Where does all the dirt come from?

I seem to have heard that granit decomposes, the feldspar breaking down into a clay, leaving the quartz as particles of sand. Organic material gets in there from growing stuff and solids from air polution settling out of the air.

Oh, ask farmerman. He knows all about clay and stuff.

Re: Where does all the dirt come from?


Dunno if the average rises but it definitely becomes more average (more level).

Wind. Believe it or not, earthworms. Definitely believe people dumping trash on ruins. Trash attracts trash.

That too. Middens are priceless finds, from what I hear.

Well, if all the old civilizations were built on mountaintops, nothing would be buried. But mountains are worn down and deposited on the plains, were most of the old stuff was built. And why was the old stuff built on plains? Because that's where the soil was. And why was the soil there? Because it was always being deposited there.

A gross over-simplification, of course, but civilizations tend to get built where soil accumulates rather than where soil gets blown away, for the simple reason that it's a lot easier to grow food in the former place than in the latter. (Think Egypt, Mesopotamia, China's great rivers, most of India, the Mississippi River...)

Also, the people who lived in Rome after the Romans didn't necessarily think all that crap was worth saving, so they threw their own garbage on top of it.

And there may be a certain amount of entropy at work, even where there isn't much soil deposition (like, say, Macchu Picchu): keeping something on top of the ground means keeping it in orderly, which doesn't happen without the input of energy. Left on it's own devices over centuries, the stuff of a civilization is going to get mixed up with its surroundings, increasing disorder (entropy) and making the universe happy.

Or something. Just talking out of my ass (Francis the Talking Ass, wasn't it?).

We haven't even considered sliding mud and volcanic ash, to say nothing of weeds growing and rotting, growing and rotting.

most all dirt (so I'm told) originates from under my finger nails.

Yes! Grabbing carbon dioxide from the air, mixing in a little light and water, and making sugar and oxygen! Those damn weeds are beautiful, aren't they?

Weeds are one of the most important products of the first agricultural revolution--they thrive best in disturbed soil and cut down on wind erosion.

Nature abhors a vacuum.

Only sunlight penetrates to Earth (plus some cosmic dust and meterorite material) and only heat leaves the planet. Everything else is recycled. So if earth is building it comes from Earth.

There is a fairly large amount of that cosmic dust...

On a cosmic time scale, you could build a whole planet out of it.

No I couldn't. I'd get tired.

Trees/plants are natural erosion deterents. They hold dirt to them and yes, when they die, they decompose into dirt. Mountains are slowly eroding into dust which is blowing/rolling/washing down to lower elevations. Rain depostis airborn dust on the ground, flooding waters deposit silt near rivers and other water bodies. Glaciers (for very old archeaology) deposit boulders/rocks/gravel/pebbles/dust onto many areas in the upper latitudes. And everything, basically, that's already been said before my post.

um?

Other sources of debris:

Broken promises
Exploded rumors
Dashed hopes
Discontinued stories
Flailing egos

roger?

what's the vector, victor?

My guess is first world cities are not being buried, as we haul out many tons of trash, dirt, dust, and rubble from old buildings out of the cities. Typically we excavate deeper than the foundations of pervious building to get a firmer foundation for each new structure.
The older practice was to leave such portions of the old structure that seemed to make a good foundation for the new.
On the other hand my lawn is at least an inch higher than 40 years ago unless my fence posts are sinking deeper. Sinking of fence posts likely accounts for only about 1% of the apparent elevation increase. Neil

Dead animals probably also contribute to formation of soil, but I guess that was stated in the original post.