Earth scientists find it handy to sort everything on our planet into four big parts, called spheres. Each one is a system of its own, and they are all linked.
| Sphere | What it holds | Examples |
|---|---|---|
| Geosphere | Solid Earth: rock, soil and the hot interior | mountains, sand, magma, the core |
| Hydrosphere | All of Earth's water, liquid and frozen | oceans, rivers, glaciers, groundwater, clouds |
| Atmosphere | The layer of gases around Earth | air, wind, water vapor |
| Biosphere | Every living thing | trees, people, bacteria, whales |
Key idea
Earth has four spheres: geosphere (rock), hydrosphere (water), atmosphere (air) and biosphere (life). Almost every event on Earth moves matter or energy between two or more of them.
Why it works
The spheres share space and trade materials all the time. Rain falls from the atmosphere into the hydrosphere. Plants (biosphere) pull water out of soil (geosphere) and breathe it into the air (atmosphere). Because matter and energy keep flowing across the boundaries, a change in one sphere usually shows up in the others.
Worked example: Rain on a hillside
Heavy rain washes soil from a hillside into a river. Which spheres are involved?
- The rain comes from clouds: atmosphere.
- The soil is broken rock and once-living matter: geosphere.
- The river is water: hydrosphere.
- If the muddy water buries plants or fish eggs, the biosphere is involved too.
Answer: At least three: atmosphere, geosphere and hydrosphere
Worked example: Where does it belong?
Sort a glacier, a volcano's ash cloud and a coral reef.
- A glacier is frozen water: hydrosphere.
- Ash is tiny bits of rock, so it belongs to the geosphere, even while it floats in the atmosphere.
- A coral reef is built by living animals: biosphere (its stony skeleton later becomes part of the geosphere).
Answer: Hydrosphere, geosphere, biosphere
Common mistake
Treating each sphere as a separate box. Most real events involve two or more spheres at once. A quick check: for any event, ask "Where did the matter come from, and where did it go?" If the answers name different spheres, they interact.