Layers of the Earth
The Earth is made up of rock, but inside the Earth, the temperature is so hot the rock melts into liquid. There are 4 different layers of the Earth. The outer layer is called the crust and the inner layer is called the core.
The layer we stand on is called the crust. It’s cool and hard. It’s made up of huge slabs of rock called tectonic plates.
How are tectonic plates formed?
Heat from the core of the Earth rises through the mantle and up to the surface. As the heat rises it moves the mantle, making the mantle rise beneath the crust. The mantle then spreads sideways and cools down. When the mantle cools down it sinks again.
This rising of the mantle has broken a part of the Earth called the lithosphere. The lithosphere is made up of the Earth’s crust and the top part of the mantle. The breaking of the lithosphere has divided the Earth’s crust into tectonic plates.
Types of tectonic plates
There are two main types of tectonic plates: oceanic and continental.
Oceanic plates are made up of oceanic crust called sima. Sima is made of silicon and magnesium. That’s how it gets its name: silicon + magnesium = sima.
Continental plates are made up of continental crust called sial. Sial is made of silicon and aluminium. Silicon + aluminium = sial.
The movement of tectonic plates
Convergent boundaries: this is when two tectonic plates push against each other. Sometimes one plate can move under the other. When this happens it’s called subduction. Convergent boundaries can create mountains and volcanoes.
Divergent boundaries: this is when two tectonic plates are pulled apart. New crust is formed by magma pushing up from the mantle and cooling down. Divergent boundaries can create valleys, rifts and lakes.
Transform boundaries: this is when two tectonic plates slide past each other. These plates are often called faults and it’s common for earthquakes to occur there.
Did you know?
- Tectonic plates move around 1 inch every year.
- The Mariana Trench is the deepest part of the ocean. It is formed by a convergent boundary between the Pacific Plate and the Mariana Plate.
- Scientists are now able to track the movement of tectonic plates using GPS.
- The Himalayan Mountains, including Mount Everest, were formed by the convergent boundary of the Indian Plate and the Eurasian Plate.
- The Red Sea formed where the African and Arabian plates pulled apart. This rift is getting larger and the Red Sea will eventually form an ocean.
