GEO 102 Lecture 23 Outline of Last Lecture I The beginning of the Earth Outline of Current Lecture II Core Differentiation III Water and Oxygen IV Tectonics Weathering Atmosphere and Climate V Weathering Thermostat and Feedback Current Lecture Core Differentiation Early Earth was homogenized Over time as short as 30 million years dense matter Ni and Fe sank to form core Acted as an electro magnet and protected 2nd atmosphere from solar wind o 1st atmosphere is lost Water Came from comets but Earth used to be so hot that it could not exist in liquid form First all vapor Light could not penetrate Cooled to condensation point Rain filled basins Oxygen Came much later Mostly from photosynthesis and chemosynthesis First oxygen from photochemical dissociation o Very small amount 2 of today Larger quantities came from photosynthesis o Seen in BIF s o Red beds o Initially from Prokaryotes Prokaryotes life before seeds Single cell organisms without a nucleus These notes represent a detailed interpretation of the professor s lecture GradeBuddy is best used as a supplement to your own notes not as a substitute Tectonics Weathering Atmosphere and Climate Extensive continents by 3 6 Ga Initial uplift led to weathering Beginning of CO2 cycle o Weathering o CaSiO3 CO2 CaCO3 SiO2 o Melting of marine critters at subductions o CaCO3 SiO2 CaSiO3 CO2 CO2 Weathering Thermostat Feedback is critical Increased tectonic activity leads to new land and uplift This leads to increased weathering Increased weathering traps CO2 in resultant sedimentary rocks Rocks are subducted and cycle resumes Feedback Hot periods increase rains and water vapor heating the Earth more Rains increase weathering Ne sedimentary rocks trap CO2 Cools the Earth and lessens precipitation and weathering Sedimentary rocks subducted and it cycles
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