PLATE TECTONCIS

THE THEORY…. … Is a scientific theory for the large scale movements of the Earths lithosphere. (The crust and the mantle- 100km thick) Earth's outermost layer, is broken into 7 large rigid pieces called plates: the African, North American, South American, Eurasian, Australian, Antarctic, and Pacific plates. The movement is caused by heat dissipation from the Earths Mantle.

THE EVIDENCE In 1912 a German Scientist called Alfred Wegener proposed that these two continents were once joined together then somehow drifted apart. He proposed that all the continents were once stuck together as one big land mass called Pangea. He believed that Pangea was intact until about 200 million years ago. If you look at a map you can see that the coast lines of many countries would fit snugly together therefore suggesting that this evidence is true.

CONVERGENT PLATE BOUNDARY Is also known as a destructive plate boundary. (due to subduction. See slide) A convergent plate boundary is one where two or more fragments of lithosphere move toward one another and collide. This causes pressure, friction, earthquakes and volcanoes.

DIVERGENT PLATE BOUNDARY … Is also known as a constructive plate boundary. The most active form of constructive plate boundaries are between oceanic plates. A constructive plate boundary is one which can lead to volcanic islands! The 2 tectonic plates move away from each other which form oceanic basins. When a volcanic island occurs…. when the plates move apart to produce gaps which molten lava rises to fill. This creates a shield volcano which would eventually build up to become a volcanic island.

SUBDUCTION ZONE ….takes place at convergent boundaries where one tectonic plate moves under the other. A subduction zone is an area on Earth where two tectonic plates move towards one another and subduction occurs. Rates of subduction are measured in centimetres per year.

TYPES OF VOLCANOES Types of volcanoes Volcanic caldera or super volcano Cinder cone Complex volcano Cryovolcano Fissure vent Guyot Lava dome Monogenetic volcanic field Mud volcano Pancake dome Polygenetic volcanic field Pyroclastic cone Pyroclastic shield Shield volcano Strato volcano (also known as a Composite volcano) Subaqueous volcano Subglacial volcano Submarine volcano Somma volcano Tuya Volcanic field Volcanic plug

THEY OCCUR WHEN A volcano is an opening, or rupture, in a planet's surface or crust, which allows hot magma, ash and gases to escape from below the surface. Volcanoes are generally found where tectonic plates are diverging or converging. Volcanoes can also form where there is stretching and thinning of the Earth's crust.

EARTHQUAKES …is the result of a sudden release of energy in the Earth's crust. Earthquakes are recorded with a seismometer, also known as a seismograph. Intensity of shaking is measured on the modified Mercalli scale.

TYPES OF WAVES seismic waves (P-waves S-waves) Body waves Surface waves Rayleigh waves Love Waves

FINDING AN EPICENTRE. rthquake/VQuakeExecute.htm rthquake/VQuakeExecute.htm