Presentation on theme: "The Wonders of Nature: We’re still drifting…"— Presentation transcript:
1The Wonders of Nature: We’re still drifting… Canadian War MuseumGr. 9 Geography (Applied)CGC1PThe Wonders of Nature: We’re still drifting…
2Something to warm us up… Watch Ice Age: Continental Drift – Scrat’s Continental Crack Up (http://www.youtube.com/watch?v=q_IYQdKkWsU)
3Structure of the Earth The Earth is made up of 4 main layers: Inner coreOuter coreMantleCrustInner CoreA mass of sold iron over 7000 degrees hot!Approx. 5000km below the crust of the earth, 2500km in diameterOuter CoreSuper-heated liquid molten lavaApprox. 3000km thickElectrical currents found here produce earth’s magnetic fieldMantleParts are hot enough to form slow moving molten rock or magmaAbout 85% of the earth’s weight
4The Crust Continental Crust thick (10-70km), buoyant, mostly old Oceanic Crustthin (~7 km), dense (sinks under continental crust), youngMantleOuter coreInner coreCrustThis is where we live!
5Structure of the EarthGeophysical surveys: gravity, magnetics, electrical etc.Acquisition: land, air, sea and satelliteGeological surveys: fieldwork, boreholes, mines
6Plate TectonicsFrom Scrat’s video, what do you think “plate tectonics” refers to?
7Plate TectonicsIf you look at a map of the world, you may notice that some of the continents fit together like pieces of a puzzle…What do you think happened?
9Continental Drift Theory Continental drift: movement of the Earth's continents relative to each other by appearing to drift across the oceanTheory developed by Alfred Wegener in 1912developed concept of Pangaea “one-earth”
12Continental Drift Theory 3 pieces of evidence for Wegener’s theory (idea) were:Rocks that were the same age and type across continentsThe shape of the continents (look like puzzle pieces that fit together)Fossils that were the sameWatch National Geographic – Continental Drift short video:
14Theory of Plate Tectonics Developed by J. Tuzo Wilson in 1968.Earth’s crust broke into 12 pieces called platesEarth’s crust is made up of many plates that move on top of the mantle.The movement of the plates causes changes to the Earth’s surface (mountains, volcanoes form…)The plates float on the interior of the Earth—like crackers in a hot bowl of soup!
15Theory of Plate Tectonics Theory of Plate Tectonics (con’t):Heat from deep inside the earth causes plates to moveEarth’s continents sit on plates, so when the plates move, the continents move with themThe movement of these plates is called PLATE TECTONICS
16Theory of Plate Tectonics On average, the plates move about as fast as fingernails grow…an inch or so every year
18Theory of Plate Tectonics Why do plates move?Because of Convection currents:The mantle is made of much denser, thicker material, because of this the plates "float" on it like oil floats on water.Movement of plates is caused by very hot material at the deepest part of the mantle rising, then cooling, sinking again and then heating, rising and repeating the cycle over and overExample: The next time you heat soup in a pot, you can watch the convection currents move in the liquid. When the convection currents flow in the mantle they also move the crust. The crust gets a free ride with these currents.