EnvironmentalManagement Continental drift • Continental drift is the movement of the Earth's continents. • This is due to the mantles’ movements which causes the tectonic plates to move • Plate tectonics is the scientific theory that attempts to explain the movements of the Earth's lithosphere that have formed the landscape features we see across the globe today. • By definition the word "plate" in ABOUT TECTONIC geologic terms means a large slab of solid rock. "Tectonics" is a part of the Greek root for "to build" and together the terms define how the Earth's surface is built up of moving plates. • So basically the earth's lithosphere is made up of many individual plates (8 major plates and other minor ones) of PLATES solid rock that floats upon the hot mantle. • Churning currents in the molten rocks below propel them along like a jumble of conveyor belts. How tectonic plates move Plate Boundries Convergent Boundries Divergent boundries Transform-fault boundries Convergent Boundries • The plates basically m,ove towards each other and destruct land – Basic movement of plates (in convergent boundrie s) – Oceanic-continental convergence – Oceanic-oceanic convergence – Continental-continental convergence Imagine these are two plates Oceanic-continental convergence When an oceanic plate pushes into and subducts* under a continental plate, the overriding continental plate is lifted up and a mountain range *forced sideways and downwards into the mantle is created. Oceanic-oceanic convergence When two oceanic plates converge one is usually subducted under the other and in the process a deep oceanic trench is formed. For example - Marianas Trench is a deep trench created as the result of the Phillipine Plate Continental-continental convergence When two continents meet head-on, neither is subducted because the continental rocks are relatively light and, like two colliding icebergs, resist downward motion. Instead, the crust tends to buckle and be pushed upward or sideways. The collision of India into Asia 50 million years ago caused the Eurasian Plate to crumple up and override the Indian Plate. After the collision, the slow continuous convergence of the two plates over millions of years pushed up the Himalayas and the Tibetan Plateau to their present heights. Divergent Boundries • Basic movement of divergent boundries • Detailed information Divergent Boundries • At divergent boundaries new crust is created as two or more plates pull away from each other. • Oceans are born and grow wider where plates diverge or pull apart. • when a diverging boundary occurs on land a 'rift', or separation will arise and over time that mass of land will break apart into distinct land masses and the surrounding water will fill the space between them Transform-fault boundries • Basic movement • Detailed information • Extra information Transform-fault boundries Transform-Fault Boundaries are where two plates are sliding horizontally past one another. These are also known as transform boundaries or more commonly as faults. Most transform faults are found on the ocean floor. They commonly offset active spreading ridges, producing zig-zag plate margins, and are generally defined by shallow earthquakes. A few, however, occur on land. Extra Information The San Andreas fault zone in California is a transform fault that connects the East Pacific Rise, a divergent boundary to the south, with the South Gorda -- Juan de Fuca -- Explorer Ridge, another divergent boundary to the north. The San Andreas is one of the few transform faults exposed on land. The San Andreas fault zone, which is about 1,300 km long and in places tens of kilometers wide, slices through two thirds of the length of California. Along it, the Pacific Plate has been grinding horizontally past the North American Plate for 10 million years, at an average rate of about 5 cm/yr. Land on the west side of the fault zone (on the Pacific Plate) is moving in a northwesterly direction relative to the land on the east side of the fault zone (on the North American Plate). Earthquakes • Though the oceanic plate as a whole sinks smoothly and continuously into the subduction trench (convergent movement), the deepest part of the subducting plate breaks into smaller pieces. These smaller pieces become locked in place for long periods of time before moving suddenly and generating large earthquakes. Such earthquakes are often accompanied by uplift of the land by as much as a few meters. • epicenter the point on Earth's surface directly above the focus point of an earthquake • focus the point below Earth's surface where rock breaks under stress and causes an earthquake (occurs at convergent and transform boundaries) Volcanoes • A volcano is a place on the Earth's surface (or any other planet's or moon's surface) where molten rock, gases and pyroclastic debris erupt through the earth's crust. Volcanoes vary quite a bit in their structure - some are cracks in the earth's crust where lava erupts, and some are domes, shields, or mountain-like structures with a crater at the summit. • Caused by divergent plates pulling apart Volcano-tectonic earthquakes • Earthquakes produced by stress changes in solid rock due to the injection or withdrawal of magma (molton rock) are called volcano-tectonic earthquakes. – These earthquakes can cause land to subside and can produce large ground cracks. These earthquakes can occur as rock is moving to fill in spaces where magma is no longer present. Volcano-tectonic earthquakes don't indicate that the volcano will be erupting but can occur at anytime. – The second category of volcanic earthquakes are long period earthquakes which are produced by the injection of magma into surrounding rock. These earthquakes are a result of pressure changes during the unsteady transport of the magma. When magma injection is sustained a lot of earthquakes are produced. This type of activity indicates that a volcano is about to erupt. Scientists use seismographs to record the signal from these earthquakes. This signal is known as volcanic tremor. Volcano-tectonic earthquakes The second category of volcanic earthquakes are long period earthquakes which are produced by the injection of magma into surrounding rock. These earthquakes are a result of pressure changes during the unsteady transport of the magma. When magma injection is sustained a lot of earthquakes are produced. This type of activity indicates that a volcano is about to erupt. Scientists use seismographs to record the signal from these earthquakes. This signal is known as volcanic tremor. A quick pic A quick pic Bibliography • http://en.wikipedia.org/wiki/Plate_tectonics • http://geography.about.com/od/physicalgeog raphy/a/Plate-Tectonics.htm • http://science.nationalgeographic.co.in/scien ce/earth/the-dynamic-earth/plate-tectonics- article/ • http://www.enchantedlearning.com/subjects/ volcano/ • http://www.platetectonics.com/book/page_5. asp