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1.4 Rock Cycle and Geological time (the Cambrian explosion (Before: corals…
1.4 Rock Cycle and Geological time
Geological Time Scale
changes in earth can be seen through changes in rock formation
the documented layers of rock are 4.8 billion years old
Eras
Cenozoic Era
dominated by animals
several ice ages
started 66 million years ago
Mesozoic Era
dominated by dinosaurs
ended when a large asteroid killed all dinosaurs
warm and wet
Paleozoic Era
400 million years before Mesozoic
Plants and animals started to inhabit earth
began with the Cambrian explosion
Precambrian Era
it is also the longest
first era of earth history
Rock
types of rock
metamorphic
igneous
sedimentary
rock age
Carbon dating to date rocks
deeper you go the older
the Cambrian explosion
Before: corals, bacteria, Simple life form
it was not an actual explosion
massive bursts of evolution
all groups can be traced back to this period
After: life forms got really different after