Listen to part of a lecture in an Earth Science class. The class has been discussing volcanoes.Okay. We know the Earth’s surface, the crust, is made up of tectonic plates,and that these huge slabs of rocky crust are slowly sliding over or under or past each other.And we said that most of the world’s volcanoes occur at the boundaries of these tectonic plateswhere you have hot molten rocks squeezing up through gaps between the plates.But some volcanoes occur not at the edges, but in the middle of a continental or oceanic plate.The Hawaiian islands, for example, are thousands of kilometers away from any plate boundary, and yetyou have vast amounts of magma, molten rock or lava, flowing up through the earth’s crust, which means, of course,that volcanic activity there can’t be explained simply by plate tectonics.So, how do we explain these volcanic anomalies, these exceptions to the general rule?Well, back in 1963, a geophysicist by the name of Wilson came up with a hot spot theoryto explain how this particular type of volcanic activity can occur and can go on for maybe tens or even hundreds of millions of years.
