The Sahara: Earth’s Greatest Desert

this video is brought to you by blinkers the first hundred people to go to blinkist.com forward slash geographics will go one week to try it out for free you'll also get 25 off if you want the full membership more on them in a bit it's the largest non-polar desert in the world covering the northern third of africa the sahara is a true beer moth from north to south it stretches over 2 000 kilometers from east to west it's two and a half times that size for most people on earth it's about as close to the platonic ideal of a desert as you can get it's no accident that its name derives from the arabic word sarah literally meaning desert yet no mere word could sum up the vastness the sheer remoteness of the sahara excluding the nile valley and the coastal regions it's thought that only 2.5 million people live here in a desert roughly the size of the united states of america including alaska and hawaii in other words this is one big mother but despite covering eight percent of our planet's land the sahara remains a mysterious place even now there's a lot of debate about everything from how old it really is to how it came to be so barren well grab yourself some sun cream because today's geographics is heading into one of the hottest most inhospitable places on earth [Music] at the top of africa lies one of the greatest deserts that has ever existed the sahara is a world unlike any other its name alone conjures images of sweeping sand dunes camel trains and ancient oases shimmering under a burning sun for millennia it was a place of mystery a great sandy barrier cutting ancient europeans off from the world beyond at least that's one way of looking at it as we're about to see where the sahara is concerned there are multiple sides to every story the first misconception you might have about africa's great desert is that it's primarily composed of sand in fact those images you're used to seeing in those travel shows only form a relatively small region of the desert proper now this is relatively small in saharan terms at 25 percent of the desert's total area the sandy parts still cover roughly 2.2 million square kilometers or an area about equal to alaska and california combined but make no mistake the vast majority of the sahara is made up of rocky plateaus not sand dunes the second common misconception is that the desert acts kind of like a barrier an impassable blank that separated the world in pre-modern times yet this blank space was more alive than you'd probably expect even back at the dawn of civilization the sahara was at the center of a web of trade networks that were vital to history great caravan trains hauled ivory gold and slaves north from sub-saharan africa far up on the mediterranean coast ships would dock laden with wine textiles and olive oil to be shipped south across the desert ocean the ancient romans would even get exotic beasts imported through the sahara for their circuses the sahara then was a living place alive not just with the few animals hardy enough to survive but with humans too when you consider the harsh climate this is actually pretty remarkable the majority of the sahara receives an average of under 70 millimeters of rain annually and of course it can get pretty damn hot but it isn't all just heat and dryness the zahara's climate hits other extremes too across any given day temperatures are liable to swing up and down by 20 celsius over an average year you might experience everything from -15c to plus 50. for our american viewers who still think in fahrenheit just imagine going from a damn cold winter's day in toronto to a damn hot summer's day in death valley but then wild swings are kind of just the sahara's thing take something as simple as its size every year the desert shrinks and grows as it cycles between its dry and wet season pulsing gently like a giant heart unlike a heart though its long-term trend is towards growth a 2018 study found that sahara's overall size had increased by 10 since 1920 but we're not here to talk about the sahara's future just yet or even its present first we're gonna dive into its past [Music] one of the choices you have to make when telling the history of the sahara is figuring out exactly where to start and yes at the beginning there would be a logical answer if only everyone could agree on when that beginning actually was from a geological point of view we know that the heavy base deep below the surface is made of folded precambrian rock that dates back billions of years we also know that the mesozoic era an impossibly long age that covers basically the entire rise and fall of the dinosaurs saw major deposits of limestone and sandstone stones which would later create huge aquifers allowing later still desert cultures to survive on fossil water if we wanted to we could even make a decent starting point out of the birth of the trans-saharan seaway some 100 million years ago a 50-meter deep stretch of salt water connecting the mediterranean with the gulf of guinea the seaway was home to everything from giant catfish to even more gigantic sea snakes in this era early mangrove swamps lined the shores and the modern wastes of northern mallee would have looked like puerto rico or at least a version of puerto rico minus the cruise ships and overweight tourists cool as the trans-saharan seaway is though it was dried up and gone by the time 50 million bc arrived which brings us to the desert itself when did it actually begin and the short answer is that no one knows the u.s geological survey or usgs notes that experts give a vast range of ages for the sahara ranging from pretty old to god dare mold and yes those are absolutely the technical terms you can trust me on that at the damn old end of the scale you have estimates ranging into the millions of years the oldest realistic one we came across was floated in a norwegian study from 2014 using computer