In such a situation, the "principle of superposition" is easily applied, and the strata towards the bottom are older, those towards the top are younger.
This orientation is not an assumption, because in virtually all situations, it is also possible to determine the original "way up" in the stratigraphic succession from "way up indicators".
The most common rocks observed in this form are sedimentary rocks (derived from what were formerly sediments), and extrusive igneous rocks (e.g., lavas, volcanic ash, and other formerly molten rocks extruded onto the Earth's surface).
The layers of rock are known as "strata", and the study of their succession is known as "stratigraphy".
In order for a layer of material to be deposited, something has to be beneath it to support it.
his document discusses the way radiometric dating and stratigraphic principles are used to establish the conventional geological time scale.I thought it would be useful to present an example where the geology is simple, and unsurprisingly, the method does work well, to show the quality of data that would have to be invalidated before a major revision of the geologic time scale could be accepted by conventional scientists.Geochronologists do not claim that radiometric dating is foolproof (no scientific method is), but it does work reliably for most samples.Cave deposits also often have distinctive structures of their own (e.g., spelothems like stalactites and stalagmites), so it is not likely that someone could mistake them for a successional sequence of rock units. Each of them is a testable hypothesis about the relationships between rock units and their characteristics.They are applied by geologists in the same sense that a "null hypothesis" is in statistics -- not necessarily correct, just testable.A common form of criticism is to cite geologically complicated situations where the application of radiometric dating is very challenging.