ERS120H5 Lecture Notes - Lecture 19: Permian, Appalachian Mountains, Middle Triassic
Document Summary
Hadean earth: dense, toxic atmosphere, comets and asteroids, closer to moon, magma ocean. Start to form kernels -> cratons: 80-89% of all continental crust. Stromatolites: cyanobacteria mats, algae grow through segment, mushroom shaped. Liquid water and dissolved co2: detoxify atmosphere. First chemical evidence of life: ~3. 8 ga: oldest bacterial cell fossils: ~3. 5 ga. Supercontinent cycle: all continents get swept up into one big continent, oceanic crust is dense and wants to subduct, drift apart, come back together. Formation of cratons: oxygenation of the atmosphere, driven by respiration of cyanobacteria, banded iron formation, enough oxygen to react. Snowball earth: runaway icehouse effect based on changes in co2, up to 4 major snowball events between 750 and 580 ma, sea ice over the entire planet, ediacaran fauna, soft body organisms, spurred evolution of more complicated organisms. Late cambrian (500 ma: passive margin, warm, shallow seas. Subduction on east coast: passive margin on west coast, warm, shallow seas.
