1. The Earth's layers
We can distinguish four layers or "spheres" in the Earth.
These "spheres" are interrelated. They are:
1.1. The geosphere
The Earth's inside is divided into three concentric layers:
a) The crust
This is the outer layer of the Earth.
It is very thin, just only a few kilometers.
It is solid and is composed by silicates.
There are two types of crust:
- Continental crust
It makes up the continents.
It is thicker than the oceanic crust.
The most common rock on it is granite.
- Oceanic crust
It makes up the ocean floor.
It is thinner than the continental crust.
The most common rock on it is basalt.
b) The mantle
This is the middle layer.
It is situated just below the crust.
It is a very thick layer, about 2.900 km thick.
It is composed by a rock called peridotite.
It is a semi-solid layer and it is divided into two parts:
- The upper mantle
- The lower mantle
c) The core
This is the inner layer.
It is situated just below the lower mantle.
It the thickest layer, about 3.500 km thick.
Its composition is mainly iron.
It is divided into two concentric layers:
- The outer core. It is liquid.
- The inner core. It is solid
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.
READING ACTIVITIES
After reading the text, copy and answer the following questions into your notebook:
Remember: you must make complete sentences.
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:
a. Atmosphere
b. Hydrosphere
c. Geosphere
d. Biosphere
Now,
check
your
answers!