Re: [Fwd: Earth Battered Through History By Comets]

Jonathan Clarke (
Thu, 26 Aug 1999 19:35:19 +1000

Greetings all

I thought that I would add my own 2 cents here. The idea of impacts or
cometary/meteoritic air bursts effecting human history is just another version of
a view of history that sees the tides of human events as reflecting natural
phenomena. Internally forced climatic changes, and volcanic eruptions are other
examples of this. None of this is new. Napier and Clube wrote a book in the
80's called "The cosmic serpent". I don't recall further details, but they
argued something similar, though with little evidence. I would say there is a
complete spectrum of ideas from the sober end, typified by the forwarded post, to
stuff that is positively Velikofsian (spelling?).

There are two issues here. One is the type of impacts that actually leave
craters, the other are the air burst types. The number of known Quaternary
craters is small, as Glenn pointed out. There are more than people often suspect
though. Andrew Glikson in 1996 compiled a list of 7 Quaternary impact sites in
Australia alone (AGSO Journal of Australian Geology and Geophysics
16(4):373-375). These were Dalgaranga (24 m wide, 3 Ky), Snelling (29 m, 5 Ky)
Veevers (70 m, 2 Ky) Henbury (14 craters 5-180 m, 4.2 Ky), Boxhole (170 m, 30
Ky), Wolfe Ck (880 m 300 Ky) and Darwin (1,000 m, 740 Ky). There are probably
others as yet undiscovered.

In contrast, Tunguska like air bursts leave almost no geological record. In
addition to Tunguska, there was the Sikote Alin (sp?) explosion in the late
40's. I recall reading in "New Scientist" that there was a similar explosion in
Brazil in the 1930's and one over the Pacific during the Gulf War. There may be
a link between these upper atmosphere explosions and the micro comets that some
believe are he impacting the earth several times each year. These could be quite
common, but most are unknown because they happen in uninhabited areas or over
ocean. Their direct environmental signifiance is small. There have been no
records of cities being obliterated by such air bursts, and had this happened
surely it would have been recorded. Maybe Sodom and Gomorrah were the exception!

However a sense of scale must be kept in mind. The Tunguska object probably had
a volume considerably less than 1 cubic km. If it was a micro comet, probably
only half of this would yield dust. As Glenn has pointed out, there is no sign
of significantly increased atmospheric dust after Tunguska. If the body strikes
the earth then there will be a significant volume of dust hoisted into the upper
atmosphere as ejecta from the crater. However we must remember that Quaternary
craters are typically small (1 km or less in diameter). The volume of
stratosphere dust would also be correspondingly small. Then there is the
frequency of impacts. This appears to be too low to cause the collapse of
empires suggested. Volcanic eruptions are more frequent and inject greater
amounts of dust (several cubic km) into the upper atmosphere than these small
impacts. Of course a really big impact (like the KT boundary event) is a
different story, but they are rare.

Several people have pointed out that impacts are flavour of the month. In the
past impacts have been down played or even denied. Now they are a recognised
phenomenon, we must be careful not to overstate the significance of these rare

God Bless


Gary Collins wrote:

> wrote:
> > The problem I have with this is the lack of brand new meteor craters to
> > support the concept. One of most recent craters is the BArringer crater and
> > it is 50 000 years old. If this hypothesis is true there should be some
> > physical evidence in the form of very young, very fresh craters. I know of
> > none. Do you?
> >
> > glenn
> >
> > Foundation, Fall and Flood
> > Adam, Apes and Anthropology
> >
> >
> > Lots of information on creation/evolution
> Can't say I do, no. But then I wouldn't expect to, it's not something I've
> studied. If *you* don't, then that's far more significant. What struck me
> as odd is that if this hypothesis is true, why has it taken so long to come
> to light. Perhaps because of lack of craters, as you suggest. It was
> reported in what I hope would be a fairly reliable source - NASA news,
> I think it was - so I guessed it should at least be something not too
> unreasonable. As I said, I haven't yet had time to look at the article
> itself, I should be able to do that today.
> What was on my mind though was something I vaguely remember
> reading about genetic studies - mtDNA I think it was, though I'm not
> entirely sure - which mentioned a surprising lack of diversity in humans
> as opposed to apes, and suggesting a more recent divergence than
> usually believed. If something like comet/asteroid collision, or indeed
> any natural disaster, like volcanoes as Kevin suggested, did occur,
> maybe more than once, and reduce the population significantly, this
> would explain the discrepancy. (This is probably old hat, anyway!)
> This is a lot longer ago than Rome, etc, I know!
> I guess the article is also of interest given the recent 'hype' about the
> likelihood of such a collision in the near future, and the various disaster
> movies which were made just a few years ago!
> /Gary