### Theory:

• 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:

Lithosphere:
• Land on which we live.
• The 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 the Indo-Gangetic plain and deep valleys.

Hydrosphere:
• The Hydrosphere comprises of all the solid, liquid, and gaseous water of Earth.
• Thickness of hydrosphere: $$10$$ 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.