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1、The Structure of the Earth and Plate Tectonics第1页，共37页。Structure of the EarthThe Earth is made up of 3 main layers:CoreMantleCrustInner coreOuter coreMantleCrust第2页，共37页。The CrustThis is where we live!The Earths crust is made of:Continental Crust- thick (10-70km)- buoyant (less dense than oceanic cr
2、ust) - mostly oldOceanic Crust- thin (7 km)- dense (sinks under continental crust)- young第3页，共37页。How do we know what the Earth is made of?Geophysical surveys: seismic, gravity, magnetics, electrical, geodesyAcquisition: land, air, sea and satelliteGeological surveys: fieldwork, boreholes, mines第4页，
3、共37页。What is Plate Tectonics?第5页，共37页。If you look at a map of the world, you may notice that some of the continents could fit together like pieces of a puzzle.第6页，共37页。Plate TectonicsThe Earths crust is divided into 12 major plates which are moved in various directions.This plate motion causes them
4、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 as a consequence of plate interaction.第7页，共37页。World Plates第8页，共37页。What are tectonic plates
5、 made of?Plates are made of rigid lithosphere.The lithosphere is made up of the crust and the upper part of the mantle.第9页，共37页。What lies beneath the tectonic plates?Below the lithosphere (which makes up the tectonic plates) is the asthenosphere.第10页，共37页。Plate Movement“Plates” of lithosphere are mo
6、ved around by the underlying hot mantle convection cells第11页，共37页。Practical Exercise 1Supercontinents!第12页，共37页。What happens at tectonic plate boundaries?第13页，共37页。DivergentConvergentTransformThree types of plate boundary第14页，共37页。Spreading ridgesAs plates move apart new material is erupted to fill
7、the gapDivergent Boundaries第15页，共37页。Age of Oceanic CrustCourtesy of www.ngdc.noaa.gov第16页，共37页。Iceland has a divergent plate boundary running through its middleIceland: An example of continental rifting第17页，共37页。There are three styles of convergent plate boundariesContinent-continent collisionConti
8、nent-oceanic crust collisionOcean-ocean collisionConvergent Boundaries第18页，共37页。Forms mountains, e.g. European Alps, HimalayasContinent-Continent Collision第19页，共37页。Himalayas第20页，共37页。Called SUBDUCTIONContinent-Oceanic Crust Collision第21页，共37页。Oceanic lithosphere subducts underneath the continental
9、lithosphereOceanic lithosphere heats and dehydrates as it subsides The melt rises forming volcanismE.g. The AndesSubduction第22页，共37页。When two oceanic plates collide, one runs over the other which causes it to sink into the mantle forming a subduction zone. The subducting plate is bent downward to fo
10、rm a very deep depression in the ocean floor called a trench. The worlds deepest parts of the ocean are found along trenches. E.g. The Mariana Trench is 11 km deep!Ocean-Ocean Plate Collision第23页，共37页。第24页，共37页。Where plates slide past each otherTransform BoundariesAbove: View of the San Andreas tran
11、sform fault第25页，共37页。第26页，共37页。Practical Exercise 2Where will the UK be in:1,000 years?1,000,000 years?1,000,000,000 years?第27页，共37页。whats the connection?Volcanoes and Plate Tectonics第28页，共37页。Volcanism is mostly focused at plate marginsPacific Ring of Fire第29页，共37页。- Subduction - Rifting - Hotspots
12、Volcanoes are formed by:第30页，共37页。Pacific Ring of FireHotspot volcanoes第31页，共37页。Hot mantle plumes breaching the surface in the middle of a tectonic plateWhat are Hotspot Volcanoes?Photo: Tom Pfeiffer / The Hawaiian island chain are examples of hotspot volcanoes.第32页，共37页。The tectonic plate moves ov
13、er a fixed hotspot forming a chain of volcanoes.The volcanoes get younger from one end to the other.第33页，共37页。whats the connection?Earthquakes and Plate Tectonics第34页，共37页。As with volcanoes, earthquakes are not randomly distributed over the globeAt the boundaries between plates, friction causes them
14、 to stick together. When built up energy causes them to break, earthquakes occur.Figure showing the distribution of earthquakes around the globe第35页，共37页。Where do earthquakes form? Figure showing the tectonic setting of earthquakes第36页，共37页。Plate Tectonics SummaryThe Earth is made up of 3 main layer
15、s (core, mantle, crust)On the surface of the Earth are tectonic plates that slowly move around the globePlates are made of crust and upper mantle (lithosphere)There are 2 types of plateThere are 3 types of plate boundariesVolcanoes and Earthquakes are closely linked to the margins of the tectonic plates第37页，共37页。
