The Arabian Peninsula, which features vast expanses of sand dunes and sand seas, is known for its extreme heat and aridity. However, a recent study revealed that the deserted region that we see today was once a region that repeatedly underwent "green" periods in the past. This was because of periods of high rainfall, which led to the formation of lakes and rivers about 9,000 years ago. 

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The paper titled, "Monsoonal imprint on late Quaternary landscapes of the Rub' al Khali Desert", has been published in Communications Earth & Environment. The study noted that abundant geological archives show evidence of an intermittently more humid past. 

Perennial lakes and extensive drainage networks characterised Arabian landscapes during the early Holocene to middle Holocene. 

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The team was led by Dr Abdallah Zaki and Professor Sébastien Castelltort of the University of Geneva, Switzerland, and Professor Abdulkader Afifi of King Abdullah University of Science and Technology (KAUST). It also included Professor Michael Petraglia from Griffith University. They documented the presence of an ancient lake, rivers and a large water-formed valley.

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'About 9,000 years ago...'

Increased rainfall during the early Holocene is the most recent of the multiple wetter periods that have occurred synchronously with insolation changes associated with orbital precessional cycles throughout the Late Pleistocene to Holocene. 

"Based on a series of ages, it appears the lake peaked about 9,000 years ago during a wet Green Arabia period that extended between 11,000 to 5,500 years ago," said the first author, Dr Abdallah Zaki as quoted by phys.org. 

It is estimated that the lake was massive, measuring 1,100 m2 in extent and 42 m in depth. 

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"Owing to increased rainfall, the lake eventually breached, causing a great flood and carving out a 150 km–long valley in the desert floor," Professor Sébastien Castelltort added. 

The scientists believe that the source of the monsoonal rains was the African monsoon as it was shown by sediments that could be traced over a distance measuring 1,100 km, which extends from the Asir Mountains along the Red Sea. 

As quoted, Professor Petraglia, who is the Director of Griffith's Australian Research Center for Human Evolution, said the research demonstrated that rainfall was sometimes strong and intensive. It resulted in rapid and large-scale landscape changes. 

"The formation of lake and riverine landscapes, together with grasslands and savanna conditions, would have led to the expansion of hunting and gathering groups and pastoral populations across what is now a dry and barren desert," Professor Petraglia said. 

(With inputs from agencies)