How Marble Bar formed

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This is a transcript of a QuickTime movie (6.9 MB) recorded in the Pilbara in 2005. Dr Martin Van Kranendonk, a geologist with the Geological Survey of Western Australia, discusses how the Marble Bar area was formed over three billion years ago.


These rocks are 3.467 billion years old, all right? So the Earth as we know it formed at about 4.55 billion so these are a billion years younger than the start of the Earth. We’re talking in big number scales now, that’s nine zeros. So that’s a lot of years in between that we get the preservation of this stuff and when Earth first formed. And so it had to cool enough so that there was enough crust that could differentiate from the mantle to form these little relic blobs that were stable on the Earth as opposed to just getting vigorously convected back down. That happened for the first billion years and meteorites came in and pounded it around. Nothing could survive really. But now Earth is getting a bit gentler, a little bit cooler. There’s enough differentiation of crust to actually preserve itself on the sea floor and remain, even though it’s tilted over and all sorts of things happened. But it did get a nucleus that allowed it to survive.




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