Ancient rivers reveal multiple Sahara Desert greenings

phys.org ^ | January 29, 2021 | University of Hawaii at Manoa

[BenLurkin]

Large parts of the Sahara Desert were green thousands of years ago, evidenced by prehistoric engravings in the desert of giraffes, crocodiles and a stone-age cave painting of humans swimming. Recently, more detailed insights were gained from a combination of sediment cores extracted from the Mediterranean Sea and results from climate computer modeling, which an international research team, including University of Hawai'i at Mānoa oceanography researcher Tobias Friedrich, examined for the first time.

The layers of the seafloor tell the story of major environmental changes in North Africa over the past 160,000 years.

Analyzing such sediments would help to better understand the timing and circumstances for the reactivation of these rivers and provide a climatic context for the development of past human populations.

Using a method called piston coring, the scientists pressed giant cylinders into the seafloor and were able to recover nearly 30-foot long columns of marine mud.

The layers of mud contain sediment particles and plant remains transported from the nearby African continent, as well as shells of microorganisms that grew in seawater, telling the story of climatic changes in the past.

From previous work, it was already known that several rivers episodically flowed across the region, which today is one of the driest areas on Earth. The team's unprecedented reconstruction continuously covers the last 160,000 years. It offers a comprehensive picture of when and why there was sufficient rainfall in the Central Sahara to reactivate these rivers.

The fertile periods generally lasted five thousand years and humidity spread over North Africa up to the Mediterranean coast. For the people of that time, this resulted in drastic changes in living conditions, which probably led to large migratory movements in North Africa.

[SunkenCiv]

NOW I remember why I built some stupid little programs to avoid compiling these by hand.

• Out Of Africa
• African Ice Core Analysis Reveals Catastrophic Droughts, Shrinking Ice Fields, Civilization Shifts
• Prehistoric Desert Town Found In Western Sahara (15,000 Years Old)
• Detritus of life abounds in the atmosphere
• Sahara Dust Cloud heads for Florida!
• Stone Age Cemetery, Artifacts Un Earthed In Sahara
• Ancient drought 'changed history'
• Ancient lakes of the Sahara
• Sahara Desert Was Once Lush and Populated
• Exodus From Drying Sahara Gave Rise to Pharaohs, Study Says
• The African Source Of The Amazon's Fertilizer
• Climate Key To Sphinx's Riddle
• Space Data Unveils Evidence of Ancient Mega-lake in Northern Darfur
• Migration of Early Humans From Africa Aided By Wet Weather
• Maltese claims extraordinary discovery in Sahara desert
• Ruins of 7,000-year-old city found in Egypt oasis
• UN vandals spray graffiti on Sahara's prehistoric art
• Egypt's Earliest Agricultural Settlement Unearthed
• The Tassili n'Ajjer [Algeria] : birthplace of ancient Egypt ?
• Sahara dried out slowly, not abruptly: study
• Once Lush Sahara Dried Up Over Millennia, Study Says
• In Search Of The Lost Sahara
• US scientists find stone age burial ground in Sahara
• Graves Found From Sahara's Green Period
• Graves Found From Sahara's Green Period
• Giant stone-age axes found in African lake basin
• Legendary Lost Persian Army Found in Sahara
• Is this the legendary lost Persian army
• Stone Age humans crossed Sahara in the rain
• Strange Ancient Crocodiles Swam the Sahara
• Remember that ash cloud? It didn't exist, says new evidence
• Ancient DNA identifies donkey ancestors, people who domesticated them
• How Earth's orbital shift shaped the Sahara
• Lost Cities of the Sahara
• Fish Swam the Sahara, Bolstering Out of Africa Theory
• Ancient Egypt was destroyed by drought, discover Scottish experts
• Lost Civilization Discovered in Sahara Desert
• Massive Underground Water Supply Found In Desert African Country (Supply could last 400 years)
• Climate and Drought Lessons from Ancient Egypt
• EARTH was a BAKING LIFELESS DESERT for 5 MILLION years
• Study Confirms Ancient River Systems in Sahara 100,000 Years Ago
• Mineral dust plays key role in cloud formation and chemistry
• Ancient bone fragments help describe diet, health of Saharan ancestors
• Violence and climate change in prehistoric Egypt and Sudan
• Before they left Africa, early modern humans were 'culturally diverse'
• NASA video shows how dust from Sahara Desert fuels Amazon rain forest
• Ancient Africans used 'no fly zones' to bring herds south
• A Carpet of Stone Tools in the Sahara
• Inside the abandoned City of Libraries
• Fossil of massive crocodile found on edge of Sahara desert
• Scientists discover 8000-year-old tiny hand prints in ancient cave were NOT made by humans
• More Evidence of a Wet Sahara
• Why humans left Africa - Climate Change
• Entomologist Confirms First Saharan Farming 10,000 Years Ago
• The problem of the wet Sahara
• Humans delayed the onset of the Sahara desert by 500 years
• Study shows the Sahara swung between lush and desert conditions every 20,000 years...
• Research links Southeast Asia megadrought to drying in Africa [mid-Holocene]

[Ozark Tom]

There is fresh water under that desert—quite hot though.

[Red Badger]

I’ve always wondered where all that sand came from.........................

[ckilmer]

Yeah, there are a couple of massive underground aquifers where the ancient lakes in the sahara used to be. the Libyans have built a canal to haul a river of underground water to their coastal cities—from one of these aquifers.

That water is fossil water. There might be at most 100 years supply—but likely only half that much. It doesn’t renew with rain like the oglala aquifer in the US midwest—because there is no rain in the sahara to renew the aquifer.

[ckilmer]

The israelis best desal plants are doing the job for $500@acre foot. They send the desalinated seawater to their cities and then clean it up once more before sending to their farms.

By contrast the newest US desalination plant is the poisiden plant in san diego. It desalinates for $2000@acre foot.