The Driest Place on Earth | How the Earth Was Made (S1, E6) | Full Episode | History

earth a 4.5 billion year old planet still  evolving as continents shift and clash   volcanoes erupt glaciers grow and  recede the earth's crust is carved   in numerous and fascinating ways leaving  a trail of geological mysteries behind   in this episode investigators are exploring the  driest place on earth the atacama desert in chile   this barren landscape is 50  times drier than death valley   now scientists are piecing together  the puzzle of how this desert was made from raging volcanoes to colossal mountains oceans the clues they uncover also provide  a window into the formation of the earth itself earth is a blue planet engulfed by water  but in this desolate chunk of northern chile   you won't find a single drop wedged between the  pacific ocean and coastal volcanoes to the west   and the andes to the east is atacama  the driest desert in the world 600 miles long and narrow on average just  100 miles wide it's the same size as iowa   now scientists are on a mission  to find out how it was made   the investigation begins in  the sleepy town of kiagua a rare green oasis its only lifeline is a stream  trickling 300 miles from the andes to the pacific   it is home to the official government rain gauge  so geologist john houston has come here to find   out how dry the driest place on earth really is  this is a pluvium meter it measures the rainfall   a government scientist it's a job with  few surprises how much rainfall has   this instrument recorded in the last 15  years less than one millimeter by year   less than one millimeter a year yes who  was it every year it rains only three   years that's incredible exactly on average it  rains three one hundredths of an inch a year it would take a century for atacama's  rainfall to fill a coffee cup how does this compare with other deserts here we have a cylinder and i'm going to show you  the difference between the amount of rainfall per   annum here and the amount of rainfall in other  deserts so if i fill this jar up right up to   about there that is roughly rainfall that you  get in the sahara now if i pull most of that away we get to that level that represents what we  have in the mojave desert five inches per annum   if i pour all that away except for that little  drop in the bottom there and that's the equivalent   of what we have here in the heart of the atacama  desert that is such a small amount of rainfall   that it means it's the driest place on earth in his quest to find out why  atacama gets so little rainfall   houston leaves the oasis behind  and heads into the desert by the side of the pan-american highway a  road which runs the length of the continent   he discovers the first clue   well here we are at the tropic of capricorn this  is one of the most important latitudes in the   world and it is absolutely critical in explaining  why the atacama desert is in this location here   most of the world's deserts straddle  one of two special latitudes in the southern hemisphere the tropic of  capricorn runs through atacama and africa's   namib and kalahari deserts in the north the  tropic of cancer runs right through the vast   sahara at these particular positions on the  planet the air is extremely dry this instrument   is called a welling hygrometer what this does  is to measure the relative humidity of the air and the reading on here gives us a relative  humidity of 10 percent that's really low   really low there aren't many places in the world  where you get a relative humidity as low as that back in the early 1700s scientists  discovered why tropical air is so dry   european ships sailing to america relied upon the  trade winds to power their crossings but english   meteorologist george hadley was mystified why they  blew westward when they should blow directly north his studies would lead scientists to  understand how air circulates around the earth   at the equator moisture-rich air gets heated by  the sun and rises as this hot wet air flows away   from the equator it quickly sheds its water  as rain by the time it reaches the two tropic   latitudes the air has lost nearly all of its  moisture resulting in no rain on the land below the mystery though is why atacama gets  so much less rain than any place else   scientists hope to crack the case  by figuring out how atacama first   formed on the hunt for clues houston  travels deep into the true desert   this closely guarded location was discovered  during routine mapping by geologists   back in the 70s but the huge significance  of their find wasn't realized until 1998 this band of boulders is the single most  important clue to atacama's beginnings it's a delicate rock called gypsum a simple test shows how fragile it is if i pour a little bit of water  on top of that you will see that   it very rapidly falls apart what's happening here  of course is that when i'm putting water on this   you see it dissolve i mean  it's just going to fall apart the survival of gypsum as a solid rock tells  scientists there hasn't been any heavy rain   since the rock formed so the next step was to  date it and figure out when this place became dry gypsum can't be directly dated   but by analyzing fossils in the surrounding  rocks the awesome age of the desert was revealed atacama is a staggering 150 million years old this gypsum here is an extremely special  gypsum if there had been any rainfall   greater than two inches in any one year this  would have dissolved and have been washed away   what that means is essentially that the  atacama desert is the oldest desert in   the world for