Re: Asteroid explosion energy distribution.
Massie (mrlab@ix.netcom.com)
Fri, 19 Mar 1999 21:05:07 -0800
Allen Roy wrote:
>
> > From: Massie <mrlab@ix.netcom.com>
> > Have you seen the astreroid crater in Arizona.
>
> One of the advantages to being free to offer part time bus driving to the
> local public school is to drive the kids on field trips. Today we just
> poped over to Meteor Crater again. So yes, I have seen Meteor Crater.
>
> > You see this and then
> > tell me that the majority of the energy is absorbed in the atmospheric
> > shock wave.
>
> Perhaps the two examples I gave confused you. The bomb at Hiroshima and
> the Tunguska asteroid both exploded in the air. Thus shock waves in the
> air were the primary used of the energy generated these explosions. The
> point of the examples was to show that atomic and asteroid explosions do
> not primarily generate heat, but that most of the energy is channeled into
> shock waves.
>
> When the asteroid is large enought to reach the ground, then you also have
> shock waves in water (mega-tsunami) and the P and S waves in the ground
> (earthquakes).
>
> > The statement that the energy is mainly dissapated in heat is in some
> > since absolutely true because all energy eventually ends up in some low
> > grade heat.
>
> This is true, but atomic and asteroid explosions generate mostly
> destructive shock waves and some heat.
>
> > But this is not the point. Let see if we can list the channels:
> > Atmospheric shock waves.
> > Water waves and ground waves (acoustic as well(shock waves are a form of
> acoustic waves.)
> > Heating of the area struck (ground or water).
> > Ejecting of fragments (they carry kinetic energy).
> >
>
> If you will notice, this is the same list I made:
> > > Thus we can conclude that the major part of the energy of the asteroids
> > > will be disipated by shock waves in the air, by evaporation and
> > > mega-tsunami in water, and by rocks and dust thrown into the atmosphere
> > > along with P and S waves in the ground. There will be some primary
> heat
> > > generated by the explosion. Secondary heat will also be generated by
> > > following fires, volcanism and plate tectonics.
>
> > What I think is howeve the real issue is that so much of this is
> > supposed to happen is such a very short time. Any of these objects
> > alone could shove the earth into a quasistable climatic state that is
> > way off of the equilibrium we enjoy. I am not just talking about some
> > extra rain storms but something a lot more catastrophic, such as the
> > proposed nuclear winter. Thus, the real impact may be difficult to gage
> > but the real problem is the theory that all of these super energetic
> > events are being postulated in 40 days or so without any justification
> > based on physical evidence or analysis of how this tremendous amount of
> > energy would impact the planets stability or the destructive events such
> > as shock waves, global fires, tsumanis, enourmous earthquakes and the
> > like.
>
> I agree. From what I have read so far, there is alot of disagreement on
> just how destructive these impacts would be. Even one as large as Chixilub
> may not initiate global climatic catastrophe by itself. I tend to think
> that many of the proposals are exagerated to try to account for the
> extinction of the dinosaurs.
>
> Most of the craters are very small. From an online list, I notice that
> only 6 or 7 craters are 100 km or larger. The average is likely about 20
> km across.
>
> The physical evidence is the craters in the strata designated as flood
> strata. The analysis is in progress. This analysis is expected to show
> that enough energy was transferred to the planet to cause a catastrophe,
> but not so much so that the Ark and those inside could not survive.
>
> Allen
1. The schock waves from Tungusta and Hiroshima and some nuclear weapons
use planes are the most effective for destruction over wide areas in the
immediate but not nescessarily the greatest energy dump mechanism.
2. Small meteriors burn up in the atmosphere dumping matter, heat, and
shock waves into the atmosphere. Immediately the shock waves dissapate
into heat so the immediate residual is heating of the atmosphere.
3. When the meterior is large enough or slow enough the coupling to the
atmosphere is lower and the object strikes the ground. In spite of the
shock waves effects on surrounding areas, greatest destruction is not
equal to greatest energy loss.
The answer lies only on carefull analysis of the energy channels for the
larger asteriods. Incidently, Tungusta is theorized as a commet and
partly becuase of hte lack of a crater.
When you get a crater 100 km in diameter you simply cannot say that more
than a tiny fraction of the energy was bled off aerodynamically. It
went into forming the crater which ejected a lot of hot gasses and rock
into the atmosphere and then caused fires when there was something to
combust and in any case a lot of difficult to model global atmospheric
effects.
If such an enormous hit struck the oceans, the modeling should be
simpler: Enourmous tsumanies world wide and lots of steam. Bert Massie