- Anything in Earth's system can be placed into one of four major subsystems: land, water, living things, or air.
- These four subsystems are called as "spheres".
- Four important spheres/ realms of earth to support life on Earth are:
- Land on which we live.
- solid outer layer of the Earth consisting of rocks and soils.
- The surface of the lithosphere (Earth surface) is very uneven.
- There are high mountain ranges like the Himalayas, Rockies and Andes, huge plains or flat areas like Indo-Gangetic plain and deep valleys.
- The Hydrosphere comprises of all the solid, liquid, and gaseous water of Earth.
- Thickness:10 to 20 kilometres
- The range of Hydrosphere is from the Earth's surface to several kilometres into the lithosphere and
- upward about 12 kilometres into the atmosphere.
- Consists of water bodies such as oceans, seas, rivers, lakes, ice caps on mountains and water vapour in the atmosphere.