Earth Sciences: Earth's Spheres

Earth Sciences: Earth's Spheres

Earth is made up of four distinct yet connect spheres. In this video lesson, you will learn about where each sphere is found on Earth, as well as some features commonly found in each.

Earth Is Divided Yet Connected

Earth is a very complex place. Although it looks like one large structure, it's actually got a lot going on that you may not see if you don't look closely. All of the processes on Earth are driven by four 'spheres,' which we describe individually, but are really all connected.

The names of each of these spheres come from Greek words that describe what they're made of: 'Geo' for 'ground,' 'hydro' for 'water,' 'bio' for 'life' and 'atmo' for 'air.' Let's look at each of the four spheres in a bit more detail to gain a better understanding of how they help make up the earth.

Geosphere

Since 'geo' means 'ground,' the geosphere describes all of the rocks, minerals and ground that are found on and in Earth. This includes all of the mountains on the surface, as well as all of the liquid rock in the mantle below us and the minerals and metals of the outer and inner cores. The continents, the ocean floor, all of the rocks on the surface, and all of the sand in the deserts are all considered part of the geosphere. Basically, if it looks like solid ground, it's part of the 'ground' sphere.

Hydrosphere

Knowing that 'hydro' means 'water,' you may have guessed that the hydrosphere is made up of all the water on Earth. This includes all of the rivers, lakes, streams, oceans, groundwater, polar ice caps, glaciers and moisture in the air (like rain and snow). The hydrosphere is found on the surface of Earth, but also extends down several miles below, as well as several miles up into the atmosphere.

Most of Earth's water is salty and in the oceans - about 97%. Two-thirds of the remaining 3% is frozen in glaciers and polar ice caps. Only 1% of the hydrosphere is liquid freshwater, and even most of this exists as groundwater down in the soil.

Biosphere

With the prefix 'life,' this means that Earth's biosphere is composed of all of the living organisms on the planet. This includes all of the plants, animals, bacteria, fungi and single-celled organisms found on Earth. Most of this life exists no deeper than about 10 feet into the ground or about 600 feet above it.

Because each individual is so small in relation to the overall planet, organisms are often grouped into biomes, which are regional communities characterized by vegetation and climate. You are likely already familiar with some of these, like deserts, grasslands and rainforests.

Atmosphere

The final sphere is one you've probably already heard of. This is the atmosphere, which is the air that surrounds Earth. This 'air' sphere is made up of mostly nitrogen, some oxygen and small amounts of many other molecules.

Most of the atmosphere is densely packed near the surface (which is where all of our weather occurs), but it extends to over 300 miles above ground. However, exactly where it ends and space begins is difficult to say! The atmosphere acts like a giant blanket, protecting us from harmful UV radiation and keeping our planet warm.

Multiple Choice

Which statement about the four spheres of Earth is true?

• They often occur in the same place and interact.

• They do not occur in the same place and do not interact.

• Scientists think there are more than four spheres of Earth.

• They describe distinct layers of Earth's interior.

Multiple Choice

Which is NOT one of Earth's four spheres?

• biosphere

• troposphere

• hydrosphere

• geosphere

• atmosphere

Multiple Choice

The interior of the Earth is part of which sphere?

• biosphere

• chromosphere

• hydrosphere

• geosphere

• atmosphere

Multiple Choice

Why is rain not part of the atmosphere?

• Because it is part of the hydrosphere.

• Because it moves between spheres.

• Because it is part of the biosphere.

• Because it is part of the geosphere.

• Because it affects plants and animals in the biosphere.

Multiple Choice

Why are plants and animals part of the biosphere?

• Because they can travel in the air.

• Because things that are unaffected by weather are part of the biosphere.

• Because they can migrate.

• Because all living things are part of the biosphere.

• Because they live on the ground.