I take it as 1416m from the sea floor. Like the others said, depends on how deep it is. I would assume though that they picked a deep section as to minimize the amount of drilling they needed to do.
To Kidder... the mantle doesn't turn to liquid as soon as it hits that inivisible line that you see in school pictures. It's a gradual change from solid to liquid. It increases at about a rate of 30 degrees C per km. At 5000m, it's about 150 degrees (according to my text).
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