Originally posted by Essan
Forgive me if someone has already raised this, but can I just say one thing: San Andreas Fault
Either the fault isn't a plate boundary, and geologist are all ignorant idiots, or else any underground connection between Nevada and the Pacific is
constantly moving, opening, closing and geologically impossible ....
You lot really should study basic geology before coming up with ideas like this
The San Andreas fault certainly exists due to slip between the Pacific plate and the North American plate and forms part of those two plates'
boundary in the region, even though it does not form the entire boundary. There are many other fault lines as you know but San Andreas is considered
the primary one. So, no real arguments there.
However, movement along the San Andreas fault is directly related to the rate of movement between the two plates that created it, and as the Pacific
Plate is moving NW (relative to the Nth American plate) at an averaged rate of around 45mm per year (ie just under two inches), it means that in a
century this slip rate results in a displacement of 4500mm, which for those who don't use metrics is about 10.5 feet.
Anyone reading this can confirm this info from various sources.
Ten and a half feet in a hundred years...Okay, so while the plates are from a geological standpoint "constantly moving" (at under two inches per
year on average as I have said), your suggestion that the alleged subterranean passages are also constantly "opening, closing and geologically
impossible" is one I cannot agree with, because your statement seeks to imply that the movement along this line is such that passages would open then
close again so rapidly that no passages could exist for long enough to have been of use to humans during the last (say) fifty years. Any such passage
that is large enough to admit the passing of a large submarine is not going to suddenly and completely close. Or, to be fair, if it did, then the
resultant surface effects would have to be on the same scale, meaning a slip of such a magnitude that devastation along or near the line would
approach totality. There has not been such a degree of movement along this fault line in the past century that would correlate with a sudden, total
closure of such a passage: ditto the opening of a new one. One of the "advantages" of the San Andreas fault and the others in the region is that
they do unlock and move quite regularly, in small increments. As we all know there are hundreds of micro quakes per day in that region, which would
make using such (alleged) passages far more viable a proposition from a point of view of safety than if the plates basically "locked" then released
at rather long intervals. Though not totally connected to this situation, a section of the Juan Fuca plate is of growing concern because it is locked
and hasn't moved much since Jan 26 1700, the last time it "unlocked" -- and unleashed a mag 9+ quake and a huge tsunami. It's of concern because
the recurrence interval for such events in
that plate's troublesome region is around 300 years.
But I digress. My apologies...Back to the existence of passages. If they exist, and allowing for the slip between the two plates in question, it is
possible that any such passages only opened during the last (say) few thousand years; it is also possible that they will completely close again in an
equally relatively short period of time and either others (possibly not navigable) will open or none will exist at all of any significant size. But to
assert they are geologically impossible? I'm sorry, I cannot agree.
I do agree, however, that a partial closure or major disturbance along the fault line could cause such changes to a passage that it would require a
lot of extremely difficult engineering work to re-open it. Even a relative minor disturbance could also be catastrophic for any submarine that
happened to be within it at the time.
[edit on 11-9-2007 by JustMike]