What is one technique that scientists use to date the fossils they find? Potassium-argon dating is a form of isotopic dating commonly used in paleontology. Scientists use the known natural decay rates for isotopes of potassium and argon to find the date of the rocks.

What type of fossils are used to date and correlate rock layers?

Fossils are used to determine the ages of rock layers. Index fossils are the most useful for this. Index fossils are of organisms that lived over a wide area.

How do you match rock layers?

Using Index Fossils to Match Rock Layers. Rock layers with the same index fossils must have formed at about the same time. The presence of more than one type of index fossil provides stronger evidence that rock layers are the same age.

What is an extrusion in rock layers?

Lava that hardens on the surface is called an extrusion. The rock layers below an extrusion are always older than the extrusion. Beneath the surface, magma may push into bodies of rock. There, the magma cools and hardens into a mass of igneous rock called an intrusion.

Why are some rock layers missing?

Something else that fits into Geologic Principles and basic stratigraphy (study of rock layers) are unconformities. Unconformities are simply gaps (missing data) in the rock record, these gaps could indicate a variety of processes. Such as: erosion, deformation, or changes in sea-level.