The Sahara or the Great Desert, in Arabic Al Sahra al-Kubra “الصحراءالكبرى” is one of major deserts on planet Earth, i.e. landscape that receives very little precipitation, rain or snow, less than 250 mm per year. It is as big as the USA and its sand can burry the whole world 20 cm deep. Desert land does not necessarily mean sand and sand dunes; many deserts are rocky surfaces as well. One third of the earth’s surface is desert lands that exist in polar, subtropical, cold winter and cool coastal regions. Deserts have no surface streams because of rapid evaporation, transpiration (by plants and subsequent release to atmosphere) or/and infiltration into the ground. Deserts have unique fauna and flora that are adapted to the harsh climate and environment conditions, i.e. intense sun, limited precipitation, severe temperature ranges, dry wind and low humidity.
The Sahara Desert is located in subtropical North Africa and it is the hottest place on the planet. The mystery of what created and changed the Sahara desert has revealed a turbulent past. The African tectonic plate collided with Europe and what was a huge sea turned gradually to land, with the Mediterranean as remaining sea, many million of years ago. Finding whales in the desert is not a climatological story but rather a geological evolution. Indeed, the Sahara has the highest fossil remains in the world, almost all of them are marine animals such as those found in Wadi Al Hitan, Egypt “Whales Valley”. The reconstruction of the evolution and the history of the Sahara were made possible through the remaining fossils of sea creatures in the desert itself along with geological information from deep sediment cores. Sediment cores are excellent archives for obtaining historical, environmental and climatological information. Whale bones in the desert showed that 40 millions years ago the Sahara was a sea bed, deep ocean sediment cores containing wind blown sand revealed that sea water dried up three millions years ago. Freshwater shells buried in sand showed that 90 000 years ago the “wobbles” of the earth’s axis (http://www.ncdc.noaa.gov/paleo/milankovitch.html) created huge freshwater lakes and rivers and turned the Sahara green every 20 000 years. Ostrich eggshell, used by prehistoric settlements for manufacturing beads, indicated that just 7000 years ago the Sahara enjoyed its final burst of life before returning into desert.
The story of the Sahara showed that it wasn’t always a barren wasteland. Life was not static, it could shift, change, evolve and it can bloom again into green terrain, i.e. in the distant future. Ground penetrating radars showed that there are huge freshwater lakes “groundwater” under the surface of the Sahara Desert. Such fossil water can be million of years old. This gives hopes for turning the desert to green land by being reclaimed for agriculture and farming. Nubian Aquifer (Egypt, Libya, Sudan and Chad) is an example of such fossil water and is already in use. Fossil water is non-renewable resource, can only be used once and is sufficient for a short period of time depending on consumption, probably can last something like 100 years. After being consumed the desert has to wait for another 15000 years before once more earth “wobbles” turns it green again.
Note. The earth wobbles in space makes it tilt around its axis on a cycle of 41 000 years with introduction of changes in the seasons. More tilt means more severe seasons, i.e. warmer summers and colder winters; less tilt means less severe seasons – colder summers and milder winters.
This new chapter of history that tells the story of the past turbulent landscape of the Sahara gives interesting information on how the earth and desert was made.