VOLCANOES

Question 1

What is meant by there term active volcano?

Answer 1

An active volcano is a volcano that is erupting now or has had at least one eruption during the past 10,000 years.

Question 2

What is meant by the term dominant volcano?

Answer 2

A dormant volcano is an active volcano that is not erupting, but supposed to erupt again

Question 3

What is meant by the term extinct volcano?

Answer 3

An extinct volcano has not had an eruption for at least 10,000 years and is not expected to erupt again as it has no magma supply.

Question 4

Describe the shape of shield volcano.

Answer 4

A shield volcano has wide base and gentle slopes.

Question 5

Describe the shape of a composite volcano.

Answer 5

A composite volcano has a narrow base and steep slopes.

Question 6

On what type of plate margin are shield volcanoes found?

Answer 6

Shield volcanoes are found on constructive plate margins.

Question 7

List the three main features of a volcano.

Answer 7

The three main features are magma chamber, main vent and crater.

Question 8

Describe the distribution of volcanoes.

Answer 8

Volcanoes are mainly found on near to constructive and destructive plate margins.

Question 9

What is meant by the term magma?

Answer 9

Magma is a hot fluid or semifluid material below or within the earth’s crust from which lava and other igneous rock is formed by cooling.

Question 10

What is meant by the term lava?

Answer 10

Lava is a hot molten or semifluid rock erupted from a volcano or fissure.

Question 11

List five hazards produced by a volcano.

Answer 11

Five hazards are lava, ash clouds, pyroclastic flows, lahars and poisonous gases.

Question 12

What is meant by the term pyroclastic flow?

Answer 12

It is a flow of volcanic ash, dust, rocks and debris that cascades down the slope of a volcano during an eruption. Pyroclastic flows are very dangerous, reaching speeds greater than 60 miles per hour and temperatures in excess of 800 degrees Farenheit

Question 13

What is meant by the term lahar?

Answer 13

It is a landslide or mudflow of volcanic fragments on the flanks of a volcano.

Question 14

List six reasons why people live near to active volcanoes.

Answer 14

Six reasons could be fertile soils, tourism, geo thermal power, health benefits from geo thermal springs. mining and quarrying , and beautiful scenery.

Question 15

List six ways that volcanoes can cause problems for people.

Answer 15

They can cause death and injury, cause ash and fumes can cause breathing difficulties, can destroy people homes leaving them homeless, destroy crops leading to malnutrition, fights can be cancelled delay people travel plans or destroy factories leaving people unemployed.

Question 16

List four things that observatories monitoring volcanic activity measure to try and predict when they are going to erupt.

Answer 16

The following can be measured; earthquake activity, the level of certain gases in the air such as carbon dioxide and sulphur dioxide, ground deformation, and tilt meters can record any changes in slope angle.

Question 17

Describe how the impact of lava flows could be reduced.

Answer 17

Temporary concrete or earth dams can divert the flow of the lava (Mt Etna) or water can be sprayed onto the lava to stop or slow its advance. (Iceland).

Question 18

Describe three ways in which the Montserrat government reduced the impact of the islands 1996 volcanic eruptions.

Answer 18

They set up exclusions zones around the slopes of the volcano that people could not enter, people were evacuated to other islands or relocated in north of the island.

Question 19

What volcano would you use to answer a case study questions on why volcanoes erupt

Answer 19

You would use the Chaiten volcano in Chile.

Question 20

Explain why the Chaiten volcano erupted.

Answer 20

A converging convection current in the mantle causes the Nazca plate to move in an easterly direction and collide with the westerly moving South American plate. As the Nazca plate is denser it starts to subduct into the mantle. As it dips into the mantle an increase in pressure causes the plate to melt forming magma. As the magma is under pressure ands less dense than the surrounding rock it rises to the surface through lines of weakness in the overlying mantle and crust and erupts into the air.