Compare and contrast relative dating and radioactive dating
However, note that because of the "principle of cross-cutting relationships", careful examination of the contact between the cave infill and the surrounding rock will reveal the true relative age relationships, as will the "principle of inclusion" if fragments of the surrounding rock are found within the infill.
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.
Geochronologists do not claim that radiometric dating is foolproof (no scientific method is), but it does work reliably for most samples.
It is these highly consistent and reliable samples, rather than the tricky ones, that have to be falsified for "young Earth" theories to have any scientific plausibility, not to mention the need to falsify huge amounts of evidence from other techniques.
The layers of rock are known as "strata", and the study of their succession is known as "stratigraphy".
Fundamental to stratigraphy are a set of simple principles, based on elementary geometry, empirical observation of the way these rocks are deposited today, and gravity.
To get to that point, there is also a historical discussion and description of non-radiometric dating methods.Many other indicators are commonly present, including ones that can even tell you the angle of the depositional surface at the time ("geopetal structures"), "assuming" that gravity was "down" at the time, which isn't much of an assumption :-).In more complicated situations, like in a mountain belt, there are often faults, folds, and other structural complications that have deformed and "chopped up" the original stratigraphy.The simplest situation for a geologist is a "layer cake" succession of sedimentary or extrusive igneous rock units arranged in nearly horizontal layers.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.