malc@tahoe.unr.edu (Malcolm L. Carlock) (01/30/88)
The following text began as an emailed reply to a friend of mine, expanding
on a theory which attributes the presence of a plate tectonics system on Earth
to the presence of life here (as opposed to apparently lifeless Mars and Venus,
which do not seem to posess such systems). However, when I was done, I realized
I'd inserted some of my own feelings on the direction the biosphere is heading
and decided I'd like to let some other people in on what I was thinking.
So here is my essay/editorial/maundering. Go ahead and flame me, but remember
that flaming increases the C02 content in the atmosphere ;-)
By the way, I would greatly appreciate any responses from people who know
more about the theory discussed here, or who can add (or subtract) from
the somewhat chilling scenario that appears lower down in this article.
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Fred (not his real name),
I found "that" theory on plate tectonics in a Time/Life book of mine called
"The Solar System". The gist of it is thus:
Diatom-like creatures in Earth's early oceans used carbon dioxide as part of
the process of building their skeletons. Over time, a large portion of the
C02 in Earth's atmosphere was locked up in the skeletons of these creatures
(which in turn were converted to limestone), reducing dramatically the C02
content in Earth's atmosphere and averting a greenhouse effect (until man
came along, anyway . . . ;-|
If the "locking up" of the C02 had not occurred, says the theory, the oceans
would probably have evaporated long ago due to the heat buildup from a
greenhouse effect.
The role of the oceans in all this is the cooling of the crustal plates such
that they are heavy enough to sink back down into the mantle at the
subduction zones (the weight of all that water probably plays a role as well).
Thus, so the theory says, early life created a high-oxygen atmosphere
amenable to stable temperatures and permanent (so far) oceans; the oceans
keep the system of plate tectonics going, and the planet is thus still
geologically "alive".
Among other things, this means that the heat of Earth's core is conserved to
some extent, since enormous vent volcanoes like Olympus Mons on Mars can't
develop. On Earth the "hot spots" upon which volcanoes form are always
"moving" relative to the crust (it's the crust that's actually moving, of
course), whereas on Mars and Venus, which seem to have no systems of plate
tectonics, a volcano can develop over a "hot spot" and sit there for millions
of years, spewing out noxious gases and the heat of the planet's core.
Heat-driven convection currents in the mantle are, after all, suspected to be
the driving force behind the movement of the continental plates. The longer
that heat is conserved, the longer (probably) our plate tectonics system can
continue to function.
If the theory is correct, then it looks as if the life/plate tectonics
combination has resulted in a stable, self-sustaining system.
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Speaking of noxious gases, the greenhouse effect, and the presence of man:
Not having enormous, regular sources of noxious gases on earth (until man),
thanks to the absence of these giant, permanent volcanoes, has probably also
helped life to flourish (stable environment).
If you are keeping up with the news, you will probably have seen an item or
two recently about the fact that the C02 content in Earth's atmosphere has
been rising incrementally, and that in the last 20 years or so the average
temperature of the Earth has _indeed_ risen by a degree or two. The predictions
from most scientific circles (and even the most respected government agencies)
on this subject are that we are _definitely_ going to see some tangible results
of the "greenhouse effect" during the next few decades, and right now there's
not much we can do about it, even if man quits producing today all the C02 he
is spewing out.
What effects do we see today? Well . . .
I read in today's paper (Reno Gazette-Journal, a Gannett affiliate) that the
US is for the most part cloudier than it was 20 and more years ago. More
water vapor in the atmosphere. Hmmmmm . . .
The re-appearance of a long-ago postponed oceanic evaporation, perhaps?
Damned scary, to think that man and his works might be capable not only of
poisoning the Earth's atmosphere and oceans, but ultimately of turning the
Earth into a corrosive, geologically dead hellhole like Venus.
Brrrrrrrr.
Worriedly,
Malcolm L. Carlock
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"Where are we?"
"The foothills."
"The foothills of what?"
"The foothills of the headlands."
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malc@tahoe.unr.edu.UUCP University of Nevada, Reno
P.S. I read several years ago that the biggest source of C02 in North
America, beside which all other sources pale to insignificance, is
flatulence from domestic livestock (especially cattle) !! (I will
try to find my source for this and post it at a later date.) I guess
the keeping of domestic livestock can be counted as one of the
"works of man" . . .g-rh@cca.CCA.COM (Richard Harter) (01/31/88)
In article <952@tahoe.unr.edu> malc@tahoe.unr.edu (Malcolm L. Carlock) writes: An interesting speculation, which I shan't repeat. You might check out the latest Scientific American, which has an article about why Earth, Mars, and Venus are the way they are. One point relevant to your theory is that life is not essential to the carbon dioxide recycling mechanism. Another is that Mars is too small for plate tectonics -- it cooled off too fast. There is strong evidence that early Mars started plate tectonics and then "froze". Is it true that Venus doesn't have plate tectonics? I don't know. >P.S. I read several years ago that the biggest source of C02 in North > America, beside which all other sources pale to insignificance, is > flatulence from domestic livestock (especially cattle) !! (I will > try to find my source for this and post it at a later date.) I guess > the keeping of domestic livestock can be counted as one of the > "works of man" . . . I believe that it is Methane, not Carbon Dioxide, that was referred to. -- In the fields of Hell where the grass grows high Are the graves of dreams allowed to die. Richard Harter, SMDS Inc.
glg@sfsup.UUCP (G.Gleason) (02/05/88)
In article <952@tahoe.unr.edu> malc@tahoe.UUCP writes: [ stuff deleted about plate-techtonics, climate shifs, C02, etc.] >The re-appearance of a long-ago postponed oceanic evaporation, perhaps? >Damned scary, to think that man and his works might be capable not only of >poisoning the Earth's atmosphere and oceans, but ultimately of turning the >Earth into a corrosive, geologically dead hellhole like Venus. >Brrrrrrrr. A scary thought indeed! You may get some replies that you are jumping to conclusions, and probably do not have much hard evidence for a coming catastrophy, but that is not the important point. The truth is that we are not able to understand the complex inter-relationships that keep the environment of our space-ship stable enough for the wheels of life to keep turning. You mention one definitly measurable global change that is a result of industrialization (as known so far). It is possible that this particular change can be coped with, but what other unseen long-term effects are occuring. It is in fact possible that the earth as a whole has already been killed. That is, that there is some effect not yet measured or understood which has the long term effect of a life-less planet. Maybe a number of effects coming together. Life, it seems, is some sort of happy accident, and as Keynes said "In the long-run, we're all dead." On the other hand, don't we have an obligation to use our best energies, to try to understand our environment well enough that we don't destroy it? Yes, in the long view, change is the only constant, and it is clear that life does cause long-term environment changes, and our current civilization may be no different. Is there more reason to fear the death of our species than death of our selves, or death of the planet? I don't pretend to know the answers to these questions, but isn't it time we stopped being so blind about it? I cannot help thinking that our planet and its inhabitents are at a crossroad, that this is a unique historical time when the planet is rapidly changing. Just for mental excercise try imagining the world in 1000 years, 1,000,000 years. There are just too many processes going on that are not sustainable, for it too look anything like today. Your example of the increase of CO2 from burning hydrocarbons, is just one. Maybe we are helpless to control these processes, but if we do not at least try to understand what is happening we do not have a chance to control them. Evolution has proceeded blindly for billions of years, should we let it continue on its blind search? Should we get involved in the process? Can we help getting involved? I don't know. Gerry Gleason