A German meteorologist, Alfred Wegener, suggested that the continents may not have always been in the same place as we see them today. He believed that they had once all been joined together in a single landmass. He made his claim in the early part of the 20th century but scientists of the time dismissed his ideas as being silly.
Less than fifty years later, scientists realised that all of the evidence suggested that Wegener was correct and in the 1960s, evidence of seafloor spreading was the final piece of evidence that showed he was correct. This led to the development of the theory of plate tectonics and we now take these ideas for granted. For your GCSE, you are expected to know how this theory explains how the natural hazards of volcanoes and earthquakes occur as well as understanding how humans deal with them.