models to map climate changes the researchers concluded the sahara had been created by tectonic plate movements around 7 to 10 million years ago that gave birth to the arabian peninsula according to their situations the arrival of the peninsula transformed north africa's rainfall patterns by reflecting less sunlight leading to slow desertification but their estimate seemed to be an outlier a much more recent study from a joint usgs spanish team placed the sahara's age at only 5 million years their evidence well that was dust every year the zahara generates a whole lot of dust that gets picked up by the winds and swept westward into the atlantic where it ends up dumped on places like the canary islands since this dust has a major effect on global ecology we'll be returning to it later in this video but for this section the important thing is that this dust leaves identifiable layers in the ground in 2020 the usgs spanish team found these layers on the canary islands dating back no later than 4.8 million years in other words the sahara as a big arid place capable of producing noticeable quantities of the stuff must have first appeared around that time although millions of years separate their estimates both of these studies placed the sahara's birth way back in the distant past but others think it came to life much closer to our own time others like archaeologist david wright who in 2017 dated the true form of the desert back to only around 9000 bc the mechanism that made the sahara possible in wright's view well that would be goats yep really goats and some humans and some cattle using sediment cause and the pollen record wright argued that the type of plants in the ancient sahara changed rapidly as humans moved in with domesticated animals basically his view is that our ancestors overgrazed the land leaving behind only scrub as a result once the desert took hold again it spread much wider and much faster than would otherwise have been the case all right but wait you might be thinking how did those ancient dudes graze goats in the frigging desert well there's something you need to know about the history of the sahara whether it began millions of years ago or only thousands of years ago the sahara hasn't spent its entire life as a barren wasteland as recently as 5500 bc it was a green and verdant paradise and hey if you want to prevent your big brain from becoming a barren desert you'll want to read plenty of books this year and if you want to maximize your reading abilities you need blinkist blinkist is an app that offers easily digestible 15-minute summaries of all the best non-fiction books in the world there's more than 3 000 of them in this app and you can either read them or listen to them personally about 90 of the time i just listen it's kind of like a podcast or an audiobook i just plug in my headphones usually on my way to work or going back from work i'll plug into one of the latest blinkist books that i'm listening to and there are 14 million active users currently using blinkers to get the best insights and need to know info from thousands of books from self-help to business to health whatever you're into it's on here for example on my blinkist list for 2021 i have one right here it's by janice kaplan and barnaby marsh it's called how luck happens and it's a whole book on basically creating luck for yourself but it's compressed into a 13-minute package that you can either read which we've got right here or you can just click these headphones in the top right and it'll start playing for you which is fantastic so if you're interested in learning big ideas in small packages head to blinkist.com forward slash geographics and the first 100 of you to do that will get to try for free and you'll also get 25 percent off if you want the full membership again seven day trial cancel at any time blinkist.com forward slash geographics and let's get back to the video [Music] if you stepped out of a time traveling delorean in north africa around the year 5500 bc you might feel pretty damn confused about where you were that's because the sahara back then wasn't a desert rather it was a vast and fertile savanna in this era there were rushing rivers and vast lakes where today only exist barren rock there were grasslands dotted with wild animals that this paradise ever existed is thanks entirely to a minor tilt as our earth spins through space it doesn't do so with north pole pointing directly upwards from its orbital plane instead our planet lurches along like a drunk uncle at a wedding tilted to one side although without the awkwardness of trying to hit on the bridesmaids over the centuries our drunk earth wobbles back and forth slightly its tilt varying per nasa between 22.1 and 24.5 degrees the upshot the northern hemisphere swings between getting more and less sunlight in summer when africa's summers get more sunlight it affects the western african monsoon season creating something known as african humid periods when everything gets wetter in north africa these periods are also known as the green sahara because it's when everything bursts into life that means this desert is forever oscillating between the sahara we know and the one far more hospitable to life recent work with core samples at mit have proven this invisible pendulum swings back and forth once every twenty thousand years nothing less than the heartbeat of the sahara itself the last of these green periods coincided with the dawn of human civilization although modern humans probably first set foot in the sahara inconceivably long ago like over 70 000 years ago the coolest evidence we have of human inhabitation comes from after the last ice age as the glaciers retreated north africa began to drift into one of its hey i'm a nice place to live in our phases as the green sahara spread more and more humans moved in and created settlements and colonized the former desert in their wake they