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Primary 5
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The Earth
The three spheres of The Earth
atmosphere
hydrosphere
geosphere
The atmosphere is the layer of gases that surrounds the Earth
It consists mostly of nitrogen but also contains oxigen, carbon dioxide and other gases
The hydrosphere is all the water that exists on Earth
glaciers rain
riversoceans
groundwater
The geosphere is the part of the Earth that includes the rocks and minerals. They make landforms , such as mountains.
The atmosphere
What is the atmosphere?It’s the layer of gases that surrounds the Earth: Nitrogene, oxygen, carbon dioxide and others. It has different layers:
Troposphere (17 km)It’s the layer where living things are found. Contains weather systems (rain, wind)Most of the gases are in the troposphere
Mesosphere (85 km)It’s the coldest layer of the lower atmosphereThis layer protects the Earth from meteors
Outer layers of atmosphereOuter space
Stratosphere (50 km)Contains the ozone layer. The ozone layer absorbs ultraviolet light from the sun and reflects it back into space
troposphere
17 km
StratosphereOzone layer
Mesosphere
Outer layers of the atmosphere
Outer space
85 km50 km
The geosphere
What is the geosphere?
The geosphere is the solid part of the Earth. It’s made up of three spheres: The core, the mantle and the crust
crust
core
mantle
The crust is the outer layer and it’s made of rocks and minerals. It forms the continents, the islands and ocean floors. We can see landforms here: mountains, valleys
The mantle is the middle layer and contains a liquid rock called magma
The core is the inner sphere and it’s made of iron (liquid and solid). It’s the hottest part of the Earth
Earthquakes and volcanoes can change or move the crust
The wind, rain, ice and rivers can also change the Earth’s crust, very slowly.
This processes are called weathering and erosion
Weathering is the breaking down of rocks into smaller pieces
by plants or by animals
It can be caused by rain and freezing temperatures
Erosion is the moving of soil and rocks to a different place
Rocks and minerals
Rocks are made of one or more minerals
We can classify rocks into three groups:
• Sedimentary rocks: they are made of sediments (chalk)
• Metamorphic rocks: (marble)
• igneus rocks:
they form when liquid magma cools
• igneus rocks:
they form when liquid magma cools: (basalt)
• Metamorphic rocks: (marble)
There are thousands of minerals on Earth and we clasify them by their different properties: colour, hardness and lustre. Diamonds, galena, talc, are some examples of minerals
The hydrosphere
What is the hydrosphere?
The hydrosphere is all the water that exists on the Earth
solid
We can find water in three states
Liquid: saltwater and freshwaterOnly 1% of all the water
Gas: water vapour
A river starts in the source
It forms meanders
It ends at the mouth
The path of a river is called a course. We can divide the course into three parts: the upper course, the middle course and the lower course
Small rivers are called tributaries