Early earth Iron and nickel went into the core and the less dense materials alumino silicates went into the crust So the earth became a layered differentiated planet planetary differentiation Big burp released water in the oceans nitrogen and co2 that created atmosphere Oceans atmosphere formed early in earth s history Earths age 4 5 billion years old This is found from uranium isotopes This whole event formed three things on earth lithosphere outer crust Hydrosphere oceans Atmosphere air The early atmosphere no atmosphere and much higher co2 and methane than today those are greenhouse gases Nitrogen which is bulk of the atmosphere today was about the Solar luminosity brightness of the sun 25 less than it is Temperature was warmer in early earth than today due to Over time sun luminosity went up and greenhouse gases went same today higher green house gas concentration down earth s temperature has stayed so there s also some sort of liquid water on earth within 100 degrees C Goldilocks Hypothesis everything is just right As the earth matured transfer of carbon dioxide to the lithosphere The state of Florida because of the large amount of limestone Florida is a giant biogenic calcium carbonate deposit Co2 from the atmosphere went into limestone Therefore the Co2 moved from the atmosphere to the limestone Limestone calcium carbonate organics kerogen all of these oil and gas deposit are among the organic deposits that have sunk from one reservoir atmosphere to another reservoir the lithosphere The removal of these gases from the atmosphere coincides with the suns luminosity increase Anaerobic anoxic means without oxygen no free oxygen There seems to have been an ocean on mars and it might have been one km deep whereas on earth it is 3 8 km But something happened on mars and we don t know what it was maybe a meteorite And removed water from that ocean Life evolved 3 8 Billions years ago 3 5 years photosynthesis carbon fixation Which means anoxogenic sensation it used sulfur and didn t produced and oxygen 3 3 billion years before present photosynthesis produces oxygen instead of sulfur Heterotrophic eats others Carbon fixation is taking a gas and turning it into a particle biomass Autotrophy self feeding This process is driven by sunlight The first life forms that were photosynthetic heterotrophic were prokaryote single celled something without a nuclear envelope so photosynthetic bacteria They survive on earth today and are now called cyanobacteria They have used to be called blue green algae until scientists discovered they were not algae but bacteria So oxygen began to be produced Life forms had to make enzymes to handle the oxygen because they weren t used to oxygen being produced they were used to an anaerobic world Initially the oxygen was used up rapidly while it was forming Stromatolites transformed the earth layers and layers of cyanobacteria which formed mountains which removed carbon from the atmosphere and moved into the earth lithosphere Finally 1 8 Billion years ago Free O2 began to build up Oxygen Revolution 6 Billion years before present Once oxygen got higher you could create multicellular organisms that could fully use the oxygen Time is depth A historical record that is in sediments on the sea floor Red layers oxygenated iron FeOH Eukaryotic Cells membranes mitochondria chloroplasts Main difference from prokaryote is that it has an organized nucleus with a membrane where the information is separated from the rest of the cell also has organelles mitochondria chloroplasts Organelles are loose with no membrane Before there was free oxygen in the atmosphere there was no ozone shield to protect the earth from the ultraviolet rays from the sun nothing could live So for 90 of earths history the surface of the earth looked like the surface of mars 600 million years ago o2 got high enough for multicellular life and an ozone shield to protect terrestrial life from UV light Important point a single life form cyanobacteria radically altered the composition of the atmosphere and caused global change Changed the continent of the earth Clicker Questions If its noon where you are and 5 30 at in England prime meridian what s your longitude 5 5 15 82 5 degrees west What is a marginal sea Gulf of Mexico 1 15 14 Evidence for continental drift plate tectonics 1 fit of coastlines 2 continous geology across continents Bathymetry is the topography of the ocean floor There were matching sequences of rock types that went across south America so when you put the continents together you see continuous rock bands Pangaea combined super continent 300 million years ago When we figured out plate tectonics we noticed that the North Pole wasn t moving that the continents were wandering Geomagnetic reversals recorded on the sea floor every 1 to 1 million years there are geomagnetic reversals Asthenosphere Molten Rigid lithosphere is above the asthenosphere The contraction brings magma up to the surface and forms new lithosphere basalt and makes a new ocean crust of the earth The new crust goes along the sea floor and is subducted Magma is molten rock inside the earth and lava at the surface MOR Mid ocean rise Diverging plate boundary It is also called a strending center In the rift valley are pillow lavas extruded magma and it gets cooled by sea water and therefore makes a pillowy shaped rock Granite less dense than basalt A convergent plate boundary two plates are meeting where two plates collide The surface expression of a convergent plate boundary is Mantle Convection convergence is driven by this called a trench Uranian isotopes can tell you how old rocks are The youngest rocks are right along the ridge The farther you go out the older the rocks are Clicker Questions 1 Where is the sea floor spreading rate greater East pacific Rise 2 Is the ancient age of the earth reflected in oceanic crust No 3 Alfred Wegener s proposal for continental drift was rejected by the scientific community because He could not find a physically plausible way to explain how continents could plow through oceanic rocks 4 You are exploring an ocean basin Which of the following evidence would you NOT expect to find in an actively spreading ocean Dredging of the mid ocean ridge would yield granite 5 What happens when plate tectonics causes two continents to collide at a convergent plate boundary Neither continent will subduct so they crumple and form mountain ranges The sea floor is 200 million years old young compared to
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