1. Geosphere: This system includes all solid, liquid and gaseous matter that constitutes the earth, it includes the crust, the mantle, and the core.

2. Hydrosphere: This system includes all of the earth's water, both in the liquid and frozen state, it includes the oceans, rivers, lakes, glaciers and groundwater.

3. Atmosphere: This system includes the layer of gases that surrounds the earth, it is made up of nitrogen, oxygen, water vapour and other gases.

4. Biosphere: This system includes all of the living things on the Earth, it includes plants, animals, and microorganism.

In addition to these four systems, earth scientists also study the interactions between these systems and how they shape the Earth's environment.