left some of the greatest art in all prehistory saharan rock art is one of those rare things that gives you a real brief glimpse into the lives of our most distant ancestors found across the modern desert in incredibly inaccessible places this ancient art contains a record of animals and cultures long since lost to history although it came from very different groups often living thousands of kilometers apart it still displays distinct themes across several periods the first is the bubulis period or large wild fauna dating from around 10 000 bc to 6000 bc it depicts wild creatures in a naturalistic way ranging from giraffes to buffalo the second category mostly comes from the same period but instead of animals it features human figures with big circles for heads because people who research prehistoric art apparently love themselves an obvious name this is known as the round head period after that comes pastoral rock art which lasted until about 2000 bc and mostly shows domestic animals this is followed by the horse period which surprise surprise features mostly pictures of ancient bojack ending around the year 180 the horse period covers art mostly created in a sahara like the one we know today but the pastoral period is different its artists weren't etching from memory or using their imaginations they were simply recording what they saw every single day a sahara where farming was a way of life sadly it was a way of life that was doomed to vanish around 5 300 bc the earth's drunk uncle wobble began to tug the sahara away from its green period the rains grew rarer before stopping altogether as their world dried up most of the cultures that had made this art retreated clustering around the na river valley where farming was still possible by 3500 bc the transformation was complete north africa was well on its way to becoming a desert again it was around this same time that a great new civilization began to rise beside the nile on the edges of the desert a great civilization that would become one of the longest lived in the ancient world they were the egyptians and their arrival heralded the beginning of the sahara's first great culture for a place mostly famous for being mostly empty the sahara has had more than its fair share of great civilizations over the centuries of these the greatest were most likely the egyptians or as the history channel knows than those dudes who got aliens to build their pyramids of course further to the south the cushite kings of nubia were equally impressive building their own steep-sided pyramids on a smaller scale but we don't want to talk much about ancient egypt or the kingdom of kush in this video because they're both super famous and will probably be featured again and again on this channel instead we want to briefly introduce you to a few lesser-known saharan civilizations the william henry harrisons of ancient culture and before you head down to the comments to shout at us about missing your favorite one we want to be clear that this is just a taster it is not the full banquet perhaps the most significant of all was the berber culture from about 2000 bc berber or to use the proper name amazing languages flowed west out of the nile valley eventually covering the northern sahara although there are many different berber cultures in the same way there are multiple european cultures they had a few things in common beside language one was their deities like in egyptian culture the berbers worshiped figures linked to the sun and moon another common experience was a relatively antagonistic relationship with rome the name berber actually comes from the latin barbarous or barbarian which gives you some idea of what the romans thought of them while some berber kingdoms would wind up falling under rome's spell though others would outlive the empire perhaps the most impressive of these were the garamantes descended from the berbers the garamantean civilization is one of the greatest forgotten cultures of all time centers in the desert of what is today libya and lasting from 1000 bc to the 6th century 80 it seems to have been the sahara's first complex urban society to develop without a whacking great river nearby we know from ancient writings and archaeological work that the garamantes had agriculture with villages and towns laid out around large stone forts we know too that they reared cattle at its height their civilization covered around 650 000 square kilometers or an area bigger than france and was made possible by one thing the garamantes were geniuses at exploiting water remember our brief mentioned earlier of those prehistoric limestone and sandstone deposits that became aquifers while those underground aquifers filled with fossil water which garamentine civilization figured out how to extract on an industrial scale at their height the garamentes created thousands of kilometers of canals to channel his underwater water to farms without evaporation on these farms they grew wheat date palms barley and more creating a series of green oases in the harsh saharan desert as the civilization grew they became the hub of a vast trade network bringing tens of thousands of slaves up from the south to maintain their canals along with luxury goods imported from the north impressive as their culture was though it was entirely dependent on all that underground fossil water not running out when it eventually did their civilization collapsed vanishing for good by the 6th century a.d but this may have been for the best just a century or so later the muslim conquest swept across north africa destroying or absorbing all the whole outburst kingdoms yet the arrival of islam didn't mean the end of the great saharan civilizations or the great berber cultures in the 11th century a confederation of muslim berber tribes founded a part saharan empire that would spread all the way north to the modern french spanish border known as el morovid