Lecture Notes - Sept. 22
Lecture Notes - Sept. 22 11883 - GEO 105 - 01
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This 3 page Class Notes was uploaded by Andrea on Tuesday September 22, 2015. The Class Notes belongs to 11883 - GEO 105 - 01 at Grand Valley State University taught by Tara Ann Kneeshaw in Fall 2015. Since its upload, it has received 84 views. For similar materials see Living with the Great Lakes in Geology at Grand Valley State University.
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Date Created: 09/22/15
Living with the Great Lakes Notes from class on September 22nd 2015 Top Hat Review Question 0 Oceanic crust is made of and continental crust is made of o Basalt and granite o is an example of a rock that formed as a result of changes due to exposure to high heat pressure or chemical An example of the kind of rock specifically not the rock cycle category 0 Marble metamorphic I Marble is actually limestone that has been compressed and overcooked Back in Time 0 In 1660 Francis Baconm proposed that the continents had once been joined 0 He explained that coastlines almost fit together like puzzle pieces I They especially fit if you added the continental shelf the shallow part of the waterjust beyond the land before it goes deep into the ocean o In 1912 Alfred Wegener provided evidence for Continental Drift 0 He used different rock types that were exactly the same but scattered among different continents and realized that the one way they could have been formed all at the same time was if the continents they were on were once together 0 He also explained this with fossils The same species of animal can be found in totally opposite sides of the world They were the same age same animal but how did they get there Well they probably were able to travel to parts of different continents because they were all together 0 He named his supercontinent Pangaea and the superocean surrounding it Panthalassa o Wegener suggested that the Earth s continents had since then been broken up and what we are currently living on is now the once large Pangaea only scattered I Explains areas of compressions mountains which formed when we were squished together and areas of expansions ocean basins and divergents that formed when we broke away Unfortunately Wegener died before he could come up with the Why which everyone was asking him Why do the continents move Next 30 Years 0 Improved seafloor images We are able to know that the seafloor is notjust flat It has underwater mountain ranges and deep ocean trenches some larger than the Grand Canyon 0 1947 Core measurements of the Atlantic ocean showed that the sediments were much thinner than originally thought or compared to the Pacific ocean O 0 Meaning That the Atlantic ocean is a fairly young ocean How can ocean be young Seafloor Spreading Seafloor Spreading o Seafloor spreading happens when faultsbreaks open in the ocean floor The rocks become very stressed Seafloor Rifts httpswwwgoog le comurlsaiamprctjampqampesrcsampsou rceimagesampcdampcadrjaampuact8ampvedOCAYQj B1 qFQoTCKjimtuJiBQCFUTng oquMOwQampurlhttps3A2F2Fen wikipediaorg2Fwiki2FSeafloorspreadingamppsigAFQjCNExotcr6VgPR7U2chszNW6Ysszampust1443026203847683 0 Elevation rises approaching the yellowred area which is the beginning of the ridge As you get to the center of the ridge the heat temperture goes extremely high This is how scientist figured out that magma is what is pushing against the rocks from underneath attempting to break through the surface Age Magnetism of the Oceanic Crust 0 Whenever you use a compass the needle points North But that wasn t always the case During times in the Earth s history the poles have flipped and South was once the dominant 0 We know this because rocks that contain metals such as Iron and ONLY rocks that contain metal such as iron form pointing to whichever pole is the dominant magnet So some rocks form pointing North but others deeper in the layers have formed pointing South 0 We know that the poles have flipped multiple times and will continue to flip based on the history shown by the rocks it s a common thing Possibly in our lifetime the poles will flip o Lithosphere The lithosphere consists of the Crust and Uppermost Mantle strong elastic Plates within the lithosphere interact with each other like bumper cars Rigid plates in the Uppermost Mantle move over the weaker more plastic flimsy layer in the Earth s Lower Mantle which are located in the Asthenosohere where temperatures are warmer making the rock like a toothpaste consistency and able to flow 0 New plates and rifts are forming in the Lithosphere layer Energy Source 0 Large thermal convection cells and rising thermal plumes from as deep as the core are what make the plates move 0 From the center of the Earth the heat rises causing rocks to also heat up and begin to rise to the surface They find the path of least resistance and as they move upward they affect the movement of rocks around them 0 Eventually once the rocks get close enough to the surface they begin to lose their heat because the heat from the core is farther away and they began to sink back to the bottom after hardening and becoming denser o Mantle plumes Rarely the mantle will be weaker in one spot that another and the granite that forms a barrier between the mantle and the Crust will allow large rocks or even magma to rise to the surface This is how we get things such as Yellowstone National Park which is essentially a supervolcano underneath the Crust and why rarely we see volcanoes in the middle of North America because the granite dividing the crust and mantle is so thick 0 7 or 8 large plates and numerous smaller ones move over the underlying Asthenosphere Large continental plates move less than 2 cm per year Oceanic plates move faster at a rate of 620 cm per year 0 The Pacific Plate is currently moving the fastest The Why 0 The why Wegner was looking for o Pangea split up due to a large rift underneath the supercontinent As it spread underneath the land masses it began to slowly rise and push the continents away Once there was enough space the water surrounding the land began to fill in where the rift was spreading and over time that water became the Atlantic Ocean 0 This is why the Pacific is older because the oldest rock surrounding the outermost areas of Pangea was pushed away from the new young rock begin created
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