EOLIAN SYSTEMS I. Wind Patterns and Arid Regions A

1
EOLIAN SYSTEMS I. Wind Patterns and Arid Regions
A. Atmospheric circulation 1. The non-tilted
Earth model i. Two-cell convection model ii.
Winds and the Coriolis effect iii. Effect of
tilt and seasons and continents
Hypothetical atmospheric convection
Tilt of the Earth and seasons
Coriolis effect
2
Modern atmospheric winds

• 2. Current six-cell model
• i. Wind patterns and movement of heat
• ii. Latent heat of vaporization
• (600cal/g) and movement of
• heat with water

Water flux in 1000 km3 Evaporation/Transperation
380 Precipitation 380 Infiltration
lt1 Groundwater lt1 Runoff 36
3
ii. Moisture by location a. Tropical and
temperate rainforests b. Tropical and polar
deserts c. Large continent deserts d.
Rain-shadow deserts
Modern climate belts
4
ReUR?/m Where Uvelocity Rhydraulic
radiusarea/wetted perimeter ?density
mviscosity
II. Fluid Mechanics A. Turbulence 1. Revisiting
of Reynolds 2. 1mm laminar sub layer 3.
Rules of entrainment a. 15 ratio up-draft to
wind speed b. Fall vs. up-draft velocity and
5x rule c. Impact threshold (Bagnold,
1941) Vdt 680d½log(30/d) Where Vdt
threshold wind velocity d grain diameter
Areas of flow cross section Area
Parameters of R
Channel
Line length Wetted Perimeter
5
B. Grain movement (use fig 17-3) 1.
Saltation 2. Suspension 3. Impact creep a. 6x
impacting grain b. About ¼ load (Bagnold,
1941) 4. Competence vs. wind speed a. .3-.15mm
and .08-2mm 5. Most sand at lt1m
http//www.msss.com/earth/antarctica/AJUS_papers/A
JUS83.html
http//en.wikipedia.org/wiki/Dune
6
III. Erosion Features A. Abrasion 1.
Ventifacts 2. Yardangs B. Deflation 1.
Deflation hollows
http//picasaweb.google.com/ChristopherBGardner/Ve
ntifacts
Yardangs on Mars
Blowouts near Lake Eyre
http//www.lpod.org/?p1301
7

• IV. Depositional Landforms
• A. Ripples
• 1. Conventional ripples and the laminar sublayer
• 2. Saltation length and surface creep (Bagnold
  and Sharp)
• 3. Long low fluid-drag ripples

(a) Megaripples developed in silicic pumice and
basaltic sands, overlying basalt flow in Iceland.
Ripple wavelengths average 35 m (vehicles in
background indicate scale) light colored
ribbons are centimetersized pumice fragments
in the troughs of the ripples. (b) Granule
ripples and smaller normal ripples in the
troughs. The granule ripples formed first then a
change in wind regime generated the normal
ripples (which can form on shorter timescales).
Note the modification to the crests of some of
the granule ripples to the upper right of the
20-cm scale (photograph by G. Erickson, U.S.
Geological Survey).
8
B. Dunes 1. General processes a. Sand traps and
dune initiation b. Slip face and angle of repose
(300-340) c. Migration rate (Bagnold, 1941) M
q/yH Where M rate of dune advance q rate of
sand flow H dune height y specific weight of
sand i. m/yr
http//en.wikipedia.org/wiki/Dune
9
http//en.wikipedia.org/wiki/Dune
2. Dune types a. Barchans b. Parabolic
dunes c. Transverse dunes
http//www.ica1.uni-stuttgart.de/gerd/dunes.html
A sand dune in Namibia.
http//en.wikipedia.org/wiki/Dune
10
http//www.keckgeology.org/files/pdf/symvol/17th/m
ongolia/stinson.pdf
d. Longitudinal dunes i. Wind funnels ii.
Seif dunes e. Star dunes
http//spaceflight.nasa.gov/gallery/images/station
/crew-13/html/iss013e75141.html
Erg Oriental, Algeria is featured in this image
photographed by an Expedition 13 crewmember
onboard the International Space Station.
http//history.nasa.gov/SP-4203/phot01.htm
Parallel ridges of sand extend for hundreds of
kilometers across the interior of Arabia in an
area called Rub-al-Khali (The Empty Quarter).
Well named! Seif dunes, as they are called, are
rarely found. The long ridges are parallel to the
prevailing winds instead of transverse, like most
dunes. The photograph covers tens of thousands of
square kilometers of area, but nowhere does one
see any signs of life. (S65-34765 Gemini IV.)
http//www.nps.gov/archive/grsa/resources/star.htm
11

