Plate Tectonics PDF

**PLATE TECTONICS** - The Earth\'s crust is divided into 7 major plates which are moved in various directions. → This plate motion causes them to collide, pull apart, or scrape against each other. → Each type of interaction causes a characteristic set of Earth structures or \"tectonic\" features....

**PLATE TECTONICS** - The Earth\'s crust is divided into 7 major plates which are moved in various directions. → This plate motion causes them to collide, pull apart, or scrape against each other. → Each type of interaction causes a characteristic set of Earth structures or \"tectonic\" features. → The word, tectonic, refers to the deformation of the crust because of plate interaction. → Made of ***RIGID LITHOSPHERE*** **LITHOSPHERE** - made up of the crust and the upper part of the mantle **ASTHENOSPHERE** - Below the lithosphere → makes up the tectonic plates **PLATE MOVEMENT** - \"Plates\" of lithosphere are moved around by the underlying hot mantle convection cells  **CONTINENTAL DRIFT THEORY** - Proponent: Alfred Wegener, a German meteorologist and arctic explorer → ***Principal Thought:*** Continents are situated on slabs of rock, or plates, and they have drifted across the surface of the Earth over time; nowever, originally, they were all joined together a he tie supercontinent at one time **PANGAEA** - The supercontinent that existed during the late Paleozoic and early Mesozoic eras → Movement of the Earth\'s tectonic plates caused it to break apart **PANTHALASSA** - The huge supercontinent was surrounded by one gigantic ocean called Panthalassa +-----------------------------------------------------------------------+ | **The Rejection of Continental Drift** | | | | 1. Most influential earth scientists were based in the Northern | | Hemisphere, whereas most of the conclusive data came from the | | Southern Hemisphere. | | | | 2. There were plausible alternative explanations to the distribution | | of fossils and glacial deposits. | | | | 3. The geophysicists could not think of a force strong enough to | | make continents able to plough through | | | | | | | | 4. Wegener assigned Pangea a far too young age (Cenozoic) and | +-----------------------------------------------------------------------+ **HARRY HESS** - an American scientist proposed the seafloor spreading in 1962 ----------------------------------------------------------------------------------------------------------------------------------------------------------------- → In November 1962, H.M.S. OWEN made a detailed magnetic survey over a central part of the Carlsberg Ridge as part of the international Indian Ocean Expedition ----------------------------------------------------------------------------------------------------------------------------------------------------------------- **SEA-FLOOR SPREADING** → *Principal Thoughts:* Ocean floors move like conveyer belts, carrying continents along with them. → Sea floor spreading theory states that new ocean crust is being created at the mid- ocean ridges (which are large mountain chains underwater) and destroyed at trenches. - **UNDERSEA MOUNTAINS DISCOVERED** - During World War II, the United States Navy needed to locate enemy submarines hiding on the bottom of shallow seas. Therefore, large areas of the ocean floor were mapped for the first time. - American geophysicist and Naval officer Harry Hess did some of the mapping. His work helped develop the theory of plate tectonics. - **MID-OCEAN RIDGES** → At the mid-ocean ridge, molten material rises from the mantle and erupts. The molten material then spreads out, pushing older rock to both sides of the ridge +-----------------------------------------------------------------------+ | **Evidence supporting the theory of sea-floor spreading** | | | | A. **MOLTEN MATERIAL** - The rocks shaped like pillows(rock pillows) | | show that molten material has erupted again and again from cracks | | along the mid-ocean ridge and cooled quickly. | | | | | | | | B. **MAGNETIC STRIPING** - Rocks that make up the ocean floor lie in | | a pattern of magnetized stripes which hold a record of the | | reversals in Earth\'s magnetic field. | | | | | | | | C. **OCEANIC DRILLING SAMPLES** - Younger rocks were found in the | | center of the ridge, older rocks were found farther away from the | | ridge at the trenches. | +-----------------------------------------------------------------------+ **TYPES OF PLATE MOVEMENT:** **01 CONVERGENT** - Plates moving towards one another +-----------------------------------------------------------------------+ | **THREE TYPES OF CONVERGENT BOUNDARIES:** | | | | 01 **Ocean-Continent** | | | |  | | | | 02 **Ocean-Ocean** | | | | 03 **Continent-Continent** | | | |  | +-----------------------------------------------------------------------+ **02 DIVERGENT** - Moves away → Production of new plates in ocean ridges **03 LATERAL PLATE** *(Strike-slip)* - Transform boundary → two tectonic plates slide past each other horizontally +-----------------------------------------------------------------------+ | **The majority of the research shows that the plates move at the | | average rate of between approximately 0.60 cm/yr to 10 cm/yr** | | | | Annually: | | | | → North Atlantic - 1 cm (0.4in) | | | | → Pacific - 4 cm (\~2 in) | +-----------------------------------------------------------------------+