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USGS CMG InfoBank: Changes in the Lithosphere

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Comment: 05:53 - 06:41 (00:48)
Source: Annenberg/CPB Resources - Earth Revealed - 7. Mountain Building
Keywords: lithosphere, plate, "continental margin", "tectonic activity", convection, greenstone, protocontinent, mantle, "Jason Saleeby"

Our transcription: At about 2 billion years ago the general tectonic pattern appears to have changed where there was a higher organization of larger plates and continental margins, which began to move into more of a rigid plate tectonic domain.
That change may have been related to the development of a thick lithosphere.
Early in Earth history, there may have been a much thinner lithosphere, which promoted a much more random and faster shorter cycle pattern of convection to give us these ancient proto-continents, which we call the "greenstone belts".
But later on as perhaps the Earth cooled, and the lithosphere thickened, then we began to drive around thicker plates, and the continents began to embed themselves into plates that had mantle roots, and they began to develop their own unique lithospheres as well.

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