L48 Anthro 150A Lecture 7: TA Notes L7
Document Summary
Geologists organize earth"s history into eras, each era may have several periods, each period may have several epochs. There are distinct times that separate each of them. Each time period is classified by the type of organisms. The changes (extinctions, new life) help us keep track of the sequence of time segments. Chart of time periods (oldest at bottom) Extinction (65mya) - only dinosaurs that survived are those that could fly; some mammals survived. Volcanic: formed from magma underneath the earth. Don"t find fossils in these vertebrates; earliest chordates) Permian extinction (251 mya)- roughly 90% of all organisms on earth go extinct. Kt boundary refers to the boundary between the cretaceous and tertiary periods. Sedimentation: little grains of soil/mineral getting deposited by wind blowing, water, etc. This forms different layers in the ground. The once loose sediments get compacted when there is a lot of pressure on the particles (ie. more layers)
