Mmmmm, not sure aboout the falling to the centre bit, but sapace is only 60 miles away.

Straight upwards.

POO

is there a spelling checker on the reply thing?

Phil, ignoring all sorts of things, the drop to the centre would be 6350/150 (miles/hour) = 42 hours. Near enough.

Silly factoid I recall hearing: the depth of the world oceans are comparable to the deepth of a drop of water on an egg.

Thanks for the maths bit Janet - the result makes it even more

quote:

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Originally posted by Janet H:
Yup, thanks.

So that brings us back to the initial question: where does this stuff come from?

Theory No 2 dead plant material: made from carbon (recycled, water (recycled), and sunlight, (Not recycled)

so its made of sunlight!?

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Actually, no, I don't think it is. Sunlight merely provides the energy required to perform the recycling of the other two. No such thing as a free lunch, even for photosynthesis.

That sunlight energy becomes stored (in carbohydrates, initially) and, once that has worked its way down the food chain and you've eaten it, it will be used up, releasing water and CO2 back into the cycle plus some residual heat (thermodynamic efficiency <100%, blah).

The cumulative heat output of countless aerobic organisms is ultimately radiated back into space, which is why we need a constant resupply of sunlight.

To press the point a little, there is no shortage of sunlight in the deserts of the world but there is no soil accumulation, just lots of weathered rock (albeit a vital soil ingredient in its own right). Therefore plants and the climate required to sustain them seem to be the vital ingredient.

Now, if we can safely bar Einsteinian matter/energy conversion processes for a minute, it becomes clear that it's ALL a matter of RECYCLING. Matter is neither created nor destroyed, merely redistributed from one place to another.

Huge amounts of CO2 come out of volcanic vents and enter the global cycle, becoming incorporated into plants. However, this is not necessarily 'new' CO2 from the breakdown of 'primordial' mineral substances. The process of deposition of foraminifera (sp?) on the seabed (forams = plankton, with carbonate shells) may be familiar to you. It didn't just form the white cliffs of Dover but similar layers in other, equally prehistoric, oceans. In places where continental drift causes submerged rock of this kind to be subducted and volcanoes happen to form, heat and pressure can chemically break down the rock and release the CO2 which was once part of the atmosphere. A very slow-going extension of the carbon cycle, if you like.

So carbon is being released in some parts of the world, circulated around the atmosphere and 'locked up' in soil deposits in other parts of the world, via the agency of living things. The redistribution is markedly uneven.

And then there's the business of nitrogen... more on that story later.

EF

Actually, come to think of this redistribution business (now I've read the TT page referenced earlier), it all starts to make sense.

Area farmed but uninhabited for generations:- soil is thin, archaeology is close to surface.

Area inhabited but not farmed:- organic waste accumulates and soil is continually gaining in depth. Floor levels continually rebuilt, to match.

In the first case, the growth of crops takes nutrients (and hence volume) out of the soil. This has to be topped up with fertiliser but, on the whole the amounts added to the soil and the amounts harvested and sold tend to balance out well (farmers are not known for wasteful extravagance), so the net accumulation rate is next to nothing.

One thing which might be interesting to research into is at what point in history this country became a net importer of foodstuffs. Being one of the worlds top economies, we're getting stuff from all parts of the world but the waste products remain here.

So, are we collectively eroding the soils of the respective exporting nations or are we making a packet out of selling them tons of chemical fertiliser?

It strikes me to see Phil trowelling back what looks like very decent quality topsoil whilst several feet down in a trench. It was a perfectly good land surface there 1000 years or more ago, why not strip back to that level? We could comfortably export millions of tons of the excess stuff to parts of the world where their soil is busily washing away in the rain or blowing away on the wind, couldn't we?


EF

quote:

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Originally posted by Janet H:
Phil, ignoring all sorts of things, the drop to the centre would be 6350/150 (miles/hour) = 42 hours. Near enough.

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I thought terminal velocity, for H.Sapiens.Parachutensis, was getting on for 200mph but I could be wrong.

Luckily, they wouldn't have to wait that long - the air pressure would asphyxiate the faller (through inability to exhale, that is) within the first few hundred miles. Pressure of an air column is one of those non-linear things and I can't do the math to set a figure on it.
Guiness Book of World Records (which I also don't have) probably would NOT have an entry on highest air pressure ever survived by a person, on account of some idiot would end up dead, trying to break it.

quote:

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Originally posted by Janet H:
Silly factoid I recall hearing: the depth of the world oceans are comparable to the deepth of a drop of water on an egg.

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And the thickness of the earth's crust is, comparatively, thinner than the skin on an apple...

EF

quote:

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Originally posted by ExsistoFelicis:
Being one of the worlds top economies, we're getting stuff from all parts of the world but the waste products remain here.

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So are you in favour of exporting our waste to land-fill sites in third world countries? I seem to remember that at least one local authority in the UK tried this before being ctiticised for exporting pollution.

Your recent posts on this thread contain a number of statements which seem to be at odds with what I understand.

An obvious example:
Area farmed but uninhabited for generations:- soil is thin, archaeology is close to surface
I was under the impression that farming caused soil migration down slopes so that artefacts can be buried quite deeply at the bottom of a hill.

There are other examples.