ESCI Exam 2 Part 1

• fission tracks- count scars left behind by radioactive decay
• Amino acid dating 2 configurations of the same amino acid which are mirror images of each other. The left side version converts to the right after death @ a calibrated rate
• Igneous intrusions

• Homology - similar bone structure
• Vestigial organs-pelvis and femur in whales Morphological hierarchy-
• Land whale found in Pakistan
• Bird dinosaurs in China

• Evolution mechanism - competing for resources causes reprodction of the adequate
• (Moths under the Industrial Revolution)

Accretion of earth from solar nebula - implosion of a pre-existing star with a solar system

• would explain density gradient-outer planet are gaseous - denser rocky planets closer to the sun - (also explains asteroid belt) – left
• over unaccreted material)
• - cold rarified cloud of gases and dust particles then begins to rotate counter clockwise (hydrogen, helium, oxygen, silicon and carbon)
• -Assumes a discoid shape – 90% of the material concentrated in the center- rotates and contracts
• -turbulence and eddies form-particle collide, accrete, gain mass and own gravitational pull, attract more mass, stronger gravitational pull – become protoplanets – inner planets rotate
• faster

heating of protoearth from isotopic decay, friction caused kinetic by gravitational collapse, and meteorite bombardment (amplified by super greenhouse effect) causing melting, differentiation of mantle and core, and outgassing(release of gases from earth interior eg water vapor, carbon dioxide, nitrogen)

partial melting – nickel and iron percolate downwards to form core(densest elements eg iron and nickel found at Earth's center) – remaining iron and metals combine with silicon and oxygen to form the mantle- lighter elements separate to form crust

First crustal rocks formed. Differentiation of oceanic and continental crust begins through subduction-recycling. Mafic rocks cool faster. First plates were ultra-mafic, subducted down, felsic rock(quartz) comes up. Continued degassing-large meteorite impacts periodically removing noble gases from protoatmosphere

• Earth experienced meteor bombardment-declined circa 3.9 Ga - debris absorbed by Sun and planets (geologic processes have erased indications of bombardment on Earth’s surface komatiite– craters on the moon are still visible)
• First stable continental crust forms

Buildup of crustal material into protocontinents. Accretion of continents via microplate tectonics. Water condensing and accumulating above basaltic crust, causing sedimentation (unoxidized) and potentially life

Beginning of oxygenation of atmosphere due to photochemical dissociation(water vapor exposed to UV radiation is broken down to 2H2 and O2) and photosynthesis. Visible evidence in banded iron formations ox, unox, ox. Shows periods of oxygen, then depletion

Free oxygen buildup in atmosphere and oxidization of earth's surface. Fully oxidized sediments. (complete red beds)