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The problem with that line of thinking is addresses in the article. The oldest large scale area of "ancient" crust on land is a mere 1.8 million years old (the
by cc439 8y ago
The problem with that line of thinking is addresses in the article. The oldest large scale area of "ancient" crust on land is a mere 1.8 million years old (the Negev Desert). The entire surface of the earth is regenerated on a scale of tens of millions of years, any depletion of surface deposits which occured ~100 million years ago would have long since been hidden by the replenishment of new crust provided by plate tectonics.
- soneil 8y agoI don't believe it covers that at all. I believe their definition of crust there is a lot more superficial than it sounds like. eg, the Chicxulub (Yucutan) crater is 66 million years ago, and clearly hasn't been recycled else we wouldn't be looking at it. We have dinosaur fossils dating ~230-240 million years, so the crust clearly hasn't been recycled that thoroughly. Indeed, the entire Pangea theory would be invisible to us if the continents didn't remain 300+ million years later. (I'm not saying we should have a fossil record of 'the others', as the article says, there's a survivor bias in fossils. Just that the fossils we do have wouldn't exist if the crust has been geologically renewed in the last few millions of years.) They're talking about surface markers like roads and buildings. To replace a previous civilization's trashheaps with geological mineral seams, you'd need to pre-date Pangea.