The Sahara swung between lush and desert conditions every 20,000 years, in sync with monsoon activity, finds a new MIT study that analyzed dust deposited off the coast of west Africa over the the last 240,000 years.

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The Sahara swung between lush and desert conditions every 20,000 years, in sync with monsoon activity, finds a new MIT study that analyzed dust deposited off the coast of west Africa over the the last 240,000 years.