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Transcript of Continental Drift
walking along land bridges
jumping on small islands
Swimming across the ocean. Another evidence- Climate Changes. Tropical plants were found in cold weather areas around the world like: Greenland Antarctica and so on.. Ice sheets scratches were also found on rocks in tropical areas. The BEST evidence there was to support Continental Drift is Geology. [A.K.A. Study of rocks] Similar rocks were found in totally different places!! Alfred Wegener 30 YEARS LATER, the hypothesis was accepted because of a man named Harry Hess.
Alfred Wegener died before the explanation of the hypothesis, during an expedition. Sadly, Alfred Wegener's hypothesis was not accepted because he could not explain HOW these big ol' continents moved, and some thought he was just insane. The Theory Tectonic Plates Some more definitions you should keep in mind! Mid-Ocean Ridges~ Huge underwater volcanic ranges
Spreading Centers~When the old crust is pushed away from the ridge to make room for new crust and is slowly spreading apart.
Ocean trenches~ These trenches are like deep canyons in the sea-floor where dense oceanic crust is sinking and being "recycled" into the asthenosphere.
Subduction~ the process of one plate being pushed under another. Tectonic Plates In 1962, Harry also published a hypothesis about sea floor spreading, giving Alfred Wegener an answer to HOW the continents were moving. At mid- ocean ridges, sea floor spreading begins to start. The melted rock, magma, rises through the openings along the Earths crust, cooling down and than begins to form new crust! Age of the sea floor: the youngest rock is the crust closer to the mid-ocean ridge, while the oldest crust is further away. A picture of Mid- Ocean ridges Uh - oh! Tectonic Plates The plate tectonics theory explains how continents drifted and the origins of volcanoes, earthquakes and mountains. Also, it explains that the Earth's lithosphere is made out of gigantic plates that float on the surface of the Earth. You may want to be aware of the layers of the Earth and a few other details before we go on! The four layers of the Earth are:
Crust There are two types of crusts:
Oceanic Crust The Lithosphere is made of the crust, and just on top of the mantle. The Asthenosphere is the upper part of the mantle and is just below the lithosphere. It is a hotter, softer rock, like tar, Tectonic plates~ The lithosphere is broken into many large and small slabs of rocks. mid- ocean ridge Younger Crust Older Crust Tectonic plates rest on the asthenosphere. The hot, soft underneath the plates and the mantle move by convection More definitions on you're way! Convection- is the transfer of heat by movement of materials.
Convection Currents- The motion of the hot, soft rock rising, than heating up and rising up again. Cold water hot Magma It's the mixture of convection currents , the spreading centers and subduction zones that correspond together to make the plates move. When the plates move the continents on top of them also moves Planet Earth! The old crust gets ridge-pushed from the mid-ocean ridge, to make some space for the new crust and slowly backing away. This is also known as Spreading Centers. The old oceanic crust that is in the process of getting destroyed or recycled goes through ocean trenches, deep canyons on the sea floor, into the asthenosphere. Than, goes into the Mantle and than into the subduction zone. When Convection currents are rotating going opposite directions the plates grow further away. When they are going the same direction, or towards each other, they are getting closer creating a mountain.