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    • author "me"
    • tags "Bramble1997"
    • description ""
    • fileName "Geography Keywords - A2"
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    • Aftershock
    • A minor earthquake or tremor following a larger and more powerful earthquake
  1. Asthenosphere
    The partial liquid layer - part of the mantle - on which the tectonic plates "float"
  2. Benioff Zone
    The zone of melting at a destructive (convergent) margin as one plate dives (subducts) beneath another
  3. Core
    The central "core" of the Earth rich in iron and nickel compromising a solid liquid inner core (1200km thick) and a liquid outer core (2300km thick)
  4. Crust
    The outermost "skin" of the earth that varies in thickness between 12 and 120km
  5. Earthquake engineering
    Mitigation approaches involving engineering solutions to reduce damage associated with ground shaking during an earthquake, such as strengthening bridge supports and the foundations of buildings
  6. Epicentre
    The point on the grounf surface immediately above the focus of an earthquake
  7. Faults
    Lines of weakness in the form of cracks in rocks along which relative movement (displacement) takes place. Sudden movement along faults is often associated with earthquakes
  8. Focus
    The point within the Earths crust where an earthquake originates - put simply, its the origin of an earthquake
  9. Fold mountains
    Montain chains such as the Alps and the Andes formed by enormous compressional forces associated with a destructive (collision) plate margin
  10. Igneous rocks
    Rocks formed by the colling of a molten magma, either underground (intrusive) or on the ground surface (extrusive)
  11. Liquefaction
    The jelly-like state of silts and clays resulting from intense ground shaking that may result in the subsidence and collapse of buildings following an earthquake
  12. Lithosphere
    Resting on the asthenosphere, this is outermost solid layer of the Earth comprising the crust and the outer mantle. Approximately 100 km thick, it is divided into several large plates and many smaller ones
  13. Magma
    Molten rock, gases, and liquids occupying vast magma chambers at great pressure deep within the mantle. On reaching the ground surface, magma is known as lava
  14. Mantle
    The concentric layer of the Earth between the crust and the outer core. The mantle is some 2870km thick
  15. Metamorphic aureole
    The zone of rock adjacent to an igneous body, such as a magma chamber, that has been affected (heated) by metamorphism and where rocks have changed in their mineralogy and/or texture
  16. Ocean trenches
    Deep gashes in the sea floor up to 10971m deep (the Marianas Trench) marking destructive plate margins
  17. Plumes
    Rising current of heat (part of convection cells) usually associated with rising magma
  18. "Ring of Fire"
    The name given to the spatial pattern (ring) of volcanoes (and earthquakes) marking plate margins around the edge of the Pacific Ocean
  19. Seismicity
    Activity associated with the transmission of seismic (shock) waves radiating outwards from the focus of an earthquake
  20. Seismometer
    Instrument used to record the shockwaves (seismic waves) associated with an earthquake. Seismometers are also used to monitor earthquake in volcanic areas to help predict eruptions
  21. Spatter cone
    A somewhat indistinct volcanic cone forming a mound up to 12m high resulting from the eruptions of "globs" of very fluid lava, typically found in Hawaii
  22. Stratovolcano
    Otherwise known as a composite volcano, a stratovolcano is made up of alternating layers of lava and ash representing a series of eruptions over many years
  23. Strike-slip fault
    A crustal crack along which movement takes place in a horizontal plane (sideways) rather than vertical (up and down). Earthquakes are often associated with strike-slip faults, for example the San Andreas Fault in California, USA and the North Anatolian Fault, Turkey
  24. Submarine volcanoes
    Volcanoes formed beneath the sea that can either be single vent volcanoes or fissure volcanoes, where lava is emitted along a crack in the Earths crust (e.g. the Mid Atlantic Ridge)
  25. Supervolcano
    A huge volcano that often takes the form of a caldera (collapsed volcano cone) and is associated with massive eruptions capable of having a global impact on people.Examples of supervolcanoes include Yellowstone in the USA and Taupo in New Zealand
  26. Tephra
    Fragmental material emitted during a volcanic eruption, often resulting from the destruction of the volcanic cone. Tephra can vary from very fine ash to volcanic bombs (over 64mm) in size
  27. Vesicular Lava
    A type of basic (rich in iron and magnesium) lava containing holes (vesicles) that represent former gas bubbles
  28. Volcanicity
    Generic term used to describe a range of volcanic activity often associated with a place or region including volcanic eruptions, geysers and hot springs
  29. Centrifugal Forces
    Are forces that cause something to move away from its centre of rotation
  30. Convection
    Is the transfer of heat in a liquid or gas in a circular motion
  31. Dormant volcano
    A volcano which has not erupted within historic times is called dormant
  32. Extinct volcano
    A volcano which has not erupted for at least 10,000 years
  33. NGOs
    Non governmental organisations such as the Red Cross, Oxfam and Greenpeace
  34. Amplification
    As seismic waves pass through softer sediment, such as sand, the wave amplitude or height increases. This results in more intense shaking of the surface
  35. Lithosphere
    The upper mantle and the crust make up the lithosphere
  36. Geoid
    When the Earth is not in fact a perfect sphere but instead that it bulges around the equator and is flatter at the poles due to centrifugal forces
