Most cliffs have some form of scree slope at their base. In arid areas or under high cliffs, these are generally exposed jumbles of fallen rock. In areas of higher moisture, a soil slope may obscure the talus. Many cliffs also feature tributarywaterfalls or rock shelters. Sometimes a cliff peters out at the end of a ridge, with tea tables or other types of rock columns remaining. Coastal erosion may lead to the formation of sea cliffs along a receding coastline.
The Ordnance Survey distinguishes between cliffs (continuous line along the top edge with projections down the face) and outcrops (continuous lines along lower edge).
The far southwestern aspect of Nanga Parbat's Rupal face, highest cliff (rock wall/mountain face) in the world. The steepest part of the face lies 2km to the northeast.
Given that a cliff need not be exactly vertical, there can be ambiguity about whether a given slope is a cliff or not, and also about how much of a certain slope to count as a cliff. For example, given a truly vertical rock wall above a very steep slope, one could count just the rock wall, or the combination. This makes listings of cliffs an inherently uncertain endeavor.
Some of the largest cliffs on Earth are found underwater. For example, an 8,000-metre drop over a 4,250-metre span can be found at a ridge sitting inside the Kermadec Trench.
The highest cliff (rock wall, mountain face) in the world, is Nanga Parbat's Rupal Flank, which rises approximately 4,600 metres, or 15,000 feet, above its base. According to other sources, the highest cliff in the world, about 1,340 m high, is the east face of Great Trango in the Karakoram mountains of northern Pakistan. This uses a fairly stringent notion of cliff, as the 1,340 m figure refers to a nearly vertical headwall of two stacked pillars; adding in a very steep approach brings the total drop from the East Face precipice to the nearby Dunge Glacier to nearly 2,000 m.
The location of the world's highest sea cliffs depends also on the definition of 'cliff' that is used. Guinness World Records states it is Kalaupapa, Hawaii, at 1,010 m high. Another contender is the north face of Mitre Peak, which drops 1683 metres to Milford Sound, New Zealand. These are subject to a less stringent definition, as the average slope of these cliffs at Kaulapapa is about 1.7, corresponding to an angle of 60 degrees, and Mitre Peak is similar. A more vertical drop into the sea can be found at Maujit Qaqarssuasia (also known as the 'Thumbnail') which is situated in the Torssukátak fjord area at the very tip of South Greenland and drops 1,560 m near-vertically.
Considering a truly vertical drop, Mount Thor on Baffin Island in ArcticCanada is often considered the highest at 1370 m (4500 ft) high in total (the top 480 m (1600 ft) is overhanging), and is said to give it the longest vertical drop on Earth at 1,250 m (4,100 ft). However, cliffs on Baffin Island, such as Polar Sun Spire, or others in remote areas of Greenland may be higher.
Trango Towers: East Face Great Trango Tower, Baltoro Muztagh, Northern Areas, Pakistan, 1,340 m (near vertical headwall), 2,100 m (very steep overall drop from East Summit to Dunge Glacier). Northwest Face drops approximately 2,200 m to the Trango Glacier below, but with a taller slab topped out with a shorter overhanging headwall of approximately 1,000 m. The Southwest "Azeem" Ridge forms the group's tallest steep rise of roughly 2,286m (7,500 feet) from the Trango Glacier to the Southwest summit.
Several big granite faces in the Arctic regions vie for the title of 'highest vertical drop on Earth', but reliable measurements are not always available. The possible contenders include (measurements are approximate):
The sheer north face of Polar Sun Spire, in the Sam Ford fjord of Baffin Island, rises 4,300 ft above the flat frozen fjord, although the lower portion of the face breaks from the vertical wall with a series of ledges and buttresses.
Ketil's west face in Tasermiut, Greenland (also known as God's Thumbnail), has been reported as 1,400 m – 1,450 m high, (although some doubt has been cast on this).
Vertical cliffs measured at approximately 1,000 m (3,280 ft) in height can be found along the Sam Ford fjord in Baffin Island, such as Walker Citadel (some climbing sources claim a 4,200 foot wall), Kiguti Peak and Great Sail Peak, while there are others in Querbitter Fjord, and in Tasermiut, Greenland.
Northwest Face of Half Dome, near El Capitan; 1,444 m (4,737 ft) total, vertical portion about 610 m (2,000 ft)
The west face of Notch Peak in the House Range of southwestern Utah, U.S.; a carbonate rock pure vertical drop of about 670 m (2,200 ft), with 4,450 feet (1,356 m) from the top of the cliff to valley floor (bottom of the canyon below the notch)
East face of the West Temple in Zion National Park Utah, believed to be the tallest sandstone cliff in the world, 670 m
The Sentinell, Western Cape, South Africa, 331 m (1,086 ft) above Hout Bay, Atlantic Ocean
Cape Point, Western Cape, South Africa, 249 m (817 ft) above Atlantic Ocean
Drakensberg Amphitheatre, South Africa 1,200 m (3,900 ft) above base, 5 km (3.1 mi) long. The Tugela Falls, the world's second tallest waterfall, falls 948 m (3,110 ft) over the edge of the cliff face.
Klein Winterhoek, Western Cape, South Africa, 1,220 m (4,000 ft) above base.
Wall of Fire, Swartberg, Western Cape, South Africa 700 m (2,300 ft) cliff composed of vertically displaced quartzite
Tsaranoro, Madagascar, 700 m (2,300 ft) above base
Karambony, Madagascar, 380 m (1,250 ft) above base.
Innumerable peaks in the Drakensberg mountains of South Africa are considered cliff formations. The Drakensberg Range is regarded, together with Ethiopia's Simien Mountains, as one of the two finest erosional mountain ranges on Earth. Because of their near-unique geological formation, the range has an extraordinarily high percentage of cliff faces making up its length, particularly along the highest portion of the range. This portion of the range is virtually uninterrupted cliff faces, ranging from 600 m (2,000 ft) to 1,200 m (3,900 ft) in height for almost 250 km (160 mi). Of all, the "Drakensberg Amphitheatre" (mentioned above) is most well known. Other notable cliffs include the Trojan Wall, Cleft Peak, Injisuthi Triplets, Cathedral Peak, Monk's Cowl, Mnweni Buttress, etc. The cliff faces of the Blyde River Canyon, technically still part of the Drakensberg, may be over 800 m (2,600 ft), with the main face of the Swadini Buttress approximately 1,000 m (3,300 ft) tall.
Cliff landforms provide unique habitat niches to a variety of plants and animals, whose preferences and needs are suited by the vertical geometry of this landform type. For example, a number of birds have decided affinities for choosing cliff locations for nesting, often driven by the defensibility of these locations as well as absence of certain predators.