If you’re going to dig your way to China, you’ll first hit the topsoil. This top layer of soil contains the most organic matter (rotting plant and animal material). It’s the best part of the soil for growing crops.
Next, you’ll reach the subsoil, which doesn’t have as much organic matter as topsoil and is not as good for growing crops. But it holds a lot of water and nutrients (plant food).
After the subsoil, you’ll arrive at the “parent material,” where there’s no organic matter. This layer is usually made up of soil particles mixed with bigger bits of rocks.
The fourth layer down is bedrock, where you’ve hit solid rock. You better have a strong shovel or you’re not going any farther.
Topsoil is the blacker soil on top. It is much better for growing crops than the lighter-colored subsoil below.
Photo: USDA NRCS