Here is much evidence that Pangaea existed and that the seven continents used to be as one. Here are just some:

1. The most obvious piece of evidence is that the eastern coast of South America fits almost perfectly with the western coast of Africa.

2. In the fossil record, remains of the therapsid Lystrosaurus as well as the plant Glossopteris have been found in South Africa, India, and Australia, three regions currently separated by thousands of miles of ocean.

3. Similarly, fossils of the freshwater reptile Mesosaurus have been found on the coasts of Brazil and West Africa.

4. A polar ice cap covered the southern end of Pangaea during the Carboniferous period, and glacial deposits of the same age and structure are found throughout the southern continents.
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. The most obvious piece of evidence is that the eastern coast of South America fits almost perfectly with the western coast of Africa.

2. In the fossil record, remains of the therapsid Lystrosaurus as well as the plant Glossopteris have been found in South Africa, India, and Australia, three regions currently separated by thousands of miles of ocean.

3. Similarly, fossils of the freshwater reptile Mesosaurus have been found on the coasts of Brazil and West Africa.

4. A polar ice cap covered the southern end of Pangaea during the Carboniferous period, and glacial deposits of the same age and structure are found throughout the southern continents.

and many more, the list is too long

Here are some pieces of evidence to prove that Pangaea did exist:
1) Fossils of the same species of dinosaurs were discovered on different continents, and as these dinosaurs could not have swam across the oceans, the must have walked from one continent to another, therefore, Pangaea existed.
2) The coasts of continents (e.g. the east coast of South America and the west coast of Africa) could be joined/fitted together almost nicely, like pieces of jigsaw puzzles.
3) Theories of continental drift and plate tectonics (which causes earthquakes...) evidently proves that the continents drifted apart.

Here are some pieces of evidence to prove that Pangaea did exist:
1) Fossils of the same species of dinosaurs were discovered on different continents, and as these dinosaurs could not have swam across the oceans, the must have walked from one continent to another, therefore, Pangaea existed.
2) The coasts of continents (e.g. the east coast of South America and the west coast of Africa) could be joined/fitted together almost nicely, like pieces of jigsaw puzzles.
3) Theories of continental drift and plate tectonics (which causes earthquakes...) evidently proves that the continents drifted apart.
4) The continents are still drifting apart very slowly and the oceans are still expanding up till today.
5) Paleozoic glacial deposits have been found on the continents forming Gondwanaland (Africa, Antarctica, South America, Australia/Oceania) and there were glacial striations left behind on rocks in this area.
6) Mountain belts/chains on different continents have quite similar rocks and ...more