Geology Reference
In-Depth Information
Find a candle and place it unlit in front of you with a box of matches at the ready.
Now take a match and light the candle, watching carefully as the flame leaps into
life.
See the flame burning easily and constantly, and contemplate the fact that what
you are seeing happens only because there is just the right amount of oxygen in
the air. Had there been just 10% more oxygen, the flame created when you lit the
match would have set you on fire, as well as the furniture in the room and then the
whole house. From there the fire would have spread far and wide without stop-
ping. Had you lived in South America, the fire would have spread over the whole
continent and thence to Central America and eventually to the whole of North
America. Anyone lighting just a single match on any island, or on any isolated
land mass would have created a similar unstoppable fiery holocaust. On the other
hand, with around 15% oxygen in the air, your brain would be unable to generate
enough energy to sustain your consciousness, and you would be unaware of the
candle, the flame or the fact that you are reading this text.
As you watch the candle flame, contemplate the miraculous constancy of oxygen
in the air that keeps the flame burning without sparking a global wildfire, and that
also keeps the flame of your consciousness alive. Become aware of your breath-
ing—take in great lungfuls of oxygen, and contemplate how its presence at just the
right concentration is the great gift of the astonishing relationships between rocks,
the living beings such as lichens, trees and mosses that weather them, oceanic al-
gae, bacteria in the ocean sediments, and that rare and life-giving chemical being,
phosphorus.
Phosphorus, one Gaia's most important chemical beings, is at the centre of the story.
Two key needs of living beings give it this centrality. It is absolutely indispensable for
making the energy-storing molecule ATP in all living beings, which is also needed for
growth and as a component of DNA. But there is another crucial fact: its scarcity. The
ultimate source of phosphorus is the weathering of rocks, and its ultimate destination,
once weathered, is the ocean sediments. There is no gaseous phosphorusbearing chem-
ical being that can transport phosphorus from sea to land, no chemical equivalent of the
gas dimethyl sulphide that so beautifully completes the sulphur cycle by raining sul-
phur onto forests, bog and fen; and so living beings are totally dependent on the cycling
of rocks for fresh supplies of the precious element—the gold of the biological world.
Contact between any acid and rocks is all that it takes to weather out their precious lodes
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