Glaciers Chapter 15
Striations
"Scratch" marks left by the glaciers path
How do glaciers form
1. Snow falls and accumulates 2. Snow becomes buried and compressed 3. Snow recrystallizes into firn (rough, granular ice) 4. Firn packs into layers of ice 5. Weight of snow and ice mass causes glacier to flow
Moraine Dammed Lakes
A lake found at higher elevation that is blocked from draining by a moraine
Kame
A mound of sediment accumulated in a glacier then deposited by a melting glacier
Lateral Moraines
Are moraines that run parallel to the glacier and run the whole length of the glacier
Basal Slip Movement
At base of glacier, increased weight causes ice to melt Can stay as water Can refreeze into slush with sand and gravel This decreases friction and glacier can flow Only the Base Moves No melt when very cold
2 mechanisms for glacial movement
Basal Slip Plastic Flow
Drift
Deposits of eroded rock that is left behind by receding glaciers
How do Glaciers move
Due to their own weight and force of gravity They erode rock as they move Rate of movements varies: cm/day to m/day
Jakobshavn Isbrae
Fastest glacier in the world 4.16 mi/yr in 1985 3.54 mi/yr in 1992 5.84 mi/yr in 2000 7.83 mi/yr in 2003
Horn
Glaciers carve out the base of the mountain leaving a pointed peak
Plastic Flow Movement
Grains of ice change shape from spherical to flat Ice Grains slip over each other, propelling the glacier not touching the ground
Drumlin
Hills that are formed when a glacier travels over a previous moraine
Terminal Moraine
Is a moraine that is perpendicular to the glacial flow and it marks the furthest advancement of the glacier
Kettle pond
Kettle formed when the depression is lower than the water table 1. Glacial chunk of ice deposited 2. Ice becomes buried 3. Ice melts into a depression and water table rises
Esker
Long, winding ridge of till
Snowline
Lowest elevation where permanent snow exists
Outwash
Materials deposited and sorted evenly by glacial melt - water
Cirque
Semi-circular basin where a glacier began
Continental Glacier
Snow accumulates over a large area at high altitudes circular or oval shape moves outwards Covers continents 1000's of meters thick
What parts of the glacier move the slowest
The bottom and sides
2 types of glaciers
Valley Continental
Calving
When chunks of a continental glacier break off and fall into the ocean
Erratic
a boulder carried by a glacier
Tarn
a glacially formed lake
Glacier
a large mass of compacted snow and ice that may move due to gravity
Moraine
an accumulation of till
Crevasse
cracks in the glacier due to its movement
When does the Glacier move fastest
during warm periods and after lots of snowfall
Where does the glacier move the fastest
on a steep slope or in the middle or center of the glacier
Valley Glacier
snow accumulates at high peaks high altitudes river like shape moves downhill up to 100km long 100's of meters thick
Ice Front
the end of the glacier
How does the snow line depending on latitude
the higher the latitude, the lower the snow line
Till
unsorted rock deposited by a melting glacier