Earth and Space Science / Unit 1: Earth as a System
1.2 The Four Spheres
Notes
Earth is a system made of four connected parts called spheres.
- Geosphere: solid and molten Earth (rocks, soil, the interior).
- Hydrosphere: all water, liquid, ice and vapor. About 97% is salt water in the oceans.
- Atmosphere: the layer of gases around Earth, mostly nitrogen (78%) and oxygen (21%).
- Biosphere: all living things.
- The spheres interact. Example: rain (atmosphere) erodes a hillside (geosphere), carries soil into a river (hydrosphere), and changes where plants grow (biosphere).
Practice
Which sphere includes glaciers and lakes?
The hydrosphere is all of Earth's water, including ice.
The two most abundant gases in the atmosphere are:
About 78% nitrogen and 21% oxygen.
A volcano erupts and ash blocks sunlight, cooling the air and killing plants. Which spheres interact?
Rock and ash (geosphere) enter the air (atmosphere) and harm living things (biosphere).
Ready for more? Take the Unit 1 test.