Moroccan sand dunes examined (Image: UCL)
Since the cinemas have just shown the second part of Dune, we cannot leave the topic without a word. You might think that the famous sand hills of sandy deserts (or erg), which are sand dunes that are constantly blown by the wind, exist only momentarily on a geological scale, because they are nothing but fine-grained, accumulated sand, and can be destroyed and destroyed. Rebuild anytime overnight. However, this is far from the case. For geologists at University College London and Aberystwyth University Stady For example, the base of a sand dune in Morocco is 13,000 years old, but the peak has only been around for a thousand years (although that's much longer than we might think).
Sand dunes can be mistaken for pyramids from the surface of the Earth, but they are not actually pyramidal or conical in shape. Aerial photographs clearly show that the base of the dune is not round, but star-shaped: the arms extend from the center to the sides and are driven by the wind. The research team examined sand dunes measuring one hundred meters high and seven hundred meters wide at their base in the Erg Chebbi sand desert in eastern Morocco (which is part of the Sahara). The dunes are called “Lala Lalia” in the Berber language, meaning “the highest sacred peak.”
Researchers Established Age of different parts of the dune. To do this, they used a method based on luminescence, which can determine when the minerals in a sand sample were last exposed to sunlight (i.e. when they were last on the surface of the dune). In this way, they determine not the age of the sand (which can be millions of years old), but when more sand has been deposited on it, blocking sunlight. According to the researchers, the quartz crystals in the sand act as “mini batteries” and store some of the energy of sunlight.
Samples taken from deep within the dunes at different elevations revealed the surprisingly ancient age of the sand hill. The dunes appear to have built up in the first 4,000 years, then stabilized in height about 9,000 years ago. At that time, Morocco's climate was somewhat wetter than it is now, so plants grew there as well (plant remains have been found in the sand). Vegetation may also have contributed to the stability of the dunes. Currently, the movement of the sand dunes is determined by the constant easterly winds: they move westward by fifty centimeters per year. When building desert infrastructure (such as roads), engineers must take into account that although sand dunes may be thousands of years old, they are constantly moving.
