Green Sahara: African Humid Periods Paced by Earth's Orbital Changes. Paleoclimate and archaeological evidence tells us that, 11,000-5,000 years ago, the Earth's slow orbital 'wobble' transformed today's Sahara desert to a land covered with vegetation and lakes.
The greening of the Sahara, associated with the African Humid Period (AHP) between ca. 14,500 and 5,000 y ago, is arguably the largest climate-induced environmental change in the Holocene; it is usually explained by the strengthening and northward expansion of the African monsoon in response to orbital forcing.
About 14,500 to 5,000 years ago, North Africa was green with vegetation and the period is known as the Green Sahara or African Humid Period. Until now, researchers have assumed that the rain was brought by an enhanced summer monsoon.
Study shows the Sahara swung between lush and desert conditions every 20,000 years, in sync with monsoon activity. The Sahara desert is one of the harshest, most inhospitable places on the planet, covering much of North Africa in some 3.6 million square miles of rock and windswept dunes.
The Sahara was once home to hippos. Sometime between 11,000 and 5,000 years ago, after the last ice age ended, the Sahara Desert transformed.
The Sahara is the world's largest hot desert, but parts of it could be made green if massive solar and wind farms set up shop there, a new study finds.
As recently as 5,000 years ago, one of the world's driest and most uninhabitable places, the Western Sahara desert, was home to a vast river system that would rank as the world's 12th largest drainage basin if it existed today.
But on a number of occasions the Sahara has been a green and pleasant land. The last time was between 15,000 and 5,000 years ago. Back then, the tropics received more radiation from the sun, and summer and winter rains reached into the heart of this now barren land.
The Sahara Desert was once underwater, in contrast to its present-day arid environment. This dramatic difference over time is recorded in the rock and fossil record of West Africa. The region was bisected by a shallow saltwater body during a time of high global sea level.
The Sahara — the world's biggest hot desert — is getting even bigger. In fact, it is currently about 10 percent larger than it was nearly a century ago, and scientists suggest that climate change is partly responsible.
Paleoclimate and archaeological evidence tells us that, 11,000-5,000 years ago, the Earth's slow orbital 'wobble' transformed today's Sahara desert to a land covered with vegetation and lakes.
But 11,000 years ago, what we know today as the world's largest hot desert would've been unrecognizable. The now-dessicated northern strip of Africa was once green and alive, pocked with lakes, rivers, grasslands and even forests.
The African humid period was not the first such phase; evidence for about 230 older such "green Sahara"/wet periods exist going back perhaps to the first appearance of the Sahara 7–8 million years ago, for example during Marine Isotope Stage 5 a and c.
The end of the glacial period brought more rain to the Sahara, from about 8000 BCE to 6000 BCE, perhaps because of low pressure areas over the collapsing ice sheets to the north. Once the ice sheets were gone, the northern Sahara dried out.
Today, the Sahara Desert is defined by undulating sand dunes, unforgiving sun, and oppressive heat. But just 10,000 years ago, it was lush and verdant. So, what spurred the shift from woodland to wasteland? A new study suggests humans played a big role.
But sandwiched between two periods of extreme dryness were a few millennia of plentiful rainfall and lush vegetation. During these few thousand years, prehistoric humans left the congested Nile Valley and established settlements around rain pools, green valleys, and rivers.
Beneath the sands of the Sahara Desert scientists have discovered evidence of a prehistoric megalake. Formed some 250,000 years ago when the Nile River pushed through a low channel near Wadi Tushka, it flooded the eastern Sahara, creating a lake that at its highest level covered more than 42,000 square miles.
The Sahara has only two permanent rivers and a handful of lakes, but it has substantial underground reservoirs, or aquifers. Its permanent rivers are the Nile and the Niger. The Nile rises in central Africa, south of the Sahara, and flows northward through Sudan and Egypt and empties into the Mediterranean.
Desert sand is largely useless to us. The overwhelming bulk of the sand we harvest goes to make concrete, and for that purpose, desert sand grains are the wrong shape. Eroded by wind rather than water, they are too smooth and rounded to lock together to form stable concrete.
As little as 6,000 years ago, the vast Sahara Desert was covered in grassland that received plenty of rainfall, but shifts in the world's weather patterns abruptly transformed the vegetated region into some of the driest land on Earth.
“It's a layer of dust that is picked up off the Sahara Desert and transported across the ocean.” The dust cloud typically arrives in Texas between mid-June and August and lasts for 3-5 days.
The Sahara cluster comprises a handful of gold mining sites in the northernmost regions of Niger and Mali: Tchibarakaten and Tabelot in the Nigerien region of Agadez, and Kidal in Mali.
185,000–20,000 years ago. Between about 133 and 122 thousand years ago (kya), the southern parts of the Saharan-Arabian Desert experienced the start of the Abbassia Pluvial, a wet period with increased monsoonal precipitation, around 100-200 mm/year.
At the time the Giza pyramid complex was built—between 2670 and 2500 BCE—the channel was about 40% as high as during the African Humid Period, a peak wet period more than 1,000 years prior. This earlier period saw relatively soggy conditions throughout northern Africa and a mostly green Sahara desert.