Science: Earth

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Science: Earth
2010-11-01 03:07:34
Rocks Volcanoes Earthquakes

Naturally caused hazards.
Show Answers:

  1. What are the three types of rocks?
    The three types of rock are: Igneous, Sedimentary and Metamorphic.
  2. What are the three steps in the rock cycle?
    Igneous rocks are formed from the cooling of molten rock from volcanic eruptions. The igneous rocks weather and layer upon each other forming sedimentary rocks. The sedimentary rocks are then put under extreme pressure and have added temperature, causing the minerals inside of them to re-crystalize forming metamorphic rocks.
  3. What is a volcano?
    A volcano is a weakness in the earths crust which allows magma to push up to the surface.
  4. What are the four different types of volcano found in NZ?
    Shield, Dome, Caldera and Cone.
  5. Why does NZ have a lot of volcanoes?
    NZ has a lot of volcanoes because it sits on the Pacific Ring of Fire.
  6. What are some other signs of volcanic activity?
    Geysers, hot pools and fumaroles.
  7. What is the Pacific Ring of Fire?
    It is the edge of the Pacific Plate where volcanoes are really common.
  8. Explain a Shield volcano.
    A shield volcano is formed from basaltic magma. It is a low cone sloping shape and deposits runny lava. A NZ example is Mt Akaroa and has more gentle explosions.
  9. Explain Cone volcanoes.
    A cone volcano is formed from andesitic magma and has steep cone sides. It deposits sticky lava in more ashy and explosive eruptions. A NZ example is Mt Taranaki.
  10. Explain Shield Volcanoes.
    Shield volcanoes are formed from rhyolitic magma. They are dome shaped and deposit stick lava in sudden explosions. A NZ example is Mt Tarawera.
  11. Explain Caldera Volcanoes.
    Caldera Volcanoes are formed from rhyolitic magma. They are holes left after very violent volcanoes. They deposit stick lava in very violent eruptions that occur due to built up pressure. A NZ example is Lake Taupo.
  12. What is a surface wave (L Wave)?
    Is the most destructive wave, is the last to be felt and occurs at the surface. Causes the jelly like movement.
  13. What is the focus?
    The focus is where the movement occurs beneath the earths crust.
  14. What is the epicenter?
    The epicenter is the point on the Earths crust directly above the focus.
  15. What are primary waves (P Waves)?
    The first wave to be felt. Caused by a longitudinal wave and produce push and pull movements. It is the fastest wave and can travel through solids and liquids.
  16. What is the secondary wave (S Wave)?
    It is also called a shear wave. The second to be felt, is caused by transverse waves. Produces up and down, side to side movement. It can only travel through solids.
  17. How do you find the epicenter of an earthquake?
    If the earthquake is detected by three or more seismographs, the position of the epicenter can be found.
  18. What is the Richter Scale?
    Describes the energy carried by an earthquake. It gives a number from 1 up to but never reaching 9 (as it is thought to be impossible to have an earthquake of this magnitude). Each higher number carries 10x the energy of the number below it. So 6 is 10x greater than 5. And 7 is 100x greater than 5.
  19. Why does NZ have a lot of earthquakes?
    Because it is partly on the Pacific plate and partly on the Indo-Australian plate. There are several fault lines running through NZ.
  20. What is an L-wave?
    An L wave is a surface wave, it causes the earth to shake like jelly and causes the most damage. It is the slowest wave.
  21. What is the plate tectonic theory?
    The theory that giant sections or plates of rock are moving across the Earths surface. It replaces the continental drift theory, in which only the continents were thought to be moving. Convection currents cause the movement of the plates.
  22. How far and in what direction are the earths crustal plates moving?
    The Earths crustal plates are moving in all directions at around 4cm per year.
  23. What are separating plates characterized by?
    Mid Oceanic Ridges.
  24. What are sliding plates characterized by?
  25. What are colliding plates characterized by?
    Deep mid-oceanic trenches; volcanic activity; faults and mountain building.
  26. What does NZ lie over?
    NZ lies over an active subduction zone, where rocks of the pacific plate are being pushed under the rocks of the indo-australian plate. This causes: earthquakes, volcanoes and hot springs to be present along the plates boundaries.