In geography and geology, a cliff is an area of rock which has a general angle defined by the vertical, or nearly vertical. Cliffs are formed by the processes of weathering and erosion, with the effect of gravity. Cliffs are common on coasts, in mountainous areas, escarpments and along rivers. Cliffs are usually formed by rock that is resistant to weathering and erosion. Sedimentary rocks most likely to form cliffs include sandstone, limestone, chalk, and dolomite. Igneous rocks such as granite and basalt also often form cliffs.
An escarpment (or scarp) is a type of cliff, formed by the movement of a geologic fault or landslides, or maybe by rock slides by falling rock which biologically changes the differential erosion of rock layers of selectioning or deforming hardness.
Most cliffs have some form of scree slope at their base. In arid areas or under high cliffs, they are generally exposed jumbles of fallen rock. In areas of higher moisture, a soil slope may obscure the talus. Many cliffs also feature tributary waterfalls or rock shelters. Sometimes a cliff peters out at the end of a ridge, with mushroom rocks 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 around most cliffs (continuous line along the topper edge with projections down the face) and outcrops (continuous lines along lower edge).
Cliff comes from the Old English word clif of essentially the same meaning, cognate with Dutch, Low German, and Old Norse klif 'cliff'. These may in turn all be from a Romance loanword into Primitive Germanic that has its origins in the Latin forms clivus / clevus ("slope" or "hillside").
Large and famous cliffs
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Given that a cliff does not need to 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. Listings of cliffs are thus inherently uncertain.
Some of the largest cliffs on Earth are found underwater. For example, an 8,000 m drop over a 4,250 m span can be found at a ridge sitting inside the Kermadec Trench.
The highest very steep non-vertical cliffs in the world are Nanga Parbat's Rupal Face and Gyala Peri's southeast face, which both rise approximately 4,600 m, or 15,000 ft, above their 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 1,683 m 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 Arctic Canada 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, other cliffs on Baffin Island, such as Polar Sun Spire in the Sam Ford Fjord, or others in remote areas of Greenland may be higher.
The following is an incomplete list of cliffs of the world.
- Ra's Sajir, Oman, 900 m (3,000 ft) above the Arabian Sea
- Tōjinbō, Sakai, Fukui prefecture, Japan 25 m above Sea of Japan
- Qingshui Cliff, Xiulin Township, Hualien County, Taiwan averaging 800 m above Pacific Ocean. The tallest peak, Qingshui Mountain, rises 2408 m directly from the Pacific Ocean.
- Theoprosopon, between Chekka and Selaata in north Lebanon jutting into the Mediterranean.
- Nanga Parbat, Rupal Face, Azad Kashmir, Pakistan, 4,600 m
- Gyala Peri, southeast face, Mêdog County, Tibet, China, 4,600 m
- Ultar Sar southwest face, Karakoram, Gilgit–Baltistan, Pakistan, 3,000 m
- Qingshui Cliff, Xiulin Township, Hualien County, Taiwan averaging 800 m above Pacific Ocean. The tallest peak, Qingshui Mountain, rises 2408 meters directly from the Pacific Ocean.
- Trango Towers: East Face Great Trango Tower, Baltoro Muztagh, Gilgit–Baltistan, 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 2,286 m (7,500 ft) from the Trango Glacier to the Southwest summit.
- Uli Biaho Towers, Baltoro Glacier, Gilgit–Baltistan, Pakistan
- Baintha Brakk (The Ogre), Panmah Muztagh, Gilgit–Baltistan, Pakistan, 2,000 m
- The Latok Group, Panmah Muztagh, Gilgit–Baltistan, Pakistan, 1,800 m
- Spantik northwest face, Karakoram, Gilgit–Baltistan, Pakistan, 2,000 m
- Shispare Sar southwest face, Karakoram, Gilgit–Baltistan, Pakistan, 3,200 m
- Hunza Peak south face, Karakoram, Gilgit–Baltistan, Pakistan, 1,700 m
- Lhotse south face, Mahalangur Himal, Nepal, 3200 m
- Lhotse northeast face, Mahalangur Himal, Nepal, 2900m
- K2 west face, Karakoram, Gilgit–Baltistan, Pakistan, 2900m
- Meru Peak, Uttarakhand, India, 1200 m
- Ramon Crater, Israel, 400 m
- Various cliffs in the Ak-Su Valley of Kyrgyzstan are high and steep.
- World's End, Horton Plains, Nuwara Eliya, Sri Lanka. It has a sheer drop of about 4000 ft (1200 m)
- Various cliffs in Zhangjiajie National Forest Park, Hunan Province, China. The cliffs can get to around 1,000 ft (300 m).
