The Great Sand Sea is an approximately 72,000 km2 (28,000 sq mi) sand desert (erg) in the Sahara between western Egypt and eastern Libya in North Africa. Most of the area is covered by dunes.
Geography of Great Sand Sea
The Great Sand Sea stretches about 650 km (400 mi) from north to south and 300 km (190 mi) from east to west. On satellite images, this desert shows a pattern of long sand ridges running in a roughly north-south direction. However, despite the apparent uniformity, the Great Sand Sea has two large areas with different mega dunes. The Egyptian Sand Sea lies parallel to the Calanshio Sand Sea of Libya, which is contiguous in the north. The dunes of the Great Sand Sea cover about 10% of the total area of the Egyptian Western Desert.
Siwa is an oasis located in Egypt, about 50 km (30 mi) east of the Libyan border, in the eastern part of the Great Sand Sea or Egyptian Sand Sea.
Although well-known to the Tuareg and traders who travelled with caravans across the Sahara, Friedrich Gerhard Rohlfs was the first European to document the Great Sand Sea. He began his Saharan expeditions in 1865 and named the great expanse of dunes the Große Sandmeer (Great Sand Sea). The Great Sand Sea (GSS) got its name from Rohlfs, who mentioned the term about the dune landscape to the west of Dakhla and Farafra. It covers an area of about 114,400 km2 and stretches in a direction of NNW-SSE over about 600 km from the Siwa Oasis in the north to the Gilf Kebir Plateau in the south of Egypt. But it was not until 1924, with the maps of Ahmed Hassanein, that Europeans appreciated the full scope of the Great Sand Sea.
Sand Properties
Several researchers studied the sand properties of the Great Sand Sea. Results of these previous studies revealed that most of the samples are composed of sands in medium to fine fractions. This is per the results of earlier studies on other Egyptian sand seas or other sand seas in other deserts. Coarse sands are found at the plinths of draa ridges, representing the particles left behind as winds remove finer grains. The distribution of sand grains showed that all samples are unimodal, except those of the plinths, which are bimodally distributed due to coarse sand grains.
Scanning electron microscopy of sand grains of the GSS reflects mechanical and chemical features on their surfaces. Besler recorded mechanical features such as holes and cracks, while EL-Baz and Prestel recorded chemical features such as pits with cracks and grooves. Kaolinite coatings were found on quartz grains on Wadi Bakht’s floor on the Gilf El-Kebir’s eastern side.
All previous studies on the minerals of the sands of the GSS concluded that they are mainly composed of quartz with small amounts of feldspar and calcareous materials. Earlier studies on heavy minerals showed they represent 0.27–1.0% of its content. These variations were attributed to differences in sand sources and local variations in wind velocities during the development of draa. Due to its significance, the percentage of the ultrastable minerals (zircon, tourmaline and rutile, ZRT) of the total nonopaque minerals was found to be 58.2% and 54.1% by Embabi and Besler consecutively. This high occurrence of ZTR indicates the recycling of sand several times. From this assumption, it can be inferred that the sands of the GSS have been recycled/reworked from older sediments.
History Background
In 1922, British archaeologist Howard Carter discovered the untouched tomb of Tutankhamun, a minor pharaoh who ruled over Egypt almost 3,300 years ago. When Carter entered the tomb for the very first time and asked if he could see anything, he famously responded:” Yes, wonderful things.” Tutankhamun’s burial chambers were filled with statues made of ivory, items made of gold and precious jewellery. In a treasure chest, Carter discovered a large pectoral, a breastplate decorated with gold and silver, various precious jewels, and a strange gemstone that the pharao wears across his chest. The breastplate shows the god Ra as a winged scarab made from a yellow-green gemstone, carrying the celestial bark with the Sun and the Moon into the sky.
Carter initially identified the gemstone as chalcedony, a common variety of the mineral quartz. In 1932, British geographer Patrick Clayton explored the Great Sand Sea along the border of modern Egypt and Libya. Here, he discovered some strange pieces of glass in the sand. The yellow-green material seemed identical to the gemstone found in Tutankhamun’s tomb. Two years later, he published a short note suggesting that the pieces of glass were the quartz-rich deposits of a wholly dried lake.
In 1998, Italian mineralogist Vincenzo de Michele analyzed the optical properties of the gemstone in King Tut‘s breastplate and confirmed that it was indeed a piece of Libyan Desert Silica Glass, as the material is nowadays called. Libyan Desert Glass consists of almost pure silicon dioxide, like quartz, but its crystal structure differs. It also contains traces of unusual elements, like iron, nickel, chromium, cobalt and iridium. It is among the rarest minerals on Earth, found only in the Great Sand Sea north of the Gilf Kebir Plateau, one of the most remote and desolate areas in the Libyan Desert.
Achaemenid Empire
According to an ancient legend, the Lost Army of Cambyses was a formation of 50,000 Persian soldiers that disappeared in the Western Desert of Egypt in 524 BC after engulfing by a sandstorm in the Great Sand Sea. Cambyses II had supposedly sent them to subjugate the Oracle of Amun at the Siwa Oasis.
Modern Record
The WWII British Long Range Desert Group spent months trying to find a way through the impenetrable sands to launch surprise attacks on the German military. Aerial surveys and expeditions have helped chart this vast expanse, but it remains one of the least-explored areas on the planet.
