A quick aside to describe one of the more intriguing features of deserts, commonly associated with the Sahara and Arabia: oases, fertile spots in the desert. They occur where the aquifer reaches the desert surface, either via natural crack in the bedrock or via well. They can range in size from a small cluster of palm trees to an area supporting a city and agriculture. Crops such as dates, cotton, olives, figs, citrus fruits, wheat and corn (maize) are grown there.
Mena Oasis, Libya.
It is thought about 90 exist in the Sahara alone, though they occur in other deserts around the world, such as in China and Peru, as well. In North Africa their spacing is broad enough that they became historically important checkpoints for trade and travel. Those who controlled an oasis and its water controlled what traffic could pass through. This was the case as well along the Silk Road through Asia.
Typical bedrock & water table beneath an oasis.
Many modern settlements began as moderate- to large-sized oases, including Las Vegas (which means “meadows”), Arizona. The local aquifer was exhausted by 1962 and the city is now fed from the Colorado River. Oases can be destroyed by overuse of the water, which kills the trees, particularly the dates which are effective at blocking the movement of sand into the water pool. For this reasons settlers at oasis locations frequently plant dates at the perimeter around the exposed water, to help prevent an influx of sand filling the pool.
Huacachina Oasis, Peru.
Tomorrow: Morocco and climate change.
Be brave, and be well.
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