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ES 9 Vocab 11

Unit 11: Historical Geology

TermDefinition
Geologic time scale list of major events in Earth's history that have been preserved in rock. Divided into Eon, Era, Period & Epochs.
Precambrian longest era on Earth, over 4 billion years; Earth cooled, formed an atmosphere & slowly simple life in oceans began to appear
Era 2nd largest unit of geologic time (minor changes in life of Earth). Divided into Periods.
Period Often the smallest unit of geologic time (minor changes in life of Earth). Our current period is divided into Epochs.
Eon largest unit of geologic time (before & after life). Divided into Eras.
Cenozoic Age of Mammals-- Mammals (all types) rule Earth for ~ 65 million years so far
Mesozoic Age of Reptiles-- Dinosaurs ruled Earth for ~ 180 million years
Extinct (extinction) ALL members of a species are dead
Relative dating comparison of rock layers to find out the order of events, but don't know exactly when they happened
Half-life the amount of time it takes for 1/2 of the radioactive elements to decay into a daughter product. This amount of time i different for each radioactive element.
Radioactive dating measuring the decay of radioactive elements to find out the exact age of a rock or fossil.
Fossil evidence of earlier life preserved in rock
Cast copy of original fossil, forms when ground water carrying minerals gets into the hole of a mold and fills it.
Mold The depression or hold left in a rock when a fossil dissolves out. It shows the shape and surface of the original fossil
Created by: toastyghosty