2010 update: See follow-on Part II here ]
If the 8.8 magnitude Chilean quake may have shortened days by an infenitisimal amount late last month, it highlights the lesser-know fact that the earth wobbles on it axis, and that mass plate-tectonic movements are the result as well as the cause of earth tremors along plate boundaries below (may need to install Google Earth plug-in as indicated).
[Footnote: here is the original link for the original 10 Jul 2005 Keyhole BBS by Alan Jones, one of the earliest in Google Earth I recall, and there's no snapshot of it on Wayback Machine except a re-route somewhere else:
http://bbs.keyhole.com/ubb/showthreaded.php?Number=161180&page=315]
So what drives these earth movements, and the resulting tremors? Forty years after Vine and Matthews at Cambridge University worked out seafloor spreading in the Indian Ocean, the iSIMM Project (Cambridge and Liverpool universities, Schlumberger and Badleys) concluded that the push of ocean ridges is more important in driving plates than the pull of continental masses. This is important in re-focussing on oceanic plates. Magnetic reversals depict the spread of ocean ridges, but what happens when polarity does reverse, or is there a record of what happens at reversal? The recent focus on catastrophism helps us see that geologic time alternated long quiescent periods and short-lived catastrophies.
Meteorite impacts, earthquakes and tsunamis have lots of press coverage. But magnetic reversals don't, because there is such a poor record of it. Onshore it has been destroyed by erosion and other geologic events. The same goes in accessible offshore coastal and island areas. Only inaccessible abyssal plains maintain that record, which can only be studied indirectly as mentioned above. The British Geological Survey has a page on the topic, reassuring us that we are not near a polarity flip. But the geologic record is not regular as mentioned above, neither is the climatic record as recent events show.
If the 8.8 magnitude Chilean quake may have shortened days by an infenitisimal amount late last month, it highlights the lesser-know fact that the earth wobbles on it axis, and that mass plate-tectonic movements are the result as well as the cause of earth tremors along plate boundaries below (may need to install Google Earth plug-in as indicated).
http://bbs.keyhole.com/ubb/showthreaded.php?Number=161180&page=315]
So what drives these earth movements, and the resulting tremors? Forty years after Vine and Matthews at Cambridge University worked out seafloor spreading in the Indian Ocean, the iSIMM Project (Cambridge and Liverpool universities, Schlumberger and Badleys) concluded that the push of ocean ridges is more important in driving plates than the pull of continental masses. This is important in re-focussing on oceanic plates. Magnetic reversals depict the spread of ocean ridges, but what happens when polarity does reverse, or is there a record of what happens at reversal? The recent focus on catastrophism helps us see that geologic time alternated long quiescent periods and short-lived catastrophies.
Meteorite impacts, earthquakes and tsunamis have lots of press coverage. But magnetic reversals don't, because there is such a poor record of it. Onshore it has been destroyed by erosion and other geologic events. The same goes in accessible offshore coastal and island areas. Only inaccessible abyssal plains maintain that record, which can only be studied indirectly as mentioned above. The British Geological Survey has a page on the topic, reassuring us that we are not near a polarity flip. But the geologic record is not regular as mentioned above, neither is the climatic record as recent events show.
I wonder if the current climate change results from approaching a magnetic reversal, as suggested once by NY Times and illustrated below from Los Alamos Labs? After all we do not know how that happens in detail, at the historic rather than geologic scale!
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