224_ingles. irune irene iara.doc.doc

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224_ingles. irune irene iara.doc.doc

  1. 1. BHINEBI:Hona hemen gure txosten, eredutzat hartuz: Irune Elicegui Iara Duran Irene Arin INDEX • What’s inside the Earth? 3
  2. 2. • The lithosphere• Tectonic plates 4 • What’s a tectonic plate? • The major tectonic plates in the World• Continents 5 • What’s continental drift? • Earthquakes • Volcanoes WHAT’S INSIDE THE EARTH?• The lithosphere 2
  3. 3. The lithosphere is underlain by the asthenosphere, the weaker,hotter, and deeper part of the upper mantle. The concept of thelithosphere as Earth’s strong outer layer was developed by Barrell,who wrote a series of papers introducing the concept. The conceptwas based on the presence of significant gravity anomalies overcontinental crust, from which he inferred that there must exist astrong upper layer (which he called the lithosphere) above a weakerlayer which could flow (which he called the asthenosphere). Thedivision of Earths outer layers into lithosphere and asthenosphereshould not be confused with the chemical subdivision of the outerEarth into mantle, and crust. All crust is in the lithosphere, butlithosphere generally contains more mantle than crust.There are two types of lithosphere:-Oceanic lithosphere, which is associated with Oceanic crust.-Continental lithosphere, which is associated with Continental crust. TECTONIC PLATES • What’s a tectonic plate? (Plate movement) 3
  4. 4. Plate tectonics describes the large scale motions of Earthslithosphere.The lithosphere is broken up into what are called tectonic plates — inthe case of Earth, there are seven major and many minor plates. Thelithospheric plates ride on the asthenosphere. These plates move inrelation to one another at one of three types of plate boundaries:convergent or collision boundaries, divergent or spreadingboundaries, and transform boundaries. Earthquakes, volcanicactivity, mountain-building, and oceanic trench formation occuralong plate boundaries. The lateral movement of the plates istypically at speeds of 50—100 mm annually. The major tectonic plateof the world:The main plates are: • African Plate covering Africa - Continental plate • Antarctic Plate covering Antarctica - Continental plate • Australian Plate covering Australia - Continental plate • Indian Plate covering Indian subcontinent and a part of Indian Ocean - Continental plate • Eurasian Plate covering Asia and Europe - Continental plate • North American Plate covering North America and north-east Siberia - Continental plate • South American Plate covering South America - Continental plate • Pacific Plate covering the Pacific Ocean - Oceanic plate CONTINENTS 4
  5. 5. Made tens of millions of years, had only one continent on our planet,called Pangea. The theory of plate tectonics explains how thedifferent plates that make up the Pangea were divided into twocontinents Laurasia and Gondwana, and divided up to theconformation having the continents.The movement of plates has caused the formation and break-up ofcontinents over time, including occasional formation of asupercontinent that contains most or all of the continents. Thesupercontinent Rodinia is thought to have formed about 1 billionyears ago and to have embodied most or all of Earths continents,and broken up into eight continents around 600 million years ago.The eight continents later re-assembled into another supercontinentcalled Pangaea; Pangaea eventually broke up into Laurasia (whichbecame North America and Eurasia) and Gondwana (which becamethe remaining continents). EARTHQUAKES 5
  6. 6. An earthquake (also known as a tremor or temblor) is the result of asudden release of energy in the Earths crust that creates seismicwaves. Earthquakes are recorded with a seismometer, also knownas a seismograph. At the Earths surface, earthquakes manifestthemselves by shaking and sometimes displacing the ground.Earthquakes are caused mostly by rupture of geological faults, butalso by volcanic activity, landslides, mine blasts, and nuclearexperiments. An earthquakes point of initial rupture is called itsfocus or hypocenter. The term epicenter refers to the point at groundlevel directly above this. TIPES OF EARTHQUAKES VOLCANOES 6
  7. 7. Volcanoes are simply vents at the earths surface through which lavaand other volcanic products are erupted. Although many volcanoesare cone-shaped, different types of volcano exist according to theirlocation an d the products they are made up of. 7

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