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Earth, the planet on which we live, is not a solid ball of rock. The Earth and its atmosphere provide everything needed to sustain life. The Earth consists of several layers, and the surface and atmosphere that we know today has changed a lot since it was first formed.
Before the 20th Century, no-one really knew how mountains were formed, or why rocks could be folded and broken. Earthquakes and volcanoes just happened, no-one had managed to satisfactorily explain why they happened. The first person to start to make sense of things was the German scientist, Alfred Wegener. He noticed that the continental shelves of some of the continents matched up closely. He also realized that identical fossils and rocks were now separated by thousands of miles of ocean. He devised the idea of continental drift. Other scientists rejected his idea as there was no mechanism to make it happen. In the 1960s, that evidence began to appear and the theory of plate tectonics was developed and is now very widely accepted.
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