Re: Report Sez Volcanic Gases Killed The Dinosaurs

[David Marjanovic <david.marjanovic@gmx.at>]

> Was the climate fluctuating during this 100,000 year period?

Not detectably, it seems.

> I think that the first ice age was before the end of the Cretaceous,

Within the Phanerozoic, there were ice ages at the end of the Ordovician, in 
the Late Carboniferous through Early Permian, in the Late Permian, and then 
never again till the late Pliocene, unless you count the existence of inland 
ice in eastern Antarctica since the late Eocene. There was none in the 
Mesozoic.

> If Deccan traps actually cooled off the oceans, they could have brought on 
> a volcanic winter and helped trigger an ice age.

No, as mentioned, they heated the Earth. That's because only explosive 
eruptions blow ash into the atmosphere; the Deccan eruptions were 
effusive -- imagine a crack where basalt flows out. This pumps lots of gases 
like carbon dioxide into the air, but nothing to counteract that greenhouse 
effect.

> Since the beginning of the Cenozoic, ice ages have occurred several times
> within any hundred thousand year period.   I think.

You're wrong. The necessary fluctuations (Milankovic cycles) have indeed 
always occurred, but usually at a much too high temperature level to trigger 
ice ages. There have only been 17 or 18 ice ages in the current series.

> But what we're actually learning causes the ice ages is that the
> current positions of the continents has rendered Earth's climate
> dangerously unstable, and ANYTHING can tip the balance.

I'd rather say that the current positions of the continents -- one continent 
at the South Pole, a ring of continents around the Arctic Ocean -- makes ice 
ages possible if the carbon dioxide level is low enough, which it is, thanks 
to (roughly) the Tibetan plateau being above the treeline. That's why only 
the most extreme interglacials (like the one 400,000 years ago) succeed in 
melting Greenland anymore; Greenland used to be ice-free well into the Mio- 
or probably Pliocene.