[DB 1507 (27); OAB 22] The claim is that the size and growth rate of river deltas proves that they cannot be very old. The error here seems to lie in thinking that the delta consists only of what are actually the very youngest delta deposits (the parts that still look like delta deposits). In fact, the Mississippi Delta, which is used by young-Earth advocates as an example, actually consists of a seven-mile-thick layer of sediment covering much of the south-central U.S. (by contrast, sedimentary rocks in most places on Earth are only one mile thick). The same is generally true at the Earth's other great river deltas. River deltas are actually a potent argument against the young-Earth hypothesis. Not only are the 7 miles of Mississippi delta sediments far more than could accumulate in 10,000 years (especially since delta deposits cannot accumulate underwater, and thus could not have been accelerated by Noah's Flood), but the observed sinking of the crust under the weight of the delta, which keeps the surface at sea level and allows the delta to continue forming, could only happen very slowly.