- Faneque, Gran Canaria, Spain, 1027 m above Atlantic Ocean
- Hornelen, Norway, 860 m above Skatestraumen
- Cape Enniberg, Faroe Islands, 750 m above North Atlantic
- Croaghaun, Achill Island, Ireland, 688 m above Atlantic Ocean
- Hvanndalabjarg, Ólafsfjörður, Iceland, 630 m above Atlantic Ocean
- Vixía Herbeira, Northern Galicia, Spain, 621 m above Atlantic Ocean
- Preikestolen, Norway, 604 m above Lysefjorden
- Slieve League, Ireland, 601 m above Atlantic Ocean
- Cabo Girão, Madeira, Portugal, 589 m above Atlantic Ocean
- Monte Solaro, Capri, Italy, 589 m above the Mediterranean Sea
- Jaizkibel, Spain, 547 m above the Bay of Biscay
- Beinisvørð, Faroe Islands, 470 m above North Atlantic
- Conachair, St Kilda, Scotland 427 m above Atlantic Ocean, highest sea cliff in the UK
- Cap Canaille, France, 394 m above Mediterranean sea is the highest sea cliff in France
- The Kame, Foula, Shetland, 376 m above the North Atlantic, second highest sea cliff in the UK
- Hangman cliffs, Devon 318 m above Bristol Channel is the highest sea cliff in England
- Benwee Head Cliffs, Erris, Co. Mayo, Ireland, 304 m above Atlantic Ocean
- Dingli Cliffs, Malta, 250 m above Mediterranean sea
- High Cliff, between Boscastle and St Gennys, 223 m above Celtic Sea
- Cliffs of Moher, Ireland, 217 m above Atlantic Ocean
- Beachy Head, England, 162 m above the English Channel
- Møns Klint, Denmark, 143 m above Baltic Sea
- Le Tréport, France, 110 m above the English Channel
- White cliffs of Dover, England, 100 m above the Strait of Dover
- Étretat, France, 84 m above the English Channel
- Kaliakra cliffs, Bulgaria, more than 70 m above the Black Sea
- Ontika Limestone cliff, Estonia, 55 m above Baltic Sea.
- Snake Island, Ukraine, 41 m above the Black Sea
- The six great north faces of the Alps (Eiger 1,500 m, Matterhorn 1,350 m, Grandes Jorasses 1,100 m, Petit Dru 1,000 m, and Piz Badile 850 m, Cima Grande di Lavaredo 450 m)
- Troll Wall, Norway 1,100 m above base
- Mięguszowiecki Szczyt north face rises to 1,043 m above Morskie Oko lake level, High Tatras, Poland
- Kjerag, Norway 984 m.
- Giewont (north face), Tatra Mountains, Poland, 852 m above Polana Strążyska glade
- Vihren peak north face, Pirin Mountain, Bulgaria 460 m to the (Golemiya Kazan)
- Dvuglav, Rila Mountain, Bulgaria 460 m (south face)
- Vratsata, Vrachanski Balkan Nature Park, Bulgaria 400 m 
- Belogradchik Rocks, Bulgaria - up to 200 m high sandstone towers
Several big granite faces in the Arctic region vie for the title of 'highest vertical drop on Earth', but reliable measurements are not always available. The possible contenders include (measurements are approximate):
Mount Thor, Baffin Island, Canada; 1,370 m (4,500 ft) total; top 480 m (1600 ft) is overhanging. This is commonly regarded as being the largest vertical drop on Earth ot:leapyear at 1,250 m (4,100 ft).
- Ketil's and its neighbor Ulamertorsuaq's west faces in Tasermiut, Greenland have been reported as over 1,000 m high. Another relevant cliff in Greenland is Agdlerussakasit's Thumbnail.
Other notable cliffs include:
- Mount Asgard, Baffin Island, Canada; vertical drop of about 1,200 m (4,000 ft).
