Geology Reference
In-Depth Information
calcium silicate rocks and from sedimentary rocks replete with organic carbon. This is
his new feedback. If oxygen in the air increases significantly, fires rage everywhere as
the vegetation on the vast land surfaces of the planet burns, leaving huge swathes of
country with severely reduced plant life. Fewer land plants weather less phosphorus out
of the rocks, and the whole biosphere suffers from phosphorus starvation. Photosynthes-
is is severely reduced in the phosphorus-poor world, and so the burial of organic car-
bon diminishes on land and in the oceans. As a result, oxygen levels in the atmosphere
plummet as oxygen-hungry chemical beings such as carbon, iron and sulphur gobble up
their highly reactive quarry. But now, with less oxygen in the air, the danger of fire re-
cedes and the land plants grow back vigorously, releasing phosphorus once again as their
roots probe, crack and dissolve the rocks in their compulsive search for nutrients. The
newly liberated phosphorus stimulates photosynthesis on land and in the oceans, and the
world's green beings increase the oxygen content of the air as more of their carbon-rich
bodies are buried in the murky sediments. The atmosphere once again teems with oxy-
gen, and the great self-regulating dance comes full circle as fires once again rage over
the continents.
We've now explored three major negative feedbacks that may have regulated oxygen
over the last 300 million years or so. Each is a Gaian journey, and all are linked, as
shown in
Figure 39
. Spend some time tracing the three journeys in this diagram until
you are familiar with how each one works to regulate the amount of oxygen in the air.
If you find it helpful, refer back to
Figure 8
to remind yourself of what the two kinds
of arrow mean (a solid arrow indicates a direct relationship between two components,
and a dashed arrow an inverse relationship). Once you have a good cognitive grasp of
Figure 39
as a 'systems diagram', you are ready to experience its deeper significance
by shifting your attention from the cognitive to the experiential mode of awareness. The
first thing to do is to transform the systems diagram into a map of oxygen regulation that
we will use for the 'journeys' below.
