Re: Bronze age Argarics may have used up natural resources

On Tue, 20 Nov 2007 10:16:58 +1300, Eric Stevens
<eric.stevens@xxxxxxxxx> wrote:


3. If it was a large meteor of solid, to do a favor to you: a
chondrite (rock, not iron); we would have found the impact crater long
ago. Impact craters do get noted by mapping geologists down to 5m
size. A 5-10m meteor would hit a considerable hole, say 20-100m. It
cannot have been larger because the crater would be a tourist
attraction, and there is no such thing. (The crater in the 4corner
country UT-AZ-NM-Co was 50m large.)

People only expect to find craters because for a long time craters
were the only experience people had of impacts in the past.

Oh no. An impact will cause very-high-velocity brittle deformation of
its target rock which leaves clear signs. Expect some rock to melt,
forming pseudotachylite (sudden rock melt, otherwise often found in
exhumed earthquake-prone faults), plus a variety of other features
which we have learned to see long ago. And I do not talk about giant
impacts like Nördlingen, I mean relatively small impacts.


In fact,
the vast majority of bolides never reach the ground to leave a crater.

correct.

I don't think 1, 2 or even 3 can explain the sudden widespread
ignition of an entire forest

agreed

but the thermal radiation from a
Tunguska-like event certainly could.

except that if there is evidence of widespread fires, but no evidence
of meteors, I would resort to more down-to-earth interpretations
instead of the most outrageous one.

Why do you want to use the meteor hypothesis by any means if there is
no evidence other than fire - which may be caused by a bunch of
reasons? Come up with a hand specimen of a meteor, and your position
would improve a bit (not much though). Right now you have nothing on
your hand except a wild idea which is of little practical value.

I don't _want_ to use it but I would like to think that the
possibility has been considered. It makes at least as much sense as
the idea that for their own peculiar reasons the local population
suddenly set about burning off all the vegetation in the region.

The human-caused fire interpretation makes a good deal more sense,
among other reasons because this systematic burning has been observed
in other places as well. And it must have been systematic because a
fire ove one mountainside would have grown back within a couple years,
seeded from nearby forests. The burning in Spain was followed by an
entirely different habitat which not only indicates environmental
disruption, but also relatively intense use, eg. as pasture as in the
Alps. It was this new use that prevented the old plant association
from growing back. Grass pastures in high mountain country will turn
back to forests if left alone even today. (Not entirely sure about
southern Spain, but sure about Calabria, which is more or less the
same thing.)

Hayabusa


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