more than 150 million years  while dinosaurs thrived and became extinct   the himalayas formed and humans  evolved atacama has been a desert gypsum also holds the key  to how this desert was made   it's a chalky mineral which  forms not in deserts but in water gypsum exists in a dissolved state in shallow   warm tropical seas as the water is  evaporated away by heat it solidifies   the existence of this one little  rock is a key piece of evidence   which reveals that before atacama  became a desert it was a seabed this really insignificant looking piece  of rock indicates that all this desert   was once under water so this gypsum  in this location in the atacama desert   is absolutely critical to understanding  the whole history of the atacama desert   in the investigation so far scientists have pieced  together evidence of how and when the desert first   formed atacama's location near the tropic of  capricorn means air is dry and no rain falls   fossils found in the surrounding gypsum  rock reveal the age of the desert   gypsum a rock that forms only in water  reveals atacama was once underwater now as scientists explore the  mystery of how atacama evolved   from ocean floor to pure desert they unearth   explosive evidence in the investigation  of how the driest place on earth was made 150 million years ago the atacama desert  was a seabed covered by ocean waters   but today some areas in the desert  are two miles above sea level   in the journey to find out how this happened   scientists take the investigation  to the eastern edge of the desert this strange landscape is the largest geyser  field in the southern hemisphere we're up at   the altario geyser field you can see around us  that there's plenty of hot springs and geysers   there's plenty of steam around and this  is because the air is cool and the water   is hot and so you have a lot  of steam and bubbling springs the boiling water is being heated deep underground the geysers and the hot  water that you find up at el tattio   are indications that you have a body of hot  rock underneath us and another indication   is you have a bunch of volcanoes surrounding  this basin the earth here is violently alive molten rock erupts onto the  surface forming volcanoes the fiery volcanoes and the boiling geysers   are evidence of a turbulent process happening  deep beneath the desert here the pacific ocean   crust is being forced underneath south america  much like a spatula going underneath a pizza this geological process is called subduction   you have the pacific plate  colliding with the continental crust   and the pacific plate is actually heavier and  it slides underneath the continental crust   and as it does so it heats because it gets to  a depth of about 60 miles and it becomes molten this crucial depth is called a melting  zone hot molten rock then thrusts upward   to form the active volcanoes that  ring the el tattio geyser field this process gives scientists a hint to  what lifted the desert out of the ocean more clues are found on the  opposite side of the desert geologists know that these coastal  hills were also once volcanoes   today they're completely dead but modern  dating techniques show that they first   erupted over 195 million years ago it's a  crucial piece of evidence which reveals when   the pacific plate first began to  force its way beneath south america at that time the desert indeed  all of chile was underwater   over time the melting zone was pushed further  and further inland first igniting the coastal volcanoes as the melting zone  passed beneath the desert   it formed new crust thickening and raising  the land the atacama desert slowly emerged 50 million years ago this same  process began to raise the andeans today the melting zone is 140 miles inland and  the molten rock it produces ignites volcanoes and fuels el tatio's geysers but as it passed under the atacama  desert it also left behind this chuki kamata the largest open pit copper mine  in the world volcanic processes concentrated the   copper ore here but it was the desert's  unique climate that locked it in place   this area of northern chile produces  some of the largest and most important   copper deposits in the world and this  is largely due to the very dry climate most of the erosion on the  earth's surface is caused by water   so here where there's so little rainfall and  there's very little surface water there's not   very much erosion and so the copper  deposit has actually remained intact as a result this barren wilderness is one of  the most valuable pieces of land on the planet the mystery of how a desert can  rise from the sea can be solved   geysers provide evidence that molten rock exists  deep underground the existence of active volcanoes   shows the movement of one continental plate under  another extinct volcanoes show this process began   at the coast and pushed inland raising the desert  above the ocean the next step is to try and figure   out what turned this ancient sea floor into  the driest place on earth a quest that spans   200 years of history and solves the riddle of what  brought these penguins to the edge of the desert the atacama desert is intriguing because it is the  driest place on earth deserts by their very nature   are dry but atacama is unique it's 50  times drier than death valley in california   and it's not because it's hotter atacama averages  around 80 degrees fahrenheit during the day   whereas temperatures in death valley regularly  soar above 110. the search for what turned this   strip of land from a regular desert into the  world's driest place begins out on the open sea one of the