system
Given the following post, respond as if you're commenting on Reddit:
human
ELI5: Dirt. What is it?

What is it composed of, at an elemental level? What in it is organic vs inorganic? How much does it vary by location? How does it come into existence?
gpt
Dirt can be a lot of varied things. It does depend a lot on location. The most basic element of dirt is usually sand and silt from eroded local stones. And as you may suspect these minerals vary a lot between different locations. But there also tends to be organic matter in the dirt as local plants and animals decompose and mix with the dirt as they do so. Some dirt is almost pure organic matter and some dirt is almost pure mineral matter. However most is a mix between these.