Aloba Arch
Arche d'Aloba
Interesting facts
- In 2016 Ray Millar measured the arch's height directly with a laser rangefinder, getting about 403 feet, or roughly 123 metres.
- In 2004 Gunter Welz of the Natural Arch and Bridge Society laser-measured the opening's base at 48 metres, then estimated the full span at about 77 metres from photographs.
- The Natural Arch and Bridge Society ranks Aloba eighth on its list of the world's longest natural arches.
- It stands about 150 feet taller than Utah's famous Rainbow Bridge.
- Aloba likely began as a buttress arch in a sandstone fin; later a stream was diverted through it and scoured the lower half, making it a natural bridge too.
- The arch is cut through two sandstone layers, a hard upper one and a softer lower one, and their boundary lies near its mid-height.
- Its opening is an upright oval roughly twice as tall as it is wide, and the lintel curves on both its upper and lower edges.
- Marsel van Oosten photographed the arch by moonlight in a 15-second exposure, an image that won a special commendation from London's Natural History Museum.
- The surrounding Ennedi massif holds thousands of rock paintings and engravings, many showing cattle, made over several thousand years.
- Gueltas in the Ennedi's canyons, such as the Guelta d'Archei, shelter a relict population of dwarf West African crocodiles left over from a wetter Sahara.
Why it is worth it
Aloba Arch stands in the Ennedi, a sandstone plateau in the far northeast of Chad, in the heart of the Sahara. It is one of the largest natural arches on Earth: the opening rises to a height of about 120 metres and spans roughly 76 metres, a curved band of rock so thin compared with its size that from a distance it looks like a doorway cut in the sky. Its dimensions come largely from photographic estimates rather than precise survey — a sign of how remote it is — but even with that uncertainty it ranks among the longest known arches outside China and the canyon country of Utah.
The comparison with the American Southwest is apt. The Ennedi has a geology much like that of the Colorado Plateau: layers of sandstone that wind and occasional water have carved into canyons, cliffs, isolated pinnacles and a number of arches. Aloba is the most spectacular of them, but the whole landscape around it is a gallery of rock forms rising abruptly from the sand and cut by deep canyons and valleys.
In 2016 UNESCO inscribed the Ennedi Massif on the World Heritage List as a natural and cultural landscape, recognising both the eroded sandstone scenery and the human history preserved in it. Very few outsiders see Aloba, and there are no facilities of any kind; the experience is of standing under an enormous stone span in near-total silence, with the Sahara light shifting across its flanks through the day. Early morning and late afternoon bring out the colour and texture of the rock.
Getting there
The arch lies in the Ennedi Plateau, about 86 km from the town of Fada in a straight line; the ground journey across open desert is considerably longer. The practical gateway is N'Djamena International Airport (NDJ), about 930 km away, from where visits are organised as multi-day 4x4 expeditions with local guides, usually via Fada. There is no public transport and no road to the arch.
On these lists
From the encyclopaedia
Aloba Arch is a natural arch located in Chad. Large natural arches are somewhat rare outside the southern and western regions of China and the Colorado Plateau of the southwest United States. Chad's Ennedi Plateau, located within the Sahara Desert in the northeast part of the country, has a geology similar to the Colorado Plateau and has produced a number of natural arches and similar landforms, although only Aloba can claim to be on the top ten list of longest arches in the world.
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