Characteristics of the geosphere

The Earth and the rest of the Solar System were formed about 5000 million years ago from a nebula, a large cloud of gas made up of mainly hydrogen and helium, and of cosmic dust. The explosion of a supernova could originate an expansive wave that caused the movement of the particles and the formation of a large disk.

The materials were concentrated by the action of gravity, originating a great mass of hydrogen and helium whose temperature increased until thermonuclear fusion reactions took place and originated the Sun.

The rest of the matter revolved around the Sun and they were grouped into planetesimals that collided and fused to give rise to the planets, which were balls of incandescent materials. These molten materials were grouped in layers according to their density. The densest materials sank to the interior of the Earth, and the less dense remained in the outer layers and around the Earth.

In this way, the structure of the Earth is made up of a series of concentric layers. The solid part, the geosphere, is divided into several layers, surrounded by another gaseous layer, the atmosphere. As it cooled, the water vapor condensed and formed liquid water, which accumulated until forming the hydrosphere. In addition, life arose throughout the Earth, occupying its surface, and constituted the biosphere.

Therefore, it can be said that the Earth is divided into four layers:

• Geosphere: it constitutes the solid part of our planet, characterized by the relief of its surface and by the layers that compose it. In this topic we are going to focus on how the geosphere is constituted.
  
• Atmosphere: it is the layer formed by the gases that form the air and that surrounds the Earth. Its existence is vital for living beings.
• Hydrosphere: it is formed by all the existing water on Earth.
• Biosphere: Although it is not really a layer, it includes all the ecosystems on Earth. That is, living beings and the environment in which they inhabit.

By Bojana Petrović [CC BY-SA 4.0 ], from Wikimedia Commons

Interactive activity: The layers of the Earth.

Interactive activity: The layers of the Earth (2).

Interactive activity: Order these materials.

The relief of the geosphere

The land surface presents a relief that leaves both emerged and submerged areas under water.

• Reliefs of the emerged areas. The emerged areas correspond to the continents and the islands. There are mountainous areas that are at a higher altitude than other areas, such as the plains.

• Reliefs of the submerged areas. In addition to the ocean floors, the continental shelves, ridges and ocean trenches stand out.

The layers of the geosphere

The Earth has a radius of about 6,370 km (it varies between 6,378 km at the equator and 6,357 km at the poles). There are different methods of studying the Earth, such as the seismic method, which have allowed us to know what the internal structure of the Earth is like even though they cannot be accessed directly. 

The Earth is divided into three layers, separated by areas called seismic discontinuities due to a change in the speed of the seismic waves that pass through them:

• Crust.
• Mantle.
• Core.

By Vectorized and translated from the English version by Jeremy Kemp. Based on elements of an illustration by USGS. http://pubs.usgs.gov/publications/text/inside.html [Public domain], from Wikimedia Commons

Interactive activity: Structure of the Geosphere.