Lecture 25-26 Earth's Structure(1)

If it was a molten mass over 4 billion years ago then

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Unformatted text preview: l༆  Much higher than expected temperatures and pressures closed the hole before they got anywhere close – 12.2km l༆  At these high temperatures and pressures (> 200 º C and > 360 MPa, the rock is more of a plasHc than a solid. 4 l༆  Why is the Earth so hot, if it’s over 4 Billion years old? Surely in that period of Hme it should have cooled down….. l༆  Well it should have. If it was a molten mass over 4 billion years ago then it should be cold and solid from the inside to the outside by now. l༆  Some of the Earth’s heat would get to the surface by conducHon. l༆  Some of the heat would get there by convecHon l༆  In the late 19th century, Lord Kelvin calculated from basic thermodynamic principles, and temperature data available at the Hme, that the Earth was about 80 million years old. ConHnents were ‘wrinkles’ on drying fruit. l༆  But he didn’t know about radioacHvity….. 5 7 ConHnental Drii 8 •  In 1912 Alfred Wegener proposed that at one Hme all of the Earth’s land mass had been joined together (he called thi...
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