Unit 4: Minerals and rocks                                                       1   2   3   4

1. The Earth's layers

We can distinguish four layers or "spheres" in the Earth.

These "spheres" are interrelated. They are:

• The geosphere. It is the solid part of the Earth.
• The atmosphere. It is the gaseous part of the Earth.
• The hydrosphere. It is the liquid part of the Earth.
• The biosphere. It is the living part of the Earth.

1.1. The geosphere

The Earth's inside is divided into three concentric layers:

The crust and the upper part of the upper mantle form the lithosphere.

This layer is divided into pieces called tectonic plates.

Below the lithosphere is a layer of semifluid rock called asthenosphere,

which forms part of the upper mantle.

1.2. The atmosphere

It is the layer of gases that surrounds the Earth.

The mixture of gases that forms the atmosphere is called air.

1.3. The hydrosphere

It is the discontinuous layer of water that covers the Earth.

This water can be as liquid water, as ice and as water vapour.

1.4. The biosphere

It is the layer formed by all living beings in the Earth.  

It constantly interacts with the lithosphere, the atmosphere and the hydrosphere.

1.1. Relate the following characteristics with the correspondent layer

        of the Earth:

a. It is just below the crust and made up of peridotite.

b. It contains all the water on the Earth.

c. It is the thinnest Earth's layer. It is only few kilometres.

d. It is composed of a mixture of gases called air.

e. It is divided into two layers, the outer one of them is liquid.

1.2. Explain which is the main differences between:

a. the inner core and the outer core

b. the upper mantle and the lower mantle

c. the continental crust and the oceanic crust

1.3. Correct the following sentences:

a. The lithosphere is the flexible outermost part of the Earth.

b. The crust and some of the core make up the lithosphere.

c. Tectonic plates are large pieces that form the asthenosphere.

d. The lithosphere is a layer of semifluid rocks.

e. The atmosphere and the hydrosphere are solid layers.

f. The biosphere is composed of all living beings in the Universe.

1.4. Listen and indicate what layer of the Earth is described: