Xref: utzoo sci.bio:857 sci.research:317 Path: utzoo!utgpu!water!watmath!clyde!rutgers!im4u!ut-sally!utah-cs!utah-gr!stride!tahoe!malc From: malc@tahoe.unr.edu (Malcolm L. Carlock) Newsgroups: sci.bio,sci.research Subject: Thoughts on Life, Plate Tectonics and the Greenhouse Effect Keywords: life, plate tectonics, greenhouse, C02, oceans Message-ID: <952@tahoe.unr.edu> Date: 29 Jan 88 22:34:44 GMT Organization: Univ. of Nev., Reno-Mathematics Lines: 108 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. ------- 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. ----- 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 ------------------------------------------------------------------------- "Where are we?" "The foothills." "The foothills of what?" "The foothills of the headlands." ------------------------------------------------------------------------- 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" . . .