In northwest Australia, the Great Sandy Desert holds great geological interest as a zone of active sand dune movement. While a variety of dune forms appear across the region, this astronaut photograph features numerous linear dunes (about 25 meters high) separated in a roughly regular fashion (0.5 to 1.5 kilometers apart).
NASA
On March 25, 2013, an astronaut aboard the International Space Station took this photo of the Great Sandy Desert in northwest Australia, showcasing linear dunes separated in a roughly regular fashion. When you fly over such dune fields—either in an airplane or the space station—the fire scars stand out. Where thin vegetation has been burned, the dunes appear red from the underlying sand; dunes appear darker where the vegetation remains.
Strings of narrow lakes that represent ancient rivers are also present in the region. The white feature down the center of the image is Lake Auld. The color is the result of a cemented combination of fine, clay-like sediment and salts from the evaporation of flood waters that occasionally fill the lake. Linear dunes can be seen entering Lake Auld on the east side. During flooding events, the sand of the dune noses is dispersed, becoming incorporated into the muds and salts of the lake floor sediments. During the long, intervening dry periods, sand can blow across the lake floor to build thinner, smaller dunes, visible as linear accumulations on the west side of the lake.
See more photos taken by astronauts.
Text credit: NASA/M. Justin Wilkinson
Image credit: NASA
在澳大利亚西北部，大沙沙漠（Great Sandy Desert）因其活跃的沙丘移动现象而具有极高的地质研究价值。尽管该地区分布着多种不同形态的沙丘，但这张航天员拍摄的照片中主要展示了大量线状沙丘，这些沙丘高约25米，彼此之间以大致规律的方式分布，间距约为0.5到1.5公里。
影像来源: NASA
这张照片拍摄于2013年3月25日，由一位国际空间站上的航天员记录下了澳大利亚西北部大沙沙漠中这些规则排列的线状沙丘。当从飞机或空间站上空飞越这些沙丘地带时，火烧痕迹会格外显眼：当稀疏的植被被烧毁后，底部的红色沙土裸露，使沙丘呈现红色；而仍覆盖植被的沙丘则显得较暗。
在该区域还可以看到一些狭长的湖泊带，这些是远古河流的遗迹。图像中央的白色地貌为奥尔德湖（Lake Auld）。其白色来源于洪水季节偶尔注入湖泊后，水分蒸发而沉积的细质黏土和盐类共同形成的硬化层。图中可以看到，东侧的线状沙丘延伸进入奥尔德湖。当发生洪水时，沙丘前缘的沙子被冲散，混入湖底的淤泥和盐分中。漫长的干旱季节里，湖床上的沙粒会被风吹动，形成更薄、更小的沙丘，在湖的西侧可见这些细长的沙脊堆积。
文字来源: NASA/M. Justin Wilkinson
图片来源: NASA
