GEOGRAPHY 12
UNIT 4AB – DESERTS, AND GLACIATION - REVIEW WORKSHEET KEY
A. DESERTS
1. The arid sediments are very susceptible to water so that when there is water, it is very
effective.
2. a) Braided streams carrying heavy sediments meet a canyon mouth and slow down,
deposit sediments = alluvial fan.
b) Mud layer forms b/w sand & gravel layers, and hardens which becomes a barrier for
ground water movement. When trapped ground water is pressurized = forms an Artesian
well.
3. Seasonally created during a flash flood.
4. After thunderstorms, fill up w/ brackish/salty water and after water evaporates/infiltrates,
leaves behind fine sediments or evaporites.
5. Bajada =large alluvial plain formed by the lateral merging of alluvial fans along base of
mtn range.
6. Bolson = flat arid valley b/w crests of 2 mountains whereas Pediment = gently sloping
bedrock plain that develops at the base of receding mountains.
7. Plateau = broad, horizontal platform capped by hard layers. Cliffs of plateau erodes,
over time becomes mesa, and mesa erodes to a butte. Plateau Mesa Butte.
8. When deep beds of soft sedimentary rock are exposed to heavy rainfall = form
badlands.
9. a) Aeolian erosion = erosion done by the wind.
b) Deflation and wind abrasion.
10. Wind lifts away the loose sediments to create bowl-like depression, through the process
of deflation.
11. a) Desert pavement = armour of pebbles and gravel to prevent deflation of materials
underneath. Desert varnish = thin coating of manganese, iron and clays ON desert
pavement.
b) Any two of the following: reg, hamada, gibber plain, serir, gobi
12. Softer bottom layers of boulder are eroded as harder top layer is polished large
boulders perched on narrow deflated base.
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13. Quartz.
14.
Windward/Stoss slope
Leeward
15. Barchan dune = horns of crescent point downwind; windward side has gentle slopes,
leeward side = steeper slopes; only 1 slip face.
16. Coastal foredunes have vegetation that trap sand moving landward from beach and
form a protective barrier for tidal land against sea storms.
17. Erg = depositional areas that can be thousands of km2
18. a) Loess = wind-deposited silt/clay that has settled out from dust storms over many
thousands of years.
b) Source of loess = dust or glacial deposits. Loess deposit is formed by wind carrying large
amount of silt and depositing it and covering another area.
19. Formation = Volcanic processes create a rock body amidst softer sedimentary rock,
softer rock (sandstone) in the cliff is progressively eroded away through fluvial action &
mass wasting, creating a peneplain. Also know as monadnock and means “island
mountain.”
20. Hoodoo = a column, pinnacle, or pillar of sedimentary rock produced in a region of
sporadic heavy rainfall by differential weathering of horizontal strata, occurring in varied &
often eccentric or grotesque forms
21.
i) Barchan/Crescent dune: a common type of dune in which the horns/cusps of the
crescent project downwind. Windward side has gentle slopes, Leeward side has steeper,
slip slopes due to decreased wind speed.
ii) Parabolic dune: crescent-shaped dune that forms around a blowout. Resembles
barchans, but the horns form up-wind while the head forms downwind; more common in
semi-arid/sub-humid envts, eg. beaches, grasslands.
iii) Transverse dune: a simple, linear, wave-like dune that forms perpendicular to the wind.
Very mobile, Form in areas with abundant sand, low winds & little vegetation.
iv) Longitudinal dune/seifs: linear dune parallel to the wind direction. Form in areas of
moderate sand abundance & variable winds.
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22. a) Yardangs = streamlined hills carved from sedimentary bedrock by the dual action of
wind abrasion & deflation.
b) Requires a STRONG unidirectional wind & an airborne sediment load; Wind cuts down
lowlands into parallel ridges, which erode s l o w l y into separate hills; Grooves are
abraded onto the sides/flanks
23. Oasis = a small area of desert containing a H2O source. Can form from a blowout; H2O
supply is usually dependent on the H2O table (fed by seasonal rains in nearby mtns) but
can be continually fed from a spring line connected to an underground aquifer
24.
a) Midlatitude deserts: arid & semi-arid land is located along 30°-50°N & S latitude; have
wide annual temp. range, eg. Sonoran Desert, SW USA
b) Polar deserts: exist in Antarctica, where mean temp. during the warmest month is less
than 10°C; have low ppt & high evaporation rates
c) Trade wind deserts: b/w 30°N & 30 °S; high level winds descend; air parcels heat up,
holding more moisture, resulting in an overall loss of moisture, eg. Sahara, N. Africa (57°C
temp.)
d) Coastal deserts: distr.’d on western continental edges near the Tropics of Cancer
(23.5°N) & Capricorn (23.5°S); affected by cold ocean currents & winter fog, eg. Atacama,
S. America is Earth’s Driest desert (1 mm ppt for every 5-20 yrs)
e) Orographic/Rain shadow deserts: receive little moisture; found on the leeward side of
mtn ranges. Most of the moisture was deposited on the windward side
25) Causes = Poor agricultural practices & land management (eg. overgrazing &
overpopulation) can speed up desertification, but also linked to global climate change.
