Glaciers Flashcards
Glacier
A stream of ice that stays mostly frozen all year and flows under the influence of gravity.
Mountain Glaciers
1.) Cirque Glacier
2.) Valley Glacier
Cirque Glacier
Mountain Glacier- forms near the top of mountains. When melting/refreezing occurs, ice wedging can occur leaving a glacier nestled into the mountain
ex: Swiss Alps
Valley Glacier
Mountain Glacier-where rivers of ice come down through valleys, eroding sides and bottoms.
-forms lateral moraines
Moraines
Poorly sorted sediment deposited by glacial processes
-tells us how far an ice sheet/glacier went
Types of Glacial Moraines
1.) End Moraine: front of glacier
2.) Lateral Moraine: At the sides of the glacier
3.) Medial Moraine: At the bottom of the glacier
Polish
Grit and dirt on the bottom of glaciers can smooth surfaces as glacial ice travels over it
Striations
Big chunks of rock dragged by glaciers can scratch surface leaving behind striations.
Eskers
Well sorted gravel deposits formed in channels below a glacier, sometimes top of rivers
Erratics
Large boulders left behind by glaciers
Fjords
Flooded Glacial valley due to glaciers forming valleys, then retreating with sea water following it.
Dropstones
Glaciers pick up rocks, goes into an ocean, breakings into an iceberg, iceberg melts and drops rocks to the bottom of the sea.
Continental Ice Sheets
1.) Antarctica
2.) Greenland
Antarctica
Ice sheet is 3-4 km thick
-weight of glaciers sheet pushes down the crust because the asthenosphere deforms plastically
-sheets bedrock below sea level
-If Ice in Antarctica melts; sea level will rise 58.3m
-90% total surface fresh water
-60% total fresh water (including groundwater)
Greenland
10% global ice volume
Small changes in Earth’s orbit around the sun have influenced Earth’s climate during “Ice Age’s”
1.) __a__ of earths orbit is governed by a __b__ year cycle
2.) The __c__ of earths spin axis changes over a __d__ year cycle.
3.) The wobble of Earth’s spin axis, its __e__ varies in a __f__ year cycle.
1.) Eccentricity; 100,000
2.) Tilt; 41,000
3.) Precession; 23,000
Pleistocene Ice Age (2.6 Ma-Present)
Last glacial max=18,000 yrs ago
-sea level dropped 120m
-Land bridge across Bering Strait
-Australia, New Guinea, and Tasmania=1 continent
Where do Glaciers Form?
High Latitudes
-solar radiation spread over larger area at high latitude
Glacial Advance
Ice accumulation> Ice Lost
Glacial Retreat
Ice Accumulation < Ice Lost
Glacial Erosion
1.) Abrasions
-form U-shaped valleys as it erodes side and bottom by picking up parts of rocks and sand through contact with surface
ex: Yosemite Valley
2.) Plucking
-Part of glacier melts due to pressure increase, when pressure equalizes; water freezes, plucking bits of rock taken with the glacier.
Milankovic Cycles
Changes in Earth’s orbital parameters (eccentricity, tilt, and procession) change the amount of exposure to solar energy/radiation.
-Glacial periods occur when Milankovic forcing leads to a cooler summer (snow isnt melted and stays for the next winter)
Which of the following two processes are most important to converting snow into glacial ice as its buried within a glacier
1.) Recrystallization
2.) Compaction
Snowball Earth
3 snowball events (2.22 Ga, 717-660Ma, and 635Ma)
evidence:
-glacial till
-drop stones
-striations
(glacier evidence covering things around the equator; so therefore the entire world).
Causes of Snowball Earth
Early sun wasn’t as intense; less solar radiation
-continents closer to equator (Pangea)
-Higher albedo (reflectivity); cooler temps
