Summary

• Earth can be considered as a system consisting of four main spheres – the lithosphere, hydrosphere, atmosphere and biosphere.

• The lithosphere (geosphere) is Earth’s solid outer layer consisting of the crust and upper mantle.

• Igneous, sedimentary and metamorphic rocks in the lithosphere are connected by a series of processes known as the rock cycle.

• The outermost region of the lithosphere consists of a thin layer soil, which is sometimes categorised as its own sphere called the pedosphere.

• The hydrosphere incorporates all the water on Earth.

• Water moves through the hydrosphere via a series of processes known as the water cycle.

• Frozen water is sometimes categorised as its own sphere called the cryosphere.

• The atmosphere is a mixture of gases, collectively known as air, that forms a layer surrounding Earth.

• The atmosphere is composed of five main layers – the troposphere, stratosphere, mesosphere, thermosphere and exosphere.

• The biosphere incorporates all parts of Earth where living organisms are found.

• The biosphere is connected by food webs consisting of producers, consumers and decomposers.

(Image: IslandHopper X, Pexels)