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Posted for fair use.....
http://www.realclearscience.com/jou...ara_once_had_a_great_river_system_109447.html
The Sahara Once Had a Mighty River System
By Ross Pomeroy
11/10/15
http://images.realclear.com/329606_5_.jpg
The Western Sahara may once have been home to a vast river system that -- if it were still around today -- would rank as the twelfth largest drainage basin worldwide. The finding is detailed in today's issue of Nature Communications.
The Sahara Desert covers roughly a quarter of Africa and is comparable in size to the continental United States. Equally awesome to viewing the desert's seemingly endless waves of sand dunes is seeing the Sahara from outer space. Lush green gives way to a solid, arid ocean of white, tan, and brown, almost as if the Earth forgot to color in the landscape. Little to no rain falls throughout, but the region does give birth to massive storms of dust, which plume out into the Atlantic Ocean.
In fact, dust, or more specifically, sediment, is what clued researchers in to the possible existence of an ancient river system in the Western Sahara. Many samples of deep sea sediments taken off the coast of Western Africa seem more typical of river-borne material than ocean-borne material, implying that a river once emptied into the ocean in the area. Geographical and climate models lent credence to the idea, but hard data was lacking.
A team of French researchers has now filled that void by using a sophisticated imaging system onboard the Japanese Advanced Land Observing Satellite. The sensor system, called PALSAR, is capable of imaging geological features buried under layers of sediment, in this case, sand, lots of sand. Pointing the satellite at the coastal section of Mauritania, the researchers spotted a large drainage system that was almost certainly connected to a long, meandering river system.
http://www.realclearscience.com/images/wysiwyg_images/drainage.jpg
The longer river system, called the Tamanrasett, may have extended across a significant portion of the Sahara. The researchers estimate that it may have held flowing water as many as nine times in the past 245,000 years, including as recently as 6,000 years ago during a so-called African Humid Period. These periods of climatic change in the region happen as a result of tiny variations in Earth's orbit around the sun, and seem to occur regularly every 20,000 years or so.
http://www.realclearscience.com/images/wysiwyg_images/saharariver.jpg
The presence of the river system suggests that the Sahara was once much greener than it is today, and could very well be so again.
Source: Skonieczny, C. et al. African Humid periods triggered the reactivation of a large river system in Western Sahara. Nat. Commun. 6:8751 doi: 10.1038/ncomms9751 (2015).
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So that begs the question as to the "current" climate change "debate" doesn't it.
Posted for fair use.....
http://www.realclearscience.com/jou...ara_once_had_a_great_river_system_109447.html
The Sahara Once Had a Mighty River System
By Ross Pomeroy
11/10/15
http://images.realclear.com/329606_5_.jpg
The Western Sahara may once have been home to a vast river system that -- if it were still around today -- would rank as the twelfth largest drainage basin worldwide. The finding is detailed in today's issue of Nature Communications.
The Sahara Desert covers roughly a quarter of Africa and is comparable in size to the continental United States. Equally awesome to viewing the desert's seemingly endless waves of sand dunes is seeing the Sahara from outer space. Lush green gives way to a solid, arid ocean of white, tan, and brown, almost as if the Earth forgot to color in the landscape. Little to no rain falls throughout, but the region does give birth to massive storms of dust, which plume out into the Atlantic Ocean.
In fact, dust, or more specifically, sediment, is what clued researchers in to the possible existence of an ancient river system in the Western Sahara. Many samples of deep sea sediments taken off the coast of Western Africa seem more typical of river-borne material than ocean-borne material, implying that a river once emptied into the ocean in the area. Geographical and climate models lent credence to the idea, but hard data was lacking.
A team of French researchers has now filled that void by using a sophisticated imaging system onboard the Japanese Advanced Land Observing Satellite. The sensor system, called PALSAR, is capable of imaging geological features buried under layers of sediment, in this case, sand, lots of sand. Pointing the satellite at the coastal section of Mauritania, the researchers spotted a large drainage system that was almost certainly connected to a long, meandering river system.
http://www.realclearscience.com/images/wysiwyg_images/drainage.jpg
The longer river system, called the Tamanrasett, may have extended across a significant portion of the Sahara. The researchers estimate that it may have held flowing water as many as nine times in the past 245,000 years, including as recently as 6,000 years ago during a so-called African Humid Period. These periods of climatic change in the region happen as a result of tiny variations in Earth's orbit around the sun, and seem to occur regularly every 20,000 years or so.
http://www.realclearscience.com/images/wysiwyg_images/saharariver.jpg
The presence of the river system suggests that the Sahara was once much greener than it is today, and could very well be so again.
Source: Skonieczny, C. et al. African Humid periods triggered the reactivation of a large river system in Western Sahara. Nat. Commun. 6:8751 doi: 10.1038/ncomms9751 (2015).
__
So that begs the question as to the "current" climate change "debate" doesn't it.
