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Creation 42(3):45–47, July 2020

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The lush green Sahara

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fern-leaves

The Sahara Desert of northern Africa is one of the driest and hottest locations on Earth (figure 1). In the eastern Sahara, it rains only once every 30 to 50 years. The Sahara Desert covers about 9,200,000 km2 (3,600,000 sq mi), comparable to the size of the entire USA. It is divided into several regions, sometimes by high mountain ranges such as the Ahaggar and Tibesti Mountains (figure 2). Some 74% of the Sahara is covered by sand, with several large ‘sand seas’, such as the Great Sand Sea of eastern Libya and western Egypt which covers 72,000 km2 (28,000 mi2) (figure 3).

Not counting the Atlas Mountains of northwest Africa, the highest peak in the Sahara Desert is Emi Koussi in the Tibesti Mountains. Its elevation is 3,445 m (11,302 ft). The mountainous areas of the Sahara have oases with playa lakes, which are normally dry and free of vegetation. Occasionally, if there is a period of exceptionally high rainfall, they have water.

South of the desert is an east-west belt called the Sahel. This is a semi-arid tropical savanna, which alternates between wet and dry depending upon the location of the shifting boundary of the Intertropical Convergence Zone (ITCZ). This zone (a.k.a. ‘the doldrums’) is where the trade winds (easterlies) of both hemispheres converge to give tropical weather, e.g. in central Africa, south of the savanna, where tropical rain forests flourish.

Courtesy of NASASahara-Desert
Figure 1. Satellite view of the Sahara Desert in North Africa with the tropical rain forest in central Africa.
(T.L. Miles, Wikipedia Commons CC-BY-SA-3.0).fig-2
Figure 2. Map showing major Dune seas (ergs) and Mountain ranges of the Sahara Red dashed line shows approximate limit of the Sahara. National borders in grey. Dune seas in yellow.
(Roland Unger, Wikipedia Commons CC-BY-SA-3.0).fig-3
Figure 3. Dunes of the Great Sand Sea near Siwa, Egypt

Well-watered during Ice Age

Both creation and secular geologists agree that the earth’s deserts and semi-arid areas were once well watered.1 Creation scientists largely attribute this to the warmer ocean water just after the Flood, warmed by the enormous volcanic eruptions that took place during the Flood. Warmer oceans generated huge amounts of evaporation, which caused the great ice sheets to build up rapidly over many parts of the world, leading to the Ice Age.2

At the same time, the extra water vapour in the atmosphere caused high rainfall at lower latitudes where it was not cold enough to form snow and ice. Thus, the post-Flood Ice Age explains why the earth’s deserts and semi-arid areas were once well watered.

This high-rainfall condition would have lasted for several centuries, until the sea had cooled off and reached equilibrium with the atmosphere, as it is today. In the runoff stage in the last part of the Flood, many lakes would have formed from the ponding of water in enclosed basins on an already waterlogged Earth. After the Flood during the Ice Age, high rainfall would have caused these lakes to grow and be sustained, along with a network of rivers and streams.

For example, during this time, the Great Salt Lake in Utah, USA, was about 12 times its current area and about 300 m (1,000 ft) deeper.3 Measuring the ancient shorelines in Death Valley, California, USA, shows that a lake 350 m (1,150 ft) deep once filled Death Valley.3 Today it is one of the hottest, driest places on Earth.


The Sahara Desert was also well watered

(David Stanley, Wikipedia commons CC-BY-2.0)Rock-paintings-Manda-Gueli-Cave
Figure 4. Rock paintings from Manda Guéli Cave in the Ennedi Mountains, Chad, Central Africa. Camels have been painted over earlier images of cattle, perhaps reflecting climatic change.

As hard as it is to believe, the Sahara Desert was once well watered too. Field and satellite pictures record evidence of large ancient lakes and rivers.4,5,6 Paleolake Chad lies at the boundary between the Sahara and the Sahel. Evidence indicates it was once much larger than it is today, covering an area of 340,000 km2 (130,000 mi2).7 Countless human artifacts, and fossils of large animals, such as elephants, giraffes, buffaloes, antelopes, rhinoceroses, and other animals have been found. In low-lying areas there are fossils of aquatic animals like hippopotamuses, crocodiles, fish, and clams.8 These are post-Flood fossils, from the Ice Age period.

