On 22 Nov, 13:12, Weatherlawyer wrote:
On Nov 22, 10:47 am, Martin Brown
wrote:



On Nov 21, 11:32 pm, Weatherlawyer wrote:
On Nov 21, 8:24 pm, Alastair wrote:

The carbon that gets subducted is the Great Barrier Reef and the White
Cliffs of Dover. The latter actually stretches from Beer, on the
Dorset/Devon border to Malta and up into the Dolomites. There is
plenty of limestone that has not been buried yet. Not all volcanoes
pump out CO2, but since all the limestone gets formed on the sea bed,
it is in the right place to get subducted.

Yes Calcium carbonate contained in shellfish exoskeletons will go into
an abyss quite easily but then what provided all the sulphur? Besides,
the narrator didn't make it plain that he was talking about
lime"stone" subduction.

It plays a part. Limestone locks up a heck of a lot of the Earths CO2.
Without it we would have a considerably higher atmospheric pressure
and a composition more like that of Venus.

There is also expected to have been a fair amount of carbon in the raw
material that the Earth was formed from based on analysis of meteorite
composition.

Lots of sulphur too. I wonder what strange creatures arrived from
outer space to supply the fossil beds of their particular biological
trait.

I suppose that that is because he didn't want to get dragged into a
chicken and egg argument about where the free calcium came from to
supply the carbonate in the first place.

Calcium is an abundant terrestrial element. See for example:http://www.daviddarling.info/encyclopedia/E/elterr.html

And calcium bicarbonate is relatively water soluble on a geological
time-scale. Liquid water makes a big difference.

It isn't as big a part or as geographically relevant as Aluminium and
Magnesium which was the thrust of the points the programme was
ignoring in the head-first rush over basic factual reportage. Perhaps
a repeat will allow you to see what my post was pointing out.

No doubt he will do better as he explains weather systems that CAN be
researched next week.

So where did the prehistoric life forms get the calcium from and why?
And how come it wasn't locked?

Calcium is in granite and other igneous rocks. The carbon dioxide in
the air dissolves in rain and forms carbonic acid. This attacks the
granite and produces calcium bicarbonate which is soluble. It is
carried by the rivers into the sea where the calcium ions are formed
into calcium carbonate as shells of marine animals or are just
precipitated if the water is warm enough.

I am not sure about sulphur but googling for "sulfur cycle" may answer
your question.

Cheers, Alastair.