GEOG 203 1nd Edition Lecture 14 Outline of Last Lecture I Changing climates a What causes climate change b Climate change vegetation and humans Outline of Current Lecture II Intro to tectonics mountains and terrain evolution III Shifting continents a Continental drift seafloor spreading and plate tectonics b Plate interactions IV Mountains and other landforms V Denudation Current Lecture Intro to tectonics mountains and terrain evolution Relief on Earth s surface Shifting Continents Continental drift seafloor spreading and plate tectonics o Plays a large role in our understanding of the earth s surface climate terrain o Francis Bacon first noted similarities of continental coastlines o Alfred Wegener German meteorologist proposed that the continents had once fit together as one Pangaea one land mass Gonduanaland south continents Laurasia north continents o Evidence for continental drift These notes represent a detailed interpretation of the professor s lecture GradeBuddy is best used as a supplement to your own notes not as a substitute Matching continental margins Arrangement of mountain belts Appalachian mountains for example would have made one line with the British Isles and Scandes Mountains Paleoclimatic evidence Glaciation of continents occurred around where the continents would have been connected to Antarctica Fossil evidence Similar fossils are distributed across southern continents in patterns suggesting they would have had to have been connected once Similar rock type Wegener s theory not widely accepted Was not a geologist was a meteorologist Had no evidence or proposed mechanism for how the continents actually moved Continental drift theory did not carry much weight until about the 1940 s when more exploration of ocean floor began Discovery of mid ocean ridge and development of theory of seafloor spreading Was proposed that in the mantle of the earth there are convection currents with particularly hot places Warming of the mantle caused it to expand and rising zone lifted up the center of the earth causing the midocean ridge Eruption of lava along the mid ocean ridge caused new formation of ocean floor pushing apart continents Relative age of the oceanic crust Older rock is found close to each continent and new rock is found along mid ocean ridges Since so much new rock is being created this means that old rock must be destroyed in order to make room for the new rock Oldest rock found is dated to 144 208 million years old the earth is much older than that meaning much of the old rock has been destroyed already old rock has been destroyed already A dozen or so plates are thought to exist all plates exist in the lithosphere Where plates interact with each other mountains and different land forms are formed interactions Diverging boundaries New crust being formed Converging boundaries ocean continent example Oceanic rock is more dense and leading to subduction of oceanic crust to continental crust Creates deep trenches in ocean floor o o o o o Plate o o o Converging boundaries ocean ocean example More dense ocean plate will subduct to less dense plate causing chain of volcanic islands o Converging boundaries continental continental example Leads to mountain building Mountains Relief on earth s surface What is geomorphology o The science of landforms their origin evolution form and spatial distribution o Landforms are a consequence of The tectonic processes that build up the earth s surface The denudational processes that wear down or rearrange the landforms Denudation First to denude means to strip to make naked of bare to uncover So denudation means all the processes that degrade or strip down the landscape anything that causes weathering or erosion Denudation wears down the land surface