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