IGCSE Geography Paper 4 CIE Practice Test

The Roundness Index measures the shape of a particle, specifically how rounded its edges are. As grains are transported, they experience abrasion that wears away sharp corners, making edges smoother and the grain more rounded. The index quantifies this degree of rounding, which helps us infer how far a grain has traveled or how much energy the environment has used to move and weather it. It’s about geometry—the actual shape of the object—not about the water’s depth, its acidity, or how fast the water is moving.