Geology Reference
In-Depth Information
life can accelerate granite and basalt weathering as much as 1,000 times relative to a
bare, lifeless surface. If you are a calcium ion in tropical rain forest granite, you might
wait only one year rather than a thousand to begin your sea-bound marriage with your
two bicarbonate ion partners.
But there is a great danger here: the weathering of granite and basalt could send the
planet into a permanently frozen ice-ball state if too much carbon dioxide from the at-
mosphere drains away as chalk to the bottom of the ocean. So why hasn't this happened?
Gaia as a whole prevents this icy fate thanks to the tectonic movements of her crust,
driven by the great powers residing in the deep interior of her rocky body. Here there is
a great deal of radioactive material left over from the supernova explosion that gave rise
to the elements of our planet. When these radioactive materials decay, a vast amount of
heat passes into the surrounding semi-molten basalt rock, which rises in great plumes
like so much hot air until it reaches the mountainous sub-sea spines, some of which run
north-south in the middle of the Atlantic and Pacific oceans. Here the newly emerged
basalt cools and spreads away from the ridges as new rock wells up behind it. All the
while chalky bodies settle on these great moving plates of sea floor basalt, as they jour-
ney slowly but surely towards a continent. In many places, the bodies of the silica-
shelled beings—the diatoms and radiolarians—settle on top of the chalky corpses, pro-
tecting them from the chalk-dissolving powers of the acidic, high-pressure deep ocean
waters. The continents themselves are mere passengers on these huge moving slabs of
basalt, for their granitic foundations are lighter than the underlying plates that carry them
about the world.
When it finally meets a continental edge, the sea floor basalt gently bends beneath
it, carrying some of the overlying calcium carbonate and silica with it into the Earth's
depths, much as a great diving whale carries down the barnacles which pepper its
thick blubbery skin. As the calcium carbonate, silica and basalt plunge into the abyssal
deeps, they melt under temperatures and pressures powerful enough to break the bonds
between calcium and carbon in the chalk, and between silicon and oxygen in the silica.
And then two extraordinary transformations happen. The first is the release of carbon
dioxide that rises upwards beneath the edge of the continent, breaking through at last in
spectacular volcanic eruptions that return vast amounts of carbon dioxide to the atmo-
sphere whilst sending treaclelike strands of red molten lava coursing down steep volcan-
ic slopes. The second is the re-creation of granite underneath the continental margins,
as the calcium, silicon and oxygen along with many other chemical beings reconfigure
themselves into the new rocky foundations of the continents, making up for granite lost
from weathering the land surfaces. What perfect recycling of both granite and carbon
dioxide! If only our industries could recycle their products so beautifully
(Figure 22)
.
