Fish River Canyon is the largest canyon in Africa: a gorge in the ǁKaras Region of southern Namibia about 160 km (100 mi) long, up to 27 km (17 mi) wide and 549 m (1,801 ft) deep at its deepest point. It was cut by the Fish River, Namibia's longest interior river, into a dry, stony plateau, and it formed in stages over hundreds of millions of years: a north–south rift around 650 million years ago set the river's course, glaciers deepened the trough about 300 million years ago, and the uplift of Africa after the break-up of Gondwana let the river saw a twisting lower canyon into hard gneiss. The lower end lies inside the ǀAi-ǀAis/Richtersveld Transfrontier Park, created in 2003, and the canyon is the second most visited attraction in Namibia.
The Oldest Layers: Gneiss Basement and Flat-Lying Dolomite
The canyon's story starts with its floor. The deepest rocks exposed in the lower gorge are gneisses, metamorphic rocks formed when older crust was buried, heated and squeezed until its minerals separated into bands. Gneiss is far harder than the sediments above it, and that hardness controls almost everything about the canyon's shape. For a long period it stopped the river from cutting down at all, which is why geologists divide Fish River Canyon into two parts: an upper canyon, where erosion was held back by the gneiss, and a lower canyon, cut only after the river finally broke through it.
Above the basement, and especially upstream, the river runs through horizontal strata of dolomite, a carbonate rock laid down in layers on the floor of shallow seas and later altered. These flat beds give the canyon rim its level, tabletop horizon. From the viewpoints near Hobas the walls show both worlds at once: banded, contorted rock deep in the gorge, and neat sedimentary layers stacked above it like the pages of a closed book.
650 to 300 Million Years Ago: A Graben and the Dwyka Ice
About 650 million years ago, movement of the Earth's plates dropped a long strip of crust between parallel faults, creating a north–south graben. A graben is a sunken block, and once it existed it acted as a natural channel. The ancient Fish River followed it southward, and over a very long time the river wore the floor of the graben into a broad, flat plain. That plain is the basis of today's upper canyon, the wide outer valley that visitors see first from the rim.
The next sculptor was ice. Around 300 million years ago, southern Africa lay over the Antarctic Circle as part of the supercontinent Gondwana, during what is now called the Late Paleozoic icehouse, an ice age that lasted from about 360 to 255 million years ago. Ice sheets spread across the region, and their deposits are preserved across southern Africa as the Dwyka Group, the lowest layer of the Karoo Supergroup. In the Fish River area this Dwyka glaciation scoured and deepened the existing trough. When the ice melted, it left a valley that was already deep and wide, but still floored by resistant gneiss that the river could barely touch.
After Gondwana: Uplift Drives the Lower Canyon into the Gneiss
The decisive change came with the break-up of Gondwana. Africa and South America began to separate as the South Atlantic opened from south to north during the Jurassic and Cretaceous; south of the Walvis Ridge, off the Namibian coast, the Etendeka lavas and the start of sea-floor spreading are dated to about 130 to 135 million years ago. As the continents parted, southern Africa rose. A higher landscape meant a steeper Fish River, and a steeper river carries more energy to cut its bed.
With that extra gradient the river finally broke through the gneiss and began cutting the lower canyon. Because it had wandered across a flat plain before the uplift, it carried its loops with it as it cut down, locking a meandering course into solid rock. That is why the inner gorge is so tightly twisted, with hairpin bends that double back on themselves again and again. Today the deepest point of the canyon is 549 m below the rim.
Size comparisons are often made with the Grand Canyon in Arizona, which is 446 km long and reaches 1,857 m deep. Within Africa, the closest rival usually cited is the Blyde River Canyon in South Africa, often ranked just behind the Fish River among the world's largest canyons and a "green canyon" covered in subtropical vegetation, which makes a useful contrast with the bare rock of the Fish River.
