Earth’s Systems

Scientists who study Earth have identified four main Earth systems: the geosphere, atmosphere, hydrosphere, and biosphere. Each system is unique, yet each interacts with the others.

Geosphere The area from the surface of Earth down to its center is called the geosphere. The geosphere is divided into three main parts: the crust, mantle, and core. 

The rigid outer shell of Earth is called the crust. There are two kinds of crust—continental crust and oceanic crust. Just below the crust is Earth’s mantle. The mantle differs from the crust both in composition and behavior. The mantle ranges in temperature from 100°C to 4000°C — much warmer than the temperatures found in Earth’s crust. Below the mantle is Earth’s core. 

Atmosphere The blanket of gases that surrounds our planet is called the atmosphere. Earth’s atmosphere contains about 78 percent nitrogen and 21 percent oxygen. The remaining 1 percent of gases in the atmosphere include water vapor, argon, carbon dioxide, and other trace gases. Earth’s atmosphere provides oxygen for living things, protects Earth’s inhabitants from harmful radiation from the Sun, and helps to keep the planet at a temperature suitable for life. 

Hydrosphere All the water on Earth, including the water in the atmosphere, makes up the hydrosphere. About 97 percent of Earth’s water exists as salt water, while the remaining 3 percent is freshwater contained in glaciers, lakes and rivers, and beneath Earth’s surface as groundwater. Only a fraction of Earth’s total amount of freshwater is in lakes and rivers.

Biosphere The biosphere includes all organisms on Earth as well as the environments in which they live. Most organisms live within a few meters of Earth’s surface, but some exist deep beneath the ocean’s surface, and others live high atop Earth’s mountains. All of Earth’s life-forms require interaction with at least one of the other systems for their survival.