Lesson 4 - What happens at a constructive margin

Question 1

Two parts are moving apart from each other, what direction are they moving in?

Answer 1

Opposite directions

Question 2

At constructive margins, what are moving in opposite directions?

Answer 2

Convection currents

Question 3

What causes the convection currents to move in opposite directions?

Answer 3

The intense heat of the Earth’s interior

Question 4

The process of what in the mantle causes the plates to move apart?

Answer 4

Slab pull

Question 5

What is created as the plates move apart?

Answer 5

Cracks and openings

Question 6

When the plates move apart, cracks and openings are created, what are they called?

Answer 6

Fissures

Question 7

What do the lines of weakness that are created when the plates move apart allow magma to do?

Answer 7

Escape from the highly pressurised interior of the Earth

Question 8

What does the magma do when it escapes?

Answer 8

Fills the faults and eventually erupts onto the surface

Question 9

What does the magma do after it erupts onto the surface?

Answer 9

Cools as new land

Question 10

Rising magma can create huge ridges of what?

Answer 10

Undersea mountains and volcanoes

Question 11

Give an example of a series of huge ridges of undersea mountains?

Answer 11

Mid Atlantic Ridge

Question 12

A central part of the ridge may feature a central valley, what has happened at a central valley?

Answer 12

A section of the crust has subsided into the magma below

Question 13

What does the split in the crust at a central valley provide?

Answer 13

A low-pressure zone where lavas can erupt to form submarine volcanoes.

Question 14

What happens as crust is pulled away from its heat source at a mid-ocean ridge?

Answer 14

It cools, contracts and sinks towards deeper regions.

Question 15

After the crust cools, contracts and sinks towards deeper regions, what is it covered in?

Answer 15

Fine sediments

Question 16

Where do transform faults occur?

Answer 16

At right angles to the boundary

Question 17

What occurs when 2 parts of a plate either side of a transform fault move at different rates?

Answer 17

Earthquakes

Question 18

At the Mid Atlantic Ridge, which is an example of a transform fault, the Eurasian plate moves away from which plate?

Answer 18

The North American plate

Question 19

At the Mid Atlantic Ridge, the Eurasian plate moves away from the North American plate by how many centimetres per year?

Answer 19

4

Question 20

Which country owes its existence to the Mid Atlantic Ridge?

Answer 20

Iceland