Geo Revision

• Of all the water on the planet, 97.5% is salt water and only 2.5% is fresh water
• 79% of the freshwater is locked up in the form of glaciers and ice sheets
• 20% of freshwater is groundwater
• The rest of the freshwater (1%) is distributed in varying proportions between surface water in lakes and rivers, and the atmosphere
• Freshwater is also very unevenly distributed with some areas being water-secure (or water-rich) and other places being water-poor
• Antarctica Glacier


  • Most of the earth's freshwater is held up in massive glaciers, ice caps and ices sheets in Greenland and Antarctica
• Uses of Freshwater


  • Domestic use- bathing, flushing toilets, cooking, drinking, washing, watering gardens, and so on
  • Industrial use- used in the production of a wide range of goods from beer, leather, steel, textiles, dyes and paints, industrial chemicals, fertilizers, etc.
  • Agricultural use- used for irrigating crops and providing drinking water for livestock
  • Leisure use- sport fishing on rivers, sailing, watering golf courses and filling swimming pools
• Water demand and consumption have been rising greatly in the last 100 years. In fact demand has trebled over the last 50 years
• Major factor behind rising water demand


  Continuing growth of the world's population
• Increase in overall economic development


  The more affluent a society becomes, the more water it demands
• There are major differences in water usage between developing countries and developed countries
• Main sources of freshwater used by people


  • Rivers and lakes
  • Reservoirs- artificial lakes created by constructing a dam across a valley and allowing it to flood
  • Aquifers and wells- much of the earth's freshwater supply lies underground and is stored in porous rocks called aquifers. The groundwater is extracted by drilling wells and boreholes into the aquifer
• The Ndakaini Reservoir


  • Located 50km Northwest of the city, the reservoir supplies 84% of all the water used in the city of Nairobi
• Some parts of the planet enjoy more than adequate amounts of freshwater. Other parts experience a water scarcity
• Very few places experience water supply and demand that are equally matched
• Many parts of Africa, Middle East and Australia are water-deficit areas largely owing to the climatic conditions
• Increasing areas in China, India and other newly industrializing countries are water-deficit areas owing to excessive demand for freshwater
• Water is moved from water-surplus areas to water-deficit areas by pipelines, tunnels and canals
• Lowland landforms


  The river and its landforms change when the river leaves the uplands and flows across lowlands
• Changes in lowlands


  1. River channel and valley become wider and deeper

  2. River discharge increases as it collects water from tributaries

  3. Lateral erosion becomes more significant

  4. Deposition starts to play a big role in the evolution of landforms
• Meanders


  Bends or loops in the river as it tries to avoid obstacles
• Formation of meanders and ox-bow lakes


  1. River becomes sluggish and flows more slowly

  2. Lateral erosion on outer bank and deposition on inner bank

  3. River may cut a shortcut across a bend to create an ox-bow lake
• Flood plain


  A river's valley that is seasonally flooded
• Levees


  Raised banks caused by deposition of heavier materials at the banks
• Formation of natural levees

  Heavier load is deposited at the banks while lighter materials are transported farthest across the flood plain
• Delta


  Huge area at the mouth of a river built up by sediments, characterized by distributaries and marshes
• Estuary


  When a river enters the sea in one channel instead of distributaries
• How a delta forms


  Deposition rate is faster than the rate at which sea waves remove deposited sediments
• Ways a river transports materials


  • Solution - soluble minerals
  • Suspension - small insoluble rock grains, sand and silt
  • Saltation - heavier materials like small stones
  • Traction - very heavy materials like boulders
• Convergent boundaries occur when two plates collide with one another, leading to the destruction of old crustal material through subduction zones or oceanic trenches.
• Divergent boundaries occur when two plates move away from each other, resulting in the formation of new crustal material (magma) at mid-ocean ridges or continental rift valleys.
• The main types of plate boundaries are divergent, convergent, and transform.
• Of all the water on the planet, 97.5% is salt water and only 2.5% is fresh water
• 79% of the freshwater is locked up in the form of glaciers and ice sheets
• 20% of freshwater is groundwater
• The rest of the freshwater (1%) is distributed in varying proportions between surface water in lakes and rivers, and the atmosphere
• Freshwater is also very unevenly distributed with some areas being water-secure (or water-rich) and other places being water-poor
• Antarctica Glacier


  • Most of the earth's freshwater is held up in massive glaciers, ice caps and ices sheets in Greenland and Antarctica
• Uses of Freshwater


  • Domestic use- bathing, flushing toilets, cooking, drinking, washing, watering gardens, and so on
  • Industrial use- used in the production of a wide range of goods from beer, leather, steel, textiles, dyes and paints, industrial chemicals, fertilizers, etc.
  • Agricultural use- used for irrigating crops and providing drinking water for livestock
  • Leisure use- sport fishing on rivers, sailing, watering golf courses and filling swimming pools
• Water demand and consumption have been rising greatly in the last 100 years. In fact demand has trebled over the last 50 years