Geoscience Reference
In-Depth Information
great, they offer unique insights into the functioning of the natural
world. Therefore, science will converge on these ideas, if not now by one
scientist, then later by another. We've seen an example of this in
chapter
5,
where Jacques Joseph Ebelmen in 1845 accurately described the geo-
logical mechanisms controlling the concentrations of atmospheric oxy-
gen. These ideas were lost, and were independently discovered by Bob
Garrels, Ed Perry, and Dick Holland some 130 years later.
3
Thus, it is
possible that in the West, we may have rediscovered much of what Ver-
nadsky understood decades ago.
It is also possible that Vernadsky's ideas have come to us by other
indirect routes. In the 1950s and 1960s Russian scientists were miles
ahead of western scientists in understanding the role of microbes in the
chemistry of natural waters and sediments. I have not yet been able to
confirm it, but given Vernadsky's status in Russian science, he must
have been a strong influence on those postwar microbial ecologists. Al-
though much of this work was published in Russian and was not readily
available to western scientists, there were several key meetings between
Russian and western scientists in the 1970s and 1980s, and outcomes of
these encounters are presented in a number of influential volumes.
4
Per-
haps, at least in part, Vernadsky came to us by this route.
Anyway, we come back to Vernadsky's reflections, and we specifically
embrace the following question: How can we know anything about
the history of atmospheric oxygen? We need clues of course. Vernadsky
found clues in old sedimentary rocks that were once part of the ancient
seafloor. As it turns out, this was an excellent idea, but it would be fair
to ask how ancient mud holds clues to the levels of atmospheric oxygen
in the past. Let's have a look.
If you have ever walked barefoot through a seaside mudflat, you've
felt the mud squishing up through your toes, and perhaps saw bubbles
forming as your feet sank into the mud. The bubbles are methane,
formed by the same methanogens we met in
chapter 2.
In this case, they
are living of of organic matter in the mud. The presence of methano-
gens tells us something about the chemistry of the mud and the ecology
of the microbes living there. Maybe you caught a whiff of sulfide. This
is formed by another group of microbes, the same sulfate reducers we
met in previous chapters as they live of of organic debris. Another clue.
There is something hard between your toes. You reach down and extract