curious things about the  atacama is that we actually see here   penguins penguins obviously like cold water and  that's really confusing when you think of onshore   we have really hot conditions in fact  the temperature of the water here is about 55 degrees fahrenheit   whereas on land the temperature is  something like 80 degrees fahrenheit   these penguins were first described by explorer  alexander von humboldt over 200 years ago   while traveling along this coast he was  puzzled by the huge variety of marine   life measuring the temperature of  the water gave him an explanation it was 20 degrees colder than expected  perfect for sea life like penguins centuries later meteorologists began to wonder  if this chilly belt of water called the humbled   current after the explorer was the reason  atacama became the driest place on earth   the humboldt current comes all the way up from  antarctica bringing with it cold water and it is   this cold water which creates this dull grey day  that we see here with a fog overlying us it causes   the air above it to cool forming a thick bank  of cold cloud and fog which clings to the shore hot dry air descends at the tropics here that  hot air sits on top of the cold heavy rain clouds   holding them down meteorologists call this  an inversion layer trapped at three thousand   feet the clouds can't rise up and shed  their rain on the high altitude desert the inversion layer prevents any moisture  that may accumulate close to the sea from   moving inland so that is one of the reasons  why this humboldt current actually contributes   to the dryness of the atacama  desert that we see just over there   but is it this inversion layer  created by the humble current   that has turned atacama into the driest desert  in the world in the desert's northern tip   in a desolate place called cabrada aroma  geologist laura evenstar is looking for clues   to solve this riddle she's trying to put a  date on when the desert became so very dry   other deserts like the mojave don't get  much rain but when they do it's dramatic   storms bring heavy rains and flash floods but not here in the cabrada  aroma which is now totally dry one way to date the last time there would have  been enough rainfall to cause a flash flood   is to try to find out how long the rocks have  been lying there undisturbed what we have here   is a miniature demonstration of what goes on  if we start having large amounts of rainfall   so this is our rainfall here and what we can see is that  when we start raining on our   desert surface it will pick up  the boulders and move them around   and then when there's no water here the  boulders just sit still and don't move the surface of cabrata aroma is strewn with rocks   so she's cracking them open to reveal evidence  of exactly when water last flooded the landscape what we do is we have to knock a bit  off and then we examine it and have   a look at whether it's got a very dark  color and hopefully we can be able to   see some of the black minerals  which is what we're looking for the tiny black crystalline minerals are pyroxenes they're crucial evidence because like microscopic  geologic clocks their chemistry changes when   exposed to cosmic radiation over time the sun  is only producing a tiny bit of the radiation   which will hit this rock the majority of it is  coming from all the stars you see in the night sky   what it does to the rock is basically  uh just bakes it a bit like a really bad   suntan so it just comes down hits  it and cooks it as the rock gets   cooked by cosmic rays the pyroxenes break  down and produce a gas called helium-3 we can record how much helium-3 is within this  rock and the more we have the longer that it has   been exposed to cosmic or solar radiation helium-3  gas is only produced in microscopic quantities   so even star takes her samples to a lab  7 000 miles away in glasgow scotland so what we do using a laser is we shoot the laser  into one of the wells and vaporize our crystals and that's releasing the helium-3 then the  helium-3 is going to go through all this   complicated machinery eventually  run through the mass spectrometer by analyzing this data she can figure  out the last time the boulders were moved   the oldish age sample we've actually  recorded has been 23 million years   so what this means is that within  certain areas of the atacama desert   these boulders have been sitting there and not  moved by water for twenty three million years seattle gamma desert is one of the  oldest undisturbed surfaces in the world   these boulders were there before humans even  started to exist they are incredibly old even start has discovered that there are  places in the desert which have been bone dry   for 23 million years this date is  a crucial clue in the investigation   because it coincides with the  birth of the humboldt current south america was once joined to antarctica   but roughly 25 million years ago these  continents split a channel opened   freezing water began to circulate round the  pole and thundered north along the coast this cold current formed an inversion  layer trapping coastal rain clouds and   starting atacama's slow transformation  into the driest place in the world but the humble current is not the only culprit   ironically the quest to find  out how the desert became so dry   comes up against one of the wettest places on  earth on the other side of atacama is the amazon   but the heavy rainfall from the rainforest  doesn't get anywhere near the desert the reason   why is in plain sight between the amazon and the  atacama desert lies the vast andes mountain range geologic