Chapter 9: Geologic TIme

Principle of Superposition

Chronological organisation of rock layers; the oldest rocks are at the bottom, and the layers
become increasingly younger towards the top.
-Bearspaw formation (youngest)
-Dinosaur Park formation
-Oldman formation (Oldest)

Stratigraphy

The science of using the arrangement and composition of rock layers to interpret geological history.

formation

A large, uninterrupted sequence of rock that is made of multiple layers that all share similar properties, and that all formed under similar conditions.

Radiometric Dating

The use of isotopic ratios to calculate age of a rock.

Radioactive Isotopes

Variations of an element that differ in the number of neutrons; has a specific half-life or rate of decay

Geologic Time Scale

A standardised series of chronological divisions that parses the Earth's history into discrete named units.

Stratigraphic Column

Geologic diagram that illustrates a sequence of rock layers, with the oldest at the bottom and the youngest at the top; often illustrates the thicknesses of each layer.

Cambrian Explosion

Dramatic diversification of aquatic animal life, occurred around 541 million years ago

Tribolites

Extinct group of marine arthropods; first evolved during the Cambrian and died out at the End-Permian Mass Extinction.

Permo-Triassic Mass Extinction

The single largest mass extinction event in Earth history; occurred 252 million years ago and wiped out an estimated 96% of all marine life and 70% of all terrestrial life.

Pangea

Supercontinent, all of earth's major landmasses, formed 300 million years ago, and broke up around 200 million years ago

Isotope Ratio

The ratio of a naturally occurring radioactive isotope and its decay products