You are seeing a breakdown of soil structure and compaction, not plants "eating" soil.

Almost all of the plant carbon, oxygen and hydrogen, which it gets from air and water. The plant might take a few grams of other substances out of the soil.

Look into Jan van Helmont's famous experiment.

Hey! The plant is not "consuming" the soil, it takes nutrients out of the soil but that's about it, nothing that would be noticeable to the human eye. Soil is made up of minerals, organic matter, water, and air. Depending on where you live the ratio of each varies. As organic matter decomposes, it turns into humus which is the final stage of organic matter, meaning it does not decompose any further. You are most likely seeing some decomposition happening, and quite possibly some sort of critter moving the soil around too, maybe it's just worms. Roots could also be responsible for moving the soil around, you should check out a timelapse of roots moving through soil, very cool! Anyways, hope this helps!