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Geology and Climate Glaciers, Deserts, and Global Climate Trends

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Title: Geology and Climate Glaciers, Deserts, and Global Climate Trends


1
Geology and ClimateGlaciers, Deserts, and
Global Climate Trends
  • Chapter 9
  • Solar heat drives evaporation, makes
    precipitation, and generates glaciers.
    Differential solar heating of land, water, and
    thus air makes the winds
  • Glaciers shape our landscape and stand for a
    large reserve of fresh water
  • Wind is not a serious hazard except the winds
    during severe storms. Winds also shape the
    earths surface, but not so efficient
  • Global climate changes can occur significantly
    over a long term

2
Glaciers and Glacial Features
  • Glaciers a mass of ice that moves over the land
    under its own weight and shape the land
  • Excellent indicator for global climate conditions
    (warm or cool). Not be developed in a single
    winter
  • Glacier Formation
  • Heat from the sun is generally constant
  • Climate factors may influence the global
    temperature budget
  • Global cooling ice will accumulate and build
    ice sheets and glaciers
  • Global warming ice sheet retreat and glaciers
    get smaller
  • Factors that change climate include composition
    of the atmosphere, pollution or particles
    suspended in the atmosphere, abnormal heat
    retention (or loss) from the oceans

3
Figure 9.2
4
Glacier Formation
  • There must be sufficient moisture in the air, and
    thus the necessary precipitation
  • The amount of winter snowfall must exceed summer
    melting
  • Snow accumulates during cold periods
  • Snow transforms to ice
  • Overlying ice will pack the ice tighter and
    thicker
  • Packing causes the ice to recrystallize into a
    denser ice called firn
  • Gravity will pull the thickened mass of ice down
    any slope
  • Types of Glaciers based on size and occurrence
  • Alpine Glaciers (also known as mountain or
    valley glaciers) occur at high altitude (cooler
    temperatures)
  • Continental Glaciers (also known as ice caps or
    ice sheets) occur near the poles (over land)
    they are larger and rarer

5
Figure 9.3
6
Figure 9.4
7
Movement and Change of Glaciers
  • Glaciers flow as plastic ice masses and at
    different rates overall movement is down slope
  • Movement is slow at the base of a glacier where
    it is in contact with and scrapes the valley
    walls
  • Movement higher in the glacier is faster
  • Glacier movement has a terminus
  • Glacier that encounter water will experience
    calving
  • Temperatures at the terminus are warm and
    evaporation, or melting, removes ice - ablation
    occurs
  • At one place on the glacier an equilibrium line
    is established
  • Above it snow accumulates
  • Below it ice ablation occurs
  • Overall glacial movement is slow and steady (a
    few tens of meters per year) surges are possible
    (several tens of meters per day)

8
Figure 9.5
9
Figure 9.6
10
Figure 9.7
11
(No Transcript)
12
Glacial Erosion and Deposition
  • Glacier Erosion very effective process
  • Large mass and solidity of a glacier will shape
    the surface of the earth
  • Sediments are picked up and carried off -
    abrasions and striations are left behind
  • Carves its own valley. U shaped valleys mark
    locations where alpine glaciers once stood
  • Glacier Deposition abundant material is
    transported on or along the sides of glaciers a
    variety of moraines will form
  • Drift, formed by till and outwash, is deposited
    at the terminus of a glacier

13
Figure 9.8
14
Figure 9.9
15
Figures 9.10 a, b, and c
16
Figures 9.12 a and b
17
Glaciers as a water source
  • Important freshwater source
  • Approximately 75 of fresh water is stored as
    glacial ice
  • Glacial meltwater may be the principal source of
    summer streamflow in the regions having glaciers
  • Overall volume of glacial ice can be manipulated
  • Cloud seeding activities in glacial areas may
    cause accumulation of increased amounts of ice
  • Dusting glaciers with black coal may cause an
    increase melt of glacial ice to occur

18
Wind and its Geologic Impacts
  • Wind is moving air, air moves in response to
    variations in air pressure
  • Wind accounts for a minor amount of sediment
    erosion and transport but regionally it is very
    important
  • Wind erosion consists of abrasion, forming
    ventifacts, or deflation, forming desert pavement
  • Vegetation is critical to reducing the effects of
    wind erosion
  • Wind Deposition principal feature of wind
    deposition is the sand dune
  • Dune Migration will occur if wind blows from
    predominately a single direction
  • Particles of sand will move by rolling, or
    saltation, up the shallower windward dune face
  • Once at the dune top they fall down the steeper
    slip face

