geography

• Lithosphere


  The solid outer part of the Earth, consisting of the crust and the solid part of the upper mantle
• Natural Systems section of the CXC Geography syllabus

  • Internal Forces
  • External Forces
  • Rivers
  • Limestone Environment
  • Coasts
  • Weather, Climate, Vegetation and Soil
• Lithosphere


  The Earth's surface is not a continuous layer, it is broken up into several large pieces called crustal plates or tectonic plates
• Internal Structure of the Earth

  Layers of the Earth
• Lithosphere


  • Has an average thickness of about 35 km
  • Is constantly changing due to processes such as volcanic eruptions, running water and wave action
• Crustal plates


  Large segments of the crust and upper mantle that float on the denser semi-molten rock beneath them and move very slowly across the surface of the planet
• Plate tectonics


  The study of crustal plates and how their movement affects the Earth's surface
• Rock


  Any hard, naturally occurring substance which is composed of minerals and is formed by geological processes
• Crustal plates in the Caribbean region

  • Caribbean Plate
  • North American Plate
  • South American Plate
  • Nazca Plate
  • Cocos Plate
• Earthquakes


  Occurrence and distribution of earthquakes
• Mineral


  A substance which is normally crystalline and is formed by geological processes
• Earthquake


  A shock or series of shocks caused by a sudden movement of crustal rocks
• Primary crustal plates


  • North American
  • South American
  • African
  • Antarctic
  • Indo-Australian
  • Eurasian
  • Pacific
• Earthquakes


  • Caused by a sudden release of pressure within the Earth's crust
  • May occur at any type of plate boundary
• Geological process


  Any natural process which modifies (changes) geological features
• There are seven primary crustal plates and several smaller ones
• How earthquakes occur


  1. Crustal plates do not always move smoothly against each other

  2. Plates may get stuck and pressure or tension builds up

  3. When pressure is released, a massive amount of energy travels through the earth's crust as seismic waves

  4. Causing the ground to shake, sometimes violently
• The Earth's crustal plates move slowly over the planet's surface, interacting in various ways
• Major classes of rock

  • Igneous
  • Sedimentary
  • Metamorphic
• Focus


  The point within the crust where the earthquake is generated, may be several miles below the surface
• Changes in Volcanic Features


  How volcanic features may change over time
• Plate boundary


  The area where the edges of two plates meet
• Igneous rocks


  • Formed when molten rock from deep within the Earth's crust (magma) finds its way into or onto the Earth's crust where it cools and hardens
  • Intrusive igneous rocks are formed when magma cools and hardens within the Earth's crust, often containing large crystals and being coarse grained
  • Extrusive igneous rocks are formed when magma (lava) reaches the Earth's surface and cools quickly, forming fine grained rocks
• Epicentre


  The point where the seismic waves reach the surface, located directly above the focus and usually where the effects of the earthquake are the worst
• Types of plate boundaries

  • Convergent
  • Divergent
  • Transcurrent
• Intrusive igneous rocks


  • Granite
  • Gabbro
• Seismograph


  An instrument used to measure and record seismic waves
• Mass Wasting Processes


  Soil creep and landslides
• Extrusive igneous rocks


  • Basalt
  • Obsidian
• Convergent boundary


  Where plates move toward each other, causing earthquakes, folding and volcanic activity
• Moment magnitude


  The amount of energy released during an earthquake, expressed using the Moment Magnitude Scale which has no upper limit
• Water Cycle


  Operation of the water cycle and definition of terms
• Subduction


  The process where oceanic crust is pushed under less dense continental crust, forming a subduction zone and ocean trench
• Sedimentary rocks

  • Formed when material deposited by agents such as rivers is compacted over time until it hardens into rock, usually in bodies of water
  • The material is deposited in layers which are often clearly visible in the resulting rock
• Mercalli scale


  A twelve point scale which rates the intensity of an earthquake based on the things which can be observed in the area where it occurred
• Island arc

  A chain of islands formed as the crust beneath the ocean is forced below another plate, creating underwater volcanoes that eventually rise above the surface
• Mercalli scale ratings

  • I: Not felt except by very few people under especially favourable conditions
  • II: Felt only by a few people at rest, especially on upper floors of buildings
  • III: Felt by people indoors, especially on upper floors of buildings. Many people do not recognize it as an earthquake. Standing motor cars may rock slightly. Vibrations are similar to the passing of a truck. Duration estimated.
  • IV: Felt indoors by many, outdoors by few during the day. At night, some people are awakened. Dishes, windows and doors are disturbed. Walls make a cracking sound. The sensation is similar to a heavy truck striking building. Standing vehicles are rocked noticeably.
  • V: Felt by nearly everyone. Many people are awakened. Some dishes and windows are broken. Unstable objects are overturned. Pendulum clocks may stop.
  • VI: Felt by all. Many are frightened. Some heavy furniture is moved. There are a few instances of fallen plaster. The damage is slight.
  • VII: Damage negligible in buildings of good design and construction and slight to moderate in well-built ordinary structures. There is considerable damage in poorly built or badly designed structures. Some chimneys are broken.
  • VIII: Damage is slight in specially designed structures but there is considerable damage in ordinary substantial buildings with partial collapse. Damage is great in poorly built structures. Chimneys, factory stacks, columns, monuments and walls are likely to fall. Heavy furniture is overturned.
  • IX: Damage considerable in specially designed structures. Well designed frame structures are likely to be tilted. Damage is great in substantial buildings, with partial collapse. Some buildings are shifted off foundations.
  • X: Some well-built wooden structures are destroyed. Most masonry and frame structures are destroyed with foundations. Rails are bent.
  • XI: Few, if any (masonry) structures remain standing. Bridges are destroyed. Rails are bent greatly.
  • XII: Damage is total. Lines of sight and level are distorted. Objects are thrown into the air.
• Sedimentary rocks

  • Limestone
  • Sandstone
• Convergent plate boundaries

  Rocks at or near these boundaries are placed under tremendous pressure
• Folding

  1. Rocks are compressed

  2. Rocks are pushed upwards forming anticlines

  3. Rocks are pushed downwards forming synclines