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GEOL 101: Intro to Geology > Iceland > Flashcards

Flashcards in Iceland Deck (5)
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1

How do ocean basins form?

Ocean basins form at divergent boundaries. The lithosphere pulls apart. The stretching and eventual breaking allows the asthenosphere to rise to the earths surface. The decompression of the asthenosphere causes it to melt, forming magma. When this magma reaches the surface and becomes lava, it cools quickly on contact with the ocean. This basalt becomes the newest part of the ocean floor. The process repeats and the ocean floor grows.

2

Use the geological features of ocean basins to determine the motions of Earth’s plates.

  • Volcanic Ridges form along divergent boundaries. 
    The plates will move away from a divergent boundary or volcanic ridge (with no trench).
  • Oceanic Trenches form at convergent boundaries (subduction zones) A volcanic ridge often (if not always) forms on the other side of this trench. Plates move toward convergent boundaries. If you see a trench and a volcanic ridge you can guess it's convergent.

3

What are the characteristics of glacial erosion and deposition?

  • Erosion:
    • Hanging Valleys
    • Glacial Valley
  • Deposition:
    • Morraines

4

Explain how rocks are metamorphosed at a spreading ridge.

The most common types of Metamorphasism at spreading ridges are:

  1. Contact Metamorphism
    Occurs at high temperatures in a small area, Usually near the edge of an igneous intrusion (dikes, fissures, or volcanoes)
  2. Hydrothermal Metamorphism
    Can happen on continental crust where rocks are changed by hot fluids that have to do with igneous intrusions. 
    Generally happens in oceanic spreading ridges. Hot water works its way down into the fractured basalt. The water and the basalt chemically react. 

5

What are the hazards of Icelandic eruptions?check

 

  • Icelandic eruptions are very mafic and similar to Hawaii's eruptions except that there are glaciers atop many of iceland's volcanoes. These glaciers melt at the explosion of a volcano. The water mixes with the lava causing it to be more felsic and explosive.
  • The water also can lift the glacier and cause flash floods. 
  • The greatest danger from these explosive volcanoes is the toxic gas emitted by them.