Monday, April 26, 2010

Geology of Sinai 2


There are a few places only in the world where as a first-time visitor you are confronted with such a mountainscape as that of the Sinai. In the snaking wadis of the south and the looming, crafted vistas of the interior, the landscape is both visually overpowering and at peace - as if nature in enacting its script has become become frozen in stone.

The region was formed as a result of tectonic plate movement: the African, Arabian and Mediterranean shields pulling away from each other, creating a great gash in the land. At the same time, the outward movement pushed against existing rock layers forming the looming Sinai Mountains. The effect was extensive, extending from what is now the Jordan River valley, south, then south east, turning at Djibouti into Kenya - thus becoming known as the Great Rift Valley.

Two gulfs were created as branches to this valley. The Gulf of Suez leading to the Suez canal, is relatively shallow [60-90 metres] compared to the impressive depths of the Gulf of Aqaba. Here dropoffs can disappear alarmingly, descents being between 1000-2000 metres in some places.

The peninsula of Sinai can be divided into a northern and a southern region. The North consists of flat lying Palaeozoic [550 million years] and more recent sediments, while the South consists essentially of metamorphic and magmatic rocks which are of Precambrian age [more than 600 million years]. This southern portion is a continuation of the Arabio-Nubian Desert. A narrow belt [30kms wide] of soft Nubian sandstone also contains most of the Sinai minerals eg. turquoise, manganese, copper.

When traveling across the flat northern part, you can see to the south, below this sandstone belt, the granite mountains rising to peaks of more than 2,638 m [7,000 feet]. The metamorphic rocks in Sinai were last formed about a thousand million years ago. At that time along the southern portion of Sinai, a north-south belt of volcanic islands were active following their deposition in a great oceanic basin. As a result, large quantities of lava accumulated in this area at the same time as assorted sediments were deposited in adjoining basins due to erosion.

This resistant magmatic rock now occupies some 60% of the southern part of the peninsula and is responsible for the magnificent peaks [Gebel Serbal] and deepest canyons [Dahab]. There were several periods of intrusion and dyke swarms before a brief burst of younger volcanic activity, Musa and Catherine.

The more pastel colored granites are much older than the reddish rock. These dykes [fine grained basaltic intrusions], having pushed their way into the original coarse grained plutonic granites, created stunning effects of color and form. To this is added the effects of sandstone weathering and coloring through leeched minerals. In some places, a whole hillside is layered in all colors - red, purple, green, cream, white, orange. In many places the evidence of past geological activity is obvious with tilted layers sitting on the underlying granite base rock.

The central El Tih plateau of Sinai is virtually unpopulated, but at the foot of El Tih, to the south are the wide wadis. In rainy years they provide some pasture and are easier to traverse. Even today these sandy courses carry sufficient water below their surface to support a remarkable variety of life. Larger wadis, like Wadi Kid and the legendary Wadi Feran, are quite fertile in places, and a careful exploration of even the smallest of wadis will reveal surprising pockets of color. In fact, it is not uncommon during certain seasons for sudden storms to send floodwaters raging down the close-hewn channels of the coastal wadis - floods that bring in their wake an explosion of plant life.

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