19
Figure 9.13
20
Figures 9.14 a and b
21
Figures 9.15 a and b
22
Figure 9.16
23
Figures 9.17 a and b
24
Figures 9.18 a and b
25
Figure 9.19
26
Wind and its Geologic Impacts
  • Wind generally does not move sand or coarser
    particles very rapidly
  • Fine dust, or silt, can be carried off long
    distances by the wind and is deposited as loess
  • Loess can originate in either desert or glacial
    areas
  • Loess, once deposited forms a porous and open
    structure holds abundant water
  • Loess does not make a good foundation material
    hydrocompaction may cause cracks to form in
    foundations or structures
  • Structures may also settle unevenly or collapse

27
Figure 9.20
28
Figure 9.21
29
Deserts and Desertification
  • Deserts regions with limited precipitation,
    people, and vegetation. The features of wind
    processes are observed
  • Causes of Natural Deserts
  • Found about 30o Latitude (north or south)
  • dry descending and warm air masses
  • Warm and dry air can hold abundant water
    evaporation rates are high
  • Topography and prevailing wind patterns establish
    rain shadow moisture extracted on windward
    slopes of mountain ranges
  • Air mass is cool and dry at maintain tops, it
    warms as it descends on leeward side of mountain
  • Causes of Desertification
  • Rapid development of desert-like conditions
    caused by human activity
  • Major and repeated disturbance to vegetation
    without complete recovery
  • Overuse of regional surface and ground water
    resources

30
Figure 9.22
31
Figure 9.23
32
Figure 9.24
33
Global ClimatePast and Present
  • Evidence of Climates Past
  • Study geologic (rock and sediment )record
  • Recent changes in soil and vegetation
    distribution
  • Oxygen isotopes (18O/16O) in shell material
  • Ice Ages and their Possible Causes
  • Changes in solar out put of energy
  • Disruption to global wind or ocean circulation
    patterns
  • Atmospheric phenomena blocking incoming solar
    radiation
  • Volcanic eruptions of ash
  • Increase in cloud cover
  • Change in chemical composition of atmosphere

34
Figures 9.25 a and b
35
Figure 9.26
36
Figure 9.27
37
Figures 9.28 a, b, and c
38
Figure 9.29
39
Figure 9.30
40
ClimatePresent and Future
  • The Greenhouse Effect involves sun light (energy)
    entering the atmosphere and a component of the
    atmosphere (CO2) trapping radiant heat (infrared
    energy)
  • The result is warming of the atmosphere and
    Global Warming
  • Increases, or decreases, in the concentration of
    CO2 in the atmosphere will show a respective
    increase, or decrease, in global warming

41
Figure 9.31
42
Figure 9.32
43
Figure 9.33
44
Figure 9.36
45
ClimatePresent and Future
  • Several centuries ago human activity did not
    adversely affect the CO2 balance of the
    atmosphere
  • The industrial revolution has placed about 30
    additional CO2 into the atmosphere
  • Global warming has occurred
  • This trend must be changed or we will suffer
    consequences
  • Rise in sea level about 20 of current land
    area would be submerged
  • Progressive expansion of marginal agricultural
    lands
  • Increase in severity of storm distribution and
    activity

46
Figure 9.37
47
ClimatePresent and Future
  • Other greenhouse gases include methane (CH4),
    nitrous oxide (NO2), CFCs, and plus others
  • These gases are becoming more concentrated in our
    atmosphere also
  • Global cooling apparently can be promoted by an
    increase of SO4 from volcanic eruptions (plus
    abundant ash and clouds)
  • To achieve a balance in global warming and
    cooling a reduction to the input of greenhouse
    gases and increase in the concentration of
    volcanic SO4 would be necessary
  • How can this be done? Should it be done?

48
Figure 9.38
49
Winds and CurrentsClimate and Commerce El Niño
  • The interplay between atmosphere and oceans is
    complex
  • Oceans are sinks for CO2
  • Generally, only the upper most part (within
    100-200 meters of the surface) of the oceans
    interact with the atmosphere
  • Directional shifts in wind direction will disrupt
    ocean circulation patterns
  • Shifts in ocean circulation patterns will cause
    normal upwelling cold, deep, nutrient rich water
    to cease
  • Shifts in the distribution of flora and fauna
    will occur
  • Fishing industries must shift their operations
  • El Niño (Southern Oscillation) is such a cyclic
    warm event occurring every four to seven years
    when warm waters from the western South Pacific
    extend eastward to South America
  • La Niña (a cold event) is the opposite and cycles
    periodically also
  • The Pacific Decadal Oscillation (PDO) is a cycle
    of fluctuation surface temperature patterns that
    occur over a 20-30 year period

50
Figure 9.39
51
Figures 9.40 a and b
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