A minuscule portion of this lush faunal heritage still persists in isolated lakes or pools in oases of the high western Sahara. This includes Dwarf Nile River crocodiles, found as recently as the early 20th century.9,10

Judging by the thousands of rock petroglyphs (figure 4), the population of the Sahara was quite large. James Wellard states:

“The Sahara is a veritable art gallery of prehistoric paintings. … The evidence is enough to show that the Sahara was one of the well-populated areas of the prehistoric world. … in the most inaccessible corners of the desert, [there are] literally thousands of figures of tropical and aquatic animals, enormous herds of cattle, hunters armed with bows and boomerangs, and even ‘domestic’ scenes of women and children and the circular huts in which they lived.”11

Others corroborate:

“Occupation is clearly testified in the frequent rock engravings that are scattered throughout the upland regions of the desert, illustrating a lush environment with Sahelian and riverine fauna and scenes of large-game hunting, livestock herding and religious ceremony … .”12

Again, we can see that a model based on biblical history, incorporating the effects of the global Flood and the associated post-Flood Ice Age, can readily explain observations that are often mystifying to secularists.

The wettest period was after the Ice Age

Based on carbon-14 measurements, the period of greatest wetness for the Sahara region in North Africa came after the post-Flood Ice Age, and is called the African Humid Period (AHP).1,2 Although the ‘absolute dates’ determined by carbon-14 dates are far too old for the biblical timescale,3 their relative ages can be useful. Carbon-14 testing of Neolithic archaeological sites in northern Africa suggests that this AHP ended well after the deglaciation that marked the end of the Ice Age. This seems contradictory, since as secularists agree, other wet areas which are now semi-arid or deserts all developed during the Ice Age, which was a wet climate period (with spans of greater and lesser wetness within that timeframe).

Cause of AHP

Secular scientists really do not know why the AHP occurred. It is known, based on the ratio of oxygen isotopes in the water, that the precipitation for the AHP came from the ITCZ, mentioned earlier, which generates a heavy rain band stretching east-west.4 But scientists do not know what would cause the ITCZ to somehow move as much as 600 km (375 mi) further north.5,6

Some models, employing Milankovitch fluctuations7 and increases in greenhouse gases, claim modest success in moving the ITCZ a little farther northward.2 However, these would only produce slight changes in the earth’s radiation balance after the Ice Age, and would be unlikely to cause the ITCZ to move so far north. Carbon dioxide is significantly higher today than it was immediately after the Ice Age. Yet, the ITCZ remains stable in its central African location, since it is locked to its average location by the average circulation of the atmosphere.

However, there is another feature of the biblical Ice Age that would affect the cause and timing of the African Humid Period. Specifically, the Ice Age lasted longer in the Southern Hemisphere (SH) than the Northern Hemisphere (NH). Glacial maximum was reached about 500 years after the Flood with deglaciation taking another 200 years, lasting a total of 700 years. However, the SH would not reach glacial maximum until perhaps 300 years later, because of the time needed to build up of the Antarctic Ice Sheet. The atmosphere and oceans of the two hemispheres have only minimal exchange of water and air between them, so each generally acts independently. And because the SH has much more ocean than the NH, it would take longer for the Southern Hemisphere oceans to cool (cooling is 75% by evaporation and 25% by cool airflow off the continents).

How does this explain the green Sahara in the AHP? It is known that today, the ITCZ migrates seasonally away from the winter hemisphere, within a range of about 10° latitude.8 Therefore, after the Ice Age ended in the Northern Hemisphere, the Ice Age in the Southern Hemisphere would have pushed the ITCZ even farther north than it shifts today as the seasons change. The SH Ice Age could easily push the ITCZ 600 km (375 mi) north into the Sahara Desert and cause the green Sahara to persist for centuries after the ice sheets had disappeared from northern regions.