their culture was super religious and puritanical in the extreme issuing most art forms although surviving architecture in their old capital of marrakesh has an austere beauty mostly what the amorovids were into though was conquering in the 11th and 12th centuries they swept through modern morocco algeria and muslim spain creating the basis for a great exchange between the deserts of north africa and alan dallas unlike the garamentis though the almoravids didn't last long by 1147 their capital had been ransacked by the rival alma hads and soon after they vanished into history so that's three great civilizations just to give you some idea of the kind of cultures this vast desert was capable of producing we could go on of course maybe by talking about the great pan saharan empires of mali and song high centered around timbuktu but this was only ever meant to be a taster a quick glimpse into an age of empires that's long since passed now though it's time to turn away from history to look at something equally fascinating how the sahara affects our modern world [Music] remember earlier when we said we were going to talk about saharan dust effects on global ecology later in the video well we're glad to say that we finally reached that point glad because the effects of saharan dust are one of the frankly coolest things that this channel has ever covered each year winds whip up across the saharan desert that pick up an average of 182 million tons of dust this dust is sent sweeping west until it eventually reaches the atlantic for millions upon millions of tons this is the end the dust winds up falling on the canary islands and other places offshore leaving a geologic climate record for north africa for future scientists to dig up and study but those millions of tons lost to the islands only make up a fraction of its overall weight for the bulk of the sahara is dust the journey is just the beginning across the season incredibly fine particles drift along in the atmosphere wending their way over the atlantic eventually reaching the americas most of them wind up drifting over the caribbean but every year about 27.7 million tons land somewhere much more important the amazon it's at this point that things get really cool despite being one of the biggest explosions of nature anywhere on earth the amazon soil isn't super great in terms of nutrients most nutrients the rainforest needs to grow come from organic matter such as dead leaves and other plants but these don't deliver quite enough to sustain the amazon's incredible biodiversity for example it's been estimated that the rainforest loses about 22 000 tons of phosphorus a year from its soils due to rain and flooding that might not sound like much compared to the whole ecosystem but it adds up over a single century this yearly loss would come to badly affect plant growth if it weren't replenished the key word in that sentence is if because guess what happens to replace it although saharan dust comes from all over the important parts are swept up in chad's bodily depression an ancient lake bed the depression soil is teeming with phosphorus every single year exactly enough of it is swept into the air and carried across thousands of kilometers of ocean to replenish the amazon's depleted supplies in other words the long-term survival of the luscious region on earth depends entirely on deposits scattered from africa's greatest desert mother nature guys even cooler than she likes to let on now the sahara is not the only place that produces lots of dust that gets transported long distances but it is the planet's single biggest source the flip side is that sadly this can cause problems while saharan dust is essential to life in the amazon basin it has a far more catastrophic effect on life closer to home the dust that's carried across the planet is unbelievably fine ranging from only 20 microns to a mere 10. particles this fine can be damaging to human lungs and downwind communities suffer atrociously in west africa for example a dust cloud only 10 micrograms thicker per meter than average can reduce the newborn baby's chances of surviving the year by up to 18 even when the dust reaches the america's heavy seasons can still cause respiratory issues some think that it even increases the likelihood of covert 19 fatalities still there's no doubt that our planet benefits overall from its existence just think without strong winds blowing over some of the driest lake bed you've never heard of in chad the amazon rainforest would be in much worse shape i mean there's the butterfly effect and then there's the sahara desert amazing as this is though it's just one facet of a desert that continues to fascinate the entire world this is one of the most extreme regions on the planet a desert that lies across 11 countries and influences the fates of countless more it's a place where twenty thousand-year-old water can be dug up to supply an entire civilization where great empires can rise and fall in the shadow of sand dunes over 300 meters high and it still has more to give to pictures one example it's thought that only a fraction of all saharan rock art has ever been documented that means there are probably tens of thousands of ancient pictures sitting out there right now waiting to tell us so much about the history of this region about its forgotten cultures animals and people the sahara then might be a mysterious place but it's one that's slowly giving up its secrets in doing so it's teaching us more about ourselves and about our world than we ever dared imagine we could know so i really hope you found that video interesting if you did please do hit that thumbs up button below don't forget to subscribe please do check out fantastic sponsor blinkist who i will link to below and thank you for watching

Channel: Geographics

Views: 776,250

Keywords:

Id: gUtw4I5el1s

Length: 22min 35sec (1355 seconds)

Published: Mon Feb 15 2021