GY 102 Topic 4 Notes
GY 102 Topic 4 Notes GY 102
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This 2 page Class Notes was uploaded by Conner Jones on Thursday February 11, 2016. The Class Notes belongs to GY 102 at University of Alabama - Tuscaloosa taught by Mary Pitts in Fall2014. Since its upload, it has received 37 views. For similar materials see Earth System Processes in Geography at University of Alabama - Tuscaloosa.
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Date Created: 02/11/16
Topic 4 – Earth’s Crustal Movements What is inside the earth? Upper layer crust (lithosphere)- stronger than asthenosphere o Continental- ex: granite o Oceanic- ex: salts Asthenosphere- hot and weak; mostly solid Thicker elevations of crust are typically land and thinner layers of crust are typically oceanic o Isostasy- relationship between crustal thickness and elevation What is plate tectonics? A geologic theory proposed to explain large scale motions of earths lithosphere Continents “adrift”, Common widespread acceptance NOW Due to convection forces in the asthenosphere and upper mantle Historical evidence o 1619 Bacon observed jig saw like fit of continents on either side of Atlantic o 1915 Wegener circumstantial evidence like fossils and paleoclimate, estimated all continents were together 225 million years ago o Fossils of same land animals and plants found on Africa and South America o Continental drift explains observations without need for land- bridge hypothesis new information o ocean sonar- 1950’s (created sea floor configurations) o remote sensing of ocean surface- 2000 o mid oceanic ridge- 40,000 miles long 600 miles wide underwater mountain range high volume of earthquakes and volcanoes on this ridge o dating ocean floor sediments – spreading three types of relative plate motions o divergent- move apart move apart at mid oceanic ridges (seafloor spreading) forms new oceanic crust o convergent- move toward each other typically happens at trench or island arc subduction – one plate moves down and other stays on top o transform- move horizontally past one another link spreading segments in mid oceanic ridges rates of plate movement o plates move very slowly (about a cm/year) o relatively, some plates move much faster than others Historical Changes in landmasses supercontinent of Rodinia (600 million years ago) o theory that all major continents were joined, forming Rodinia, a huge supercontinent centered over the south pole o Evidence of widespread glaciation Dispersal of continents (500 million years ago) o North America and Europe were separated Supercontinent of Pangaea (280 million years ago) o All the continents were joined in one supercontinent called Pangaea Gondwana and Laurasia (150 million years ago) o Continents on either side of Atlantic are moving away from each other o Southern continents formed Gondwana Present o Current configuration of continents
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