The Structure Of The Earth

Question 1

List the four layers of the Earth.

Answer 1

1. Solid outer crust
2. Thick, viscous mantle
3. Liquid outer core
4. Dense, solid inner core

Question 2

How thick is the crust?

Answer 2

About 20 km

Question 3

What is the crust mainly made of?

Answer 3

Basalt rock

Question 4

How thick is the mantle?

Answer 4

2900 km

Question 5

Where is the mantle?

Answer 5

Below the crust

Question 6

What is the mantle mainly made of?

Answer 6

Silica and minerals of iron, magnesium and other metals.

Question 7

What is the lithosphere?

Answer 7

The crust and the upper, solid part of the mantle.

Question 8

What is the core mainly made of?

Answer 8

Iron and nickel

Question 9

What can we study to tell that there is a change of solid to liquid halfway through the Earth?

Answer 9

The paths of earthquake waves as they travel through the Earth

Question 10

What do earthquake waves reveal about the inside structure of the Earth?

Answer 10

The outer core is liquid and the inner core is solid.

Question 11

What is believed to create all heat inside the Earth?

Answer 11

Radioactive decay

Question 12

What does heat inside the Earth cause?

Answer 12

Convection currents, which cause plates to move.

Question 13

What is the crust cracked into?

Answer 13

Pieces called tectonic plates.

Question 14

What does ‘tectonic’ mean?

Answer 14

Within the crust of the Earth.

Question 15

How fast do plates move?

Answer 15

Slowly, about 1 to 2 cm every year.

Question 16

What is usually located at the boundary of tectonic plates?

Answer 16

Volcanic and/or earthquake activity.

Question 17

In what three ways can tectonic plates interact with each other?

Answer 17

They can:

1. Slide past each other
2. Collide
3. Move apart

Question 18

How is an earthquake caused?

Answer 18

Plates sliding past each other catch and pressure builds up. The pressure can be suddenly released in an earthquake.

Question 19

What precaution is taken in light of a potential earthquake?

Answer 19

Earthquake-proof buildings are constructed that can withstand shaking.

Question 20

Where do earthquakes cause the most destruction and why?

Answer 20

In poorer countries, because cities are overcrowded and buildings are poorly constructed. There may be improper emergency services.

Question 21

How are volcanoes formed?

Answer 21

Volcanoes are formed where an oceanic plate collides with a continental plate.
The oceanic plate is less dense and is forced underneath the continental plate.
Friction causes the descending rock to melt.
The molten rock is forced to the surface, forming volcanoes.

Question 22

What two tectonic features are formed where an oceanic plate collides with a continental plate?

Answer 22

1. Volcanoes

2. Sometimes earthquakes

Question 23

How can earthquakes be formed where an oceanic plate collides with a continental plate?

Answer 23

The oceanic plate grinds past the continental plate as it bends and descends into the mantle.

Question 24

What forms on the ocean floor where the oceanic plate is being forced down?

Answer 24

A deep ocean trench

Question 25

What happens to the continental crust as the oceanic plate bends underneath it?

Answer 25

The continental crust crumples and folds to form mountains along the coast.

Question 26

How does the rock of the mantle change as you go from the bottom to the top?

Answer 26

The rock is soft and viscous at the bottom and becomes more hard and solid near the top.