Wow en-Namous is a dormant volcano that lies at the southernmost tip of the vast volcanic field of Al Harouj Al Aswad in central Libya. The volcanic field, which is the largest basaltic-basanitic field in Northern Africa, links the much smaller Jabal Assoda and Gheryan volcanic fields to the north with Jabal Eghei volcanic field of northeastern Tibesti to the south. These basalts, basanites, and locally, phonolites and nepheline-bearing trachytes define a broad northwesterly-southeasterly volcanic belt of Tertiary to Quaternary age.  The emplacement of these rocks, shown chemically to belong to the alkaline olivine basalt series, suggests an aborted intra-crtaonic rifting.

Wow en-Namous is a composite, somewhat elliptical cinder cone whose ENE-WSW and NNW-SSE axes measure about 1,250 and 800 m, respectively. With respect to its rather large, nearly circular caldera measuring approximately 5 km in diameter, the cone is off centered toward the northwest.   It is notable that the caldera is of comparable height and relief as the cone itself.  The cone has a complete rim and a smooth, but rather narrow bowl-shaped floor. Within the caldera bowl, three large, brackish lakes of irregular shapes and a number of smaller, seasonal lakes surround the cone except for its northwestern side.  The cone itself is asymmetric and shows shifting of centers of igneous activity in easterly and northerly directions. Repeated discharge of magma led to subsidence and easterly down tilting and topographic prominence of isolated peaks on the western rim.  The northwesterly slopes are also steeper than their southeasterly counterparts.  Relatively deep rills characterize the southern slopes and signify wetter climatic conditions during previous times subsequent to evolution of the structure.

Wow en-Namous is a unique structure in that it is the only explosive basaltic-basanitic volcano that can be found within the midst of fissure and vent basaltic-basanitic flows that make up the bulk of the NW-SE belt of volcanic fields of Libya. Lava flows are virtually absent in Wow en-Namous and the structure is a build-up of a massive sequence of tephra. The main ejecta, making up the body of the composite cone, consists mainly of vesicular lapilli of fresh-looking black basalt. Lapilli also blankets the caldera bowl and mantles the sandy plains beyond its rim for several kilometers.  Bombs and blocks abound in the immediate vicinity of the cone, but a few bombs may also occur near the caldera’s periphery. The bombs are spindle shaped or rounded.  The former are commonly tapered on both ends, brownish in color, vesicular and range in length from 10 to 30 cm. The rounded bombs, which range in diameter from 7-15 cm on average, are also brownish in color, less vesicular, and  include also dunite nodules that are coated with a thin basaltic skin. On the other hand, the blocks are ubiquitously dense, black in color and, on average, of relatively larger dimensions than the bombs.  These blocks appear to represent rock fragments torn off from the walls of the main volcanic vent.

The main cone consists largely of a 130-140 m thick sequence of (poorly sorted) lapilli agglomerate that appears from a distance to be well stratified.  The agglomerate, locally including bombs and some ash, shows no welding effects and is somewhat friable and suggests that ejecta was considerably cooled prior to cone build up. In a small area on the southern part of the main cone, however, there is evidence of a much quieter eruptive activity that is manifested in brownish basaltic spatter.  This basalt is also vesicular and consists of seemingly welded swarms of twisted stems that bear some resemblance to ribbon bombs.  The twisted basaltic ribbons also enclose lapilli and bombs such as those of the agglomerate and are thus of a younger age.  It is obvious that the rather restricted occurrence of this spatter argues against an origin as bombs, but at the same time, its congealed appearance is not typical of the spatter cited in the literature.  Formation of the “spatter” is consistent with a declining magmatic pressure during the waning stages of a volcanic cycle whereby the magma reservoir is nearly exhausted and all volatile content has escaped.  At such time, volcanism is somewhat quiescent.

One of the prominent features of the slopes of the main cone is the curling up and outward bulging of ash-and-sand thin crust adjacent to what appears to be gashes and cracks.  The latter  are suspected to be outlets of volcanic gases emanating from depth.  Best developed on the northern slopes, the underside of the thin crust shows nodular to botroidal accumulation of white salts and yellow sulfur, and these may reach a thickness of 5 cm.  Sulfur may also occur in the vicinity as small thin tablets scattered around or in the form of yellow staining on adjacent rocks.