The rate at which geomorphological processes wear away land surfaces. Rates vary widely, depending on both processes and environments, as shown by the following figures: glacial abrasion, 1000 B (bubnoff units); soil creep (under a temperate, maritime climate), 1–5 B; solifluction (cold climate), 25–250 B; slope wash, 2–200 B; solutional loss, 2–100 B; sea cliff retreat (rocks of medium hardness), 4000 B; soil erosion resulting from human activity, 2000–8000 B.