Transcript Minerals and Rocks

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What is environmental geology?
•
Geology – Study of rocks and minerals that comprise earth’s surface and
interior and the natural processes that shape the earth’s surface and interior
over all time scales.
•
Environmental Geology – Study of interactions and feedbacks between
people, geologic processes, and geologic materials.
•
Environmental geologists are in some sense applied geologists – they bring
collective geologic knowledge to bear on problems important to people.
Earth as a
closed system
– implies
nearly
everything is
cycled,
recycled
Population: 6.2 billion in 2002
Growth rate: 1.2%
49 poorest countries: 2.4%
Industrial countries: 0.25%
Are the earth’s resources really infinite, as this writer implies? If they are, then
why conserve anything ?
A man with a political agenda: manipulating the numbers
Can global grain
production keep
up with
population ?
Since Y2000, it
has not and grain
stocks have been
drawn down to
multi-decade
lows.
Course Information
Everything you need to know is on the
course web site:
www.geology.wisc.edu/courses/g106/
Course Overview
I. Fundamentals:
Minerals and Rocks
• Basic Vocabulary of Geology
• Foundations and Building Materials
• Important Natural Resources
• Impacts on Human Health
Plate Tectonics
• Unified theory that explains
distribution of mountain belts, deep
sea trenches, earthquakes, volcanoes,
and the “rock cycle”
II. Natural hazards resulting from
internal and surface processes:
Earthquakes, volcanic eruptions,
landslides
Above: landslide onto Gokuna glacier triggered by 11/03/02 Denali M=7.9 EQ
Left: Pyroclastic flow during 1991 eruption of Mt. Uzu, Japan
III. Additional surface processes:
Streams, coasts, glaciers and deserts
IV. Resources
Water, Minerals, Energy
V. Waste Disposal,
Pollution and Health
Get your CPS “clickers” ready if you
have already registered them
Earth and other planets in the
solar system formed
A.
B.
C.
D.
Approximately 6000 years ago
20-40 million years ago
Approximately 100 million years ago
Over 4.5 billion years ago
Example participation question
Environmental Significance
of Geologic Time
Perspectives on rates of natural
processes and human impacts
• Rising and falling of
tides - 1 day
• Drift of continents by
3 cm - 1 year
• Recurrence of large
earthquakes on a
major fault - 10s to
100s of years
• Deposition of 1 cm of
sediment on the
seafloor - 1000 yrs
• Advance and retreat
of ice sheets - 10,000
to 100,000 yrs
• Life span of a large
volcano - 1 to 10
million yrs
How do we determine the age of the Earth?
(see Appendix A)
Relative Dating – Qualitative answer only
Order of Events: (for figure
below) 1) deposition of
limestone and shale, 2) basalt
intrusion, 3) tilting, 4)
erosion, 5) deposition of
sandstone, 6) lava flow
Correlation: similar fossils indicate
strata deposited at similar times in the
past, “faunal succession” over time
+ Uniformitarianism: similar
geologic processes in the past as
we observe today
Age of the Earth (continued)
Quantitative estimates
Rate of Heat Loss:
Estimate of 20-40 million
years by British physicist
Lord Kelvin in late 1800s
Incorrect
because
didn’t
account for
radioactive
decay which
adds heat
Salt in the oceans: Irish physicist
John Joly, in 1899, assumed pure
water at start, and estimated how long
it would take for rivers to deliver salt
from erosion of rocks.
Estimate of 100
million years did not
consider varying
rates of weathering
or removal of salt by
formation of
evaporite rocks
Age of the Earth (continued)
Quantitative estimates
Radiometric Dating: Measures of concentrations of parent and
daughter isotopes in a rock used to determine rock age. Meteorites
and moon rocks yield ages of about 4.5 billion years
Earth and other planets in the
solar system formed
A. Approximately 6000 years ago: 17th
century estimate by Ussher on basis of
generations in the Bible
B. 20-40 million years ago: 19th century
estimate by Kelvin on basis of heat loss
C. Approximately 100 million years ago: 1899
estimate by Joly on basis of salt in the
ocean
 D. Over 4.5 billion years ago: current
estimate based on radiometric dating of
meteorites and moon rocks
If Earth’s history is equated to a 24hour day, approximately when did
modern humans (homo sapiens) arrive
on the scene?
A. 1 hour ago
B. 10 minutes ago
C. 1 minute ago
D. 10 seconds ago
E. 1 second ago
1 hour  190 million years
1 minute  3 million years
Another participation question – will be repeated for credit during the next lecture