The History of the Earth

The Formation of the Earth

The Earth is thought to have been formed about 4.6 billion years ago by collisions in the giant disc-shaped cloud of material that also formed the Sun. Gravity slowly gathered this gas and dust together into clumps that became asteroids and small early planets called planetesimals. These objects collided repeatedly and gradually got bigger, building up the planets in the Solar Syste, including the Earth.

The details of how the Earth formed are still being worked out. Scientists study meteorites and the oldest rocks on Earth to understand what happened in these earliest times in the Solar System. They also observe other solar systems in our galaxy, the Milky Way.

Pangaea and the Continental Drift

Pangaea was a single super continent that existed during the late Palaeozoic and the late Mesozoic eras. It formed approximately 300 million years ago and then began to break apart 100 million years afterwards. Unlike the current formation of earth, much of the land mass was in the Southern Hemisphere. Pangaea was the first reconstructed super continent and was surrounded by a super ocean known as Panthalassa.

There is a lot of evidence to prove the existence of Pangaea for example...

~Fossils of the Mesosaurus was found in South America and Africa

~Fossils of the early fern Glossopteris was found in every continent.

~The Appalachian Mountain chain which extends from the southeastern United States to the Caledonides of Ireland, Britain, Greenland, and Scandinavia.

The two major areas of Pangaea were Laurasia and Gondwanaland. The separation of Pangaea was the start of the great Continental Drift. All of the continents in the world were a part of Pangaea until the tectonic plates slowly started to shift. Evidence for this is that South America wraps around the bottom of Africa and the fossils of Cynognathus was found in both of these countries. Below their is a map where you can see for yourself.  

Why do tectonic plates continue to move?

Tectonic plates move because they are floating on top of the liquid mantle. The mantle itself moves due to convection currents: hot rock rises, gives off some heat, then falls. This creates vast swirls of moving liquid rock under the crust of the earth, which jostles the plates of crust on top. Because of the constant movement, the tectonic plates cause earthquakes and tsunamis.

It is thought that the Americas will reconnect with Asia by closure of the Arctic Ocean and the Caribbean Sea. This will form the Supercontinent Amasia.

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