Geological feature of the place

Being in a place of interface between two tectonic mega structures, the African and Somali plates, which are pulling apart(referred to us, rifting) and away from the Arabian plate, awash National Park occurs in one of the most geologically active regions in the world. The phenomena of rifting and volcanism has been an ongoing process since at least 40 million years(Myr)ago,and with in Ethiopia it is estimated to have started some 25to 30 Myr.(stager 1990).however in the region of Awash national Park volcanism is started to have persisted for as long as 5 myr(Gibson 1967of ).As a result ,these activities have played a major role in the formation of both the structure ,the hydrology and ,and the soils of the lands throughout the conservation area .While the Geology has been described in detail by both Gibson(1967 and no date) and Robertson(1970),we have chosen to briefly describe it again in order for the reader to have a better understanding of its influence on the hydrology and soils of the area.

Dominating the Scenery in the Conservation Area is Fantale Mountain. Its creation, along with several subsequent eruptions from its crater has contributed to the general structure of the area surrounding it. Foremost are three generations of welded tuff flows ,which have covered large parts of the mountainside, resulting in the appearance of a smooth, undulating surface. Two of these flows also spread as far as the surrounding plains, flowing freely over the surface, burying features of small relief while flowing around the larger features. The result was a general leveling of most of the plains areas.

Welded tuff originates as a viscous flow which is made up of a mixture of solid fragments, liquid droplets and large amounts of hot gas. Once cool it solidifies as a compressed mass with hard crystalline droplets. After these flows came several geologic incidents which resulted in isolated punctuations in the relief of the plains. The first of these was a stretching and fracturing of the land, giving rise to several long fissures in the area. These fissures or large cracks, are steep sided with some as long as 2 km and as deep as 60m.The best evidence for this activity can be found close to the foot of Fantale Mountain where the Welded tuff is dissected by several of these cracks. To the north, along the upper foothills in the “key Afer”area,are also several fissures, two of which have active steam vents in them. This hot steam has colored the surrounding tuff soils red, hence the Amharic name “Key Afer”. These same fracture lines have also contributed to the formation of another type of geologic feature referred to as “cinder cone” or “tuff ring”.

More recent geologic activity has resulted in the eruption of fresh lava from several of these fissures. One of the more obvious flow is the one which crosses the main highway near Lake Beseka .This flow which is believed to have occurred either in the 13 century or 19 century, poured down from the outer slopes of the Dinbeeba crater (or small Sabober crater)and travelled all the way to the shores of Lake Beseka(Gibson no date).

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