscape with many disruptions to economic activity

• roads impassable
• roof collapse
• crops smothered
• engine damage

Question 10

What are lahars? Are they a threat to people?

Answer 10

Mudflows of volcanic material, second greatest threat to people after pyroclastic flows
Ash and debris can mix with water and then move rapidly

Question 11

What can cause lahars?

Answer 11

Localised rainfall/electric storms caused by eruption events can trigger lahars.
May also be influenced by the collapse of a crater lake or rapid snow or ice melting

Question 12

Where are Lahars most common?

Answer 12

River valleys and low lying areas

Question 13

What can cause volcanic landslides?

Answer 13

Ground deformation of volcanic slopes by rising magma before an eruption or during

Question 14

What does VEI stand for?

Answer 14

Volcanic explosivity index

Question 15

How many levels are there to the VEI? With 0 being the highest or lowest?

Answer 15

0-8. Zero being the least explosive

Question 16

How many hours would an eruption with a VEI of 3 have and would it be considered as non explosive, small, moderate, large or very large?

Answer 16

1-12 hours

Moderate/large

Question 17

Stat human reasons why some volcanoes are more hazardous than others

Answer 17

• proximity to population
  - major cities is more hazardous than remote area
  - high pop density out large numbers of people at risk - trickier to control and evacuate
• predictions forecasts and reactions
  - monitoring

Question 18

How can monitoring a volcano reduce the size of a hazard?

Answer 18

Creating warning and evacuation plans for people at risk

It can be beneficial to have evidence of past eruptions to suggest likely eruptive scenarios

Question 19

How can the viscosity of magma have a direct impact on how hazardous a volcanic eruption is?

Answer 19

The more viscous the greater the potential for explosive eruptions

Question 20

How can the material ejected vary the danger posed on a population from a volcanic eruption?

Answer 20

Non-explosive - lava flows = no serious hazard

Explosive = tephra or pyroclastic flows - ash can be carried further and have impact on further afield e.g. Aircraft etc

Question 21

What are jökulhlaups and how do they form?

Answer 21

Large fast moving glacier-outburst floods

The form when a volcano erupts beneath a glacier

Question 22

Name 4 impacts jökukhlaups can have

Answer 22

• difficulty of getting aid and emergency workers around
• debris can destroy infrastructure
• wash away crops and farmland - land left unusable
• threatens lives of people and animals

Question 23

Other than bringing massive floods, why else can jökulhlaups be dangerous?

Answer 23

They also carry enormous boulders,huge blocks of ice and icebergs.

Question 24

What are some primary impacts caused by volcanic materials such as pyroclastic flow, lava, ash etc?

Answer 24

Destruction of natural landscape
Destruction of human settlement
Destruction if infrastructure and transport routes
Human casualties

Question 25

What are some secondary impacts occurring as a result of the primary impacts?

Answer 25

Reduction in food supply
Homelessness and resettlement
Reduction in economic activity
Spread of disease