Earth Science The Earth’s surface is constantly changing. Some changes happen very slowly over long periods of time, such as weathering, erosion, and uplift. Other changes happen abruptly, such as landslides, volcanic eruptions, and earthquakes. All around us, we see the visible effects of the building up and breaking down of the Earth’s surface.

If you could cut Earth in half, you would find it made up of layers. At its center is a solid core of metal, which is surrounded by a liquid metal core. The liquid core spins as the earth rotates, which creates Earth's magnetic field. Together, these two parts of the core are about 2,200 miles (3,520 km) thick and unimaginably hot. If you could cut Earth in half, you would find it made up of layers. At its center is a solid core of metal, which is surrounded by a liquid metal core. The liquid core spins as the earth rotates, which creates Earth's magnetic field. Together, these two parts of the core are about 2,200 miles (3,520 km) thick and unimaginably hot.

The uppermost part of the mantle is more solid and cooler than the rest of the mantle. It combines with the thin, solid crust to form a layer called the lithosphere. It is this layer that has been broken into pieces, or tectonic plates. So where are the plates?

These plates float on a part of the mantle that is made mostly of melted rock. Although we cannot feel it, the plates are slowly, but constantly, moving––carrying with them the continents and oceans that rest on Earth's crust.

They are moving very slowly, but constantly. (Most plates are moving about as fast as your fingernails are growing -- not very fast!) Currently Earth’s surface layers are divided into nine very large plates and several smaller ones.

Pangaea In 1915, the German geologist and meteorologist Alfred Wegener first proposed the theory of continental drift, which states that parts of the Earth's crust slowly drift atop a liquid core. The fossil record supports the theories of continental drift and plate tectonics. Wegener hypothesized that there was a gigantic supercontinent 200 million years ago, which he named Pangaea, meaning "All-earth". Alfred WegenerPangaea

A volcano is an opening in Earth’s crust that allows hot, melted rock, ash, and gases to erupt outward. Hot rock deep in the Earth expands and is forced out the opening. As the rock cools, it may form a mountain on Earth’s surface, or it may flow and form a large flat layer of rock.

Earthquakes are energy waves passing through Earth caused by a sudden shift of Earth’s crust along a fault. A fault is a crack in Earth’s crust that allows the crust to slip.

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