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Year 8: Tectonics: Revision worksheet Inner Core Outer Core Mantle Crust Tsunamis are tidal waves triggered by underwater earthquakes. The rate of travel of a tsunami is between 400- 600 miles per hour. They usually occur at destructive plate margins. The tsunami in SE Asia occurred on the 26th Conservative Collision Destructive December 2004. The earthquake measured 9.0 on the Richter Scale and occurred off the northern tip of Sumatra. The tsunami spread across the Indian Ocean and hit coastal Constructive areas of Sri Lanka, India, Bangladesh, Myanmar, Indonesia and Malaysia. The death toll is believed to be 290,000. 1. Constructive plate margin At a constructive plate boundary, two plates move apart. As the two plates move apart, magma rises up to fill the gap. This causes volcanoes. However, since the magma can escape easily at the surface the volcano does not erupt with much force. 2. Destructive plate margin A destructive plate boundary is found where a continental plate meets an oceanic plate. The oceanic plate descends under the continental plate because it is denser. As the plate descends it starts to melt due to the friction caused by the movement between the plates. This melted plate is now hot, liquid rock (magma). The magma rises through the gaps in the continental plate. If it reaches the surface, the liquid rock forms a volcano. 3. Collision plate margin Collision boundaries occur when two plates of similar densities move together (i.e. a continental plate and a continental plate). This causes the material between them to buckle and rise up, forming fold mountains. SS2017 Year 8: Tectonics: Revision worksheet 4. Conservative plate margin Conservative plate boundaries exist where two plates do not directly collide but slide past each other along a fault (weakness). No volcanoes are found along these plate boundaries, but earthquakes do occur. An example of such a boundary is the San Andreas Fault in California. 7 8 5 5 3 1 2 6 4 1. Nazca 2. South American 3. African 4. Antarctican 5. Pacific 6. Indo-Australian 7. Eurasian 8. North American Roof timber bolted to walls Steel bracings Emergency escape stairs Emergency water supply SS2017 Basement reinforced to prevent collapse Shatter proof windows Joists bolted to frame Automatic cutoff valves for gas pipes Emergency bin (and water) Deep foundations Year 8: Tectonics: Revision worksheet What is Continental Drift? Do all volcanoes erupt? In 1912, a German scientist called Alfred * Active volcano – liable to erupt e.g. Mt Wegener proposed that South America and Africa Etna. were once joined together and had thus moved apart. * Dormant (sleeping) volcano – a volcano which has not erupted for many years. For He believed that all the continents were once example, Mt Pinatubo erupted in 1991 after joined together as one big land mass called 500 years of dormancy. Pangaea until about 200 million years ago. Evidence for Continental Drift: * Pattern of rocks * Shapes of continents * Extinct volcano – a volcano which has not erupted for many thousands or millions of years e.g. Edinburgh. Types of volcano: * Study of fossils Cone Shield SS2017 Composite Year 8: Tectonics: Revision worksheet Advantages of living in volcanic Disadvantages of living in volcanic areas: areas: * Fertile soils * Minerals * Tourism * Toxic gases * Fire * Disease * New land * Heat for electricity * Crops destroyed * Illness/death Useful links: http://www.bbc.co.uk/schools/gcsebitesize/geography/natural_hazards/ https://www.youtube.com/watch?v=mpMXEPN2EeA Notes: _______________________________________________________________________ _______________________________________________________________________ _______________________________________________________________________ _______________________________________________________________________ _______________________________________________________________________ _______________________________________________________________________ _______________________________________________________________________ _______________________________________________________________________ _______________________________________________________________________ _______________________________________________________________________ _______________________________________________________________________ _______________________________________________________________________ _______________________________________________________________________ _______________________________________________________________________ _______________________________________________________________________ _______________________________________________________________________ _______________________________________________________________________ _______________________________________________________________________ _______________________________________________________________________ SS2017