Fossil relative dating lab
This is because it is not possible for a younger layer to slip beneath a layer previously deposited.
The only disturbance that the layers experience is bioturbation, in which animals and/or plants move things in the layers.
Observation of modern marine and non-marine sediments in a wide variety of environments supports this generalization (although cross-bedding is inclined, the overall orientation of cross-bedded units is horizontal).
The law of superposition states that a sedimentary rock layer in a tectonically undisturbed sequence is younger than the one beneath it and older than the one above it.
The principle of original horizontality states that the deposition of sediments occurs as essentially horizontal beds.A similar situation with igneous rocks occurs when xenoliths are found.These foreign bodies are picked up as magma or lava flows, and are incorporated, later to cool in the matrix.Geologists still use the following principles today as a means to provide information about geologic history and the timing of geologic events.The principle of Uniformitarianism states that the geologic processes observed in operation that modify the Earth's crust at present have worked in much the same way over geologic time.
The principle of faunal succession is based on the appearance of fossils in sedimentary rocks.