evidence suggests the andes finally grew  high enough some 10 million years ago to prevent   any rain from reaching the desert it's  called a rain shadow effect and it's   the final factor which drove atacama  to become the driest place on earth the evidence for what turned atacama  so incredibly dry is mounting the humboldt current creates a  weather system that allows no rainfall   helium-3 in rock shows that the process  of desiccation began 23 million years ago   the rising andes 10 million  years ago made it dryer still the investigation would seem to be conclusive   atacama has been a barren essentially  rainless landscape for millions of years   but then something happened to blow that  conclusion wide open tiny shards of stone revealed   that an ancient civilization once lived here but  how could people live in the world's driest desert the atacama desert is by far the driest place  on earth and by piecing together the evidence   scientists believed it had  been so for millions of years yet at a remote site called guanajuatos   paleo ecologist claudio latoure made an intriguing  discovery which paints a more complex picture this is an extraordinary find and this  was probably a little knife or a scraper   that's been broken off and discarded that  probably still cut to the untrained eye   it looks like a simple rock shard but  latoure can see it's been worked into a tool and he's found hundreds of them they're clues  that reveal ancient humans once lived here this was not just a temporary residence this was  something where people were living and working and   banging away rocks and making artifacts and living  off this landscape using the resources at hand as water is essential for life it seems impossible   that any kind of plant animal  or human life could survive here latorre suspects that some regions of this  57 000 square mile desert were once much   wetter not millions of years ago but  during the time humans walked the earth in 1997 he set off on a mission to hunt for  evidence today he's retracing that journey changes in the climate can be seen in the rocks  so latorre examines the cliff layer by layer   he finds a crucial piece of evidence this is actually where the  interesting part of the story comes in   this chalky rock is called diatomite it's made from the crushed remains of fossilized  algae microscopic life forms which only live in   fresh water what this rock is telling  us is that we had basically a wetland whereas you look at the landscape  across the day and we see that   it's basically about as dry as you can get sometime in the past there was water on the  surface of the desert latorre's next task   was to find out when radiocarbon dating is  one of the most accurate methods of dating   but using this method means sampling something  organic so littori combed the desert for clues   the way we work is basically poking our heads  into every little hole in crevice that we can find   when we found this place we  couldn't believe our eyes he accidentally and luckily stumbled upon the most  important piece of evidence in this investigation   at the back of the cave was a vast nest it's made from the feces of thousands  of generations of tiny mammals   the size and shape of the pellets told  latorre those animals were chinchilla rats and it also contained the  critical clue he was searching for organic material when we found this site one of  the most exciting discoveries that we made was   the fact that it's full of grasses now look  across the landscape today and tell me where   those grasses are and we immediately knew that we  were talking about some major vegetation change   this grass looks as fresh and crisp as if  it was collected yesterday but when latori   carbon dated grass from the nest what he found was  amazing the grass was more than 11 000 years old what i have in my hands here is an ancient  ecosystem this is about as clear an indicator you   can get better than anything else you can think  of that water increased in the past in this area the nest reveals strong evidence that  plants and mammals did exist here   they weren't alone underneath the thick layer  of nest is another layer rich with tiny handmade   tools if we look around you know we can find  actually evidence of this past human quotation   there's just full of little  shards here on the floor   some regions of atacama have been constantly  dry for 23 million years but this evidence   shows that other regions like guanacaros  were very different eleven thousand years ago   it's a fossilized snapshot of a diverse  ecosystem briefly bursting into life   grasses grow and wetlands flourish in this  wetter time tiny mammals thrive and breed   while game like vicuna and llamas meant humans  could live in this rich and fertile environment so it's wonderful to know that by looking at  something as mundane as a rodent rodenest you can   actually find clues that enabled you to understand  the past human colonization of the atacama desert   which is no mean feat in itself given the  fact that it's such a harsh climate today the date of the rat's nest gives scientists a  possible theory of where the water came from eleven thousand years ago the last ice age  was at an end the global climate was changing more rain fell high in the andes  flowing down to the desert in rivers in some places groundwater pooled forming wetlands   others remained untouched by water  as they had for millions of years but just a thousand years  later the climate changed again   rivers dried up grasses died rats and humans  disappeared now every drop of groundwater has   been sucked down into the