Which weathering process describes the reaction of minerals expanding during chemical weathering?

The process of spheroidal weathering is characterized by the way in which minerals expand and contract due to chemical weathering, which leads to the breakdown of rock into more rounded shapes. This occurs as a result of the alteration of minerals within the rock, where hydration or chemical reactions can lead to expansion. As minerals absorb water or react chemically, they can increase in volume, creating stress within the rock structure. Over time, this differential expansion can cause the rock to weaken and break apart, leading to a rounded weathered form.

In contrast, other weathering processes like frost wedging involve mechanical stress from freezing and thawing of water. Exfoliation refers specifically to the peeling away of layers from the outer part of rocks due to pressure release, rather than chemical reactions. Frost heaving is also a mechanical process that occurs when water in the soil freezes and expands, lifting the soil and rocks upward. Thus, spheroidal weathering is distinct in its focus on the chemical changes that lead to physical expansion of minerals, making it the most accurate choice in describing the process of mineral expansion during weathering.