What term refers to the development of rounded boulders due to concentric shell spalling?

The term that refers to the development of rounded boulders due to concentric shell spalling is known as spheroidally weathered boulders. This process involves the weathering of rock in such a way that layers peel away or spall off concentrically, leading to a rounded appearance. This type of weathering is often a physical process, typically facilitated by the alternation of wetting and drying, or warming and cooling, which causes outer layers of the boulder to expand and contract, eventually leading to the formation of smooth, rounded shapes.

In contrast, frost heaving primarily involves the movement of soil particles as water freezes and expands, which can disrupt the surface but does not create rounded boulders specifically. Exfoliation refers to the peeling away of outer layers of rock, often related to thermal stress but not necessarily resulting in the rounded boulders characteristic of spheroidal weathering. Chemical weathering involves the alteration of minerals and rocks due to chemical reactions, which can change the composition of rocks but does not directly lead to the rounded appearance seen in spheroidally weathered boulders.