Glaciers

• An ice age is a period of time when much of Earth’s land is covered in glacier.
• A glacier is a thick ice mass that moves slowly over the surface
• About 15,000 years ago up to 30% of Earth’s land was covered by glaciers
• Today glaciers cover 10% of Earth’s land
• Glaciers shaped placed such as cape cod, Long Island, the Great Lakes
• Glaciers originate places where snow falls more than melt
• The snow line is the lowest elevation that remains covered in snow all year
• At the poles the snow line is at sea level
• At the equator the snow line is at the top of tall mountains
• Snow about the snow line accumulates and compacts
• Compressed snow recrystallizes into coarse grained crystals and pressure from snow above changes grains into interlocking crystals
• Glaciers appear to be motionless
• Gravity slowly pulls the mass of ice downhill
• As it moves it accumulate, transports, and deposits sediments
• Valley glaciers:

  • thousands of glaciers exist in high mountains worldwide
  • glaciers advance a few cm to a few m each day
  • valley glaciers originate in valleys once occupied by streams
  • flow between steep rock walls from the top of a mountain valley
  • can be long or short , wide or narrow, single or with branching tributaries
• Ice sheets are enormous ice masses that flow in all directions from one or more centers and cover everything but the highest land.
• Ice sheets are sometimes called continental glaciers because they cover large regions such as Antarctica and Greenland.
• Ice sheets are much bigger than valley glaciers.
• There are two ice sheets left in the world.
• Ice sheets combined cover 10% of Earth’s land.
• Ice sheets cover about 80% of Greenland.
• In some places, the ice sheet in Greenland rises to 3000 m above sea level.
• The Antarctic ice sheet is 4300 m thick in places.
• Ice sheets account for 90% of the worlds ice and hold nearly 2/3 of the earth’s fresh water.
• If melted, sea level could rise 60-70 meters and many coastal cities would flood.
• How glacier’s Move

  • the movement of glaciers is referred to as flow
  • glacial flow happens in two ways