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Lecture 2

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Environmental Science
Lisa Tutty

Jan 14, 2013 EESA06 Lecture 2 Notes  All of geoscience has been based on the theory of plate tectonics  More test questions come from this chapter than average***  In 1500s and 1600s, people noticed that the coastlines of various continents looked like they fit together  Beaumont said that over time, Earth was getting smaller (contracting) because it was cooling down; this is not true  If the Earth was getting smaller, why would coastlines fit together?  Hilgenberg thought that the Earth was expanding, that the continents were together than spreading apart; also not true  Geoscientists found that there used to be ice cover in areas that there is not ice cover now  If you move continents and put them together, there is consistent glaciation; supported idea that continents used to be closer together than they are presently  Fossils of Mesoaurus are found on both sides of the Atlantic ocean even though the organism could not possibly travel that far; maybe there used to be land bridges?  Inconsistent with the idea that the Earth is shrinking because Mesosaurus could not travel the Atlantic ocean if it was even bigger than it is now  Mountain belts are located along the edges of continents  Isostasy-> a floating body is going to replace as much volume as its weight  There is oceanic and continental crust  Oceanic crust tends to be much lower and covered with water, while the continental crust is above sea level and is not covered with water  Continental crust is less dense  Crusts have different densities and are floating in the mantle; if Earth was contracting, this wouldn’t be a valid theory  Alfred Wegener came up with the idea that continents move around the Earths surface  Had well travelled friends from the Southern hemisphere and came up with evidence that other people in the Northern hemisphere did not see  Wegener thought the Atlantic Ocean was quite young and that South America and Africa were joined together  Wegener thought that continents plow through sea flow, which isn’t realistic  Supercontinent Pangea means ‘all the lands’; when Pangea breaks up, you form the oceans  The Pacific ocean is much older and deeper than the Atlantic ocean  Technology from war used to find submarines and explosives was used to enable mapping of oceans floor; send sound waves down to the bottom to find out the distance  Found a mid-oceanic ridge (MOR) in the Atlantic Jan 14, 2013  Holmes published a theory that Wegener’s idea was a good start; plates didn’t move by plowing through floor, but rather moved by convection of the mantle (hot water rising, cold water sinking)  Tharp found through mapping that there was a canyon down center of ridge of Atlantic ocean; found large percentage of earthquakes in Ocean fell along the ridge  Earthquakes are not randomly distributed  Underwater topography is called bathymetry; is not a flat floor, also has ridges  Bullard noticed that oceanic ridges had higher heat flow but no one knew why  Die
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