Why do Mauritius's sand dunes spontaneously separate into a vibrant, seven-colored striped landscape?
In short: In the Chamarel plain of Mauritius, a surreal geological formation displays sand dunes striped in seven distinct hues. These sands, ranging from violet to yellow, settle into layered patterns on their own. While the colors originate from volcanic decomposition, the mechanism behind their consistent, spontaneous separation remains a scientific mystery.
The Seven Coloured Earths represent a striking geological anomaly located in the Rivière Noire District. This small expanse of dunes features sand in approximately red, brown, violet, green, blue, purple, and yellow shades. Since the earth was first exposed, rainfall has sculpted the hillside into intricate, meringue-like patterns, creating a visual effect that has drawn tourists since the 1960s. To preserve this fragile landscape, the dunes are enclosed by wooden fencing, and visitors are restricted to viewing the scenery from designated observation outposts.
The origin of these colors lies in the decomposition of volcanic basalt rock. Over time, this rock weathered into clay and was further transformed into ferralitic soil through total hydrolysis. The presence of iron and aluminium is responsible for the red-anthracite and blue-purplish tones, respectively. It is widely believed that the varying shades resulted from the molten volcanic rock cooling at different rates, which were dictated by fluctuating external temperatures during the formation process.
The most intriguing aspect of the site is the spontaneous layering of the sands. If one were to take a handful of these differently colored sands and mix them together, they would eventually settle back into a distinct, layered spectrum. While this phenomenon can be observed on a small scale, the precise physical mechanism that causes the sands to consistently separate in the natural environment remains a subject of ongoing scientific curiosity and is not yet fully clarified. Despite the lack of a definitive explanation, the site remains a celebrated landmark, with local curio shops even selling small test-tubes filled with the distinctively colored earths as souvenirs.
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Sources
- Summary by Intellect · source: Seven Coloured Earths
- Also: Wikidata — Seven Coloured Earths · CC0
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