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geo time scale

TermDefinition
Eon the largest group; divided by the CAMBRIAN BOUNDARY (about 550 million years ago) when the variety of life forms explodes; billions of years ago
Era mass extinctions mark the boundaries between the eras; hundreds of millions of years long
period blocks of time when a unique rock series was laid down; tens of millions of years long
Epoch divisions of the most recent periods; several million years ago
molds and casts acids eat away the skeletonor shell and leave an impression (mold) in the rock; if the mold fills with minerals, it becomes a cast
tracks and trails imprints are left in mud which later hardens; dinosaur tracks are fairly common
carbonization oils leave the plant, and the remaining matter becomes a layer of carbon; in other cases, nitrogen, hydrogen, and oygen are distilled from the plant; most common method of fossilizing plants
petrifaction minerals in plant cells crystallize; minerals enter openings or cavities in shells or bone; common with plants
replacement object buried in mud has its molecules replaced by minerals; rare
recrystallization mineral aragonite in shells turns into calcite; preserves the general shape of the animal
soft tissue preservation mummification, frozen in ice
traps whole organisms locked in tar pits, asphalt, amber, ect.
cenozoic quaternary, tertairy, halocene, pleistocene, pliocene, miocene oligocene, eocene, palecene
mesozoic cretaceous, jurassic, triassic
paleozoic permian, carboniferious, devonian, silurian, ordovician, cambrian
precambrian proterzoic, archaean, hadean
fossil are the imprints or remains of organisims that were once alive
Created by: aaronbrown1
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