The Physical Structure of the Earth

The Earth is made up of three main layers: the crust, the mantle, and the core.
These layers are classified based on their chemical composition and physical properties.

The crust is the Earth’s outermost layer and is thinnest beneath the oceans and thickest beneath continental land masses.
There are two types of crust: the oceanic crust and the continental crust.
Oceanic crust is denser but thinner, composed mostly of basalt, while continental crust is less dense but thicker, mainly composed of granite.
The boundary between the crust and the mantle is known as the Mohorovičić discontinuity (or simply the Moho).

Beneath the crust lies the mantle, which makes up about 84% of Earth’s volume and is rich in silicate minerals.
The mantle is divided into the upper and lower mantle, with the upper mantle consisting of peridotite, a rock denser than crustal rocks.
Convection currents in the upper mantle, driven by heat from the core, are believed to be the force behind plate tectonics.

The core is the innermost layer and is divided into two parts: the liquid outer core and the solid inner core.
Primarily composed of iron and nickel, the core generates the Earth’s magnetic field through the geomagnetic dynamo process.
The boundary separating these two parts is known as the Bullerwell discontinuity.

The Earth’s lithosphere consists of the crust and the solidified top part of the upper mantle.
Below the lithosphere lies the asthenosphere, a part of the mantle that behaves plasticly and flows slowly, allowing the tectonic plates to move on its surface.

The Earth’s lithosphere is divided into numerous tectonic plates that float on the semi-fluid asthenosphere below.
These plates interact at their borders causing seismic activity, volcanic eruptions, the creation of mountain ranges, and oceanic trenches.
There are three types of plate boundaries: divergent (plates moving apart), convergent (plates moving together), and transform (plates sliding past each other).