canyons gorges ravines passes gulfs gaps defiles flumes gills notches saddles chasms linns cols gullies cuts arroyos valleys channels ditch gulleys trenches fissures cloughs dongas coulees clove crevasses chines bunnies barrancas abysses khors nullahs rifts hollows crevices pits clefts breaks voids openings passages glens cavities interstices apertures rent crack fractures slits craters holes crannies watercourses vales dales dips routes shafts paths passageways corridors space rupture division separation orifices slots interspaces lacunae vacuity furrows splits cleavage indentation chimneys breaches schisms checks rimes gashes chinks depression combes dells denes indentures dint caves caverns potholes pockets concavity dimples excavation pockmarks dugouts recess chambers