Rivers meander over their course as they continuously erode and deposit sediment. Harold Fisk, a geologist and cartographer working for the US Army Corps of Engineers, mapped the meanders of the mighty Mississippi in 1944 and the results are mesmerizing. They also beautifully illustrate geology’s Law of Superposition: newer and younger sediments are deposited on top of older sediments. We see thousand of years of course changes. You can unravel the layers by eye by noting which layer cuts others