Hazards - Volcanoes

Question 1

At what 4 places is volcanic activity found?

Answer 1

Oceanic ridges
Rift Valleys
Subduction Zones
Hot spots

Question 2

How are the 2 different types of volcano?

Answer 2

Shield

Composite

Question 3

What are shield volcanoes?

Answer 3

Big volcanoes made from layers of solidified balsatic lava with gently sloping sides

Question 4

What are composite volcanoes?

Answer 4

Smaller volcanoes made of alternating layers of andesitic lava and ash with steep slopes above 10 degrees

Question 5

What types of volcanoes form at destructive boundaries?

Answer 5

Composite

Question 6

Where do shield volcanoes form?

Answer 6

At constructive boundaries or hot spots

Question 7

What kind of eruptions do composite volcanoes do?

Answer 7

Explosive

Question 8

What kind of eruptions do shield volcanoes do?

Answer 8

Effusive

Question 9

What is a volcano?

Answer 9

An opening in the crust of the Earth connected underground to a magma chamber from which molten lava, gases, steam and pyroclastic material are ejected.

Question 10

What impacts the shape and form and type of eruption of a volcano?

Answer 10

Its lava

Question 11

What is the difference between effusive and explosive eruptions?

Answer 11

Explosive is arbourne

Effusive is landbound

Question 12

What is tephra?

Answer 12

Explosive material under 64mm

Question 13

What is a volcanic bomb?

Answer 13

Explosive material over 64mm

Question 14

What is the Benioff zone?

Answer 14

Part of the subduction zone where oceanic plate melt into magma

Question 15

How do volcanoes form in rift valleys?

Answer 15

The crust in rift valleys is much thinner than in neighbouring areas. Magma forces its way to the surface through the thinning crust

Question 16

What are hot spots?

Answer 16

Small areas of the Earth’s crust where an unusually high heat flow leads to volcanic activity

Question 17

How do volcanoes form over hot spots?

Answer 17

Column of upwelling magma melts the overlying crust and molten magma is forced through the crust. The plate moves over the hotspot, forming a succession of volcanoes.

Question 18

How can volcanoes that are not directly above hot spots still erupt?

Answer 18

As the plate moves it drags the head of the magma plume with it

Question 19

What is the main method of measuring the magnitude of volcanic eruptions?

Answer 19

Volcanic explosivity index

Question 20

What percentage of volcanoes lie on plate margins?

Answer 20

95%

Question 21

What are active volcanoes?

Answer 21

Volcanoes that have erupted in the last 2,000 years

Question 22

What are dormant volcanoes?

Answer 22

Volcanoes that haven’t erupted in the last 10,000 years

Question 23

What are extinct volcanoes?

Answer 23

Volcanoes that aren’t going to erupt again

Question 24

What percentage of the Earth’s surface is made of silica?

Answer 24

95%

Question 25

What are the primary hazards of volcanoes?

Answer 25

``` Tephra Pyroclastic flows Nuee ardentes Lava flows Volcanic gases ```

Question 26

What are the secondary hazards of volcanoes?

Answer 26

``` Lahars Acid rain Flooding TSunamis Volcanic landslides Climate change ```

Question 27

What are pyroclastic flows?

Answer 27

Very hot gas charged high velocity flows made up of a mixture of gas and tephra that flow down the sides of the volcano

Question 28

What are lahars?

Answer 28

Mud flows formed by the combination of melted snow and ice and volcanic gases, which quickly move down the course of river valleys

Question 29

How do volcanic eruptions cause flooding?

Answer 29

Eruptions melt glacier and ice caps

Question 30

How do volcanic eruptions cause acid rain?

Answer 30

Eruptions emit sulphur dioxide which combines with atmospheric moisture to form acid rain

Question 31

What type of lava do shield volcanoes have?

Answer 31

Basic, non-viscous

Question 32

What type of lava do composite volcanoes have?

Answer 32

Acidic, viscous

Question 33

Are shield or composite volcanoes hotter?

Answer 33

Shield

Question 34

What percentage of silica is basic lava?

Answer 34

45%

Question 35

What percentage of silica is acidic lava?

Answer 35

66%