Name the three layers that make up the Earth. Describe plate tectonics and seismology.
Identify the three types of rock that the Earth’s crust is composed of: igneous, sedimentary and metamorphic.
The Earth is a huge rock that orbits the Sun. It was formed approximately 4,600 million years ago in molten (liquid) form. Over time, it cooled to become the Earth we live on today.
The Layers of the Earth The Earth is made up of three layers: 1. The crust 2. The mantle 3. The core.
1. The Crust
The outside layer of the Earth is the crust. The oceans and continents lie on top of the crust.
Along with the atmosphere, the crust is the part of Earth that can support life. This is the called the biosphere.
2. The Mantle Beneath the Earth’s crust is the mantle.
The mantle is mostly made up of solid rock, except for the upper mantle, which is made of liquid called magma. Magma is a mixture of hot molten or semi-molten rock.
Outer core
3. The Core The centre of the Earth is the core. It is the hottest part of the planet. The core is made up of two layers: zz z z
z
Fig. 22.1.1 The structure of the Earth
Inner core
Key Words
Crust Mantle Magma Core
Plate tectonics Seismology Igneous
Sedimentary Metamorphic
Crust Mantle
22.1
The outer core is a thick liquid made up of molten iron and nickel.
The inner core is also made up of iron and nickel, but here they are in a solid state because of the very high pressure.
As the core is mostly made up of metal, the Earth has its own magnetic field. This magnetic field has a big influence on natural processes and is one of the reasons life has survived on Earth.
Learn more about the Earth’s magnetic field in Physical World 18.1