Today's Fish River: Late-Summer Floods, Long Pools and Two Dams
The river that built the canyon is still at work, but only in bursts. The Fish River is about 650 km long. It rises in the Naukluft Mountains and flows some 150 km to the Hardap Dam near Mariental, then south through the canyon to join the Orange River on the border with South Africa, about 100 km from the Atlantic Ocean. Its flow is seasonal. It usually floods in late summer after inland rains, and for the rest of the year it shrinks to a chain of long, narrow pools; in winter parts of it dry up completely.
Two dams now shape that flow upstream of the canyon. The Hardap Dam, built between 1960 and 1963, holds about 320 million m³ across a surface of 25 km² and supplies water to Mariental. Below it, all the water reaching the canyon comes from tributaries. Mariental flooded in 1923 and 1934 before the dam existed, and again in 1972, 1974, 1976, 2000 and 2006 after it was built, so the reservoir is now kept no more than 70 per cent full. Further downstream, the Neckartal Dam near Berseba, about 40 km northwest of Keetmanshoop, was completed in October 2018 at a cost of about N$5.7 billion. It has more than three times Hardap's capacity, first overflowed on 19 January 2021, and was built for a 5,000-hectare irrigation scheme that has yet to be established.
The same rainy seasons reach the canyon floor. Severe floods in 1972, 1974 and 1988 forced the resort at ǀAi-ǀAis to close, and the 1972 flood destroyed the camp except for one building on higher ground. Because summer flooding and heat make the gorge dangerous, the canyon's hiking season is confined to the southern winter.
What the Rocks Built: Hobas, the Five-Day Trail and the ǀAi-ǀAis Springs
The upper and lower canyons were declared a national monument in 1962. Public viewpoints are reached from Hobas, a campsite with camel thorn trees about 70 km north of ǀAi-ǀAis, which houses the offices of the Ministry of Environment and Tourism and Namibia Wildlife Resorts. That northern part of the canyon belongs to the transfrontier park; the rest of the gorge is privately owned.
The canyon floor is best known for its hiking trail. It starts at a car park 13 km west of Hobas with a steep descent of about 2 km, where chains help hikers over the first 100 m, and then follows roughly 88 km of the river floor to ǀAi-ǀAis, usually over five days. The route is unmarked and has no facilities, and open fires are banned. Permits are issued only between 1 May and 15 September, because summer brings flash floods and temperatures of up to 48°C by day and 30°C at night. Groups must have between 3 and 30 people, every hiker must be over 12, and each needs a doctor's certificate of fitness. In the hiking season temperatures usually range from about 5°C to 30°C.
The trail ends at ǀAi-ǀAis, whose name in Khoekhoe means "fire-fire", or scalding hot. Sulphurous springs rise from deep beneath the riverbed at about 60°C, rich in sulphur, chloride and fluoride, and form an oasis in an extremely arid area 128 km west of Karasburg. Local tradition holds that a Nama shepherd found them in 1850. German forces used the springs as a base during the Nama uprising of 1903 to 1907, and South African troops recovered there in 1915 during the South West Africa Campaign. The springs became a national monument in 1964, a rest camp opened in 1965, and the resort was officially opened on 16 March 1971.
In 2003 the presidents of Namibia and South Africa signed a memorandum on 17 August that joined the ǀAi-ǀAis Hot Springs Game Park with South Africa's Richtersveld National Park across the Orange River, forming the ǀAi-ǀAis/Richtersveld Transfrontier Park. A tourist crossing at Sendelingsdrift opened in 2007. The park receives an average of only 68 mm of rain a year, yet more than 360 plant species have been recorded in a single square kilometre, including quiver trees, tall aloes and the half-mens, a succulent with an unbranched stem up to 4 m tall. Nama herders still move livestock across this landscape in search of sparse rain, and the Nama language survives here more strongly than anywhere else in Namaqualand. For the wider setting of the canyon, see our guide to Namibia, or compare its 549 m with the much deeper gorge described in the geography of the Grand Canyon.