A cliff is a vertical or very steep natural wall of rock. 

Cliffs are common on coasts, in mountainous areas, escarpments and along rivers. Cliffs are usually formed by rock that is resistant to erosion and weathering. 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 a landslide. Cliffs are known for forming major geographical features such as waterfalls.

The tallest cliff in the solar system may be Verona Rupes, an approximately 20 km (12 mile) high cliff on Miranda, a moon of the planet Uranus. 

The Ordnance Survey distinguishes between cliffs (continuous line along the top edge with projections down the face) and outcrops (continuous lines along lower edge).

Major cliffs

Asia
Above Sea
The Cliff of Kurosakitakao, Mikurajima, Tokyo prefecture, Japan 480 m above Pacific Ocean

Above Land
 Nanga Parbat, Pakistan Occupied Kashmir, 4600 m
 Great Trango Towers, Baltoro Muztagh, Northern Areas, Pakistan, 1340 m
 Uli Biaho Towers, Baltoro Glacier, Northern Areas, Pakistan
 Baintha Brakk (The Ogre), Panmah Muztagh, Northern Areas, Pakistan
 The Latok Group, Panmah Muztagh, Northern Areas, Pakistan
 Various cliffs in the Ak-Su Valley of Kyrgyzstan cliffs are high and steep.
 Masada, Israel, Dead Sea

Europe
Above Sea
Hornelen, Norway, 860 m above Frøysjøen
Cape Enniberg, Faroe Islands, 750 m above North Atlantic
Croaghaun, Achill Island, Ireland, 668 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, 589 m above Atlantic Ocean
Conachair, St Kilda, Scotland 427 m above Atlantic Ocean 
Cap Canaille, France, 416 m above Mediterranean Sea is the highest sea cliff in France
St John's Head (Hoy Orkney Islands Scotland) at 335 m is the  most vertical sea cliff in the UK 
Hangman cliffs, Devon, 318 m above Bristol Channel is the highest sea cliff in England
 White Cliffs of Dover, above the English Channel

Above land
Troll Wall, Norway 1100 m above base
Mięguszowiecki Szczyt north face rises to 1043 m above Morskie Oko lake level, High Tatras, Poland
Kjerag, Norway 984 m
Mały Kieżmarski Szczyt (north face), Tatra Mountains, Slovakia about 900 m denivelation (vertical rise)
Giewont (north face), Tatra Mountains, Poland, 852 m above Polana Strążyska glade
Kazalnica Mięguszowiecka, Tatra Mountains, Poland, 576 m above the Czarny Staw pod Rysami
The six great north faces of the Alps (Cima Grande di Lavaredo, Eiger, Grandes Jorasses, Matterhorn, Petit Dru and Piz Badile)

North America
 Mount Thor, Baffin Island, Canada; 1,370 m (4,500 ft) total; top 480 m (1,600 ft) is overhanging. This is commonly regarded as being the largest purely vertical drop on Earth at 1,250 m (4,100 ft). 
 The sheer north face of Polar Sun Spire, in the Sam Ford fjord of Baffin Island, has been reported as exceeding Mount Thor's west face in height. 
 Ketil's west face in Tasermiut, Greenland (also known as God's Thumbnail), has been reported as 1,400 – 1,450 m high, but there are arguments.

Other notable cliffs include:
 Mount Asgard, Baffin Island, Canada; vertical drop of about 1,200 m (4,000 ft).
 A variety of other 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, Kiguti Peak and Great Sail Peak, whilst there are others in Querbitter Fjord, and in Tasermiut, Greenland.
 El Capitan, Yosemite Valley, Sierra Nevada, California, United States; about 900 m (3,000 ft) high
 Northwest Face of Half Dome, near El Capitan; 1,340 m (4,400 ft) total, vertical portion about 610 m (2,000 ft)
 Painted Wall in Black Canyon of the Gunnison National Park, Colorado, United States; 685 m (2,250 ft)
 The west face of Notch Peak in southwestern Utah, United States; a limestone cliff of about 670 m (2,200 ft)
 All faces of Devil's Tower, Wyoming, United States
 Various faces of Shiprock, New Mexico, United States
 The North Face of North Twin Peak, Rocky Mountains, Alberta, Canada
 All walls of the Stawamus Chief, Squamish, British Columbia, Canada
 Calvert Cliffs along the Chesapeake Bay in Maryland
 Mt Siyeh Glacier National Park North Face 4200 ft sheer cliff

South America

 Autana Tepui, Venezuela, stands 1,300 m above the forest floor.
 Auyan Tepui, Venezuela, about 1000 m  (location of Angel Falls) (the falls are 979 m, the highest in the world)
 Pared de Gocta, Peru, 771 m
 Fortaleza canyon, Aparados da Serra National Park, Brazil, about 720 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
 Various faces of the Torres del Paine group, Patagonia, Chile

Africa
Above Sea
Kogelberg, Western Cape, South Africa, 1289 m above False Bay, Atlantic Ocean
Table Mountain, Cape Town, Western Cape, South Africa, 1086 m above Atlantic Ocean
Twelve Apostles, Cape Town, South Africa. A series of 17 precipitous peaks (all sharp cliff faces) ranging from ca 700 m to 1067 m above the Atlantic Ocean 
Risco de Faneque, Gran Canaria-Canary Islands, Spain, 1027 m above Atlantic Ocean
Guguy's Cliffs, Gran Canaria-Canary Islands, Spain, 725 m above Atlantic Ocean
La Mérica, La Gomera-Canary Islands, Spain, 711 m above Atlantic Ocean
Andén Verde, Gran Canaria-Canary Islands, Spain, 690 m above Atlantic Ocean
Karbonkelberg, Western Cape, South Africa, 653 m above Hout Bay, Atlantic Ocean
La Peña's Cliffs, El Hierro-Canary Islands, Spain, 652 m above Atlantic Ocean
Los Gigantes, Tenerife-Canary Islands, Spain, 637 m above Atlantic Ocean

Oceania
Above Sea
 Kalaupapa, Hawaii, 1010 m above Pacific Ocean

References

Footnotes

Landforms