evidence that an organism once existed in an area; can be a part of the organism's body or a trace fossil which is a mark or print left by the organism

fossils

the record of geologic time, divided into eons, eras, periods, epochs, and ages

geologic time scale

the information about Earth's history that can be gathered from fossils

fossil record

the permanent loss of a population or species

extinction

fossils of organisms belonging to species that existed in large numbers for a relatively short amount of geologic time; used to date the rocks in which they are found

index fossil

extinct marine arthropods that form one of the earliest known groups of arthropods, the first appearance of these in the fossil record flourished throughout the lower Paleozoic time period

trilobite

the scientific law stating that, in undisturbed rock layers, each layer is younger than the layer beneath it, and older than the layer above it

law of superposition

the dating of events based solely upon the order in which they occurred

relative age

the process of comparing objects or events to determine which are younger or older, without knowing their specific ages

relative dating

the age given in years, of a fossil, a rock, a feature, or an event; usually determined through radiometric dating

absolute age

the process of measuring the specific age of an object or event in terms of years, a time range, or actual date

absolute dating

measurement of the amount of radioactive material (usually carbon 14) that an object contains; can be used to estimate the age of the object

radioactive dating (radiometric)

a type of rock formed by gravity pressing fragments of other rocks and minerals together as they settle on land or under the ocean over a long period of time

sedimentary rocks

a type of rock that forms when melted rock cools and hardens

igneous rock

a sample of ice taken by a hollow tube from a glacier or other large ice body

ice core

the average weather conditions in an area

climate

a crack in a body of rock that the rock can move along

fault

an imagined horizontal line across the plane

strike

The relative displacement of originally neighboring points on opposing walls of a fault

slip

the angle of inclination measured downward from horizontal.

dip

a large natural structure on the earth's surface such as a mountain, a plain, or a valley

landform

a break in time in an otherwise continuous rock record

unconformity