Shifting Sands

Star dunes are found on the Earth, Mars and Titan (Saturn's largest moon). From the ground, they look like pyramids but they can be seen to be star-shaped, when viewed from directly above. Geoff Duller (Aberystwyth University) carried out studies on the Lala Lallia star dune in Morocco's Erg Chebbi. This enormous dune, created by prevailing winds, is 100 m high and 700 m wide. The wind is also moving the structure west, by about 50cm per year (https://www.theguardian.com/science/2024/mar/04/scientists-unearth-mysteries-of-giant-moving-moroccan-star-dune). Duller used a luminescence technique, to determine when Lala Lallia's quartz sand grains were last exposed to light. He confirmed that parts of the dune's base were 13,000 years old. That base continued to build up until about 9000 years ago, when it presumably became wetter. Remnants of root systems, suggest that plant colonisation occurred at this time. Duller was surprised, however, to find that the upper part of the dune was only formed in the last 1000 years or so. Star dunes appear to have phases of growth and consolidation. Understanding them is important, if one wants to build roads or pipelines in an area.