The Earth's structure
The Earth is made up of different layers.
- The inner core is in the centre and is the hottest part of the Earth. It is solid and made up of iron and nickel with temperatures of up to 5,500°C.
- The outer core is the layer surrounding the inner core. It is a liquid layer, also made up of iron and nickel.
- The mantle is the widest section of the Earth. It has a thickness of approximately 2,900 kilometres. The upper part of the mantle is called the The upper part of the Earth’s mantle, where the rocks are more fluid.. It is made up of semi-molten rock called magma.
- The crust is the surface of the Earth. It is a rock layer forming the upper part of the lithosphere. The The lithosphere is the outer layer of the Earth, which includes both the crust and the upper layers of the mantle. is split into tectonic plates.
Demonstrating the movement of the Earth's crust and how tectonic plates interact at plate boundaries
The theory of plate tectonics
The crust is the outer layer of the Earth. It is the solid rock layer upon which we live. It is either continental or oceanic. The surface of the Earth's crust found underneath large land masses. is typically 30-50 kilometres thick, whilst The surface of the Earth's crust found underneath the oceans, forming the ocean floor. is only five to ten kilometres thick. Oceanic crust is denser, can be When one crustal plate is forced beneath the other. and is constantly being destroyed and replaced at plate boundaries. Continental crust is older, lighter and cannot be destroyed.
Why do plates move?
One explanation for plate movements is slab pull. Plates are extremely heavy so gravity acts upon them, pulling them apart.
Alternatively, as shown in the diagram, convection currents under the Earth’s crust transfer heat, which rises through the surface and cools back down in a circular motion.
The convection currents move the plates. Where convection currents diverge near the Earth's crust, plates move apart.
Where convection currents converge, plates move towards each other, plates converge and the plates move together, also known as ridge push. The movement of the plates, and the activity inside the Earth, is described as the theory of plate tectonics.