system
Given the following post, respond as if you're commenting on Reddit:
human
ELI5: Where did all the soil come from?

When the Earth was being formed it was essentially a ball of rock. How did soil come to be if there was nothing but lava and rock?
Or am I just missing something here?

Edit: Wow guys, thanks for the replies.
gpt
TL;WR :: Erosion, Dissolution, and Poop

1. Gross mechanical processes turn large chunks into small chunks.
2. Chemical processes dissolve things, particularly water and such.
3. Biology is chock full of gross mechanical and chemical processes.

So there's a difference between "dirt" and "soil".

Dirt (and silt, and clay, and sand) is the mechanical, un-living accumulation of fine particles of minerals and metals and ash and whatever.

Soil is what happens when dirt is full of living material and organic byproducts (recently living but now shredded or dead stuff).

So dirt is formed by grinding up and dissolving rocks and such.

When a little dirt shows up somewhere then hardy organisms tend to show up just a little later - or in the case of lichen and moss, sometimes really super hardy organisms show up first.

Windblown dirt-and-dust collects in the crevices and then organisms (bacteria, fungus, algae, whatever) take shelter in the dirt-and-dust and use the mineral wealth of the dirt to thrive. As they grow and die there's now more mineral wealth along with some fixed carbon and nitrogen in the little microscopic corpses and poop stuck to the dust and dirt, and larger organisms can show up.

With more sticky and more crevices comes more dirt and dust, with more dirt and dust comes more places to get sticky and so on.

So if you grab a selection of moss you'll find that dirt is collecting between the fibers and becoming soil.

If you look at a decaying woodpile, you'll find the same thing.

So all these small cycles add up over thousands of square miles of dirt and dust, over millions of years.

Eventually you've got herds of bison and cows and deer and raccoons and prairie dogs and spiders and bugs and whatever constantly living and pooping and dying. Turning more and more dirt into thicker and better soil that's full of more and more diverse things like bacteria and fungus and bugs and worms and microscopic plants and animals and so on.

We'd be neck-deep in soil... but soil has enemies too.

Soil can get washed away, which at natural levels is good for the water right there and down-stream. Soil can be crushed until it suffocates and becomes packed dirt again. Soil can be buried under dirt or ash and so sufficate. Soil can be dried out until it's just dust.

Soil can also be killed by too much acid or too much alkali or to much salt (salt being what you get when you mix acid and alkali).

And some biological systems "don't like" soil.

For instance "rainforests" tend to have very little soil. The rainforests are deeply invested in the nitrogen and nitric acid cycles. So all their biological value is in the living plants. The ground beneath the plants is very acidic and so there's lots of dirt but only a tiny layer of soil. This is a _necessary_ configuration, but when someone decides to burn down some rainforest to create a cow pasture or farm, they'll use up the tiny, crappy layer of soil in just a year or two.

It's easy for something disruptive, like a farm, to "use up" the soil and then there's nothing left but dirt. Especially if the local soil is the result of buffalo and grass and wolves and prairie dogs, but the farmer drives off all of that and just plants corn or wheat. The soil was used to a diet of all that other stuff and now it starves... like trying to make your dog a vegan, it's just not the right food for the organism at hand.