Re: Plate techtonics and asteroid hits

Florian <first_name@xxxxxxxxxxxxx> wrote:
Jim Willemin <jim***willemin@hot***mail.com> wrote:

first_name@xxxxxxxxxxxxx (Florian) wrote in
news:1i2jtrr.1d9yhc319o12yqN%first_name@xxxxxxxxxxxxx:

David Iain Greig <dgreig@xxxxxxxxxxxx> wrote:

One possible answer would be crustal buckling due to expansion, which
could well have pushed oceanic crust upwards.

That is one possibility.

But obduction also occurs if oceanic floor is pushed over continental
crust by a plume. The papuan ultrabasic belt is good example. See
Fig7, Kugler "Subduction and Overthrusting"
http://www.lulu.com/content/421591


Maxlow clais a constant
earth radius to 1.5Bya, but allows some folding may have occurred.

I just posted an issue in another thread - a planet of 1700km radius
has an escape velocity so low it could not retain an atmosphere.
So much for early life...

Except you failed to calculate the correct escape velocity.
So much for ... ;-)


yes but - the moon has an escape velocity of about 2.4 km/sec; a dwarf
planet with a 1700 km radius and mean density of 5.5 has an escape
velocity of 3 km/sec; Mars has an escape velocity of about 5 km/sec.
Thus the atmospheric pressure of such a hypothetical dwarf planet would
be much closer to that of the Moon (i.e nil) than Mars (roughly 1% of
earth's atmospheric pressure). While David may have misplaced a decimal
point, the correction makes very little difference in his argument - a
small early Earth ain't gots no atmosphere, and we KNOW that it in fact
did.

Titan has an escape velocity about 2.6 km/s and a dense atmosphere. It
is more complicated than you think.

Yes, and a temperature of 90K. What does that do to the kinetic energy
of the gases in Titan's atmosphere?

--D.

.

Relevant Pages

  • Re: Plate techtonics and asteroid hits
    ... earth radius to 1.5Bya, but allows some folding may have occurred. ... I just posted an issue in another thread - a planet of 1700km radius ... has an escape velocity so low it could not retain an atmosphere. ... Except you failed to calculate the correct escape velocity. ...
    (talk.origins)
  • Re: "The Scarcity of Life Bearing Planets"
    ... acquire a thermal velocity greater than the planet's escape velocity. ... must occur at an altitude at which the atmosphere is sufficiently thin so ...
    (sci.physics)
  • Re: Minimum gravity for breathable planet atmosphere
    ... It's not so much a matter of gees as it is of escape velocity, ... thickness of atmosphere is not only dependent on escape speed - Venus ... but liquid water temperature and dense breathable atmosphere ...
    (rec.arts.sf.science)
  • Re: Star formation
    ... The Earth massive as it is, is too slight to have hydrogen in the ... atmosphere. ... just about, the escape velocity. ... how did stars form from ...
    (uk.sci.astronomy)
  • Re: Plate techtonics and asteroid hits
    ... well have pushed oceanic crust upwards. ... But obduction also occurs if oceanic floor is pushed over continental ... earth radius to 1.5Bya, but allows some folding may have occurred. ... Except you failed to calculate the correct escape velocity. ...
    (talk.origins)