Chapter 1, Environmental Geology by C' Montgomery

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Chapter 1, Environmental Geology by C. Montgomery
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Who are you?

• 57 freshman
• 25 sophomores
• 14 junior
• 4 senior

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Who Are You?

• 29 business majors
• 8 psychology majors
• 8 education majors
• 6 journalism majors
• 6 english, poli sci or history
• 5 arts sensu lato
• 5 undecided
• 4 landscape architect
• 1 each sp comm, pub manage, arabic,
  biochemistry, computer science, microbiology

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Where are you from?

• 42 Atlanta region
• 35 Georgia outside Atlanta
• 14 Southeast outside GA
• 8 US outside SE
• 1 outside US

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Why are you taking the course?

• 65 satisfy degree requirement
• 21 interested in earth science
• 19 interested in environmental issues

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These are observations Are these observations
Indicative of global warming?
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Maybethese are 1. local 2. short-lived
These are observations Are these observations
Indicative of global warming?
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Note difference between observations
(temperature) and model or interpretation (global
warming)
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Note difference between observations
(temperature) and model or interpretation (global
warming) our goal is to make you
Environmentally literatei.e., to make
objective Interpretations of data such as these
unusually Warm temperatures
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We need average, Global yearly Temperatures
such As this graph shows And indeed the Earth
seems to be warming
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It would be useful To have a second Distinct set
of Observations to Support the warming model
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Annual shrinkage of global ice appears to confirm
the Idea that the earth is warming
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But nature is complex
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Ice caps record climate change Going back more
than 100,000 years
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Observations of Ice characteristics Can yield a
Temperature record
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Vostok ice core an Ice core from
Antarctica That preserves a record Of past climate
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Vostok ice core an Ice core from
Antarctica That preserves a record Of past
climate shows That about 10,000 years Ago it
was slightly warmer Than nowand 20,000 Years
ago, much colder
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Nature is complexsimple explanations of Natural
phenomena are to be viewed skeptically
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Perspective drawing of solar systemnot to scale
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This arrangement of planets suggests that the
solar system Formed from a rotating disk and the
planets coalesced from dust
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Earths Place in the Solar System
All these planets are visible with the naked eye
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EarthOne of the 4 relatively small terrestrial
planets
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Each terrestrial planet is quite distinct
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Mercury dense, no atmosphere
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Venus CO2 Atmosphere (4 N2, 0.015
SO2) Surface P 100 x that of Earth Surface
T 475 C
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Mars CO2 Atmosphere (3 N2, 2 Ar, 0.13
O2) Surface pressure 0.006 x Earth Surface
temperature - 60 C
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Earth N2 (78), O2 (21), H2O (lt4)
CO2 (0.035) Surface T 20 C
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Moon no atmosphere Surface littered with impact
craters
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Moon is special Because we have Been there and
Brought back samples
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Back to Earth Its unusual Characteristics
Liquid water stable on most of the surface
atmosphere is O2-rich and CO2- poor
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Earths topography key aspects
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Topography blue is low, red is high
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Earths topography
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Plots of area at a given elevation Note the
bimodal curve for Earth versus the smoother
Curves for the other terrestrial planets
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Earths topography

• Key features
• Continent/ocean dichotomy, i.e., bimodal
  distribution of elevations
• Mid-ocean ridge system 80,000 km long,
• 1500-2500 km wide, 2-3 km above abyssal plain.
• Long narrow continental mountain ranges
• Deep sea trenches adjacent to arcs of volcanic
• islands

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Note volcanoes Are not randomly Distributed Deep
sea trench Parallel to Volcanic chain
Source Natl Geog.
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Indonesian Volcanoes Looking Parallel To
volcanic chain
Source Natl Geog.
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Earth cross section
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• Earth is stratified into crust, mantle, core

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Earth as an avocado
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• Earth is stratified into crust, mantle, core
• Densest material at center

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Earths core is thought to Be similar to the
material that Makes up iron meteorites 90
metallic iron (Fe) and 10 metallic nickel (Ni)
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• Earth is stratified into crust, mantle, core
• Densest material at center
• Core 12 gm/cm3
• Mantle 4 gm/cm3

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• Earth is stratified into crust, mantle, core
• Densest material at center
• Core 12 gm/cm3
• Mantle 4 gm/cm3
• Crust
• Oceanic 2.95 gm/cm3
• Continental 2.75 gm/cm3

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• And, continental crust is about 4 x thicker (40
  km) than oceanic crust (10 km

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Cartoon above suggests that Continental crust is
somewhat Like an iceberg in behavior
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• Does the Earths interior behave like a viscous
  fluid over long periods of time?

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• Does the Earths interior behave like a viscous
  fluid over long periods of time?
• YES!!!...but it is not
  liquid