Dating Rocks

Absolute Age (Absolute dating/Radioactive Dating): The actual age of a rock or fossil, occurs through a process of radioactive dating.

Best Rock Dating Radiometric

Radioactive Dating of Age: This is a way to measure the age of a rock or fossil by determining the decay of radioactive isotopes within it, providing a precise numerical age.

Igneous rocks are the best types of rock samples to use for radiometric dating because when igneous rocks form the minerals in them often contain only a parent isotope and none of the daughter isotope. This makes the isotope percentage easier to interpret and helps dating to be more accurate.

Half-Life: This is the time needed for half of a sample of a radioactive element to undergo radioactive decay and form daughter isotopes. After Half-life has passed, one-half of the parent isotope has changed into daughter isotopes.

Relative Dating: Determines the age of rock layers or fossils based upon positioning underground( 6 principles of rock dating, Idex fossils, Ordering of rock layers).

Principles of Superposition: The oldest layer is on the bottom, and the youngest is on the top.

Principle of Original Horizontality: Rocks/Sediments are deposited horizontally, later forces will push and tilt, and reflect tectonic forces and weathering and erosion over the years.

Principle of Lateral Continuity: Once sediments have been deposited, erosion occurs throughout a large area which takes away the layers of rock. The layer beside the lateral continuity is still the same age as before.

Principle of Cross-Cutting Relationships: Igneous intrusions or faults are younger than the rock it cuts across

Principle of Inclusions: Rock fragments in a layer are older than the rock itself. Determines which layer is the oldest upon the inclusions.

Bake Zone: This area that surrounds the igneous intrusion that baked the rocks.

The principle of fossil succession states that fossil organisms succeed in one another in a definite and determinable order. Therefore, any time period can be recognized by its fossil content.

Unconformities: Surface which represents geological time not represented in the rock record. (Three Types)

Disconformity: Surface of erosion or nondeposition between beds that are parallel to one another. Wavy surface on top of flat surface.

Angular Unconformity: Erosional surface on tilted or folded strata over which younger strata are deposited. Layers are always deposited horizontally and then shifted.

Nonconformity: Erosional surface cut into igneous or metamorphic rocks, overlain by sedimentary rocks.