1. CH 7 Glaciers, Deserts, & Wind
Ice Age – when much of earth’s land is covered in glaciers
The last one ended 15,000 years ago
Glacier – a thick mass of slow moving ice
They cover ~ 10 % of earth today
Form by compaction, melting, and recrystallization of snow
Firn = blue ice (the glacier look)
Snow line – lowest elevation that remains snow covered all year

2. 2 Types of Glaciers Valley (alpine) – Alaska, Alps, Himalayas
Smaller
More common
In high elevations (mountains)
Sharpen features
Ice sheet (continental) – Greenland, Antarctica
Larger
Only 2
At high latitudes (poles)
Round features

3. Movement Plastic flow Basal slip Move fastest at top and middle…why??
Brittle on the surface but they flow underneath
50 m depth limit
Basal slip
Ice melts on bottom due to enormous pressure and friction
Slides on the layer of water
Will squish you big time
Move fastest at top and middle…why??
Forms crevasses (cracks) & pressure ridges

4. Glacier Budget
Is the balance or unbalance between the upper end accumulation and the lower end loss
Advance – when accumulation exceeds loss
Retreat – when loss exceeds accumulation
Stationary – when loss = accumulation
Calving – breaking off of ice chunks making iceberges
Only 10 % is above water

5. Erosion by Valley Glaciers
Plowing and plucking – bulldozing and picking up
Glacial trough – “U” shaped valley
Hanging valley – tributary/side valleys
Cirque – bowl shape depression at top
Tarn – cirque filled with water

6. Erosion by Valley Glaciers
Pater noster – tarns connected by a stream
Arete – narrow, sharp ridge
Horn – pyramid shaped sharp peak
Fiord – “U” shaped valley filled with water
Col – saddle between 2 horns
Nunatack – lonely rocks

7. Glacial Deposits Drift – any sediment of glacial origin
Till = deposited directly by the glacier (unsorted)
Stratified drift = deposited by glacial meltwater (sorted)
Moraines – the most common type of till
Lateral – sides
Medial – middle
Terminal - end

8. Glacial Deposits Outwash plain – ramplike sediment accumulation
Erratic – rock that does not belong
Kettle – depression in outwash plain
Kame – rounded mounds
Esker – sinuous/winding ridge of sediment
Drumlin – tear dropped shaped hills
Roche mountonnes – sheep rocks
Rock flour – pulverized rock (silt)
Glacial milk – rock flour added to water

9. Causes of Ice Ages
Milankovitch Theory – variations in the earth – sun relationships
Eccentricity – change orbital shape of earth
Obliquity - change in earth’s tilt
Precession – wobble of the earth
Effects of ice ages
Lakes, crustal rebounding, sea level changes

10. Deserts Less moisture = less weathering
Most weathering is mechanical, (mostly water)
Ephemeral streams = only flow after rains
Alluvial fans = triangular, fan/cone shape
Playa lakes = flat, shallow lake

11. Wind Erosion Deflation – blowing away of small sediments
- forms desert pavement (big sediment left behind)
Abrasion – sandblasting
- forms ventifacts (polished rocks)

12. Wind Deposits Loess – blankets of silt Sand dunes – mounds of sand
Glaciers and rivers
Sand dunes – mounds of sand
Shapes depend on wind speed and direction, and the amount of sand and vegetation
Beaches and deserts
Crescent shaped
Cross section and cross bedding

13. Sand Dunes (page 206) Barchan Parabolic Barchanoid Star Transverse
Longitudinal