Transcript PowerPoint Presentation - Modeling the Geochemical Carbon

Modeling the Geochemical
Carbon Cycle
By: Robert A. Berner
and
Antonio C. Lasaga
Presented by: Kristin Hepper
What is the Geochemical Carbon
cycle?
• It is the transfer of carbon between
sedimentary rocks
• Carbon Dioxide is the chief player
Why study the geochemical
carbon cycle?
• Fossil-fuels = energy
• The consequences of fossil-fuel burning are
astronomical
• Greenhouse effect
The Greenhouse Effect
• Swedish chemist
Svante August
Arrhenius, 1896
• Found that carbon
dioxide allows shortwavelength solar
radiation to penetrate
the atmosphere, but
traps this energy when
it is reradiated by the
earth at longer
wavelengths
• Any current greenhouse warming is
primarily due to the burning of fossil fuels
How does the carbon get out of
the rocks?
-Chemical Weathering
It is the natural analogue to the burning of fossil fuels
Chemical Weathering
• Sedimentary rocks are attacked by acids (carbonic
acid)
• Causes them to break down
• End result = 2 bicarbonate ions
What happens next?
• One goes into the atmosphere
• The second goes into the groundwater
• Marine organisms use the bicarbonate ions
to construct their skeletons and shells
Finally…
• The organisms die
• Their bodies are deposited and eventually
buried on the seafloor
Somewhere out to sea…
To sum up…
• Carbonic acid in the soil
• Two bicarbonate ions
-one is transformed into carbon dioxide
and goes into the atmosphere
-and the other is used by marine
organisms eventually becoming
sedimentary rock
Radiolarian chert at the Marin
Headlands
How does the rest of the carbon
get back up into the atmosphere?
It has to do with plate tectonics…
Specifically, volcanic eruptions
and related phenomena
Subduction zones
• Degassing is the main mechanism
• It happens at mid ocean ridges as well
What did our authors Berner and
Lasaga do?
• They used computer
models to run the
geochemical cycle
backwards
• To calculate planetary
carbon dioxide levels
from the past
What did they find?
• Fluctuations of
atmospheric carbon
dioxide
• Time scale is in the
millions of years
• They think that these
changes rival the much
quicker changes being
caused today by
humans
Remember…
• The geochemical cycle could not function
without tectonics
• Tectonism and climate are intimately linked
Carbon dioxide has always
influenced global temperature
and will continue to do so
Therefore…
By better understanding where
we have come from, we can
better predict where we are
headed.