Internal structure of Earth

The internal structure of Earth is the way Earth is built inside, with different layers that have unique properties. These layers include an outer silicate crust, a soft layer called the asthenosphere, a solid mantle, a liquid outer core, and a solid inner core. The movement of the liquid outer core is what creates Earth's magnetic field, which protects us from harmful space rays.

Scientists learn about Earth's inside by looking at the land and oceans, studying rocks brought up by volcanoes, and analyzing seismic waves that travel through the planet. They also study Earth's gravitational and magnetic fields, and perform experiments with rocks under extreme pressures and temperatures to understand what happens deep inside Earth. This helps us know how our planet works and why it behaves the way it does.

Global properties

Note: In chondrite model (1), the light element in the core is assumed to be Si. Chondrite model (2) is a model of chemical composition of the mantle corresponding to the model of core shown in chondrite model (1).

We can learn about Earth by studying how its gravity pulls on objects. Scientists measure this pull to find out how much Earth weighs. They also watch how satellites move around Earth to help calculate its mass. Through careful experiments, they have found that Earth’s average density is 5.515 g/cm³. Earth’s mass is about 6×10²⁴ kg.

Layers

The Earth is made up of several layers, each with its own unique properties. These layers include the crust, which is the thin outer layer we live on, and the mantle, which is a thick layer below the crust made of hot, flowing rock. Deep inside the Earth, there is a liquid outer core and a solid inner core. The movement of the liquid outer core helps create Earth's magnetic field, which protects us from harmful space rays.

The structure of Earth can be understood by looking at how it behaves mechanically and chemically. Mechanically, Earth is divided into layers like the lithosphere, asthenosphere, mesospheric mantle, outer core, and inner core. Chemically, it is divided into the crust, upper mantle, lower mantle, outer core, and inner core. These layers are found at increasing depths below the surface.

Earth's crust varies in depth from 5 to 70 kilometres and is the outermost layer. The thinner parts under the oceans are called oceanic crust, while the thicker parts under continents are called continental crust. The mantle, which is the thickest layer, extends to a depth of 2,890 kilometres. It is made of hot, flowing rock and is divided into an upper and lower mantle.

Earth's outer core is a fluid layer about 2,260 kilometres thick, made mostly of iron and nickel. Below this lies the solid inner core, discovered in 1936, which is primarily composed of iron and nickel. The inner core is solid because it can transmit certain types of seismic waves. The core plays a key role in generating Earth's magnetic field, which is vital for protecting life on our planet.

Seismology

Main article: Seismology

Scientists learned about Earth's layers by studying waves from earthquakes. These waves move at different speeds through different layers, bending and reflecting like light. This helps us understand how Earth is built inside.