- El Capitan, Yosemite Valley, California, United States; 900 m (3,000 ft)
- Toroweap (a.k.a. Tuweep), Grand Canyon, Arizona, United States; 900 m (3,000 ft)
- Painted Wall in Black Canyon of the Gunnison National Park, Colorado, United States; 685 m (2,250 ft)
- Northwest Face of Half Dome, near El Capitan, California, United States; 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, United States believed to be the tallest sandstone cliff in the world, 670 m
- All faces of Devils Tower, Wyoming, United States, 195 m
- Faces of Shiprock, New Mexico, United States, 400 m
- Cap Éternité of Saguenay River, Quebec, Canada, 347 m
- The North Face of North Twin Peak, Rocky Mountains, Alberta, Canada, 1,200 m
- Raftsmen's Acropolis, a rock face of the Montagne des Érables, Quebec, Canada, 800 m
- Rockwall, Kootenay National Park, British Columbia, Canada, 30 km of mostly unbroken cliffs up to 900 m 
- All walls of the Stawamus Chief, Squamish, British Columbia, Canada, up to 500 m
- Calvert Cliffs along the Chesapeake Bay in Maryland, U.S. 25 m
- Mount Siyeh, Glacier National Park (U.S.) north face, 1,270 m (4,170 ft)
- Longs Peak Diamond, Rocky Mountain National Park, Colorado, United States, 400 m
- Royal Gorge cliffs, Colorado, United States, 350 m
- Doublet Peak, southwest face, Wind River Range, Wyoming, United States, 370 m
- Big Sandy Mountain, east face buttress, Wind River Range, Wyoming, 550 m
- Temple Peak, east face, Wind River Range, Wyoming, 400 m
- East Temple Peak, north face, Wind River Range, Wyoming, 450 m
- Uncompahgre Peak, northeast face, San Juan Range, Colorado, 275 m (550 m rise above surrounding plateau)
- Grand Teton, north face Teton Range, Wyoming 760 m (2,490 ft)
- Ättestupan Cliff, northern side of Kaiser Franz Joseph Fjord, Greenland 1,300 m (4,300 ft)
- Pared Sur Cerro Aconcagua. Las Heras, Mendoza, Argentina, 2,700 m
- Scratched Stone (Pedra Riscada), São José do Divino/MG, Minas Gerais, Brazil, 1,480 m
- All faces of Auyan Tepui, along with all other Tepuis, Venezuela, Brazil, and Guyana, Auyan Tepui is about 1,000 m (location of Angel Falls) (the falls are 979 m, the highest in the world)
- Pared de Gocta, Peru, 771 m
- Pedra Azul, Pedra Azul State Park, Espirito Santo, Brazil, 540 m
- Pão de Açúcar/Sugar Loaf, Rio de Janeiro, Brazil, 395 m
- All faces of Cerro Torre, Patagonia, Chile-Argentina
- All faces of Cerro Chalten (Fitz Roy), Patagonia, Argentina-Chile, 1200 m
- Faces of the Torres del Paine group, Patagonia, Chile, up to 900 m
- Kogelberg, Western Cape, South Africa, 1,289 m (4,229 ft) above False Bay, Atlantic Ocean
- Table Mountain, Cape Town, Western Cape, South Africa, 1,086 m (3,563 ft) above Atlantic Ocean
- Karbonkelberg, Cape Town, Western Cape, South Africa, 653 m (2,142 ft) above Hout Bay, Atlantic Ocean
- Los Gigantes, Tenerife, Canary Islands, Spain, 637 m (2,090 ft) above Atlantic Ocean
- Chapman's Peak, Western Cape, South Africa, 596 m (1,955 ft) above Atlantic Ocean
- Anaga's Cliffs, Tenerife, Canary Islands, Spain, 592 m (1,942 ft) above Atlantic Ocean
- Cape Hangklip, Western Cape, South Africa, 453.1 m (1,487 ft) above False 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.
- Mount Meru, Tanzania Caldera Cliffs, 1,500 m (4,900 ft)
- 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.
- Mitre Peak, New Zealand, 1,683 m above Milford Sound
- The Lion, New Zealand, 1,302 m above Milford Sound (drops from approx 1280m to sea level in a very short distance)
- The Elephant, New Zealand, has cliffs falling approx 1180m into Milford Sound, and a 900m drop in less than 300m horizontally
- Kalaupapa, Hawaii, 1,010 m above Pacific Ocean
- Great Australian Bight
- Zuytdorp Cliffs in Western Australia
- Ball's Pyramid, a sea stack 562m high and only 200m across at its base
- The Twelve Apostles (Victoria). A series of sea stacks in Australia, ranging from approximately 50 to 70 m above the Bass Strait
- Tasman National Park, Tasmania, has 300m dolerite sea cliffs dropping directly to the ocean in columnar form
- Lovers Leap, Highcliff, and The Chasm, on Otago Peninsula, New Zealand, all 200 to 300 m above the Pacific Ocean
- Mount Banks in the Blue Mountains National Park, New South Wales, Australia: west of its saddle there is a 490 m fall within 100 M horizontally.
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.
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