• C. Interdune areas
• 1. Wind deflation surfaces and desert pavement
• 2. Wadis

Neales River
Gibber Plain near Lake Eyre
12
3. Terminal splays and playas 4. Dry-land
Rivers and floodplains

•     
• Back
• 3 of 12
• Next
• Close
• Channel Country in flood
• Print this picture

Channel Country in Flood, Australia
Channel Country in Flood, Australia
Lake Eyre and Neales Delta

•     
• Back
• 4 of 12
• Next
• Close
• Channel Country in flood
• Print this picture

13
GLACIAL PROCESSES AND LANDFORMS Glacial
Processes I. Mass Balance and Anatomy of a
Glacier A. Basic Anatomy 1. Zone of
accumulation 2. Zone of ablation 3.
Equilibrium line
http//en.wikipedia.org/wiki/ImagePlucking_LMB.pn
g
Zone of Accumulation
Equilibrium Line
Zone of Ablation
The Upper Grindelwald Glacier and the
Schreckhorn, showing accumulation and ablation
zones
14
B. Zone of accumulation 1. Precipitation,
avalanching, drifting 2. Snow - firn- ice a.
Temperature and time and depth to ice i. Years
to a couple century ii. Meters to 10s
meters 3. Rock glaciers and insulation vs. albedo
South view of the terminus of the thinning and
retreating Schwan Glaciers located south of the
Tasnuna River and west of the Copper River,
north-central Chugach Mountains, Alaska. Note the
ice-marginal lake that has developed in front of
the retreating terminus. Much of the terminus is
debris-covered.
http//www.earthscienceworld.org/images/index.html
15
http//www.earthscienceworld.org/images/index.html
C. Zone of ablation 1. Evaporation/sublimation
vs. melting vs. calving 2. Pressure melting and
subglacial runoff
http//www.earthscienceworld.org/images/index.html
This is an aerial view of the retreating terminus
of Alaska's Muir Glacier calving into Muir Inlet.
The terminus with its seracs and crevasses is
nearly 60 meters high at this point. This glacier
has retreated over 120 kilometers in the past 200
years.
Carrying a full load of sediments, this
subglacial stream works its way from under
Alaska's Bering Glacier and around ice boulders
in this 1994 photograph.
16
D. Equilibrium line 1. Relationship to point of
greatest discharge 2. Relationship to firn
line a. Accumulation vs. ablation vs. flow rate
i. Glacial flow lines ii. Stagnation vs.
advance vs. retreat iii. Seasonality
http//www.earthscienceworld.org/images/index.html
This aerial view of an Alaskan Glacier shows many
glacial features both erosional and depositional.
17
II. Glacial flow processes A. Plastic flow 1.
Intragranular shifting a. Vertical c-axis and
translation along the basal plate/basal-plane
gliding 2. Pressure melting and refreezing at
lower stress (regelation) a. 1 degree C for
every 140 bars 3. Intergranular shifting
18
4. Limiting factors on plastic limit a. Plastic
at 1 bar (1kg/cm2) b. Temperature
factor Strain rate (S) ktn k constant
decreasing with temperature n exponent 2 4
increasing with temperature t shear stress
c. Slope factor t rgtsina t shear
stress r density of ice (.9 g/cm3) g gravity
(980 cm/s2) t thickness of glacier sina
slope of ice surface
19
http//www.earthscienceworld.org/images/index.html
This aerial view of an Alaskan glacier
illustrates the three types of cravasses,
transverse, longitudinal, and splaying. Such
intense crevassing indicates an actively moving
glacier.
B. Internal shearing 1. Brittle vs. plastic
flow 2. Effects of compressive flow vs.
extending flow 3. Crevasses a. Transverse vs.
chevron vs. longitudinal vs. radial 4. Minor
relative to plastic flow
20
C. Basal sliding 1. Importance of pressure
melting 2. Deformation of till D. Surges 1.
101 102 velocity increase 2. Typical of zone
of ablation 3. Role of build up and thresholds
of basal water
http//www.earthscienceworld.org/images/index.html
The surface of Alaska's Bering Glacier displays
crevasses and fractures due to surging.
21
