Geology Reference
In-Depth Information
In the cool surface waters of the sea you are sucked into the embrace of a marine
alga protected by tiny wheels of solid chalk. You soon become part of one of these
wheels.
The alga lives its short life and dies. You slowly sink towards the ocean deeps,
cherishing the memories of your brief journey in the air above.
Sinking, sinking into the depths, you leave behind the upper sunlit reaches of the
sea and eventually settle into the chalky sediments in the darkness at the bottom
of the ocean.
Slowly you feel the weight of new chalky deposits accumulating above you, and
slowly, ever so slowly, the pressure packs you closer and closer together into lime-
stone. The great journey is complete, and now you must wait for another 300 mil-
lion years before you once again explode into the atmosphere through a volcano.
Carbon in the Short Term
People often react to the story of carbon's great chalk journey by asking whether the car-
bon dioxide we are adding to the atmosphere through our manic burning of fossil fuels
could be rapidly removed in this way. Sadly, the process is too slow to make any differ-
ence over the next century or so. It may take a carbon atom emitted into the atmosphere
in the diesel exhaust of the train that I'm riding on today about half a million to a mil-
lion years to find itself in chalk or limestone at the bottom of the ocean—far too long to
make any difference in preventing climate change.
So what about carbon dioxide's journeys in the much shorter term? Carbon travels
through Gaia through a set of nested loops, each operating at its own particular pace. A
carbon atom can get swept into any of these journeys, depending on where it happens to
be at crucial moments, and it is very likely that virtually all the carbon atoms on the plan-
et have experienced what it is like to pass through each of them. Amongst the shortest
of carbon journeys are those that take as little as a year to complete. The global effect of
this cycle can be seen in the now famous data collected from the Mauna Loa observat-
ory in Hawaii
(Figure 25)
—the first warning of our serious impact on Gaia's climate.
