The Earth Layers, Rocks and Minerals.

The atmosphere.

Is the gaseous part of the Earth.
It is a mixture of gases composed of nitrogen, oxygen, carbon dioxide, water vapour and ozone.

Structure of the atmosphere: The atmosphere has different horizontal layers:
the troposphere, stratosphere, mesosphere and thermosphere.



The troposphere is the layer closest to the Earth, and it is the layer in which we live.
Te stratosphere lies above the troposphere. This layer has the ozone layer in it.
The ozone layer  protects all life on earth from the harmful and potentially lethal ultraviolet radiation emitted by the Sun.

The atmospheric pressure is the weight of the atmosphere on the Earth.

The Hydrosphere.

Is the water found in the Earth.

· 97% of water is in the oceans and we can't drink it.
· Only 3% of water is freshwater. Most of it is stored at the polar icecaps in the form of ice.
· A part of the freshwater is groundwater, and a little quantity is the so called surface water.

The water cycle is a continuous cycle in which water changes from water vapour in the atmosphere to liquid water on the Earth, and back to water vapour again.
The four processes are: evaporation, transpiration, condensation and precipitation.



Earthquake analysis around the Earth allows to establish the Earth's internal structure. It is believed that the Earth has three different layers: crust, mantle and core

The crust and the external part of the mantle is divided into tectonic plates.

Mineral: is a natural solid substance with a definite chemical composition.
Some mineral properties are:

· Lustre
· Hardness
· Colour
· Transparency
· Magnetism



Rocks: are natural substances formed by one or more minerals or made of remains of living things.

- Granite is formed by 3 minerals.
- Marble is formed by 1 mineral.
- Coal and petrol are made of remains of living things.

There are three types of rocks:

a) Sedimentary rocks: formed when sediments are compacted.
b) Igneous rocks: formed when magma cools down.
c) Metamorphic rocks: from rocks subjected to high pressure or high temperature.