Revision on the restless earth


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Revision on the restless earth

  1. 1. Revision Time:
  2. 2. Inside the Earth
  3. 3.  The earths crust is split into a series of plates. The places where plates meet are called plate boundaries. These plates float on the heavy molten rock of the mantle. Continental drift means that the continents of the world are carried along by the plates beneath them. Plates can collide and seperate.
  4. 4.  The Plates: Eurasian Plate African Plate Pacific Plate Nazca Plate Australian Plate
  5. 5. When Plates collide Fold mountains are formed Earthquakes occur
  6. 6. When plates separate Volcanic islands, volcanic mountains and mid ocean ridges are formed.
  7. 7. Folding and fold mountains Fold mountains are created when two plates collide. When the plates compress ( push together) the earths crust begins to arch upwards.
  8. 8.  Young fold mountains include the Alps and the Rocky mountains,these were formed about 35million years ago. Irelands fold mountains are very old and tend to be flat. They were formed 250 million years ago.
  9. 9. Earthquakes Earthquakes happen when two plates collide or slip past one another . When the plates compress ( crush together) cracks form in the earths crust. The area of compression is called the focus. The focus sends out shock waves through the crust, reaching the surface. The area of the surface hit by the worst shock wave is called the epicentre.
  10. 10.  The epicentre is the most dangerous area of an earthquake. A seismograph measures the earthquakes strength. Earthquakes are rated on the Richter Scale
  11. 11.  Earthquakes can cause buildings to collapse, roads to crack, mudslides and tsunamis.
  12. 12. Volcanic Activity Where plates seperate or collide the earths crust cracks and lets through hot liquid rock called magma. The magma forces its way up through a long hole in the mantle known as a vent Once the magma hits the earths surface it is now called lava. When plates seperate the lava may form ridges in the earths surface known as mid ocean ridges. The most famous ridge is the Mid Atlantic Ridge.
  13. 13. The Mid Atlantic Ridge The Mid Atlantic Ridge was created when the Eurasian and the American Plates seperated. The Mid Atlantic Ridge starts at the top of the Atlantic Ocean and runs all the way through down to the bottom. Iceland is a volcanic Island on the Mid Atlantic Ridge. Famous volcanos in Iceland include Mount Krafla and the island of Surtsey.
  14. 14. The formation of a volcano: When the magma reaches the top of the vent, it bursts through the earths surface. Lava, ash and mud explode from the surface. The hot lava then flows and spreads out destroying the land around it. When the lava cools and hardens it becomes cone shaped and eventually creates a volcanic mountain.
  15. 15.  Volcanos can be active, dormant or extinct. Active : erupts regularly Dormant: has not erupted for along time Extinct: has not erupted in historic times.
  16. 16. The Pacific Ring of Fire This is an area in the Pacific Ocean where there are huge amounts of volcanos and earthquakes. There have also been numerous tsunamis in and around the ring.
  17. 17.  Best of luck in the test