Given a scientific passage and an answer, generate a question for the given answer.
Q: Passage: Soil develops over time and forms soil horizons. Soil horizons are different layers of soil with depth. The most weathering occurs in the top layer. This layer is most exposed to weather! It is where fresh water comes into contact with the soil. Each layer lower is weathered just a little bit less than the layer above. As water moves down through the layers, it is able to do less work to change the soil. Answer: top layer
A:
Which layer of soil experiences the most weathering?