Four Main Processes:

1
Lecture 17
Tectonic-scale Climate Change Text book Ch. 4,
p64-67, 71-80, 82-86.

• Four Main Processes
• Land-ocean spatial configuration control where
  ice sheets form
• Spread of sea floor volcanoes and oxidation of
  organic carbon in sedimentary rocks, control
  release of CO2 in the atmosphere
• Chemical weathering control CO2 removal process,
  a thermostat of the earths climate
• Uplift-mountain effect expose fragmented and
  fresh rock for chemical weathering

2
How does tectonics influence climate?
Hundreds of millions of years
Plate tectonics and drift concentrated continents
at higher latitudes allowed for more ice cover,
which reflected more sunlight and created a
positive feedback to cause greater cooling.
3
Earths climate history

• Early Earths history (4.5BY-570MY)
• 3.7 BY May have been 10C warmer
• 2.7-1.8BY widespread glaciers, snowball earth
• 1.8-1 BY warm and ice-free, maybe due to
  catastrophic events, e.g., volcanoes, cometary
  impact, overturn stagnant ocean
• 850-590MY at least two ice ages

4

• 580-0MY
• 580-225MY climate changes was generally colder
  than the period of 225-65MY.
• 225-65MY climate was generally warmer with
  perhaps the warmest during mid-Cretaceous
  (100MY).
• 65-0MY Earths climate became colder with time.
• Why?

Snowball earth
5

• In-Class Question Can you link the tectonic
  movement to the following climate change?
• 580-225MY climate changes was generally colder
  than the period of 225-65MY.
• 225-65MY climate was generally warmer with
  perhaps the warmest during mid-Cretaceous
  (100MY).
• 65-0MY Earths climate became colder with time.

warmest
coldest
6
Tectonic-scale Carbon Dioxide Fluctuations (p.
71-75)
Seafloor spreading leads to increased periods of
volcanic degassing of CO2, which causes
warming. Higher temperatures leads to increased
weathering, which will remove CO2 from the
atmosphere and reverse warming in a negative
feedback loop.
7
Earths Climate History in the Last 550 Myr

1. Over the past 550 Myr, three Icehouse periods
   (430, 325-240, 35-0 Myr ago).

2. For most of the last 550 Myr or the earths
entire history, the climate was much warmer than
today.
3. Tectonic-scale climate change is caused by
plate tectonics
Land/ocean positions and sizes
Ocean floor spreading/CO2 increase
Mountain building (uplift) weathering / CO2
decrease
4. Other causes.
Part II p. 82-83 Ch. 4, 5, 6, 7
8
Chemical weathering (chemical breakdown of
minerals or rocks)-a thermostat of earths
climate (Ch. 4, p75-80)
Carbonic acid
Examples (Calcite)
(calcium ions) Limestone
carbon dioxide water ? dissolved ions
bicarbonate CaCO3 CO2
H2O ? Ca2 2HCO3-
9
Cretaceous ? Greenhouse Earth
Warm period of dinosaurs Evidence No record of
glaciers or polar ice caps Faunal/floral zone
latitudinal shift Isotopes ? warmer
oceans Environments shift with near tropics to
the poles Oceans/Atmosphere/Land Features Sea
level 100-200 m higher because of no polar ice
caps Intense storms (hurricanes) because of
warmer waters Stronger hydrologic cycle Less wind
because lower T and P gradients globally More
plants, more flowers extent of dry land reduced
by flooding Causes Sun-Earth relationship Land-s
ea configuration More oceans in low
latitudes?lower albedo More land in high
latitudes?more plants More CO2 in atmosphere (4-8
x)
10
The World 100 Myr Ago (p. 82-85)
Flooding of The Continents
11
1. The last time atmospheric CO2 concentrations
and temperatures were much higher than today was
in the age of dinosaurs.2. Agriculture
revolution began 10,000 years ago.3. Human
population explosion in the past 100 years.
Today 6 billion
PRESENT
100,000 years
12
Sea levels were much higher than today, and Texas
was mostly under water
What about Texas?
13
Climate change was one important reason that the
dinosaurs disappeared.
14
Global Cooling Trend in the Last 55 Myr
Ch. 7
Causes decrease in ocean floor spreading rate
uplift weathering ocean heat transport through
gateways ice-albedo feedbacks
Cooling from leaf outline
Cooling from ocean isotopes
Decrease in spreading rate
15
Summary

• Four Main Processes control the link between
  tectonic movement and climate
• Land-ocean spatial configuration control where
  ice sheets form
• Spread of sea floor volcanoes and oxidation of
  organic carbon in sedimentary rocks, control
  release of CO2 in the atmosphere
• Chemical weathering control CO2 removal process,
  a thermostat of the earths climate
• Uplift-mountain effect expose fragmented and
  fresh rock for chemical weathering