ccs013@castor.ucdavis.edu (Jason) (05/13/89)
In article <6101@nfs4.rl.ac.uk> kgd@inf.rl.ac.uk (Keith Dancey) writes: >>Sun for months or years, and causing mass extinctions of life -- including, >>many believe, the dinosaurs. >My understanding is that the demise of the dinosaurs extended over a period >of order of magnitude of a thousand years. ...etc.... Please correct me if I am wrong, but is this one of the theories (proofs) behind the "asteroid theory" of the extinction of the dinosaurs ?: Layers of Iridium were found deep into the earth's crust ( i.e. in the layers of the Grand Canyon). Now, being that Iridium is rare on earth but found to be relatively more bountiful in asteroids and meteors, it is suggested that the layer of this element was put on our planet by an extremely large (or as previously mentioned a few extremely large) asteroid(s) which hit earth and caused the clouds of dust ...etc., which eventually killed off the dinosaurs. This dust, if the theory is accurate, was filled with Iridium and when settled created a solid layer over years of rain, erosion ...etc... Is this a widely accepted view? What are the opposing ideas? ___ ___ __ ___ )___ __________________________________ ( | '__| (__ / / / / | II Corinthians 10:17 | \ | (__)\ __) /__/ / / +--------------------------------+ \_| Internet: jygabler@ucdavis |"Why me?!", Garion said. "Do we | | BITNET: jygabler@ucdavis | we have to go thru that again",| | UUCP: ucdavis!jygabler | the dry voice retorted. |
saouter@irisa.UUCP (saouter yannick) (05/17/89)
In article <4300@ucdavis.ucdavis.edu>, ccs013@castor.ucdavis.edu (Jason) writes: > > In article <6101@nfs4.rl.ac.uk> kgd@inf.rl.ac.uk (Keith Dancey) writes: > >>Sun for months or years, and causing mass extinctions of life -- including, > >>many believe, the dinosaurs. > >My understanding is that the demise of the dinosaurs extended over a period > >of order of magnitude of a thousand years. > > ...etc.... > > Please correct me if I am wrong, but is this one of the theories (proofs) behind > the "asteroid theory" of the extinction of the dinosaurs ?: > > Layers of Iridium were found deep into the earth's crust ( i.e. in the layers > of the Grand Canyon). Now, being that Iridium is rare on earth but found > to be relatively more bountiful in asteroids and meteors, it is suggested > that the layer of this element was put on our planet by an extremely large > (or as previously mentioned a few extremely large) asteroid(s) which hit > earth and caused the clouds of dust ...etc., which eventually killed off the > dinosaurs. This dust, if the theory is accurate, was filled with Iridium and > when settled created a solid layer over years of rain, erosion ...etc... > I have heard about it,too. Dinosaurs might have been killed, in this theory for few reasons : - Herbivorous ones starved to death as the big forests burned with the energy developped with the hit,and as the others plants died because of the Sun to be darkened by the clouds. Then carnivorous ones starved to death,too. - They might have choked with the carbonic anhydrid developped by the fires. - The fishes died with the disappearance of the plancton, due to the first reason. - They could have died with the chill of the Earth due to the clouds. - Moreover Iridium is poisonous. However, all the dinosaurs would have been to disappear, that is to say, even turtles and iguanes. And when all the creatures to be killed, then a great time would be needed to repair this catastrophe (the first oxygen producers appears in the sea 2 000 000 000 years ago, and this hit occurs 65 000 000 years ago). saouter@sigle.irisa.fr
ethan@ut-emx.UUCP (Ethan Tecumseh Vishniac) (05/17/89)
In article <1212@irisa.UUCP>, saouter@irisa.UUCP (saouter yannick) writes: > > - Moreover Iridium is poisonous. In sufficient quantities it is. In this case the amounts are probably not biologically significant. > > However, all the dinosaurs would have been to disappear, that is to say, even > turtles and iguanes. And when all the creatures to be killed, then a great time > would be needed to repair this catastrophe (the first oxygen producers appears > in the sea 2 000 000 000 years ago, and this hit occurs 65 000 000 years ago). Actually, turtles and iguanas are not dinosaurs, and they did not disappear at the end of the Mesozoic. My understanding is that the extinction of terrestrial life can be summed up with the statement that everything weighing more than 20kg died off. However, the extinction was more sweeping than this and many tiny (and, of course, large) oceanic organisms died as well. It is also true that this is not the most dramatic mass extinction in the fossil record. -- I'm not afraid of dying Ethan Vishniac, Dept of Astronomy, Univ. of Texas I just don't want to be {charm,ut-sally,emx,noao}!utastro!ethan there when it happens. (arpanet) ethan@astro.AS.UTEXAS.EDU - Woody Allen (bitnet) ethan%astro.as.utexas.edu@CUNYVM.CUNY.EDU These must be my opinions. Who else would bother?
