The perceptible downward sliding, falling, or flowing of masses of soil, rock, and debris (mixtures of soil and weathered rock fragments). Landslides range in size from a few cubic yards to over 3.5 × 10⁹ ft³ (1 × 10⁹ m³), their velocities range from an inch or so per day to over 300 ft/s (100 m/s), and their displacements may be about an inch to several miles.