III. Glacial Classification A. Thermal 1.
Temperate vs. Polar vs. Subpolar B.
Morphological 1. Alpine vs. piedmont vs. ice
sheet/ice cap C. Dynamic 1. Advancing vs.
retreating vs. stagnant
http//www.earthscienceworld.org/images/index.html
http//www.earthscienceworld.org/images/index.html
This is a south view of thinning and retreating
terminus of Wortmanns Glacier in Alaska's Chugach
Mountains. The large amount of debris at the
terminus, trimlines, and elevated lateral
moraines are signs of retreat.
View of the southern hemisphere and Antarctica.
This view was created by mosaicing together
several images taken by Galileo over a 24 hour
period to make an entirely sunlit image of the
South Pole.
22
Glacial striations and glacier in Switzerland.
http//www.earthscienceworld.org/images/index.html
IV. Erosion and Transport Processes A.
Abrasion 1. Grinding of rock flour,
striations/grooves, faceted stones 2.
Factors a. Amount and type of debris at
base b. Basal melting i. Basal sliding ii.
Removal of rock flour iii. Introduction of new
cutting rock c. Thickness of ice
http//www.earthscienceworld.org/images/index.html
This subglacial stream, laden with suspended rock
flour, emerges from under a glacier and flows
past the till of a terminal moraine in Alaska's
Glacier National Park.
23
http//www.earthscienceworld.org/images/index.html
B. Plucking/Quarrying 1. Importance of
joints 2. Importance of freeze/thaw C.
Subglacial water 1. Films vs. tunneling D.
Addition 1. Avalanche vs. wind
The Good Friday earthquake of 1964 triggered a
large rock avalanche that fell 600 meters (2000
feet) and then spread 5 km (3 miles) across the
Sherman Glacier, resulting in a blanket 3-6
meters (10-20 feet) thick. The avalanche is
dramatically visible because it contrasts with
the white glacial ice.
http//www.earthscienceworld.org/images/index.html
24
http//www.earthscienceworld.org/images/index.html
V. Deposits A. Diamictons 1. Directly from
melting and deposition from suspension a.
Viscosity and yield strength and lack of sorting
or rounding or stratification 2. Till a.
Lodgement till i. Shearing and resultant
folding/thrusting ii. Compaction iii. Grain
elongation trends b. Ablation till i.
Saturation ii. Plastic flow
Pleistocene Till, Ca
http//www.earthscienceworld.org/images/index.html
25
http//www.earthscienceworld.org/images/index.html
3. Glaciomarine and glaciolacustrine drift a.
Role of icebergs b. Characteristics i. Marine
vs. fresh aqueous fossils and taphonomy ii.
Faceted stones iii. Regional extent iv. High Na
in clay fraction
Lodestone in a glacier deposit. Pleistocene in
age. Lacustrine sediment from the western
formation of North Illinois.
http//www.earthscienceworld.org/images/index.html
This debris covered iceberg was calved from the
terminus of Alaska's Sheridan Glacier.
26
http//www.earthscienceworld.org/images/index.html
B. Stratified and sorted sediments 1.
Outwash a. Braided fluvial with a glacial
bent 2. Glaciolacustrine a. Varves 3.
Glacioeolian a. Dunes b. Loess c. Role of rock
flour i. Half silt with clay and sand ii.
Pseudomatrix clay iii. Angularity and angle of
repose iv. Partitioning by paleosols
Braided streams run on top of the outwash plain
next to the stagnant, downwasting, debris-covered
ice of the Casement Glacier at Alaska's Muir
Inlet.
Proterozoic varves, Canada
http//ns.geo.edu.ro/paleomag/loess-Most.htm
27
http//www.earthscienceworld.org/images/index.html
Glacial Landforms I. Erosional Landforms A.
Cirques 1. Morphology a. Headwall and bowl b.
Tarns c. Aretes and Horns 2. Processes a.
Naviation processes i. Bergschrund crevasse ii.
Freeze/thaw and mass wasting b. Head cutting vs.
down cutting c. Preferred orientation d.
Reoccupation
A bergschrund is the crevasse at the head of a
glacier that separates flowing ice from stagnant
ice or the rock wall. If water gets into the