saouter@irisa.UUCP (saouter yannick) (05/18/89)
In article <13111@ut-emx.UUCP>, ethan@ut-emx.UUCP (Ethan Tecumseh Vishniac) writes: > It is also true that this is not the most dramatic mass extinction in the > fossil record. Such collisions occurs about every 50 000 000 years and I've heard that others species have disappeared as suddenly as the dinosaurs did, so earlier collisions might be the cause for that, too. Does anyone knows others example of strange disappearance ?
ncramer@bbn.com (Nichael Cramer) (05/19/89)
In article <1216@irisa.UUCP> saouter@irisa.UUCP (saouter yannick) writes: >In article <13111@ut-emx.UUCP>, ethan@ut-emx.UUCP (Ethan Tecumseh Vishniac) writes: >> It is also true that this is not the most dramatic mass extinction in the >> fossil record. > >Such collisions occurs about every 50 000 000 years and I've heard that others >species have disappeared as suddenly as the dinosaurs did, so earlier >collisions might be the cause for that, too. > >Does anyone knows others example of strange disappearance ? I don't remember the numbers (in species/yr) offhand, but I've read arguements (e.g. by S J Gould) that claim that we are *now* in the midst of the one of greatest (if not in fact _the_ greatest) of mass extinctions of all time. If I recall right, the numbers work out to ~1 species/100,000 increase in human population.
cramer@optilink.UUCP (Clayton Cramer) (05/19/89)
In article <40171@bbn.COM>, ncramer@bbn.com (Nichael Cramer) writes: > In article <1216@irisa.UUCP> saouter@irisa.UUCP (saouter yannick) writes: > >In article <13111@ut-emx.UUCP>, ethan@ut-emx.UUCP (Ethan Tecumseh Vishniac) writes: # ## It is also true that this is not the most dramatic mass extinction in the # ## fossil record. # # # #Such collisions occurs about every 50 000 000 years and I've heard that others # #species have disappeared as suddenly as the dinosaurs did, so earlier # #collisions might be the cause for that, too. # # # #Does anyone knows others example of strange disappearance ? # # I don't remember the numbers (in species/yr) offhand, but I've read # arguements (e.g. by S J Gould) that claim that we are *now* in the midst of # the one of greatest (if not in fact _the_ greatest) of mass extinctions of # all time. # # If I recall right, the numbers work out to ~1 species/100,000 increase in # human population. I've read that the current rate of extinction is about 15 species/century -- which is clearly far lower than ~1 species/100,000 increase in human population. Of course, we still don't know all the species on the planet, and I very much doubt that we notice many that come and go anyway. One of the Paleozoic extinctions involved 99% of all species then alive being killed off. But over what time scale? -- Clayton E. Cramer {pyramid,pixar,tekbspa}!optilink!cramer Assault rifle possession is a victimless crime. ---------------------------------------------------------------------------- Disclaimer? You must be kidding! No company would hold opinions like mine!
ncramer@bbn.com (Nichael Cramer) (05/20/89)
In article <1493@optilink.UUCP> cramer@optilink.UUCP (Clayton Cramer) writes: >In article <40171@bbn.COM>, ncramer@bbn.com (Nichael Cramer) writes: ># #Does anyone knows others example of strange disappearance ? ># ># I don't remember the numbers (in species/yr) offhand, but I've read ># arguements (e.g. by S J Gould) that claim that we are *now* in the midst of ># the one of greatest (if not in fact _the_ greatest) of mass extinctions of ># all time. ># ># If I recall right, the numbers work out to ~1 species/100,000 increase in ># human population. > >I've read that the current rate of extinction is about 15 species/century -- >which is clearly far lower than ~1 species/100,000 increase in human >population. CLAYTON I checked my source for the above after I got home last night, and he was claiming a loss of 10,000 species/yr but he didn't cite any sources. This does sound very high. But on the other hand, it seems equally difficult to believe we've only lost 13-14 species in all of the 20th century. (I've also seen figures in the 1-10/yr range.) Do you (or anyone else) have specific references for what the actual value of this rate is? Thanks NICHAEL
c60a-1hb@web-2c.berkeley.edu (The Daimyo) (05/21/89)
In article <40227@bbn.COM> ncramer@labs-n.bbn.com (Nichael Cramer) writes: >In article <1493@optilink.UUCP> cramer@optilink.UUCP (Clayton Cramer) writes: >>In article <40171@bbn.COM>, ncramer@bbn.com (Nichael Cramer) writes: >># #Does anyone knows others example of strange disappearance ? >># >># I don't remember the numbers (in species/yr) offhand, but I've read >># arguements (e.g. by S J Gould) that claim that we are *now* in the midst of >># the one of greatest (if not in fact _the_ greatest) of mass extinctions of >># all time. >># >># If I recall right, the numbers work out to ~1 species/100,000 increase in >># human population. >> >>I've read that the current rate of extinction is about 15 species/century -- >>which is clearly far lower than ~1 species/100,000 increase in human >>population. > >I checked my source for the above after I got home last night, and he was >claiming a loss of 10,000 species/yr but he didn't cite any sources. This >does sound very high. But on the other hand, it seems equally difficult to >believe we've only lost 13-14 species in all of the 20th century. (I've >also seen figures in the 1-10/yr range.) > >Do you (or anyone else) have specific references for what the actual value >of this rate