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