Week 7 Notes part 2
Week 7 Notes part 2 80176 - GEOL 1010 - 001
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80176 - GEOL 1010 - 001
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This 5 page Class Notes was uploaded by Sarah Canterbury on Monday March 7, 2016. The Class Notes belongs to 80176 - GEOL 1010 - 001 at Clemson University taught by Alan B Coulson in Fall 2015. Since its upload, it has received 13 views. For similar materials see Physical Geology in Environmental Science at Clemson University.
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Date Created: 03/07/16
Lecture 13—3/1/16 Geology in the News New study suggests oxygen buildup on earth might have started during the Archean Eon instead of the Proterozoic Eon 1.8 billion years earlier More implications for life on earth Review from Lecture 12 Climate vs Weather Why climate is difficult to study Milankovitch cycles The Atmosphere’s effects on climate Hadley cycles El Nino system Part 1 The Hydrosphere All the water that’s present on earth Water has a very high heat capacity Heat capacity: measurement of how much heat something can retain Ex) Gulf Stream: important because pushes warmer waters towards Europe, leading to a fairly pleasant climate Use ocean currents to move warmer waters towards the north or south directions Oceanic Heat Transfer Thermohaline Circulation Red line indicates the surface of the ocean and Blue line indicates the bottom of the ocean Shows how heat is transported in the ocean Why does the water sink? As water loses heat energy to the environment, it cools down. The colder water gets, the denser it get, so it sinks. Also, the water gets saltier because water evaporates. The saltier water gets, the denser it gets, so it sinks Slowing down in recent decades Temperatures are increasing, less cold water Increased temperature melts glacier, adding fresh water to ocean, decreasing the salt content, making it much more difficult for water to get denser and sink Negative feedback loop- balancing effect; self-regulating system ** Study Tip: focus more on how things function—not on definitions** Biosphere Plants Draws down CO2 for photosynthesis Affects albedo Animals Release CO2 and methane (greenhouse gases) Increased greenhouse gases increase temperatures Biological pump: interaction of biosphere, atmosphere, hydrosphere, and lithosphere Cryosphere Refers to all the snow and ice on earth Ice covers about 9% of land surface Most land surfaces albedo ~15-20%; Snow Ice Albedo~40-90% The Lithosphere Tectonics affects climate in several ways 1) Continental position Control where the continents are At one point, Antarctica was one of the only areas without snow/ice 2) Continental size: big continent or several small continents When you have one large continent, tend to have dry, arid climates on the interior since so far away from the ocean 3) Collision Zone Uplift Rain Shadows: one side of a mountain gets a lot of precipitation and the other side hardly gets any because as condensed water rises, is becomes more dense and falls back to the earth as rain before it can travel over the tip of the mountain Ex) Pacific Northwest 4) Land Bridges A small piece of land that connects two larger pieces of land Control ocean current patterns Ex) When Antarctica was connected to South America, it didn’t have so much ice, but when it got disconnected, it changes the water currents and Antarctica began to have a lot of ice and snow Part 2 Instrument and historical records only go back so far Knowing how earth reacted to previous climate changes helps predict for the future Recording climate Air trapped in glacial ice Each of the bubbles have been trapped since the ice froze over it Ex) if that piece of glacial ice is 50,000 years old, we can learn a lot about the atmosphere from that time Ice Cores Have direct record of what was in the atmosphere up to > 1 million years ago Ice cores from Greenland & Antarctica >2 miles (3300 m) Proxies Substitute of some type Different proxies record different aspects of climate on different timescales Always have to think about what type of proxy you’re using ** Study Hint: air bubbles in ice were NOT a proxy. ** Proxy Rules Always consider the nature of the proxy Ex) Tree ring Climate proxies -Tree ring width: wide rings indicate good climate for the tree and vice versa -Biogeography: study of where plants and animals live Many animals will only live where there are certain types of climates Ex) crocodile fossils found in islands off of Canada- indicates that Canada’s climate has changed -Stable isotopes Measure as a ratio: ex) 18O/16O Bigger number goes on top Different atomic weights = different amounts of each isotope get incorporated into molecules Key: the ratio in some materials changes with climate variables Ex) at one temperature, you add a certain ratio of 18O/16O to a growing shell, but at a different temperature you add a different ratio Oxygen Isotopes Ex) many invertebrate & plankton shells Extract oxygen from the shell and can tell at what temperature the shell was formed, allowing us to build temperature records back in time Ex) 18O/16O in bones of fish indicate the temperature of the water when the fish was alive Equation: T = 111.4 – 4.3 * (Df – Dw) T – water temp Df – ratio in fish bone Dw – ratio in seawater (= 1.0) Other temp proxies Some trace metals in shells Ex) Mg/Ca Amount of replacement depends on temperature Why do we want multiple temp proxies? Need several proxies because you need to double check and double check more If you only use 1 proxy, there could be something wrong, giving you inaccurate data Stable Carbon Isotopes 13C/12C Both isotopes form CO2 in the atmosphere Ex) 13CO2/12CO2 Plants take in both types of CO2 for photosynthesis The 13C/12C ratio in each plant depends on the plant’s photosynthetic style C3 plants vs C4 plants ** Study hint: C3 and C4 do not refer to carbon isotopes; they refer to types of plants** C3 plants are typically found in cooler, wetter climates C4 plants are typically found in hotter, drier climates Each of these are taking in different amounts of carbon due to the differences in their photosynthetic styles Animals eat the plants and inherit the plant’s isotopic ratio The 13C/12C ratio in animals’ fossils reflects the types of plants in the area, and therefore give us clues about the climate at the time