is? There is a theory that was proposed by the late Dr. Luis Alvarez and Dr. Richard Muller on the topic of mass extinctions. In the geological record there is evidence of mass extinctions at regular intervals thru out earth's history. These extinctions occurred (don't quote me on this, I'm doing it by memory) I think every 300 million years, at a almost frightening regular interval. The extinctions of the dinosaurs was one and about 300 million years later, the extinction of pre-historic mammals another. Before then, the geological record shows extinction after extinction at roughly 300 million year intervals. The theory proposed states that our Sun may have a companion star. For years, astronomers and astrophysicists had assumed that our sun was different from the rest of the stars in the universe in that it was not part of a binary system. This theory states that our sun may have a companion star that at its closest point to the earth (it still looks like a normal star from a telescope at its closest point) crosses thru the comet belt with enough gravitational disturbance to knock about a 300,000 (I think) or so comets out of the cloud into the inner solar system. The odds worked out that one would hit the earth. For more information consult the book "Nemesis: the Death Star" by Dr. Richard Muller. Extinctions on the smaller scale, aka caused by man, continue on this planet in several key places : 1South America 2Africa ...etc. the list goes on. The destruction of the Amazon to make farm land is by far one of the fastest destruction of both animal and plant species in the world. The uniqueness of the Amazon enviroment is such that the plant and animal species that live there cannot be found anywhere in the world. In fact in a recent shuttle picture, the Amazon area was nothing but smoke as the forest is being burned down. In Africa, the desert grows. Man's own folly is to blame for that disaster as well. The interference of well meaning foreigners to help the people has led to the destruction of thousands of acres of land. The digging of wells in areas with lush vegetation was not only not productive but is the direct cause of the growing deserts. Herd animals, wild life, and man flock for miles around just to get to this plentiful source of water. In their rampage, the vegetation is stripped, trees are cut down and tender vegetation trampled. What's left in a matter of months is a wasteland, a addition to already expanding desert. Destruction of trees has had a direct impact on the ecosystem in Africa. In areas where there are trees it rains. In areas where there were trees not long ago, it will rain for a few years more. In areas where trees were cut down a long time ago, there is desert. The ecosystem is destroyed the moment the native habitat is destroyed, and the weather adjusts accordingly. The famine in Africa will continue, probably and sadly, forever, unless the the ecosystem is restored. In the United States, coal burning plants have destroyed forest land on the Eastern Sea Board and all over Eastern Canada. Lakes have so much acid content in them that the water is poisonous. In Europe, a similar situation exists in Germany, where a huge portion of forest land has been labeled as doomed from the acid rain. In Chicago, the marble off the buildings is being dissolved by the acid rain, of which sulfuric acid is a member. When the habitats go, so do the life forms that live within them. Hopefully something can be done to stop this. Soon I hope. Albert Sze-Wei Wang ------------------------------ The Daimyo | c60a-1hb@widow.berkeley.edu | ------------------------------
cramer@optilink.UUCP (Clayton Cramer) (05/22/89)
In article <40227@bbn.COM>, ncramer@bbn.com (Nichael Cramer) writes: > In article <1493@optilink.UUCP> cramer@optilink.UUCP (Clayton Cramer) writes: > >In article <40171@bbn.COM>, ncramer@bbn.com (Nichael Cramer) writes: # ## #Does anyone knows others example of strange disappearance ? # ## # ## I don't remember the numbers (in species/yr) offhand, but I've read # ## arguements (e.g. by S J Gould) that claim that we are *now* in the midst of # ## the one of greatest (if not in fact _the_ greatest) of mass extinctions of # ## all time. # ## # ## If I recall right, the numbers work out to ~1 species/100,000 increase in # ## human population. # # # #I've read that the current rate of extinction is about 15 species/century -- # #which is clearly far lower than ~1 species/100,000 increase in human # #population. # # CLAYTON # # I checked my source for the above after I got home last night, and he was # claiming a loss of 10,000 species/yr but he didn't cite any sources. This # does sound very high. But on the other hand, it seems equally difficult to # believe we've only lost 13-14 species in all of the 20th century. (I've # also seen figures in the 1-10/yr range.) # # Do you (or anyone else) have specific references for what the actual value # of this rate is? # # Thanks # NICHAEL Nope. I sure would like to see some numbers. Now that I think about it, I think what I had read (in a newspaper, so probably false) was that over the time man has been on the planet, there has been an average loss of 15 species/century -- not the same as the rate for this century. -- Clayton E. Cramer {pyramid,pixar,tekbspa}!optilink!cramer Assault rifle possession is a victimless crime. ---------------------------------------------------------------------------- Disclaimer? You must be kidding! No company would hold opinions like mine!