Topic 3: The Earth's core, mantle and crust

Question 1

Name the 5 layers of the Earth in order.

Answer 1

1. Crust.
2. Upper mantle.
3. Lower mantle.
4. Outer core (liquid).
5. Inner core (solid).

Question 2

Describe the core of the Earth.

Answer 2

The core is the innermost layer of the Earth. It is divided into to two parts: the inner core and the outer core.

THE INNER CORE:

1. Is at the centre of the Earth.
2. Temperatures up to 5 500°C.
3. Is a solid.
4. Made of iron and nickel.
5. About 1 220 km thick.

THE OUTER CORE:

1. Surrounds the inner core.
2. Temperatures similar to the inner core.
3. Is a liquid.
4. Made of iron and nickel.
5. About 2 250 km thick.

Question 3

Describe the mantle of the Earth.

Answer 3

The mantle of the Earth is divided into two layers: the upper and lower mantle; between the crust and the core. It is about 2 900 km thick.

THE UPPER MANTLE:

1. About 670 km thick.
2. Bends and flows under pressure = semi-molten.
3. Temperatures range from 500°C to 900°C.
4. Made of minerals rich in iron, silica, magnesium and oxygen.

THE LOWER MANTLE:

1. About 2 230 km thick.
2. Is a solid.
3. Temperatures over 4 000°C (at the boundary of the core)
4. Made of minerals rich in iron, silica, magnesium and oxygen.

Question 4

Describe the crust of the Earth.

Answer 4

The crust ranges from 5 to 70 km in depth and has variable thickness. There are two types of the crust.

OCEANIC CRUST:

1. Denser than the continental crust.
2. Made of igneous rock - rich in iron and magnesium.
3. Forms the surfaces of ocean basins.
4. Between 5-10 km thick.

CONTINENTAL CRUST:

1. Thicker than the oceanic crust = less dense.
2. Made of granite rock - rich in feldspar with quartz and silica.
3. Forms the surface of the continents and the shallow seabed near the shores.
4. Between 35-70 km thick.

Question 5

Define “semi-molten”.

Answer 5

Half way between a solid and a liquid.