  37. How thick is the crust?
    It varies from 5-10km on the oceanic crust to nearly 70km on the continental plates
  38. Continental Plates
    Plates which are land masses
  39. Oceanic plates
    Plates which form the oceans
  40. SiMa
    A shortened version for silica and magnesium which makes up the oceanic plate made from basalt
  41. SiAl
    A shortened version of silica and aluminium which makes up the continental plate which is made of mainly granite rocks
  42. Whats the oceanic plate made up of?
    An occasionally broken layer of basalt rocks known as SiMa (silica and magnesium)
  43. Whats the continental plate made up of?
    Bodies of mainly granite rocks known as SiAl (because they are made up of silica and aluminium)
  44. How thick is the mantle?
  45. What characteristics does the mantle have?
    Due to the great heat and oressure within this zone, the mainly silicate rocks are in a thick, liquid state which becomes denser the deeper you go
  46. How old is the earth?
    4600 million years old
  47. Characteristics of the asthenosphere?
    A layer of softer, almost plastic-like rock. The asthenosphere can move very slowly carrying the lithosphere on top.
  48. What happens to the densities in the mantle?
    Densities within the mantle increase as you go down into the lower mantle
  49. How can we learn about the inner structure of the earth if we cant visit there?
    The depth and hot temperature mean that we cannot drill into or physically see most of the earth. Instead, scientists map the interior by watching how seismic waves, either from earthquakes or man made blasts, travel through the various layers
  50. What are the rocks like in the upper part of the mantle?
    Are solid and sit on top of the asthenosphere
  51. Whats at the centre of the Earth?
    The core
  52. What temperature is the core?
    Can reach above 5000 degrees celcius
  53. What is the core made up of?
    It is mostly made of iron and nickel
  54. Whats the density of the core?
    The core is 4 times denser than the crust
  55. How is the earths magnetic field created?
    It is thought that as the Earth rotates, the liquid outer core spins, creating the earths magnetic field
  56. How thick is the asthenosphere?
  57. How thick is the outercore?
  58. How thick is the inner core?
    12000 km
  59. How is the core made up?
    The core is actually made up of two parts. The outercore is semi-liquid and consists mainly of iron. The inner core is solid and is made up of an iron-nickel alloy
  60. What makes the tectonic plates?
    Convection currents
  61. Who was the person who first started to develop tectonic theory?
    Alfred Wegener
  62. When did people first notice the close fit between the east coast of South America and the west coast of Africa?
    As far back as 1620
  63. When did Alfred Wegener suggest his theory of continental drift?
    In 1912
  64. Whats the supercontinent called?
  65. What did Wegener suggest?
    He suggested that all the present continents were originally joined together to form a single supercontinent called Pangea before drifting apart in Laurasia in the north and Gondwanaland in the South. Laurasia and Gondwanaland then broke up to form the continental arrangement we know today
  66. What was Wegeners theory based on? (Evidence)
    • -The jigsaw fit of South America and Africa
    • -Matching rock sequences (of age and type) linking northwest Scotland and eastern Canada
    • -coal (formed only under warm, wet conditions) found beneath the Antarctic ice cap. Only if Antarctica was once positioned in warmer latitudes can this be explained
    • -Permian fossil brachiopods in India match those in Australia
    • -A unique Permian fossil reptile called mesosaurus is found only in South west Africa and Brazil
    • -Glacial deposits and scratches on rocks (called strations) in Brazil match those in West Africa
  67. When and how was the Mid-Atlantic ridge discovered?
    In the 1950s, nuclear submarines began monitoring and mapping the ocean floors with great accuracy. The Mid-Atlantic Ridge, an underwater mountain chain, was discovered, as were similar features in the Pacific. These ridges together with deep ocean trenches were found to be seismically active - in other words, prone to earthquakes
  68. What happened in 1962 in terms of tectonic plates?
    In 1962, an American geologist named Harry Hess updated Wegeners idea. He studied the age of the rocks on the Atlantic Ocean floor, finding the youngest in the middle and oldest near the USA and the Caribbean. With the newest rocks still being formed in Iceland, this was compelling evidence that the Atlantic sea floor was spreading outwards from centre, a concept known as sea floor spreading.
  69. How fast do the tectonic plates move?
    Around 5cm a year - as fast as your finger nails
  70. Sea floor spreading
    The idea that the sea floor is speading outwards from the centre
  71. How often does the Earths magnetic field switch polarity?
    Every 400,000 years or so
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2015-04-09 14:24:02
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