According to HGTV, it takes at least 500 years to make just 1 inch of topsoil, and there are more living organisms in just 1 tablespoon of soil than there are people living on the planet. Some of the soil on Earth is stardust from the remains of stars that has been caught by the Earth's gravitational pull and brought down to the surface.
Although bacteria are generally considered bad, the bacteria are what keeps the soil healthy and perfect for growing plants. There are billions of bacteria in 1 square yard of dirt. These bacteria also help regulate the soil's pH level and aid in the degrading of organic matter.
As earthworms move through dirt, they end up eating some of it. What they excrete from their bodies helps improve the overall quality of soil. This is why having earthworms in a garden is considered a good thing. Scientists have not found evidence of the existence of earthworms in North America before the last Ice Age, nearly 10,000 years ago, suggesting they are not native.
Weather helps to break down rocks, which eventually end up becoming soil. Clay is formed when the break-down process is stopped. There is enough clay in the Earth to cover the entire surface of the planet with a 1-mile-thick cover.