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Re: extinction



> Perhaps rather than the Deccan Traps, the "so-called" Shiva
> Crater may be more to one's liking.

While I obviously can't rule out multiple impacts around the K-T (of which
Chicxulub was simply the biggest), which would explain the multiple Ir
anomalies, the "Shiva Crater" is described as "science-fiction" by Köberl. I
haven't asked him why, but there are several problems with the Shiva affair
when I just look at Chatterjee's description of it (in his 1997 book The
Rise of Birds):
- Its shape. It should be round. Not necessarily circular, ellipsoid or
perhaps even tear-shaped will do, but even the latter can hardly mean that
the feature has an actual pointed tip, which the "Shiva Crater" has. The
"central uplift" is also quite suspect in shape.
- Its size. 300 x 600 km would be impressive even for a P-Tr crater; for the
K-T it looks like just too much. Chatterjee tries to explain this away by
hypothesizing that the impactor came from the southwest, therefore had to
run after the Earth's rotation (unlike Chicxulub), and therefore the energy
set free from its impact was rather small. The size of the crater, which
depends only on the energy of the impact and not directly on the size of the
impactor, falsifies this. The energy does depend on half the mass of the
impactor, but also on the square of its velocity -- by assuming it came from
the southwest, Chatterjee implicitely predicts quite a small crater.
- It is beyond me why Chatterjee thinks the impactor came from the
southeast, toward the tip of the tear, and not from the opposite direction,
which to me looks much more logical.