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FW: Dinosaur Extinction: Impact vs Volcanoes

There's still some thinking about the Chixulub crater being volcanic in
origin; certainly one of the Pemex geologists who cored the structure
originally is of the opinion that the crater is volcanic and not an
astrobleme!  Also, the Deccan Traps in India represent a massive
volcanic upheaval at the KT time; the idea to explain the Traps--that an
impact can trigger distant volcanics--is a tenuous theory.  Now on to
tektites!  Tektites have strong igneous trends and don't even resemble
real impact glasses which are messy, unfined, and full of inclusions of
local rock--compare Henbury material to a real tektite (no inclusions of
local material found anywhere on a tektite).  Not even close!  I believe
some so-called impactites are in fact tektites, like Darwin and Libyan
Desert glasses, et al.  Muong-Nong layered tektites--formed apparently
by slow and successive layering of microtektite falls--strongly resemble
layered obsidians found at California's Mono Craters and Coso Domes
regions (and elsewhere), but lack the water and volatiles of terrestrial
obsidians.  I believe tektites are most likely extraterrestrial volcanic
glasses, derived from lunar silicic volcanoes (because the cosmic ray
tracks show many tektites have been in space less than + - 90,000
years).  Could it be that periodic volcanic explosions on the
Moon--sending giant meteorites of silicic lava and trailing showers of
tektites--cause some extinctions in the geologic record?  Many of the
microtektites found on the Moon by Apollo astronauts are indeed
pyroclastic volcanic glasses and resemble microtektites found on
Earth--with silica ranges from rhyolitic (75% SiO2) on down into the
basaltic (basic) range.  Another curious observation: certain asteroids,
with unidentified albedos, orbit between the Earth and the Moon.  My
hunch is that these are lunar ejecta from impacts and volcanic
eruptions; some will be found to be glass asteroids--that is, lunar
volcanic domes blasted into space during periodic eruptions.  The domes
could easily reach lunar escape velocity if propelled by hydrogen gas
(rather than steam as Earth's volcanoes) in the lunar interior.
Hydrogen has been identified as one of the elements outgassed by the
Moon.  Domes of viscous (though rare) silicic lava might be the source
of many (Muong Nong) if not all the tektites on Earth.

> -----Original Message-----
> From:	Frank Stroik [SMTP:autumnbreeze71@hotmail.com]
> Sent:	Tuesday, September 22, 1998 10:02 PM
> To:	meteorite-list@meteoritecentral.com; STUARTATK@aol.com
> Subject:	Re: Dinosaur Extinction: Impact vs Volcanoes
> 
> Determining extinction from evolution in the fossil record is
> difficult 
> to say the least. In the case of the late cretaceous, we see rapid 
> speciation, and the rise of new groups of vertebrates. 
> 
> For example, Mosasaurs are marine lizards related most closely to 
> snakes, and monitor lizards. In the last 20 million years of the 
> cretaceous these lizards originated, and divided into roughly 4
> families 
> with numerous species originating as well. As suddenly as they appear,
> 
> they disappear at the K/T boundary. 
> 
> Although dinosaurs are the most recognized of the animals suffering 
> extinction, they make poor models of what exactly happens during an 
> extinction. They are sporadically preserved, and there simply is not 
> enough material to actually use to theorize with. It is hard to say
> what 
> was happening in their evolutionary history at this point in time, 
> although there are those who think they can. 
> 
> Now, what am I talking about? In the latest cretaceous, some animals 
> show a decline, while others show expansion. This leads to the
> conundrum 
> of what is exactly happening. Can we have decline and diversification
> at 
> the same time? The answer is yes.
> 
> The nature of the fossil record( this is my area of study for those 
> interested) is based wholly on presentational bias. In the case of the
> 
> dinosaurs, they are terrestrial dwelling animals, and therefore are
> less 
> likely to be preserved. This is because conditions do not favor 
> preservation on land, as think about an animal dying in a forest, does
> 
> it get covered quickly enough to be preserved? Probably not. 
> However, In the marine environment, constant detritus and the likes
> are 
> perpetually raining down on the sea floor. This tends to cover animals
> 
> quickly, thereby preserving their skeletons.
> 
> So to think about it more clearly, if it was not preserved, does not 
> mean that it was not there. Extinction is best gauged by marine
> species 
> decline and disappearance. In the latest cretaceous most marine
> species 
> were doing fine, then suddenly gone. This is how we know there was an 
> extinction.
> 
> Now about the volcanic hypothesis, and dinosaur relation. This idea is
> 
> most likely wrong. As stated above dinosaurs are preserved
> sporadically, 
> and therefore have a bias in the fossil record. If this gradual
> decrease 
> is apparent in the marine record, then we would have to rethink the 
> impact theory. 
> As for dinosaurs, it seems as though they went on diversifying until
> the 
> end, and the environments which best preserved their skeletons were
> not 
> as common. 
> 
> Did an impact do in the species that went extinct at the end of the 
> cretaceous? I don't know. I have my doubts based on the fossil record.
> 
> However, I tend to steer clear of this debate, as I am not thrilled 
> about rehashing same data sets, and ideas. 
> 
> Could a volcano form tektites? I don't' know. People have discussed
> this 
> before, and say no. About all I can say bout it is, it  would seem
> hard 
> to get shocked quartz from a volcanic explosion. If a mechanism can be
> 
> shown to generate shocked quartz in a volcano, then we might have an 
> answer.  
> 
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