On Nov 22, 1:38 pm, Alastair wrote:
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 get the impression (zenning it in a most geological manner, I admit)
that the incidence of limestone in volcanoes is instrumental in
producing types of eruptions.

You'd think a geologist would have been a little more forthcoming on
the chemistry. But there again as a primer that will probably end up
on the schools programmes slot...

Oofque!

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

You are not supposed to be sure about the sulphur. It is not part of
the grand explanation.

Nevertheless the facts remain that vast deposits of this organic
chemical arrived carbon like and at similar strata levels and that
volcanoes are remarkably rich in it. IIRC without looking it up,
volcanoes produce glass and gas and are a rich source of suphur.

But back to the carbon cycle... The carbon dioxide was already in the
system before the volcanoes occurred?

Which just leaves the questions about how all life forms knew that
magnesium was a trace element and that calcium was going to be a lot
more useful.

Bloody clever them sponges. Maybe there is hope for some of the
relatively higher life forms on here.