GEOS - 4. Igneous Rocks & Processes

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GEOS - 4. Igneous Rocks & Processes
2015-02-18 09:46:07
geology igneous

For Exam 1
Show Answers:

  1. What processes create igneous rocks?
    Cool & crystallizing magma; volcanism
  2. What is magma?
    liquid rock
  3. What is lava?
    Magma after it reaches earth's surface
  4. Where on Earth are igneous rocks created ?
    Pacific ring of fire, around volcanoes
  5. What happens at subduction zones?
    A lot of water is released, changing the melting point of rocks,thus creating magma which cools into solid rock
  6. What happens at midocean ridges?
    The asthenosphere is rising upwards; when magma rises it'll form new oceanic crust
  7. What is the relationship between hotspots and volcanoes?
    A hotspot makes a volcano and the plate moves making it so the volcano is no longer over the hotspot, so the hotspot makes a new one. A chain of volanoes is formed (like Hawaii)
  8. Define felsic
    Feldspar and silica rich; richer than aluminum
  9. What minerals compose felsic rocks?
    Mica, clay, feldspar, quartz
  10. Where in the earth can felsic rocks be found?
  11. Define mafic
    magnesium & rich rich
  12. What are examples of mafic rocks: olivine, pyroxen, amphibole
  13. Where in the earth can mafic rocks be found?
  14. Define ultramafic
    No feldspar at all
  15. In the Bowen's reaction series, what is the order of the discontinuous ferromagnesian series from ultramafic to rhyolitic?
    Oliving, augite, hornblend, biotite, orthoclase
  16. Crystallization happens in the opposite direction of ___.
  17. Do mafic minerals crystallize first or last out of a melt?
  18. Do felsic minerals crystallize first or last out of a melt?
  19. Do mafic minerals melt first or last when a rock is heated?
  20. Do felsic minerals melt first or last when a rock is heated?
  21. What does plutonic mean?
    It cooled inside the earth, not on the surface like volcanic rocks
  22. Volcanic is [hotter/colder] than plutonic.
  23. Volcanic rocks crystallize [faster/slower] than plutonic rocks
  24. What happens as a result of volcanic rocks crystallizing fast?
    Smaller crystals are made
  25. Describe granite.
    • Large crystals
    • Cooled underground
    • Light-colored, felsic
    • Contains mostly quartz and orthoclase
    • Phaneritic intrustive
  26. Describe Rhyolite
    • Small crystals
    • Cooled underground
    • Light-colored, felsic
    • Contains mostly quartz and orthoclase
    • Aphanitic extrusive
  27. Describe diorite
    • Plutonic
    • Intermediate
    • Coarse-grained
    • Phaneritic
  28. Describe andesite
    • Intermediate rock
    • Volcanic
    • Fine-grained
    • Aphanitic
  29. Describe gabbro
    • Big crystals
    • Mafic
    • Intrusive
  30. Describe basalt
    • Formed at the surface
    • Need microscope to see crystals
    • felsic
    • volcanic
  31. Descibe peridotite
    • Ultramafic
    • Plutonic
  32. Does felsic magma have high or low viscosity?
  33. Does mafic magma have high or low viscosity?
  34. Define pyroclastic eruption
    Buoyancy forces push up felsic magma, making the volcano "bang" instead of flow
  35. Define pyroclastic.
    Material that is blasted into the air through explosive eruptions
  36. What is a caldera?
    A depression that is equal to or greater than 1.6 km in diameter
  37. Define aphanetic
    crystals too small to be seen by the naked eye
  38. Define phaneritic
    Composed of an interlocking network of large crystals that are easily visible
  39. Lava cone rows from ___ eruptions, where lithospheric plates are being pulled apart.
  40. Composite volcanoes are formed when ___.
    a volcano erupts both lava and abundant pyroclastic material
  41. Define bomb.
    • > 64 mm; are hot enough to be viscous at the time of impact
    • Clasts this size can be carried for as much as 5 km from vent
  42. Define lahar
    • ash + water = mud
    • What happens to the rock surrounding a plutonic intrusion?
    • The heat from the magma will metamorphose the immediate surrounding rocks
  43. What is a dike?
    The vertical plumbing of a crack
  44. Define pluton.
    bodies of rock formed by the inrusion of magma; they get left behind last; it erodes slower than volcanic and sedimentary rocks
  45. What happens to climate as a result of ash in the atmosphere?
    global cooling bc the sun can't get through it; climate change for about a year
  46. What is hydrothermal alteration?
    The process of water from rain and snowmelt being warmed bc of high heat flow emanating from the magma chamber and then reacting rapidly with minerals
  47. Describe unfractured plutonic rocks
    • Cool very slowly w/ larger crystals
    • very strong
    • very low permeability
  48. Describe volcanic rocks
    • Shrink when they're cooling
    • Cool fast --> shrink cracks
    • Very weak and permeable
  49. Where are the active volcanoes in the USA?
    along west coast and along the island of Alaska
  50. How many global volcanoes were erupting last week? Where are they?
    17; most along the pacific ring of fire
  51. What are the hazards of volcanoes?
    Gas, lahars, landslides, lava flows, pyroclastic flows, tephra
  52. How are volcanoes monitored and how are eruptions predicted?
    Movement of thrust faults, tilt of ground, earthquakes