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re: impacts

hi all,
FWIW, meteorites enter the earths atmosphere at speeds of 7-42 miles/sec,
so there is a wide variance of energy released compared to Iridium etc 
released. Any ideas on effect of small high-speed object versus large low- 
speed object?

In my pond in England frogs (_Rana temporaria_) hibernate in mud at the bottom 
of the pond but I have seen them swim up under 3 inches of ice in mid
-winter, so they can still be active at low temps, I've also seen them spawning 
in (naturally) very acidic and polluted water, so modern decrease might be
 more to do with manmade chemicals like dioxins etc.
Tadpoles also overwinter as tadpoles if food is short and they are also
 omnivorous unlike the adults.
In Australia there is a species of frog or toad which lives in the desert and
estivates during the dry season by burrowing and secreting an impermeable 
mucus around itself, reactivating when the burrow becomes flooded .
   American red-eared slider terrapins (_Pseudemys_ sp.) also hibernate during
 winter, while I've seen a program concerning terrapins in Africa? which burrow 
to escape the dry season.
  Reptiles become torpid and eat less when cold, would they then take longer
 to reach sexual maturity?

If there is major volcanic activity would there be oceanic transgressions rather
than regressions? ie. by increase of oceanic ridges, or would cooling by
volcanic dust create polar ice sheets to cause regression?  
I believe as Antarctica arrived at the South pole and the Arctic ocean was
created by landlocking, this caused global cooling, so a combination of factors
probably gave mammals their big chance.

Phil Virgin