Solutions = Improve agricultural methods & land management, eg. rotate crops; H2O
management through control of irrigation practices; this will ↓ salinization of soil; Sand
fences prevent spread of sand dunes; Plant vegetation (tree fences, grass belts) on the
windward side will stabilize the dunes.
B. GLACIATION
1. ~77%
2. The whiteness of glaciers reflect much of solar radiation so influence heat balance of
Earth.
3. A glacier forms in any area that is permanently cold and has a year-to-year surplus of
snow; glacier moves b/c the pressure on the bottom layers of thick ice cause the ice to
become plastic and gravity is able to pull the glacier downward moving.
4. Alpine glaciers = long, narrow mountain glaciers that occupy a former river valley.
Ice sheets = Continental glaciers, ice spreads outward over surrounding lowlands.
5. Glacial trough = deep, steep-sided rock trench of U-shaped cross section formed by
alpine glacier erosion.
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6. Outlet glaciers occurs when ice sheets extend outward to reach the sea, if they break
off, they form icebergs, or larger ice shelves.
ALPINE GLACIER EROSIONAL FEATURES
7. Cirque is the area at the head of the trough where snow accumulates during the
formation of an alpine glacier.
8. Residual snow in a cirque melts = small round lake tarn.
9. Firn = old snow layers that become further compacted and crystallized.
10. Crevasse = the breaking of ice in a glacier, increasing pressure & gravity will create a
vertical fissure.
11.
12. i) Ice push = as the glacier descends down a valley, it can dislodge & move rock debris
creates moraines.
ii) Abrasion = erosion caused by rock fragments held within the ice that scrape & grind
against bedrock.
iii) Plucking = as ice lifts out blocks of bedrock that have become loosened at their joints via
freeze-thaw action.
13. Arête = sharp, knife-like divide or crest formed between two cirques.
Col = formed by 2 headward-eroding cirques that reduce an arête to form a high pass or
saddle-like narrow depression.
14. Mountain peak = peak formed from 2 or less cirques growing together.
Pyramidal peak = a sharp, jagged peak formed from 3 or more cirques growing together.
15. Crevasse = open vertical fissure in glacier.
Bergschrund = forms when a crevasse opens along the headwall.
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16. Hanging valley = is a tributary glacier that carves a SMALLER U-shaped trough; its valley
floor is typically stranded high above the main valley floor.
17. Fiords.
18. Truncated spurs = triangular rock faces along the vertical walls of the U-shaped trough,
formed from erosion of the main glacier.
ALPINE GLACIATION DEPOSITIONAL FEATURES
19. Glacial drift = refers to any glacial deposit, whether sorted or unsorted.
Stratified drift = refers to sediments deposited by glacial melt-H2O that are sorted by size.
20. Erratic = large boulders that have been carried hundreds of kms by a glacier.
21. i) Lateral moraine: formed b/w the ice edge & the adjacent trough wall.
ii) Medial moraine: a long, narrow, centrally deposited ridge; created by the merging of
the lateral moraines of two joining glaciers.
iii) Terminal moraine: an embankment at the terminus (farthest extent) of an alpine
glacier.
iv) End/Recessional moraine: similar to terminal moraine, but forms at places where glacier
temporarily halted ie. found BEHIND the terminal moraine.
v) Ground/till moraine: till that covers bedrock.
CONTINENTAL GLACIER EROSIONAL AND DEPOSITIONAL LANDFORMS
22. Interlobate moraine = till formed from 2 lobes of ice sheets that came together; the
“lateral” moraines fused.
23. Outwash plain = Flat, gently sloping depositional plains of outwash, made of stratified
drift left by melt-H2O streams.
24. Esker = a long, sinuous ridge of sediment form deposited on the floor of a former ice
tunnel; it consists of sand & gravel & runs parallel to the ice.
25. Ice blocks = a large isolated ice chunk that remains in ground moraine, an outwash
plain or valley floor after a glacier has retreated.
26. Kame = an isolated hill of poorly sorted drift deposited by H2O or ice.
Drumlin = a smoothly rounded, oval hill of deposited till.
27. Kame Delta = flat-topped hills deposited in standing H2O (ie. lake) at an ice margin;
made of FINE sediment; very isolated, composed of well-washed/sorted sands.
28. Spillways = deep, narrow valleys carved by melt-H2O streams that had a HIGH volume
of H2O. Need warm climate to create melt- H2O streams.
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29. roche moutonnée = an asymmetrical hill created by erosion. Upstream (stoss) side has
a gentle slope that is polished & smoothed by glacier; Downstream (leeward) side is
jagged & steep due to plucking.
30. Crag & Tail = an asymmetrical hill created by the presence of erosion-resistant volcanic
plugs (called crags). As the glacier sweeps across the crag, a tapered tail of till is formed
on the leeward side of the crag.
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