bergschrund and freezes to the rock wall as well
as the moving glacier plucking may occur,
removing material from the rock wall and
increasing the size of the cirque.
http//www.earthscienceworld.org/images/index.html
Several retreating unnamed, small valley glaciers
and several recently deglacierized cirques and
ridges north of the terminus of Tonsina Glacier,
north-central Chugach Mountains, Alaska. Much of
the ice disappeared during the last few decades
of the twentieth century. Note the fresh moraine
deposits and the tarn lakes.
28
B. Glacial troughs 1. Morphology and
Processes a. U-shaped valleys i. Distribution
of shear stress b. Perched valleys and
truncated spurs c. Paternoster lakes and
cyclopean stairs i. Differential erosion ii.
Tributary junctions iii. Glacial
knickpoints d. Fjords
http//www.earthscienceworld.org/images/index.html
http//www.earthscienceworld.org/images/index.html
Fjord on southeastern Alaska.
29
C. Finger lakes 1. Valley ice vs. divide
ice D. Streamlined forms 1. Whaleback rocks
and rock drumlins 2. Roche mountonnees
New York's Finger Lakes. Lake Ontario appears at
top, Oneida Lake upper right, Cazenovia Lake
directly below.
http//www.earthscienceworld.org/images/index.html
30
Push moraines as seen here at Alaska's Harriman
Glacier are composed of unsorted till. Meltwater
from the glacier becomes outwash and sorts and
deposits materal in an outwash plain.
http//www.earthscienceworld.org/images/index.html
II. Depositional Landforms A. Moraines 1.
General processes a. Role of ablation b. Role
of push c. Till generation 2. Processes and
characteristics of moraine types a. End
moraine b. Push moraine c. Dead-ice
moraine d. Recessional moraine
Folded layers of ice mark the terminus of
Alaska's Columbia Glacier as till piles up in a
terminal moraine and a subglacial stream carries
away the meltwater.
http//www.earthscienceworld.org/images/index.html
http//www.earthscienceworld.org/images/index.html
This is a view of the terminal moraine and
recessional moraines along with the ice-marginal
lake and outlet river of Alaska's Tazlina
Glacier.
31
http//www.earthscienceworld.org/images/index.html
A large medial moraine separates the streams
draining the meltwater from the two arms of
Alaska's Trimble Glacier.
d. Recessional moraine e. Lateral moraine f.
Medial moraine g. Rogen moraines h. Ground
moraine
http//www.earthscienceworld.org/images/index.html
Glaciers fusing together in the southwest of
Canada's Yukon.
Medial Moraine
Ground Moraine
Terminal Moraine
Outwash
Glacial Deposits, New Zealand
32
B. Drumlins and flutes 1. Characteristics a.
Elliptical hills and long ridges b. A few km to
several km long, a few 100 m wide and 10 m
tall c. Till or bedrock or mixed d. Flow
orientation 2. Processes a. Role of
streamlining b. Role of uncertainty
http//www.earthscienceworld.org/images/index.html
Glacial drumlin at Cranes Beach Massachusetts.
33
C. Stagnant-ice landforms 1. Eskers 2.
Kames a. Kame lake b. Kame terraces c. Kame
deltas and fans 3. Kettles
http//www.earthscienceworld.org/images/index.html
http//www.earthscienceworld.org/images/index.html
This ground moraine contains kames and kettles
caused by fragments of the glacier being buried
in the till and later melting.
Alaska's retreating Bering Glacier leaves behind
this debris covered, stagnant ice on its east
flank.
34
D. Glacial lakes F.
Outwash Plains
http//www.earthscienceworld.org/images/index.html
Meltwater from the glacial lake formed by
Alaska's Nellie Juan Glacier escapes by breaching
a terminal moraine. Tarns can be seen in the
cirques on both sides of the glacier.
http//www.earthscienceworld.org/images/index.html
Braided streams run on top of the outwash plain
next to the stagnant, downwasting, debris-covered
ice of the Casement Glacier at Alaska's Muir
Inlet.