Earth's HIstory Flashcards
(13 cards)
Uniformitarianism
The principle that geologic processes that occured in the past can be explained by current geologic processes. Most changes happen slowly over time, although some sudden events also shape Earth’s history.
Fossil
The preserved remains or traces of an organism that lived long ago, usually found in sedimentary rock. Fossils can be bones, shells, burrows, or even whole organisms trapped in amber or ice.
Trace Fossil
A fossilized structure formed in sedimentary rock by animal activity, such as tracks, burrows, or coprolites (fossilized dung), providing clues about the animal’s behavior and movement.
Climate
The average weather conditions in an area over a long period of time, mainly determined by temperature and precipitation.
Ice core
A long cylinder of ice drilled from icecaps that contain layers showing past climate conditions, such as precipitation amounts and atmospheric gas concentrations when the ice formed.
Relative Dating
A method of determining whether an object or event is older or younger than other objects or events without determining their exact age.
Superposition
A principle stating that in indisturbed layers of sedimentary rock, the oldest layers are at the bottom and the youngest are at the top.
Uncomformity
A surface where rock has eroded away, producing a break or gap in th egeologic record.
Geographic Column
An ordered arrangment of rock layers that provides a record or Earth’s history.
Radioactive Decay
The process in which a radioactive isotope breaks down into a stable isotope of the same or another element, releasing particles and energy.
Radiometric Dating
A method of determining the absolute age of a material by measuring the decay of its radioactive isotopes.
Half-life
The time required for half of a quantity of a radioactive isotope to decay into a stable form.
Absolute Dating
A method of measuring the actual age of an event or object in years, often using radiometric dating.
