31 The Changing Face of the Earth
Before
After
Flooding of Mississippi & Illinois Rivers 1993
PS 100 -- Chapter 31
1
At which type of plate boundary would you
expect to find large, deep focus
earthquakes, but no volcanoes?
1.
2.
3.
4.
Continent-continent
collision boundary
Continental rift
boundary
Transform boundary
Ocean-ocean
collision boundary
PS 100 -- Chapter 31
25%
1
25%
2
25%
3
25%
4
2
What is a Natural System?





Group of natural, interdependent parts or
components
Interactions between parts forms the system
Forces drive the system
All systems tend toward a state of maximum
disorder (entropy) called equilibrium
Earth’s two major systems are:
 Hydrologic
System
 Tectonic System
PS 100 -- Chapter 31
3
Hydrologic System

System of moving
water
 Rivers
 Oceans,
Effects of Hydrologic
System
 Erosion
Lakes
 Glaciers
 Groundwater
 Water

Vapor in
Atmosphere
 Transportation
of
Sediment
 Deposition of
Sediment
 Creation of Numerous
Landforms
PS 100 -- Chapter 31
4
Hydrologic System
PS 100 -- Chapter 31
5
Where is Water Found in the
Hydrologic System?
Glaciers
Groundwater
0.7
Ocean
Glaciers
0.013
Lakes
All
Other
0.0184
97%
2.2
&
Rivers
0.0045
Soil
0.0009
Atmosphere
PS 100 -- Chapter 31
6
What Forces Drive this System?

Solar Radiation
~342 W/m2 = ~342 joules/sec m2
 Causes evaporation
 Average

Gravity
 Pulls
water down slopes
 Causing erosion, transportation of sediment
PS 100 -- Chapter 31
7
Subsystems of Hydrologic System





River Systems
Glacial Systems
Groundwater
Systems
Ocean/Shoreline
Systems
Desert Systems
PS 100 -- Chapter 31
8
Rivers




Primary mechanism for
erosion
Move sediment from
mountains to oceans
Also carry dissolved ions
(salts)
Can be easily disturbed
by human activity



Dams
Pollution
Irrigation
PS 100 -- Chapter 31
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PS 100 -- Chapter 31
10
PS 100 -- Chapter 31
11
Glaciers




Rivers of Ice
Very effective agents of erosion
Carve different topography than rivers
Many glaciers are currently shrinking due to global
warming
PS 100 -- Chapter 31
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PS 100 -- Chapter 31
13
2004
1875
Pasterze Glacier, Austria
PS 100 -- Chapter 31
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PS 100 -- Chapter 31
15
Groundwater

Rocks can hold a lot of
water!




Porosity
Permeability
Groundwater is a major
source of drinking and
irrigation water
Groundwater is often
affected by human
activity



Overpumping
Pollution
Irrigation
PS 100 -- Chapter 31
16
Water Table
PS 100 -- Chapter 31
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20
Oceans & Shorelines


Beautiful, but
changeable
Shorelines are places
of active…
 Erosion
 Transportation
 Deposition

Human activity can
have a significant
effect on shorelines
PS 100 -- Chapter 31
21
PS 100 -- Chapter 31
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PS 100 -- Chapter 31
NASA23
PS 100 -- Chapter 31
Smiley Pool,24
Dallas
Morning News
PS 100 -- Chapter 31
25
17 July 2001
17 Sep 2004: After Ivan
31 Aug 2005: After Katrina
Dauphin Barrier Island: Alabama
PS 100 -- Chapter 31
National Geographic
26
Barrier islands and wetlands
No barrier islands or wetlands:
Effects of artificial subsidence &
27
PS 100 -- Chaptersea
31
level rise
National Geographic
Deserts

Dominated by wind
 Carries
light-weight
particles (sand & dust)
 Leaves the rest behind

Human effects
 Desertification


Overgrazing
Poor Farming Practices
 Destruction

of Soil
Irrigation adds salts
PS 100 -- Chapter 31
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29
PS 100 -- Chapter 31
30
Climate Change


All of these systems are affected by the
changing climate
Earth’s climate changes naturally over time
 At
times in the past the Earth has been much cooler
and at other times much warmer

Human activity can speed up the rate at which
these changes occur
 Pollution


CO2 and CH4 can help hold heat around the Earth
Particulates (dust and smoke) can reflect sunlight and lead to
cooling of the Earth
PS 100 -- Chapter 31
31
What is Earth’s Past History?
How do we know?
PS 100 -- Chapter 31
32
PS 100 -- Chapter 31
33
What Causes Climate Change?

Amount of Solar Radiation Reaching the Earth
 Milankovich




Cycles
Distance of Earth from Sun (100,000 yr cycle)
Tilt of Earth on its axis (41,000 yr cycle)
Precession of Earth on its axis (23,000 yr cycle)
Amount of Solar Radiation Trapped in the Lower
Atmosphere
 Greenhouse



Effect
Carbon Dioxide
Methane
Water Vapor
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37
What is the evidence that Earth is warming up?
PS 100 -- Chapter 31
38
ICE CORE DATA
PS 100 -- Chapter 31
39
Recent Sea Level Changes
PS 100 -- Chapter 31
40
Possible Human Effects on
Climate

Declining CO2 trend reversed 8000 years ago


Correlates with clearing of European forests & beginning of rice
cultivation
Declining CH4 trend reversed 5000 years ago

Correlates with flooding of lowlands and beginning of rice
cultivation
PS 100 -- Chapter 31
41
Should we do anything?
PS 100 -- Chapter 31
42
Geologic record
indicates that past
sea level changes
when polar
glaciers melt have
been hundreds of
meters. The cost
would be
catastrophic.
PS 100 -- Chapter 31
43
Risk, Cost, & Benefit


Cost of reducing greenhouse emissions will
certainly be billions of dollars
Certainty of global warming is not 100%
 Current

predictions depend on imperfect models
Environmental and economic consequences
could be truly catastrophic
 Some
say global warming could cause the end of
technological civilization

As voters & consumers, these are your issues
PS 100 -- Chapter 31
44
Climate change is caused mainly by changes in
the balance between the amount of solar radiation
received and the amount of heat radiated back into
space by the Earth.
PS 100 -- Chapter 31
ls
e
50%
Fa
2.
True
False
Tr
ue
1.
50%
45