Naked Science Forum
Non Life Sciences => Geology, Palaeontology & Archaeology => Topic started by: Geezer on 01/07/2010 04:54:31
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If the continents were not eternally zipping around the planet and smashing into each other, would they ultimately erode to the point where the entire surface of our planet was under water?
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With the exception of "hot spot" created shield volcanoes (Olympus Mons on Mars), impact crater rims and polar ice caps, the short answer is "yes"
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Thank you Bass.
I seem to remember that the whole notion of continental drift is quite new (or, at least, it's not as old as me).
Was there a theory to explain why the continents would not erode if they were static, or was it never really considered?
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Was there a theory to explain why the continents would not erode if they were static, or was it never really considered?
That's a pretty good point and I'm a bit surprised, now that you've mentioned it, that geologists of the past didn't wonder about it too. I would guess that before plate tectonics, it was assumed that all volcanoes were due to hotspots, but arguing against that assumption is the non-random distribution of volcanoes. So with hindsight, it seems to me that the non-random distribution of volcanoes should have suggested that all volcanoes were not due to hotspots, and that another mechanism for causing them was in action.
Ain't hindsight a wonderful thing [:D]
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Continental Drift was not a settled theory when I was in undergraduate school and majoring in Geology. The new magnetic field reversals were just published and A. A. Meyerhoff was furiously publishing refutations of Continental drift as If he were the only geologist in the world. In one way, he was - one of the few who had yet to be converted. All of the professors WHO EXPRESSED AN OPINION usually would qualify their comments with "evidence suggest" or it is "evidence is becoming more and more convincing" yada, yada, yada.
Albert Wegener, a Danish weatherman was the first to publish his theory in modern times that they MIGHT have moved. He did this in 1912. Wegener was inspired by the
HOWEVER, the first person to suggest it was one of Geezer's childhood contemporaries in the mid 16th century. In 1596, Abraham Ortelius in his work Thesaurus Geographicus ... suggested that the Americas were "torn away from Europe and Africa ... by earthquakes and floods" and went on to say: "The vestiges of the rupture reveal themselves, if someone brings forward a map of the world and considers carefully the coasts of the three [continents]. WIKIPEDIA http://en.wikipedia.org/wiki/Continental_drift
By the time I got out of school in '71 Meyehoff was still publishing but not too many were listening anymore. Too much evidence had been accumulated.
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Hang about!
Are you saying everyone knew the continents would erode to the point of submersion, but they simply ignored it?
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Continental Drift was not a settled theory when I was in undergraduate school and majoring in Geology.
Thats because JimBob finished his undergrad sometime in the late Pleistocene. [;D] [;D] [;D]
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Continental Drift was not a settled theory when I was in undergraduate school and majoring in Geology.
Thats because JimBob finished his undergrad sometime in the late Pleistocene. [;D] [;D] [;D]
But I didn't just throw out the books because they were old. I kept them and an old ideas came around again. How else could I document my article on Wikipedia?????
[:P] [:P] [:P]
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Frethack:
Are you saying JimBob has a degree in Plasticine, or was his certificate made out of Plasticine?
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Humor him frethack, he is a sick old man who is just not aware that the web can be used to find the definition of Pleistocene.
And he is further debilitated by being born Scottish. All that oatmeal makes your brain cells stick together, impeding thought of any sort.
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oats, not just a healthy meal, but you can make beer out of it, fermentation, saved our soles and rather livened up ,our drinking water. the scots must of invented beer
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Thank you Bass.
I seem to remember that the whole notion of continental drift is quite new (or, at least, it's not as old as me).
Was there a theory to explain why the continents would not erode if they were static, or was it never really considered?
That's a great question. Why would mountains, earthquakes and volcanoes exist in a static world? One of the most confusing was the existence of marine fossils at the top of mountian ranges. A number of theories were put foward through the years, volcanoes being the work of the devil, the great flood, the "raisin" theory, asteroid impacts, etc.
The latest theory espoused before plate tectonics was geosynclines. According to this theory, great prisms of sediment would accumulate in ocean basins along the edge of continents. As sediments were deposited, their weight would downwarp the crust, pressing the lower crust into the mantle. Eventually the mantle would rebound, shoving the accumulated sediments upward into mountain ranges. This also handily explained why igneous and metamorphic rocks were found in the roots of mountain ranges- due to the immense heat and pressures that existed at the bottom of the geosyncline. The Gulf of Mexico was touted as a modern analogue of geosynclines.
Obviously, the geosyncline theory had serious flaws- not the least of which was the existence of thrust faults, large strike-slip faults (such as the San Andreas), the Pacific ring of fire, the exitense of mid-oceanic ridges, magnetic pole wander, and the limited age of oceanic sediments.
Of course, plate tectonics isn't perfect either. To date, we still don't have a completely satisfactory driving force to push (pull?) the continents? How does on shove relatively light oceanic crust deep into much more dense mantle? How do you explain the ages and positions of some mountains (Rockies, Andes)? Nonuniform magnetic stripes? Among other problems. At some point a new paradigm will emerge- one I'm sure will retain much of present plate tectonic theory.
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How does on shove relatively light oceanic crust deep into much more dense mantle?
From memory of a course 10 years ago, and a mate of mine who was doing a PhD in the general area:
The crust is basaltic and is the lightest fraction of the hot mantle upwelling at the mid ocean ridges. What is left is therefore denser than most of the mantle (at the same temperature), and makes up the bottom half of the lithosphere and moves with the crust.
At the mid ocean ridges the lithosphere is hot, so buoyant, but by the time it gets to a subduction zone it has cooled over 10s of millions of years, and now the crust+lithosphere is denser than the mantle so should sink into it even though the basaltic crust should float.
I guess some of the basaltic stuff will melt off the slab as it goes down increasing its density.
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oats, not just a healthy meal, but you can make beer out of it, fermentation, saved our soles and rather livened up ,our drinking water. the scots must of invented beer
Don't really know where this came from, but had to comment....
Unfortunately, I'm pretty sure it was the Ancient Egyptains who invented beer. Sorry! :-)
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So you're saying the Ancient Egytians came from Scotland then?
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must have been continental drift sometime along the way..ponders egyptian scots
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Well, they all wore kilts, didn't they?
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with the beer thing if you look at the last word in your encyclopedia Britannica, it might just come up with a word begining with z...lol and i cant remember the rest of it that is the name of the Egyptian beer