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Part 2 The Heart of Dryness

We began our trip in Cairo. From there we drove to the Dakhla Oasis and from there into the Sahara Desert.

Our path from Dakhla is shown in Fig, 1 which shows the rainfall rate for this region of the Sahara (from Vance 1987).

rainfall map of Sahara

Our first stop was in the very dry region at a site called Prince Kemal el Din Hussein Monument. Fig 2.

This monument is a commemorative stone that was placed circa 1930 to honor Prince Kemal who lead many expeditions in the area in the 1920's. We collected a soil sample on the shoulder of the ridge in the background about 1 km from the monument. This is probably the driest part of the Sahara.

Photo and map of Prince Kemel Monument

We continued to Jebel Uweinat, a large sandstone formation that sits on the triple border of Egypt, Lybia, and Sudan. Fig 3

Over several days we hiked extensively around Jebel Uweinat searching for algae growing under small quartz rocks. In the Atacama desert the percentage of quartz rocks that are colonized by algae decreases from about 30% in the wet end to less than 0.1% in the arid core. The presence of these algae is a indicator of the dryness of the area.

In the Jebel Uweinat area the quartz stones were very sparsely colonized. In one site on the Sudan side of Uweinat we found colonization of about 1%.

 

aerial photo and map of Jebel Uwaynat
Jebel Uweinat is a sandstone mountain with many valleys and basins Fig 4. Rain only falls there about once a decade but the mountain collects the water and is seeps underground. Trees and plants thrive just after a rain and those with deep roots can grow on the stored water. photo of sandstone mountain
photo of Wadi valley in bloomIt had rained a few months before were arrived and the flowers in the valleys (Wadi) were in bloom. Fig 5. acacia trees line the valley
The Acacia trees line the valleys and take water from the subsurface. Fig 6.
photo of a spring
There are springs in the valley of Jebel Uweinat that have water persistently Fig 7.
inscription in rock Feb. 1934Apparently they tap into the water collected during the infrequent rains. An inscription by the spring dates to 1934. Fig 8.
Although Jebel Uweinat is made of sandstone we did not find any evidence for endolithic algae which are known to grown just below the surface of sandstone in hot and cold deserts. This was a bit puzzling since we expected that if there was any hypolithic algae then there would also be endolithic algae if sandstone is present.

From Jebel Uweinat we continued northeast to another large sandstone formation, Gilf Kebir. Here again we found sparse hypolithic algae and no endolithic algae.

At Gilf Kebir we visited the cave of the swimmers. Fig 9. There are many locations in the area of Jebel Uweinat and Gilf Kebir that have prehistoric rock art. A common theme for the rock art is drawings of wild animals such as giraffes. Some of these show depictions of swimmers.

Cave with rock art

When people lived in this area 5000 to 10,000 years ago there was considerably more water. Apparently even lakes for swimmers.

We discovered some evidence for such lake. Fig 10. We found reef-like carbonate structures that look very similar to structures we find on the bottom of carbonate lakes such as Pavilion Lake in Canada.

reef-like structures in Sahara compared with same in Canada

From Gilf Kebir, we drove north toward wetter locations stopping in the great sand sea. Here we found extensive colonization of quartz rocks

quartz rock

close up of quartz rock
Our four trucks fully loaded. We carried all of our fuel and water and food for 18 days in the desert. We covered a total of 4000 km. photo of trucks in the desert

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Back to Here Today; Gone to Mars

 

 

 

 

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NASA Official: Mark León
Last Updated: May 2005
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