Structure Of The Earth

Question 1

Lithosphere

Answer 1

The lithosphere is the uppermost layer of the Earth.
It is cool and brittle. It includes the very top of the mantle and, above this, the crust.

Question 2

Two types of crust

Answer 2

Continental and oceanic

Question 3

Continental crust

Answer 3

Continental crust forms the land. This is made mostly of granite, which is a low density igneous rock. Continental crust is on average 30-50 km thick.

Question 4

Oceanic crust

Answer 4

Under the oceans is oceanic crust. This is much thinner, usually 6-8 km thick. It is also denser and made of an igneous rock called basalt.

Question 5

Asthenosphere

Answer 5

asthenosphere is partly molten rock and partly solid rock.
The asthenosphere is in the top layer of the mantle.

Question 6

Earthquake waves

Answer 6

Earthquake waves tell us about the physical state of the Earth. They speed up, change direction or stop when they meet a new layer in the Earth. It’s mainly due to this that we know anything about the core. Some waves travel easily through the crust, mantle and inner core, but not through the outer core. This suggests that the outer core has a different physical state and may be liquid, not solid.

Question 7

How is the curst formed

Answer 7

The crust forms the Earth’s surface. It is a rock layer forming the upper part of the lithosphere. The lithosphere is split into tectonic plates. These plates move very slowly, at 2-5 cm per year, on a layer called the asthenosphere.

Question 8

Parts of the mantle

Answer 8

Lithosphere
Asthenosphere

Question 9

Inner core

Answer 9

The inner core is in the centre and is the hottest part of the Earth. It is solid and made up of iron and nickel with temperatures of up to 5,500°C.

Question 10

Outer core

Answer 10

The outer core is the layer surrounding the inner core. It is a liquid layer, also made up of iron and nickel.

Question 11

Mantle

Answer 11

The mantle is the thickest section of the Earth at approximately 2,900 km. The mantle is made up of semi-molten rock called magma.

Question 12

Plate tectonics

Answer 12

The Earth’s crust is broken into
tectonic plates
. It was once believed that
convection currents
in the mantle caused the plates to move. However, it is now recognised to be more complicated than this. Mechanisms called
slab pull
and ridge push are believed to move the tectonic plates. Ridge push is where the new crust formed at divergent
plate margins