Given a scientific passage and an answer, generate a question for the given answer.
Q: Passage: Weathering changes solid rock into pieces. These pieces are called sediments. Sediments are described in the chapter Earth's Materials and Crust . Sediments are different sizes of rock particles. Boulders are sediments; so is gravel. At the other end, silt and clay are also sediments. Weathering may also cause the minerals at the Earth's surface to change form. The new minerals that form are stable at the Earth's surface. There are two types of weathering, mechanical and chemical. These are discussed in the next two concepts. Answer: weathering
A:
Over time, what changes solid rock into pieces?