1. theory that pieces of Earth's lithosphere, called plates, move about slowly on top of the asthenosphere.
    plate tectonics
  2. 3 ideas that support continental drift.
    • -N. and S. America outline fits into Western Europe and Africa
    • -fossils of same species seperated by oceans
    • -distinctive rocks found on Appalachian Mountain chain.
  3. Who is Alfred Wegener?
    he hypothesized that the continents were once joined in a single supercontinent, which then broke into pieces that moved apart.
  4. What was pangaea?
  5. the continents move slowly across Earth's surface.
    continental drift
  6. What is the mid-ocean ridge?
    chain of underwater mountains that was discovered in the 50's
  7. What is the Atlantic mid-ocean ridge?
    deep valley running the length of its crest
  8. more dense, oceanic plate
    basalt 3.0 g/cm3
  9. less dense continental plate
    granite (2.7 g/cm3)
  10. where is new oceanic crust created at?
    mid-ocean ridges (AKA spreading center, divergent, rift zone)
  11. Where is old ocean crust destroyed at?
    subduction zones
  12. process in which new oceanic crust is created at mid-ocean ridges as older crust moves away
    sea-floor spreading
  13. oceanic plates sink into the mantle
  14. edges of oceanic plates where subduction occurs
    subduction zones
  15. as plates sink through subduction zones, it bends, forming a depression in the ocean floor.
  16. What two things did the rock samples from each side of the mid-ocean ridges show identical patterns of?
    • -magnetic field reversal in rock crystals
    • -aging of rock away from ridge
  17. how often is ocean floor renewed?
    about every 200 million years
  18. how old is the oldest continental rock?
    4.3 billion years old
  19. Why do plates move?
    • 1. rock of the asthenosphere is partially melted
    • 2. extreme heat from the mantle causes rock in the lower asthenosphere to expand->less dense-> rises
    • 3. rising hotter magma pushes older-cooler, more dense magma to sink (convection)
    • 4. friction between moving magma and lithosphere causes plates to move slowly.
  20. if both plates are continental, what happens?
    the crust buckles, thickens, and creates a mountain chain.
  21. what are two convergent boundaries?
    • cont. vs cont. (Ex. india vs. Eurasia)
    • oceanic vs. cont. (Nazca vs. S. Amer.)
  22. What is one type of divergent boudary?
    Mid-ocean ridge (ex. N. Amer. and S. Amer. vs. Eurasia and African)
  23. What are two sources of heat causing convection currents?
    • -heat from Earth's formation
    • -decay of radioactive isotopes inside earth
  24. What is a divergent boundary?
    plates move away from eachother (ex. mid-ocean ridge)
  25. What is a convergent boundary?
    plates come together; collide
  26. What two plates form the Andes mountains?
    Nazca and S. Amer
  27. What two plates form the Himalayas?
    Tibet and India
  28. What is a transform boundary?
    plates slide past each other, moving in opposite directions.
  29. A movement of Earth's lithosphere that occurs when rocks in the lithosphere suddenly shift, releasing sroted energy
  30. energy released during an earthquake is carred by these vibrations
    seismic waves
  31. force that squeezes rock together, stretches or pulls them apart, or puches them in diff. direction
  32. break in a mass of rock along which movement occurs
    fault (ex. san andreas)
  33. bend in layers of rock
  34. why do earthquakes occur?
    because stress forces have exceeded the strength of rock
  35. location beneath Earth's surface where an earthquake begins
  36. location on Earth's surface directly above the focus
  37. What are P waves?
    • (primary waves) longitudinal waves similar to sound waves.
    • -compress and expand ground
    • -fastest seismic waves
    • -travel through solids and liquids
  38. What are compression waves?
    expansion waves (like a "slinky")
  39. What are S waves?
    • (secondary waves) transverse waves, like light and other eletromagnetic radiation
    • -cannot travel through liquids.
  40. What are surface waves?
    • waves that develop when seismic waves reach earths surface
    • -move more slowly that P waves and S waves
    • -produce larger ground movements and greater damage
  41. What are siesmographs?
    detect and record seismic waves
  42. what are seismograms?
    record of an earthquake on a seismograph
  43. What scale rates earthquakes based on measurements of the times and amplitudes of seismic waves by certain seismographs?
    richter scale
  44. What scale gives a measurement of the amount of energy released by an earthquake?
    moment magnitude scale
  45. What is the largest earthquake?
    Mw 9.5, occured in southern chile in 1960
  46. What scale ranges from 1-12, based on observations of intensity of ground shaking and damage in the areas affected by an earthquake?
    Mercalli scale
  47. What happens when seismic waves interact with boundaries?
    either reflected,refracted, or defracted
  48. How do we know that Earth's core is mostly iron?
    P waves travel through it at a speed that matches labratory exper. on iron
  49. mountain that forms when magma reaches the surface
  50. pocket in which magma collects before a volcanic eruption
    magma chamber
  51. Where do mafic eruptions occur at?
    divergent rift zones and hot spots(hawaii)
  52. narrow, vertical channel
  53. opening in the ground where magma escapes to the surface
  54. top of central vent in most volcanoes is a bowl-shaped pit
  55. The hollow shel that collapses inward, creating a huge depression
  56. what are the 3 main factors that determine the viscosity of magma?
    temperature, water content, silica content
  57. What is the magma with high viscosity like? low viscosity?
    thick and resists flowing; thin and flows easily
  58. What is a quiet eruption?
    low-silica and hot magma
  59. four characteristics about mafic magma.
    • -lower silica
    • -lower gas
    • -lava forms darker rocks
    • -hotter than felsic magma
  60. lava that erupts in a stream of low-viscosity lava is called a
    lava flow
  61. Ash, cinders, etc. ejected from a volcano (esp. subduction boundary)
  62. three characteristics about felsic magma
    • -lava forms lighter rock
    • -higher gas
    • -erupts at subduction zones
  63. What is a explosive eruption?
    • -high-silica magma
    • -lava solidifies into particles that range in size from fine dust and ash, to pebble-sized cinders, to bombs
  64. region where hot rocks extends deep within the mantle to the surface
    hot spot
  65. quiet eruption of low-viscosity laca produces wide, flat volcano
    shield volcano
  66. eruption that is entirely ash and cinders, result will be a small, steep-sided volcano.
    cinder cone volcano
  67. forms from an explosive eruption that produces a combination of lava and ash
    composite volcano
  68. What are the 3 major locations volcanos occur at?
    mid-ocean ridges, subduction zones, and hot spots
  69. when the outer rock of volcano erodes what does it leave through?
    volcanic neck
  70. largest of all igneous intrusions; form cores of many of Earth's mountain ranges
  71. formed when magma sqeezes in cracks parallel to rock layers
  72. formed when magma enters a crack cutting across layers
  73. area on opposite side where an earthquake takes place
    shadow zone
Card Set
Chapter 22