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23 Cards in this Set

  • Front
  • Back

fossils

preserved remains of living things that are buried by sediments

mold

a hollow area in sediment in the shape of an organism or part of an organism

cast

a solid copy of the shape of an organism

petrified fossils

fossils in which minerals replace all or part of an organism

carbon film

an extremely thin coating of carbon on rock

trace fossils

provide evidence of activities of an organism, for example dinosaur footprints

preserved remains

remains of the entire organism in tar, amber, or ice

paleontologists

scientists who study fossils

evolution

the change in living things over time

extinct

when an organism no longer exists and will never again live on Earth

sediment

small solid materials that come from rocks or living things

sedimentary rock

the type of rock that is made of hardened sediment, many fossils are found here

fossil record

what scientists study to learn about the history of life, past environments on Earth, and how different groups of organisms have changed over time

relative age of a rock

the age of the rock compared to the ages of other rocks

absolute age of a rock

the number of years since the rock formed

law of superposition

in undisturbed horizontal sedimentary rock layers the oldest layer is at the bottom., Each higher layer is younger than the layers below it.

extrusion

Lava that hardens on the surface and forms igneous rock. Always younger than the rocks below it.

intrusion

Magma pushing from below the surface, then cools and hardens into an igneous rock. Always younger than the rock layers around and beneath it

fault

A break in Earth's crust. Always younger than the rock it cuts through.

index fossil

a fossil that must be widely distributed and represent an organism that existed for a geologically short period of time. Useful in telling relative age of the rock layers.

radioactive decay

process by which elements break down and release particles and energy. During this the atoms of one element break down to form atoms of another element.

half-life

the time it takes for half of the radioactive atoms to decay

radioactive dating

used by geologists to determine the absolute ages of rocks