Stokes’ law (with further modifications in light of the shapes of the particles) tells how fast a particle will settle through a fluid. Smaller particles have a high ratio of surface area to mass, so friction slows them down a lot. This determines how quickly a layer could be deposited - how big are the pieces in it? Walther’s law describes the pattern - what types of facies are usually found in a sequence. But Walther’s law requires slow, gradual change. Tsunamis mix everything up and don’t produce a pattern like Walther’s. Actual major floods, such as the refilling of the Mediterranean after the Messinian, do not follow Walther’s law. Instead, there is an abrupt change from one facies to a quite different one. Such a change can also occur if there is a long gap of nondeposition between one layer and the next. Examining the contact layer is a good clue. For example, in an ocean setting, there will often be evidence that the contact between layers was sitting exposed on the ocean floor for a long time. Animals make holes down into the lower layer, there may be chemical changes at the surface, if the lower layer is hard there may be attached organisms like corals or oysters growing on it, there’s often an accumulation of worn bone and teeth. Such surfaces would have no time to form during a flood geology flood, as Kurt Wise pointed out. But they are found throughout the geologic record.
Michael Tuomey’s 1848 Geology of South Carolina has a short section discussing how geology supports a biblical picture. He briefly dismisses young-earth concerns as a thing of the past, noting that about five minutes of studying the rocks should be enough to show that they are quite old. He doesn’t accept the evolutionary ideas favored by a minority in his day, but particularly focuses on the fact that the geological and biblical records both pointed back to a beginning, not to the eternal cycles popular in “Enlightenment” imagination.
His estimate of five minutes, though, presupposes the understanding that had developed over 200 years. Steno, in the 1660’s, was the first to publish on understanding the pattern of rock layers. In particular, he pointed out that layers underneath would be older than those above, and layers with matching features found in different places could be identified as being the same layer (among other patterns). Building on this, by the late 1600’s, it was clear that there were a lot of geological layers, and people began to suspect that they might require a while to form. By the early 1700’s, it was clear that a single flood was not a possible explanation - the layers did not show hydraulic sorting, and looked like ordinary accumulations of sediment such as could be seen slowly piling up today. As people looked at various parts of Europe, and eventually other regions in the world, they began to see that some of the same layers could be recognized quite widely, as well as finding that the total number of layers was quite large. They also began to notice that the fossils also showed patterns, with different types in different layers. The accumulated evidence by the 1770’s firmly established a vast, though quite uncertain, age of the earth. (Much of this work was done by Christians, in part because most of the educated were clergy.) The progress in a geological understanding of the age of the earth should not be confused with religious or philosophical speculations, though both atheistic and young-earth sources often do so. About 1800, Cuvier firmly established that extinction had occurred and the use of fossils to identify layers was on solid scientific ground. All of the geological layers seemed to be pre-human, in contrast to deistic speculation about eternal cycles of the earth and humanity. Likewise, the observed pattern was for simper life to dominate the older layers, while more complex organisms gradually added to the sequence. No fixed patterns in sea level, temperature, etc. were apparent; instead, one had to go out and observe the rocks to determine what the conditions were at their formation.