Waw an Namus
Interesting facts
- The collapse that formed the caldera displaced more than 800 million cubic metres of rock.
- Ripples of dark volcanic grit around the crater, some up to 1.5 metres high, have been studied as an analogue for similar megaripples on Mars.
- Trade winds have carried the black tephra more than 100 kilometres to the southwest across the desert.
- The largest lake covers about 0.15 square kilometres and is 12.5 metres deep; the deepest pool reaches 15 to 16 metres.
- The lakes lose around 1.5 million cubic metres of water a year to evaporation and survive only because groundwater keeps refilling them.
- Isotope analysis shows that the lake water is young, certainly less than 8,000 years old rather than an ancient fossil reserve.
- The magma that built the volcano rose from the mantle about 130 kilometres down, carrying fragments of mantle rock to the surface.
- Reeds up to four metres tall grow over part of the largest lake, in one of the driest landscapes on Earth.
- Early geologists estimated the central cone at less than about a thousand years old, while one later dating attempt returned an uncertainty larger than the age itself.
- Birds recorded at the oasis include lanner falcons, bluethroats, northern shovelers, black-necked grebes and water rails.
Why it is worth it
Seen from above, Waw an Namus looks like a black ink stain on the yellow sand of the central Sahara. A dark apron of volcanic ash and cinders spreads for 10 to 20 kilometres around a caldera some 4 kilometres wide and about 100 metres deep, and the contrast is sharp enough to be picked out on images taken from space. Inside the crater, against all expectation in one of the driest places on Earth, lie small lakes fringed with reeds and palms, some of them tinted red, around a black cone of scoria.
The volcano stands in isolation in the eastern Fezzan region of Libya, far from any settlement; the old caravan route between Kufra and Sabha passes nearby, and ancient graves have been found at the site. Its name is usually translated as "oasis of mosquitoes", after the insects that breed in its waters. The central cone rises about 140 metres from the crater floor and has a summit crater of its own, around 150 metres across and 80 metres deep. A smaller crater lies to the northwest, where salty mud rather than lava was erupted. The dark ash blanket covers roughly 300 square kilometres; the wind has heaped it into ripples and has carried it far to the southwest.
The lakes are fed by groundwater and springs, and together cover about 0.3 square kilometres; they lose much of their water to evaporation and shrink with the seasons. Acacias, date and doum palms, tamarisks and tall reeds grow around them, and the oasis attracts water birds, including ducks, grebes, coots and moorhens, some of which are probably migrants spending the winter. Hot springs with sulphurous water are still active.
How old Waw an Namus is remains uncertain. One potassium-argon date points to about 200,000 years ago, but the fresh look of the cone, the absence of Neolithic artefacts and the way the caldera cuts across a Holocene drainage system have led some researchers to suggest it formed only a few thousand years ago.
Getting there
Waw an Namus lies deep in the Libyan desert, roughly 400 km from the city of Sabha, whose airport, Sabha Airport (SEB), is the nearest, about 402 km away.
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From the encyclopaedia
Waw an Namus is a volcano in Libya. Of either Pleistocene or Holocene age, it is located within the eastern Fezzan region. The origin of the volcanism there and at Al Haruj farther north is not clear. Radiometric dating has yielded an age of about 200,000 years, but other circumstantial evidence points to a formation of the volcano during Holocene or even historical times.
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