Transcript ch23

Classroom presentations
to accompany
Understanding Earth, 3rd edition
prepared by
Peter Copeland and William Dupré
University of Houston
Chapter 23
Earth systems, Cycles, and Human Impacts
Earth
Systems
Synthesized by R.B. Husar, Washington University
Human
Impacts
Greenhouse effect
• Visible light from the sun is converted
to infrared, infrared is reflected off the
underside of the atmosphere, thus
keeping this heat.
• The same thing happens in a
greenhouse
Greenhouse Effect
Fig. 23.1
Greenhouse gases
Not all of the atmosphere causes the
greenhouse effect. The most important
components of this phenomenon are
H2O
CO2
NH4
NO2
CO
CFC’s
3.5 Billion Year Old Fossils
M.Abbey/Photo Researchers
Fig. 23.2
Photosynthesis
and Respiration
in the
Carbon Cycle
Fig. 23.3
Kunio Owaki/The Stock Market
Fig. 23.4a
Kunio Owaki/The Stock Market
Fig. 23.4b
2.2 Billion-Year-Old Soil Formed
in an Oxygen-poor Atmosphere
Courtesy of H.D. Holland
Fig. 23.5
Fig. 23.6
Calcium Fluxes
Into and Out of the Ocean
Fig. 23.7
Earth in the Cosmos
Core
Mantle
Lithosphere
Atmoshere
System
Major
Reservoirs
and Fluxes
of the
Earth
System
Gas Exchange with the Atmosphere
Fig. 23.8
Long-term Average Pattern
El Niño Conditions
Geochemical Carbon Cycle
Fig. 23.9
Marine Life
During the
Phanerozoic
Eon
Fig. 23.10
Extinction of the Dinosaurs
End of the Cretaceous ~ 65 M yr.ago
Hypothesis favored by many (but not all):
• Large meteorite (~10 km across) or
comet struck the Earth, producing large
dust cloud.
• No sunlight; plants die, animals die.
Where did it hit?
• If a big meteorite hit, where is the
crater?
• Most of the Earth's surface is oceanic
crust; therefore the meteorite could
have been destroyed.
• Recent evidence suggests that the
location of the impact was Yucatan
Peninsula, Mexico.
Chicxulub
Impact
Crater
B. Sharpton,
Lunar and Planetary Institute
Fig. 23.11
Evidence:
• Clay layer at K–T boundary: First found
in Italy, now seen in at least 75 other
locations (both marine and nonmarine)
• High concentration (300 ) of Iridium
(Ir) in this clay. Ir very rare on Earth,
abundant in meteorites (Isotopes and
soot, as well).
• shocked quartz
Strata at Gubbio, Italy
Michael M. Follo
Cretaceous-Tertiary Boundary
Tertiary
K–T
Boundary
Cretaceous
Michael M. Follo
Fig. 23.12
El Niño
Event
Warm Water
Synthesized by R.B. Husar, Washington University
Greenhouse effect
Over the past 160,000 years there is
strong correlation between the amount
of CO2 in the atmosphere and the
temperature of the oceans.
Anthropogenic changing of the
greenhouse effect?
• Burning of fossils fuels has CO2 as one of
its by-products.
• CO2 in the atmosphere has increased by
20% in the past ~150 years.
• The average surface temperature on
Earth has increased.
• Increase in surface temperature also
correlated with sunspot activity.
Anthropogenic changing of the
greenhouse effect?
• At the current rate of increase, the
concentration of CO2 in the
atmosphere will double in 60 to 70
years.
• Plants use CO2 in photosynthesis,
removing it from the atmosphere.
• Deforestation can increase
greenhouse effect.
Global Warming Trend
Fig. 23.13
Ozone
• Molecule of three oxygen atoms
(most oxygen is found in
diatomic molecules)
• Very effective in blocking
ultraviolet (UV) radiation
• Found in high concentrations in
the upper atmosphere
Chloroflourocarbons (CFCs)
• Synthetic chemicals used primarily
in refrigeration applications
• At high altitudes in the atmosphere
(10–50 km), UV radiation breaks
these chemicals down into smaller
components including free chlorine
(Cl).
CFCs and ozone breakdown
• Free Cl is a catalyst that promotes the
breakdown of ozone to O + O2.
• One Cl atom will eliminate thousands
of O3 molecules before it ultimately
combines with something else.
Consequences of increased UV
• Too much UV radiation can cause
sunburn; in extreme doses it can cause
skin cancer and cataracts.
• Can also be harmful to phytoplankton,
an important part of the oceanic food
chain.
Evidence for ozone depletion
• Since 1965 the amount of ozone
above Antarctica in the summer has
decreased by 30 to 50%.
• Same phenomenon seen to a lesser
degree in other parts of the world.
Montreal protocols
• A set of international agreements
designed to decrease the
concentration of CFCs in the
atmosphere
• However, if CFC use were
immediately stopped, ozone would
probably still keep decreasing in the
upper atmosphere.
Projected Ozone Trends With and
Without the Montreal Protocol
Fig. 23.14
Acid rain
• Both natural and anthropogenic
processes cause acidification of
precipitation.
• Natural: CO2 —> H2CO3 (carbonic acid);
acids from volcanoes (H2S mostly)
• Anthropogenic: Oxides of N are byproducts (nitric acid)
Acid rain
• Since the 1950s the pH of precipitation in
eastern North America has decreased
(i.e., more acidic) significantly over a large
area.
• Other regions effected include eastern
Europe and China.
• Consequences of more acidic
precipitation include problems for fish and
other wildlife and increased chemical
weathering, especially of regions with lots
of carbonate rocks.
Before
Westfalisches Amt fur Denkmalpflege
Fig. 23.15
After
Westfalisches Amt fur Denkmalpflege
Fig. 23.15
Acidity of Precipitation
Fig. 23.16
Value of Earth’s Ecosystems
in 1994 Dollars per Hectare
Courtesy of Robert Constanza
Population Growth in Developed and
Developing Countries
Fig. 23.17