My question stems from archeologists that say there’s evidence of water erosion on the Sphinx, however, that’s just speculation. There are though settlements and sites in Iraq and Iran that used to be river basins and are now desert. So I just don’t understand how they could use any kind of wear marks in any stone foundation or bedrock cause of wind erosion. I get the example look at the Grand Canyon, but that’s millions of years, scientists today seem to be able to get within 1000 of years and I don’t understand how they can tell the difference between.
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It is because since water erosion is so slow and predictable that when a certain amount of material is removed, as long as you know how much was removed, as well as how much water passes there you can easily average out how long it would take. Keep in mind that the erosion on the sphinx occurs slower than that of the Grand Canyon because the grand canyon is a constant river and the sphinx get occasionally rained on.
It’s not just signs of erosion that scientists can look for.
Obviously big physical indicators like canyons can tell you where a river was, but there are also some not-so-obvious signs. Over time, rivers change shape by widening, and making bigger and bigger curves. Sometimes, those curves get cut off when the river changes course again, leaving a large body of water that’s completely disconnected from a source/outlet. These can create temporary bogs that animals and plants will get trapped in, and over time those organisms fossilize.
With those fossils, scientists can use Carbon-14 dating to get a fairly accurate estimate of when the bog was catching animals, and they can use that data to estimate the timeframe that the river existed in.
Another is soil composition, the exact breakdown of minerals. Scientists/geologists can analyze the exact physical and chemical makeup of the dirt in a given area. If they notice a high concentration of minerals that are out of place for that area, it could be evidence of a river carrying sediment from one location to another.
Yet another indicator can be man-made. Early civilization was required to be near a fresh source of water before the invention of aqueducts. A long, thin, winding town might be an indicator of a river-adjacent society.
I’m no expert, and my last example is based on a single documentary I watched as a kid, so do take this with a grain of salt.
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