LC: Volcanoes

Question 1

The forces at work along crustal plate boundaries are _______ and _______.

Answer 1

The forces at work along crustal plate boundaries are collision** and **separation.

Question 2

What is the Lithosphere?

Answer 2

The lithosphere is the solid, outer part of the Earth, including the brittle upper portion of the mantle and the crust.

Question 3

What is Plate Tectonic Theory?

Answer 3

Plate Tectonic Theory describes how the earth’s crust/lithosphere is split into large slabs called plates.

Question 4

The plates move because heat from the earth’s core causes the upper mantle to flow in huge slow-moving _______ _________.

Answer 4

The plates move because heat from the earth’s core causes the upper mantle to flow in huge slow-moving convection currents.

Question 5

These convection currents drag the plates along with them, causing them to collide and separate, forming _________ and ________ plate boundaries.

Answer 5

These convection currents drag the plates along with them, causing them to collide and separate, forming destructive and constructive plate boundaries.

Question 6

What three situations do Destructive Plate boundaries occur in?

Answer 6

1. Where oceanic and continental plates collide.
2. Where two continental plates collide.
3. Where two oceanic plates collide.

Question 7

Whats an example of where oceanic and continental plates collide?

Answer 7

The Pacific colliding with the South American plate

Question 8

Whats an example of where two continental plates collide?

Answer 8

The Indian plate colliding with the Eurasian plate.

Question 9

Whats an example of where two oceanic plates collide?

Answer 9

The Pacific plate colliding with the Philippine plate.

Question 10

When plates collide, the ________ and denser ________ plate slides down into the mantle and is destroyed and recycled.

Answer 10

When plates collide, the heavier** and denser **Oceanic plate slides down into the mantle and is destroyed and recycled.

Question 11

What is the process called when the heavier denser Oceanic plate slides down into the mantle and is destroyed and recycled?

Answer 11

Subduction.

Question 12

Subduction causes the formation of explosive ________ _________ on land (e.g. the Andes), or _______ ________ _______ in the sea (e.g. Japan).

Answer 12

Subduction causes the formation of explosive volcanic mountains on land (e.g. the Andes), or volcanic island arcs in the sea (e.g. Japan).

Question 13

Deep ocean ___________ form at the boundary of the colliding plates.

Answer 13

Deep ocean trenches form at the boundary of the colliding plates.

Question 14

Whats an example of a trench?

Answer 14

The Marianas Trench is 11 kilometres deep

Question 15

What happens when two continental plates collide?

Answer 15

In the case of two continental plates colliding (e.g. the Indian and Eurasian plates), neither will sink as they are less dense than the mantle material below.

Question 16

What is formed when two continental plates collide?

Answer 16

Both will be destroyed by folding and uplifted to form fold mountains, such as the Himalayas.

Question 17

Shallow __________ often occur at the boundary of the colliding continental plates

Answer 17

Shallow earthquakes often occur at the boundary of the colliding continental plates.

Question 18

_____________ plate boundaries are places where new crust is formed.

Answer 18

Constructive plate boundaries are places where new crust is formed.

Question 19

Whats an example of where two plates move away from each other?

Answer 19

The Eurasian plate is separating from the North American plate.

Question 20

Why do two plates move away from each other?

Answer 20

Two mantle convection currents flowing away from each other moving the plates apart.

Question 21

Convection currents flowing away from each other split the lithosphere above and drags the plates apart forming a _____ _______.

Answer 21

Convection currents flowing away from each other split the lithosphere above and drags the plates apart forming a Rift Valley.

Question 22

Magma from the mantle is able to force its way up through the Rift Valley and flow out onto the seabed.

The magma cools and __________ into _________ _________ rock.

Answer 22

Magma from the mantle is able to force its way up through the Rift Valley and flow out onto the seabed.

The magma cools and solidifies into igneous basalt rock.

Question 23

When new ocean floor is formed, what is the process called?

Answer 23

When new ocean floor is formed, this process is called seafloor spreading.

Question 24

As the lava cools on the surface undersea, it forms large chains of undersea volcanic mountains called _______ _______ _______.

Answer 24

As the lava cools on the surface it forms large chains of undersea volcanic mountains called mid ocean ridges.

Question 25

Sometimes these undersea volcanic mountains appear above the water as _______ \_\_\_\_\_\_\_\_.

Answer 25

Sometimes these undersea volcanic mountains appear above the water as _volcanic_ _islands_.

Question 26

Whats is an example of a Volcanic island?

Answer 26

Iceland.

Question 27

Unlike at destructive place boundaries the volcanoes at constructive plate boundaries are less \_\_\_\_\_\_\_\_\_.

Answer 27

Unlike at destructive place boundaries the volcanoes at constructive plate boundaries are less _explosive_.

Question 28

Why are volcanoes at constructive plate boundaries less explosive?

Answer 28

This is because the magma contains less silica. As a result, it is very fluid which allows gases to escape. ## Footnote *\* The silica content of the magma determines how thick the magma is, how easily it flows and how easily dissolved gases within the magma can escape*

Question 29

Provide 2 examples of Seafloor Speading?

Answer 29

1. The East Pacific Rise where the crust moves apart by 11 centimetres per year. 2. The Mid Atlantic Ridge separates by 2-4 centimetres per year.