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“Sometimes it is the people no one can imagine anything of, who do the things no one can imagine.” - Alan Turing
EARTH'S HISTORY 1
LESSON 5: GEOLOGIC TIME SCALE | FOSSIL FORMATION
GEOLOGIC TIME SCALING
FOSSIL FORMATION
FOR YOUR NOTEBOOK:
GEOLOGIC TIME SCALE | FOSSIL FORMATION
Lesson 5:
Fossil Section
Original Preservation- remains of plants and animals that have been altered very little since the organisms’ deaths (Ex. mosquito in amber, mammoths in the La Brea Tar Pits)
Altered hard parts- shells, bones, or cell walls can become fossils through through different means:
Mineral Replacement- the pore spaces of an organism’s buried hard parts are filled in with minerals from groundwater (petrified wood)
Recrystallization- buried hard parts are subjected to changes in temperature and pressure over time
Molds- form when sediment covers the original hard part of an organism and the hard part is removed by erosion or weathering. The mold can then become filled with material to create a cast of the shell.
Geologic Time Scale: (Click button to view notes for it) (Get colorful!)
ORIGINAL PRESERVATION EXAMPLE
TO FOSSILIZE, SHELLS UNDERGO RECRYSTALLIZATION
SIMILAR TO METAMORPHIC ROCK FORMATION
AMMONITES FORM MOLDS IN ROCK
THESE ARE EXCELLENT INDEX FOSSILS
(EASY TO IDENTIFY)