References and notes

  1. Lécuyer, C., Lézine, A.-M., Fourel, F., Gasse, F., Sylvestre, F., Pailles, C., Grenier, C., Travi, Y., and Barral, A., I-n-Atei paleolake documents past environmental changes in central Sahara at the time of the “Green Sahara”: Charchola, carbon isotope and diatom records, Palaeogeography, Palaeoclimatology, Palaeoecology 441:834–844, 2016.
  2. Otto-Bliesner, B.L., Russell, J.M., Clark, P.U., Liu, Z., Overpeck, J.T., Konecky, B., deMenocal, P., Nicholson, S.E., He, F., and Lu, Z., Coherent changes of southeastern equatorial and northern African rainfall during the last deglaciation, Science 346:1,223–1,227, 2014.
  3. The excessive ages are because scientists do not correct for the way the Flood altered the ratio of radioactive carbon to normal carbon. It should be noted that carbon-14 consistently provides evidence against ages of millions of years. See Radio-carbon dating.
  4. Hoelzmann, P., Kruse, H.-J., Rottinger, F., Precipitation estimates for the eastern Saharan palaeomonsoon based on a water balance model of the West Nubian Palaeolake Basin, Global and Planetary Change 26:103–120, 2000.
  5. Braconnot, P., Joussaume, S. de Noblet, N. and Ramstein, G., Mid-Holocene and Last Glacial Maximum African monsoon changes as simulated within the Paleoclimate Modelling Intercomparison Project, Global and Planetary Change 26:51–66, 2000.
  6. Notaro, M., Wang, Y., Liu, Z., Gallimore, R., and Levis, S., Combined statistical and dynamical assessment of simulated vegetation-rainfall interactions in North Africa during the mid-Holocene, Global Change Biology 14:347–368, 2008.
  7. Oard, M.J., The Frozen Record: Examining the Ice Core History of the Greenland and Antarctic Ice Sheets, Institute for Creation Research, Dallas, TX, 2005.
  8. Bahr, A., Hoffmann, J., Schönfeld, J., Schmidt, M.W., Nürnberg, D., Batenburg, S.J., and Voigt, S., Low -latitude expressions of high-latitude forcing during Heinrich Stadial 1 and the Younger Dryas in northern South America, Global and Planetary Change 160:1–9, 2018.


References and notes

  1. Oard, M.J., Frozen in Time: Woolly Mammoths, the Ice Age, and the Biblical Key to Their Secrets, Master Books, Green Forest, AR, pp. 41–44, 2004. Return to text.
  2. The continents were cooled by the ongoing cooling effect of atmospheric aerosols from the volcanism during the Flood. Return to text.
  3. Lifton, N., et al., In situ cosmogenic nuclide production rate calibration for the CRONUS-Earth project from Lake Bonneville, Utah, shoreline features, Quaternary Geochronology 26:56–69, 2015. Return to text.
  4. Pachur, H.-J. and Kröpelin, S., Wadi Howar: paleoclimatic evidence from an extinct river system in the southeastern Sahara, Science 237:298–300, 1987. Return to text.
  5. Paillou, P., Schuster, M., Tooth, S., Farr, T., Rosenqvist, A., Lopez, S., and Malezieux, J.-M., Mapping of the major paleodrainage system in eastern Libya using orbital imaging radar: the Kufrah River, Earth and Planetary Science Letters 277:327–333, 2009. Return to text.
  6. Chorowicz, J. and Fabre, J., organization of drainage networks from space imagery in the Tanezrouft plateau (Western Sahara): implications for recent intracratonic deformations, Geomorphology 21:139–151, 1997. Return to text.
  7. Hoelzmann, P., Kruse, H.-J., and Rottinger, F., Precipitation estimates for the eastern Saharan palaeomonsoon based on a water balance model of the West Nubian palaeolake basin, Global and Planetary Change 26:105–120, 2000. Return to text.
  8. Kröpelin, S. and Soulié-Märsche, I., Charophyte remains from Wadi Howar as evidence for deep mid-Holocene freshwater lakes in the eastern Sahara of Northwest Sudan, Quaternary Research 36:210–223, 1991. Return to text.
  9. Charlesworth, J.K., The Quaternary Era, Edward Arnold, London, U.K., p. 1,113, 1957. Return to text.
  10. Drake, N.A., Blench, R.M., Armitage, S.J., Bristow, C.S., and White, K.H., Ancient watercourses and biogeography of the Sahara explain the peopling of the desert, Proceedings of the National Academy of Science 108(2):458–462, 2011. Return to text.
  11. Wellard, J., The Great Sahara, E.P. Duggon & Co., New York, NY, pp. 33,34, 1964. Return to text.
  12. Manning, K. and Timpson, A., The demographic response to Holocene climate change in the Sahara, Quaternary Science Reviews 101:28–35, 2014. Return to text.