the change in population of a species over time.
evidence of past life preserved in rock.
a fossil found in a narrow time range but widely distributed around the earth; used to date rock layers
an explanation that ties together many hypothesis and observations.
any method of measuring the age of an event or object in years. the actual age for a rock or mineral
Continental drift theory
theory that states that the gradual shifting of Earth's plates causes continents to change their global positions over time
Law of superposition
states that the oldest rocks lie on the bottom and the youngest rocks are on top of any undisturbed sequence of sedimentary rocks.
the theory that explains how large pieces of the Earth's outermost layer called tectonic plates move and change shape.
the process by which the age of a rock is determined by measuring the amount of radioactive isotopes present in the rock or rock sample
the method used for absolute dating.
the process in which a radioactive isotope tends to break down into a stable isotope of the same element or another element.
uses information about rock layers and the fossil record to determine the age relationships between rocks
the largest division of geologic time
a subdivision of a geologic period
a unit of geologic time that includes two or more periods
Geologic Time scale
the standard method used to divide the Earth's long natural history into manageable parts
era that began about 66 million years ago, known as the "Age of Mammals"
era that began 245 million years ago, known as the age of the dinosaurs
era that began about 544 million years ago and lasted for almost 300 million years
a subdivision of the eras in geologic time