From: Mike Lorrey (mlorrey@datamann.com)
Date: Wed Jun 27 2001 - 07:52:21 MDT
Doug Jones wrote:
>
> Mike Lorrey wrote:
> >
> > Significant volcanic activity would have resulted from a change in the
> > orbit of the moon caused by the influence of a number of close flybys
> > over several million years of the object that wound up colliding at 65
> > million years. For example, an impact or flyby of the moon which would
> > have caused it to either come closer to earth (increasing tidal stress
> > but decreasing tortional stress on earth's rotational velocity) on a
> > faster orbit or else move away from earth into a slower orbit (thus
> > decreasing tidal stress but increasing tortional stress on earth's
> > rotational velocity) would have significantly affected tectonic forces
> > during that period. Also a change in the moon's angle of inclination
> > would have caused similar release of tectonic forces.
>
> Mike, any object large enough to significantly perturb the moon's orbit
> would be large enough to pasteurize the planet on impact. Back of the
> envelope calculation:
>
> Earth: 5.97 E24 kg
> Moon: 7.35 E22 kg
> Juno: 2 E19 kg
> (1/3675 of moon- Any smaller object is not credible for causing orbital
> changes to the moon.)
>
> Impact velocity: 20 km/s (minimum possible is 11.2)
>
> Impact energy: 4E27 joules
>
> Chixulub is estimated at 100 million MT, a mere 1E23 J, 40,000 times
> less energy than this impactor. I think you're kinda talking off the
> top of your head about orbital perterbation of the moon leading to tidal
> perterbation of the earth...
Actually, not. You are forgetting repetition. How many times did the
object fly by the earth and moon? We don't know. The evidence stated
earlier indicates the possibility of a 4 million year period. If the
object was a Near Earth Asteroid, that gives the possibility of an
average of 4 million near misses to perturb the moon's orbit.
To create volcanic/tectonic problems, all that is required is for the
moon's orbit to change faster than the earth's tectonics can adjust.
Sustained vulcanism in terrestrial bodies after the primordial period of
cooling in our solar system can be shown to be exclusively caused by
tidal forces:
Venus's volcanos : caused by solar tides (which are 4 times greater than
the sun's influence on earth, which is significant enough to cause the
moon to crab out of its tidally locked rotational rate) and Venus' slow
retrograde 240 earth day long day.
Earth's volcanos : caused by the moon
Io's volcanos : caused by jupiter
Ice volcanos on icy moons: caused by the tidal influence of Jupiter or
Saturn (whichever they orbit).
Note that Mars, which has no source of tidal influence, has a cooled
core and is now volcanically dead. The earth's moon, which a) has no
significant heavy metal content, b) is made up almost exclusively of
crustal material blasted off of primordial earth by a planetesimal, and
c) is of too small a diameter for earth to exert significant enough
tortional forces to cause a differential in rotational velocity between
its geological layers (as occurs between our core and mantle layers),
and d) does not rotate with respect to the earth, so any tortional
forces exerted by earth's tidal influence do not do any actual work.
Additionally, as I said, the Yucatan impactor could merely have been a
calved fragment of a larger body that broke up either from impact with
the moon, or from the moon and earths gravity exerting too much repeated
stress upon its structure.
This archive was generated by hypermail 2.1.5 : Sat Nov 02 2002 - 08:08:18 MST