I was also surprised by the statement that the oldest extant large-scale surface is ~1.8 Ma old. There is a citation provided for this [1]. It seems the point i

I was also surprised by the statement that the oldest extant large-scale surface is ~1.8 Ma old. There is a citation provided for this [1]. It seems the point is that older features like mountain ranges are subject to significant erosion (as you point out, a marine environment can become alpine during the life of a mountain range) and that this could destroy or disperse most evidence of an industrial civilisation that lives for only a few centuries. The oldest surface which preserves archaeological evidence, due to its low rate of erosion, is merely in the millions of years, whereas what we know about earlier periods is extrapolated from a tiny sample of exposed sections of the earth’s crust. Meanwhile, the seabed is recycled on the 100 Ma scale, and eukaryotic life has been around for 2 Ga. That is a lot of recycling. [1] http://geomorphology.sese.asu.edu/Papers/Matmon%20et%20al.%20-%202009%20-%20Desert%20pavement--coated%20surfaces%20in%20extreme%20desert%20(1).pdf http://geomorphology.sese.asu.edu/Papers/Matmon%20et%20al.%2...