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Earth's History

By Lea Waterman
Across
Process in which a radioactive isotope tends to break down into a stable isotope of the same element or another element.
Rock formed from heat, pressure, and chemicals.
Rock formed when sediments are deposited in layers.
States that in layers of sedimentary rocks, younger rocks normally lie on top of older rocks if the layers have not been disturbed.
Any method of measuring the age of an event or object in years.
Amount of time required for half of an original sample of radioactive material to decay or undergo radioactive transformation
Remains or traces (whole or part) of past plant and animal life that has been preserved in sedimentary rock
Atom of substance that has the same number of protons but a different number of neutrons as another atom of the same substance.
Very long period of time the Earth has existed.
Break in the geologic record created when rock layers are eroded or when sediment is not deposited for a long period of time.
Down
Idea that geologic processes that occurred in the past can be explained by current geologic processes.
The various chemical and mechanical processes that cause rock formations to break down; these include water, wind and ice (glacial).
Method of determining the absolute age of an object by comparing the relative percentages of a radioactive parent isotope and a stable daughter isotope.
Any method of determining whether an event or object is older or younger than other events or objects.
Rock formed after melted rock cools and solidifies.
Stable element into which a radioactive element breaks down
Fossilized mark that formed in sedimentary rock by the movement of an animal on or within soft sediment.
Fossil that is used to establish the age of a rock layer because the fossil is distinct, abundant, and widespread and the species that formed the fossil existed for only a short span of geologic time.
Historical sequence of life indicated by fossils found in layers of Earth's crust.
The movement of weathered particles from one location to another.