L1 Extent Of Ice


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L1 Extent Of Ice

  1. 1. Key idea: The amount of ice on a global and continental level has changed in the past.
  2. 2. Lesson objectives <ul><li>To describe the time scale and extent of maximum ice cover in the northern hemisphere from the last Ice Age (Pleistocene) </li></ul><ul><li>To describe the present extent of ice cover. </li></ul><ul><li>To understand the contrasts and evidence of changes – global temperatures. </li></ul><ul><li>Ref NT pg 123 </li></ul>
  3. 3. Key terms: <ul><li>Glacial period – a period of ice advance associated with falling temperatures </li></ul><ul><li>Interglacial – a period of ice retreat associated with rising temperatures </li></ul><ul><li>Ice sheet – a large body of ice over 50 000km 2 in extent </li></ul><ul><li>Ice cap – a smaller body of ice less than </li></ul><ul><li>50 000km 2 in extent </li></ul><ul><li>Glacier – a finger of ice usually extending downhill from an ice cap and occupying a valley </li></ul>
  4. 4. Pleistocene Ice Age <ul><li>Began 2 million years ago </li></ul><ul><li>At its peak 30% of the Earth’s surface was covered in ice </li></ul><ul><li>Ice reached a far south as New York and Berlin </li></ul><ul><li>Ended 10,000 years ago </li></ul>
  5. 5. What has the ice age got to do with the UK?
  6. 6. http://uk.youtube.com/watch?v=GoVPRJbvg1w
  7. 7. Temperature fluctuations <ul><li>Climate change is a natural occurrence due to: </li></ul><ul><li>Subtle variations in the earth’s orbit </li></ul><ul><li>Slight changes in its tilt towards the sun </li></ul><ul><li>Variations in the global pattern of ocean currents which move heat around the world </li></ul><ul><li>Currently slight changes in the ocean currents of the west coast of S. America result in the El Nino effect which impacts upon patterns of rainfall and the development of tropical storms. </li></ul>
  8. 8. What causes an ice age? <ul><li>Changes in the circulation of the atmosphere and the oceans. </li></ul><ul><li>Winds and ocean currents help to circulate heat from the equator towards the poles. </li></ul><ul><li>It is thought that massive earth movements could change the heat circulation. </li></ul><ul><li>This could reduce temperatures and increase snowfall in polar regions </li></ul>
  9. 9. <ul><li>The Earth sometimes receives less heat from the sun due to: </li></ul><ul><li>A decrease in the sun’s energy output caused by sun spots </li></ul><ul><li>An increase in cloud cover </li></ul><ul><li>An increase in atmospheric dust caused by volcanic eruptions </li></ul><ul><li>A change in the angle of tilt of the Earth’s N-S axis </li></ul><ul><li>A change in the Earth’s orbit taking it further from the sun </li></ul>
  10. 12. Present day global ice <ul><li>1. At present there are two ice sheets in the world. </li></ul><ul><li>Antarctica </li></ul><ul><li>14 million km 2 </li></ul><ul><li>Holds 90% of all fresh water </li></ul><ul><li>ice is 4000m thick. Only the highest peaks emerge through the surface of the ice. These are called nunataks </li></ul><ul><li>Greenland </li></ul><ul><li>1.7km 2 </li></ul><ul><li>2. Ice caps </li></ul><ul><li>Usually found in mountainous areas where temperatures are lower – </li></ul><ul><li>Iceland (Vatnajokull) and Norway </li></ul>
  11. 13. <ul><li>3. A valley glacier is a moving mass of ice in which movement is contained within a valley. It begins in an upland area and follows the route of a pre-existing river valley. Examples can be found in the fold mountains – Alps, Andes, Rockies etc </li></ul><ul><li>Mer de Glace near Chamonix </li></ul><ul><li>Franz Joseph, Fox Glacier, New Zealand </li></ul>
  12. 14. <ul><li>Evidence from ice cores and sediments suggests there may have been up to 20 glacials during the Pleistocene </li></ul><ul><li>18,000 years ago the ice reached its maximum extent </li></ul><ul><li>Ice covered most of the UK, several hundred metres thick in places </li></ul><ul><li>The last glaciers melted in Britain about 10,000 years ago </li></ul>
  13. 16. tasks <ul><li>On a blank outline map show the maximum extent of ice covering the British Isles. Include arrows to show the direction of ice flow. </li></ul><ul><li>Label the four upland areas in the British Isles from where ice spread onto lower ground </li></ul><ul><li>Why were these areas source areas for ice during the glacial period? </li></ul>