Glacial Movement + Sediment

Glacial Movement + Sediment

1. Glacier processes are different to river processes

2. FREEZE -THAW WEATHERING

   • Freeze-thaw weathering will always take place
   • Liquid water enters a crack in a rock
     • It freezes + expands by 10%
       • Puts strain on the rock
       • Temperature rises + ice thaws
         • Water enters the crack again
   • This process happens repeatedly
     • Eventually, sections of the rock break away

3. GLACIERS ERODE THEIR SURROUNDINGS BY:

   • Abrasion
     • Material produced by freeze-thaw and is carried by moving ice and erodes the area that it covers
   • Plucking
     • Meltwater beneath the glacier freezes onto the rock, as the ice moves foward (carried by the meltwater) it plucks the piece of rock from its position under the glacier - this rock adds to the material which is used in abrasion

4. HOLLOWS

   • Snow that falls into the winter doesn't melt in the summer during glacial times -> it accumulates and builds up in HOLLOWS
   • Snow fills hollows + becomes compressed + air is squeezed out
   • Over time, pressure increases -> snow becomes glacial ice
   • Erosion and weathering by plucking, abrasion and freeze-thaw widens hollow + the glacier becomes bigger
   • Rotational Slip
     • Gravity encourages ice to move. Meltwater trickles down base and acts as a lubricantt, helps ice move in a circular motion.
     • It causes further erosion by scraping debris + ice against hollow
   • Hollows widen into a cirques/corries

5. RETREATING + ADVANCING

   • Glaciers deposit sediment when they retreat (melt)
     • Occurs becuase of temperature rising
     • Melting isn't permanent
   • Temperature fluctuates between winter + summer
     • Glaciers advance + retreat throughout the year

6. DEPOSITION

   • Any material deposited by glacies is called till
     • Material deposited by galciers varies in size from boulders to grains of sand
   • Streams
     • When streams leave glaciers -> heavier material is deposited first
       • -> lighter material is carried further
     • Material deposited by meltwater streams is called outwash
     • Most melting occurs at the snout of the glacier. If the glacier freezes and advances -> material will be pushed forward = buldozing