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Geologic Time

Molds and casts Acids eat away the skeleton or shell and leave an impression in the rock. If the mold fills with minerals, it becomes a cast.
Tracks and trails Imprints are left in the mud, which later hardens. Dinosaur tracks are fairly common,
Carbonization Oils leave the plant and the remaining matter becomes a layer of carbo. In other cases nitrogen, hydrogen, and oxygen are distilled from the plant. Most common method of fossilizing plants.
Petrifaction Minerals in the plant cells crystalize; minerals enter openings or cavities in shells or bones. Common with plants.
Replacement Object buried in mud has its molecules replaced by minerals. It is rare.
Recrystallization Mineral aragorite in shells turns to calaite. Preserves the general shape of the animal.
Soft tissue preservation Mummification, frozen in ice. Fossils are relatively young and do not last long.
Traps Whole organismslocked in tar pits, asphalt, amber, ect.
Fossils Are the imprints or remains of organisms that were once alive. They provide evidence for the Geologic Time Scale.
Cenozoic Quaternary, teriary, halocane, pleistocane, pliocene, miocene, oligocene, eocene, palocene
Mesozoic Cretaceous, Jurassic, Triassic
Palezoic Permian, Carboniferous, Devonian, Silurian, Ordovician, Cambrian
Proterozoic Archaeon, Hadean, Precambrian
Eon The largest group; divided by the Cambrian Boundary (about 550 millions of years ago) when the variety of life forms exploded; billions of years long.
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 years long.
Epoch Divisions of the most recent periods; sereral million years long.
Humans Eon: Phanerozoic, Era: Cenozoic, Period: Quaternary, Epoch: Holocene, Years Ago: 11,000-Present
Rise of Mammals Eon: Phanerozoic, Era: Cenozoic, Period: Tertiary, Epoch: Paleocene, Years Ago: 65-54
Birds Eon: Phanerozoic, Era: Mesozoic, Period: Jurassic, Years Ago: 208-146
Created by: kelseylyall