parched earth latorre  demonstrates how deep that water is today   so just to give you an idea of how much change  has gone on since the wetland was formally at   the surface here's a little experiment that we can  do this is a well and i'll drop this little rock   and we're gonna count and we're gonna see how  long it takes for that rock to hit the water so that takes almost four seconds to reach  the water that's well over 200 feet below   the surface is where the water table is today  it's about as dry as it gets it's a it's what   we call absolute desert no plants no wildlife  nothing no surface running water whatsoever the investigation of this driest  place on earth took a surprising turn   tools show humans lived here diatomite  reveals the climate was once wetter   rats dung and grass dates a diverse  ecosystem to 11 000 years ago yet this extraordinary desert has more  secrets to tell not just about life in   one of the most extreme environments on our  planet but also about life on other planets today scientists suspect atacama  is the driest it has ever been   so they're investigating whether there's  any source of water left here at all and nasa scientist alfonso davila knows that if  there's water there's a chance there could be   life here too but when he first arrived the signs  didn't look good when i came here for the first   time i drove for a couple of thousand miles and  when i got back to my base camp i realized that   i didn't have a single insect smashed against my  windshield that has never happened to me anywhere   else in the world and i think that's a very good  example of how hard this environment is for life   since the 1960s nasa scientists have been  hunting for bacterial life in the desert's   thin soils yet they found nothing until 2005  when they came across a strange white landscape by chance one of davila's colleagues picked up  a rock smashed it open and discovered something   completely unexpected yeah you can see  very nicely a green layer inside the crust under the microscope the significance of this  pale green blur zoomed sharply into focus to our   surprise we saw a green microorganisms living  inside the rock so that came as a big surprise   because nobody was expecting microorganisms  in the middle of the driest place on earth completely by accident hidden  inside a rock they discovered life   this mineral is sodium chloride  otherwise known as halite it's a very   common mineral in the atacama desert  and it's also very common mineral   in kitchens around the world as this is  exactly the same salt we use to spice our food   salt can preserve food by killing off bacteria but  here strangely it was harboring a colony of green   microbes to find out how they survive davila laid  out a series of sensors that measure humidity   his research shows that although on average the  air in the desert is around 10 percent humidity   on rare occasions it rises as high as 75 percent this momentary increase in water  vapor is the only source of water and it's this water that gives rise to life the  distinctive property of salt is its capability   to extract water vapor from the atmosphere  and forms a liquid solution inside the rug as   moisture from the air is sucked into the salt the  microbes allow the rock to bring the water to them life is actually very robust  it's uh very flexible and it can   really adapt to some of the most  extreme conditions that we see on earth   nasa believes this discovery in the atacama  desert can reveal something about life on mars   in 1976 the viking lander detected  water in mars thin atmosphere in 2008 nasa's mars odyssey orbiter found  evidence of salt on the planet's surface   now when humans finally get to mars they won't  be looking for life in the thin martian soils but inside the rocks unfortunately it's going  to be a long time until we see humans walking   on mars until then we come to the atacama  desert and we study this type of rocks   which likely hold the clue to  understanding life on earth   and also to understanding the potential for  life in other planets in our solar system so it's possible that an accidental  discovery in the driest place on earth   will one day lead scientists to crack open a  martian rock and discover little green alien life the investigation into how the driest place on  earth was made has revealed an awesome earth story   spanning 150 million years gypsum a rock which  forms in water shows the desert was once a seabed   hot geysers show that immense volcanic activity  under the desert raised it above the ocean tiny pyroxene crystals revealed the first  areas of the desert which became completely dry   23 million years ago rat nests reveal a small  pocket of life that bloomed in the desert   at the end of the last ice age tiny green  organisms in salt show that even here   life clings on today this place is unique on earth  absolute perfect desert and the investigation   into how it formed has shed light on another  chapter in the story of how the earth was made you

Channel: HISTORY

Views: 946,312

Keywords: history, history channel, history shows, history channel shows, how the earth was made, history how the earth was made, how the earth was made show, how the earth was made full episodes, how the earth was made clips, How the Earth Was Made season 1 episode 6, How the Earth Was Made se1 ep6, How the Earth Was Made s1 e6, How the Earth Was Made s01, How the Earth Was Made 1X6, episode 6, Atacama Desert, Driest Place on Earth, watch history clips, watch history channnel, full eps

Id: SO6j3Ckn7rs

Length: 45min 12sec (2712 seconds)

Published: Sun Jan 31 2021