Volcanoes

Question 1

What are volcanoes?

Answer 1

Openings in the earths crust through which lava, ash and gases erupt.

Question 2

How to volcanoes occur?

Answer 2

As tectonic plates move, pressure builds and hot magma and gases push up from the mantle to the earths crust - and erupt.

Question 3

What is lava?

Answer 3

Magma once its reached the earths surface.

Question 4

How many volcanoes are active today and how many people are at risk?

Answer 4

1,900

500 million worldwide

Question 5

What are the primary hazards of volcanoes?

Answer 5

Lava flows
Pyroclastic flows
Tephra and ash falls
Gas eruptions

Question 6

What are lava flows?

Answer 6

Streams of lava that have erupted from a volcano onto the earths surface.

They can reach 1170c and can take years to cool completely.

Question 7

Why are lava flows hazards?

Answer 7

Generally not a threat to humans because most move so slowly people can get out of the way.
However, they do destroy everything in their path.

Question 8

What are pyroclastic flows?

Answer 8

They are a mix of dense hot rock, lava, ash and gases ejected from a volcano, which move very quickly across the earths surface (100km per hour)

They’re one of the greatest volcanic hazards.
Destroy everything they touch and are extremely hot - 700c

Question 9

What are tephras?

Answer 9

Pieces of volcanic rock and ash that blast into the air during volcanic eruptions.

Question 10

How are tephras a hazard?

Answer 10

Larger pieces tend to fall near the volcano, where they can cause injury or death, as well as infrastructure damage.

The smaller pieces can travel for thousands of km

Question 11

What are ash falls?

Answer 11

Where the ash lands, it covers everything

Question 12

How are ash falls a hazard?

Answer 12

causing poor visibility and slippery roads.
Roofs can collapse under the weight
Engines can get clogged up and stop working

Question 13

What are gas eruptions?

Answer 13

Magma contains dissolved gases that are released into the atmosphere during a volcanic eruption (some are potential hazards to people, animals and structures).

They include water vapour (80%), carbon dioxide and sulphur dioxide - they can travel for thousands of km once in the air

Question 14

What are the secondary hazards?

Answer 14

Lahars

Jokulhlaup

Question 15

What are lahars?

Answer 15

Masses of rock, mud and water that travel quickly down the sides of a volcano.

They vary in size and speed but can be hundreds of metres wide and can flow at tens of metres per second

Question 16

How are lahars formed?

Answer 16

Caused when an eruption quickly melts snow and ice

Or heavy rainfall during or after an eruption erodes loose rock and soil - causing it to surge downslope

Question 17

What are jokulhlaups?

Answer 17

The heat of a volcanic eruption can melt the snow and ice in a glacier, causing heavy and sudden floods

Question 18

How can jokulhlaups dangerous?

Answer 18

They suddenly release large amounts of water, rock, gravel and ice that can catch people unawares, and flood and damage land and structures

Question 19

What are the social, economic and environmental impacts?

Answer 19

Loss of life 
Migration to other countries - older people stay, younger go
Destruction of main services/cities
Loss of economy 
Destroyed infrastructure 
Huge unemployment 
Loss of farmland - less food/income

Question 20

How do you measure volcanic eruptions?

Answer 20

Volcanic explosivity index (VEI)

Question 21

What does the VEI do?

Answer 21

Describes and compares the size or magnitude of volcanic eruptions

Question 22

How does the VEI work?

Answer 22

Uses a scale from 0 (non-explosive) to 8 (extremely large).

Its logarithmic - with each number increasing by a factor of ten

Question 23

What factors does the VEI use to assign a number?

Answer 23

The amount and height of the volcanic material ejected (tephra and ash fall)
How long the eruption lasts
Qualitative descriptive terms (such as ‘gentle’, ‘explosive’)

Question 24

How do you predict eruptions?

Answer 24

Unlike earthquakes, scientists can often predict eruptions with some accuracy.

Question 25

How can eruptions be predicted?

Answer 25

Equipment placed on volcanoes as well as remote equipment (GPS and satellite-based radar) scientists can monitor a volcano for signs that it might erupt.

Question 26

What are the signs of an eruption?

Answer 26

Small earthquakes - as the magma rises to the surface, it breaks the rock, causing small earthquakes which scientists can detect on seismograms.

Changes to the surface of the volcano - as it pushes upwards, the magma builds pressure (causing the surface of the volcano to swell)

Changes to the ‘tilt’ of the volcano - as the magma moves inside the volcano, it changes the slope angle or ‘tilt’ of the volcano.