Comment: 03:09 - 03:59 (00:50)
Source: Annenberg/CPB Resources - Earth Revealed - 14. Intrusive Igneous Rocks
Keywords: volcano, "David Sigurdson", heat, radioactivity, isotope, potassium, thorium, uranium, decay, magma
Our transcription: Some of the original heat that results in the formation of magma comes from the original formation of the Earth.
As the materials came together that formed the Earth, they produced an enormous amount of compression.
Now, that was some four and a half billion years ago.
Some of that heat still remains in the interior of the Earth.
Another source is from radioactive isotopes.
Potassium, thorium, and uranium have all contributed as a result of radioactive decay to heating of the Earth, particularly in the earlier history of the Earth when these isotopes were more abundant.
Now, there's another contribution that comes from the tidal effects of the sun and the moon.
As the result of these tides, the Earth is being constantly being squeezed and flexed, and that tends to build up some heat in the Earth's interior as well.
Geology School Keywords