Geography and Islands

• Physical environment


  • Relief
  • Climate
  • Soil
  • Vegetation
• Landscape


  An area or a region that has common geographical features
• Systems approach


  Uses the systems model to understand a physical environment and the interactions within it
• System


  Has inputs (things going into the system), through-puts (things that go through the system and experience certain changes) and outputs (things that come out of the system)
• Closed system


  Inputs and outputs do not cross boundaries into or from other systems, outputs are fed back to become inputs again
• Open system


  Inputs often come from elsewhere - from the outputs of other systems
• Elements of the physical environment

  • Climate
  • Relief or geology
  • Soil
  • Vegetation
• The Pacific Ocean covers 1/3 of the Earth's surface
• Types of islands


  Different physical geographic characteristics
• Humans first reached the larger islands that rim the Western Pacific about 20,000 years ago
• About 5,000 years ago, people sailed out into the Pacific Ocean and went to Melanesia and later to Micronesia
• About 2,500 years ago, Polynesian navigators sailed into the central and eastern Pacific and landed on some of the most remote islands in the world
• Low islands


  • Small
  • Some have forests
  • Many have open vegetation
  • Some have no vegetation at all
  • Poor source of food and water
• Low islands


  Found around the edges of large reefs that rise steeply from the deep ocean floor or formed on top of reefs that are offshore from the high islands
• The low islands of the coral reefs are the main focus of these sections of this chapter
• Already, many of these island ecosystems have been changed permanently by human occupation
• High islands


  Often rising steeply from the sea, made up of dark rocks called basalts, basalts produce rich, red, volcanic soils
• Light, continental rocks


  • Make up the top layer
  • About 40 km thick
• Denser rocks


  • Below the continental rocks
  • Below the ocean basins
  • Found at a depth of between 40 km and 70 km
• Lithosphere or crust


  The first two layers
• Continental lithosphere or crust


  Seems to float on the denser oceanic lithosphere or crust
• The bulk of the continental crust is below the surface
• Drilling down through the lithosphere

  1. You would reach the asthenosphere

  2. You would be deep inside the Earth
• Asthenosphere


  Also known as the upper mantle
• Mesosphere


  • Contains large amounts of magma
  • Also referred to as the lower mantle
• Magma


  Molten rock that can rise through weaker points to the Earth's surface, forming volcanoes
• Core of the Earth

  • The bottom 3500 kilometres
  • Thought to be very dense
  • Made up of an outer core that is fluid and a solid inner core
• Convection currents


  1. Rise within the asthenosphere and spread beneath the solid lithospheric crust

  2. Can force magma through cracks in the lithosphere to the surface, causing volcanic activity
• Volcanic activity occurs mainly below the oceans
• Mid-ocean ridges


  • Huge ridges of material forced upwards and sideways
  • The youngest parts of the Earth's lithosphere
  • Form areas of sea-floor spreading
• Tectonic plates


  Large sections the lithosphere is broken up into
• Plate collision


  1. One plate slides below the other to form a subduction zone

  2. Ocean floor is dragged down and forms deep ocean trenches
• This keeps the Earth the same size
• Ocean trenches are the deepest parts of the ocean floor
• Ocean trenches are found at the edges of plates that are disappearing back into the asthenosphere
• Great forces are involved in the collision of plates, causing volcanoes and earthquakes
• Continental drift


  Continents are moved around at the same speed as the oceanic plate that is carrying them
• Speeds can be up to 9 cm per year
• Oceanic plate colliding with a continent


  The more dense oceanic plate moves down below the less dense continental plate
• Fold mountains


  • Produced when two plates carrying continental crust collide