GCSE Geology WJEC

Earth's structure

Earth's Structure

Inner Core

• The inner core is the central part of the earth.
• It is mostly composed of iron and nickel, giving it strong magnetic properties.
• Pressure at the inner core is extremely high - about 3 million times atmospheric pressure.
• Despite the high temperatures (up to 5700°C), the inner core is solid due to immense pressure exerted on it.

Outer Core

• Surrounding the inner core is the outer core.
• This is a layer of molten iron and nickel. Its temperatures range between 4000°C and 5700°C.
• The outer core is responsible for the creation of Earth's magnetic field through a process known as the dynamo effect.

Mantle

• Above the outer core lies the mantle, the thickest layer of the Earth.
• It's divided into the upper mantle and the lower mantle, each with different geological properties.
• The mantle is composed mostly of silicate rocks, rich in iron and magnesium.
• The upper layers of the mantle mix with the plates of the crust, forming a region called the asthenosphere.

Crust

• The uppermost layer of the earth is called the crust.
• It is relatively thin compared to the other layers, with depths ranging from 5km to 70km.
• Two types of crust exist: the oceanic crust (density around 3.0g/cm³) and the continental crust (density around 2.7g/cm³).
• The crust is mainly comprised of silicate rocks and is broken up into numerous tectonic plates.

Lithosphere

• The lithosphere is the rigid outermost shell of a planet.
• Earth's lithosphere includes the crust and the uppermost mantle.
• The lithosphere is broken into a number of tectonic plates that float on the semi-fluid asthenosphere beneath.