The Deepest Place on Earth | How the Earth Was Made (S1, E2) | Full Episode | History

earth a 4.5 billion-year-old planet still evolving  as continents shift and clash volcanoes erupt   and 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 the marianas trench  the deepest point on earth is explored   its sheer walls cut seven miles into the pacific  ocean the mystery of what created this deep dark   chasm takes science detectives on some of  the most dangerous dives ever attempted deep   into the abyss scouring the ocean floor  scientists uncover a strange undersea world   of fiery mountains bizarre mud volcanoes and  the largest geological structure on earth   discoveries from this unique underwater  world will revolutionize our understanding   of the powerful forces that shape not  just the trench but the earth itself hidden deep beneath the waves of the  western pacific lies the marianas trench the deepest point of all the oceans the first step on the journey of what created this  mysterious scar in the earth's crust and how it   continues to mold the planet takes us back to 1872  when a british research vessel hms challenger set   out on the first ever mission to map the ocean  floor throughout most of recorded history men   have just assumed that beyond a certain level the  sea was pretty flat pretty dead fairly lifeless they weren't expecting to  find anything very interesting for four years the challenger crisscrossed  the oceans covering 70 000 miles   a third of the distance to the moon the  crew plumbed the depths every 140 miles   using a total of 249 miles of rope and hundreds of  pounds of lead weight it was tedious back-breaking   work but at the time it was the only way  to measure the depth of the ocean floor when they got to the western pacific  200 miles off the island of guam   the crew routinely lowered  the rope for a measurement but the weight kept on dropping and dropping a big  surprise nobody thought the ocean was this deep   so all of a sudden we've got  scientists saying why is that eventually the weight struck the bottom at 4475   fathoms nearly five miles  beneath the ocean's surface the scientists will be going wow we've  found something and what does it mean   is it a little hole is it a big hole what kind  of feature is it down there there's a whole lot   of questions you get when you find this one  spectacular reading the challenger expedition   marked the birth of modern oceanography and  provided the first crude map of the ocean floor it showed how the ocean floor  gently slopes away from the land   and then plummets thousands  of feet into vast flat plains   but the western pacific is different it drops  off again into the five mile deep hole a hole   that blew right out of the water the long-held  belief that the sea floor was flat and featureless and it spawned a mystery because  nobody could understand how this   strange underwater feature came about it would  be 75 years before any answers emerged it took   a revolutionary new technology sonar to push the  investigation forward to the next crucial stage sonar was first developed in the early  1900s and then perfected during the 1940s   to detect submarines lurking in the deep the system works by pumping sound waves through  the water the waves bounce off solid objects and   are reflected back to a detector by measuring the  time it takes for the sound waves to bounce back   scientists realized they could build a remarkably  accurate picture of the world beneath the waves   the world's major navy spend a lot of time and  effort developing submarine hunting technology   then the hydrographers discover that you  can use this to chart the bottom of the sea   and it's an awful lot cheaper and easier than  using large numbers of sailors pulling on ropes in 1951 a british navy research ship returned to  the deep hole found by the challenger expedition but this time they were armed with  sophisticated new sonar equipment and the results were amazing detailed sonar maps revealed that the deep  hole in the pacific ocean floor isn't a hole   at all but part of a massive trench 30 times  deeper than the empire state building is high it runs twice the length of california  1500 miles from the southeast of guam   to the northwest of the mariana islands people were probably astounded by what they  were seeing because clearly the ocean floor had   enormous changes in relief was very mountainous  in some places had great deeps in other places   to a geologist this would be extremely  exciting even within the trench itself   there are remarkable variations at its  southern end lies the greatest surprise of all the seafloor drops down another  two miles to its lowest point   a staggering seven miles beneath the waves scientists had discovered the  deepest part of the oceans   even today it is the lowest  known point on the planet they named this part of the trench the challenger  deep in honor of the ship that discovered it   to get a sense of just how deep trenches  are if we take the height of mount everest   we would still have about a mile of water  above us before we get to the ocean's surface but how the marianas trench was formed  remained a mystery investigators decided   the best way to find the answer was  to dive to the bottom of the trench to see for themselves the  lowest point on the planet   the challenger deep but they faced a major problem at the bottom of the trench they would have to   contend with pressure a thousand  times stronger than at the surface   that's the equivalent of being squeezed on  all sides by the weight of 50 jumbo jets to demonstrate the effects of such pressure  scientists use a dummy head today what we're   going to do is actually put one of these  styrofoam wig heads in the pressure chamber   and expose it to the pressure we would see in the  marianas trench that's about 16 000 psi a human   skull would be crushed to a pulp but the rubbery  head will only have all the air squeezed out wow it's smaller and here's what the  original size was just for comparison   quite dramatic pretty stark difference  between something that hasn't been seven   miles deep in the ocean and something that  has glad i'm not going there at the mariana   trench human life is impossible we're not  equipped to resist those kinds of pressures   and so it's necessary to protect  humans from that type of an environment the challenge to engineers was how to accomplish  this in 1953 swiss scientist auguste picard   designed the trieste a pioneering vehicle  that could withstand the crushing pressures the submersible was dominated  by a 50-foot long hull   filled with light aviation gasoline  and lead weights to control buoyancy   slung underneath it was a tiny six-foot  spherical cabin with five-inch thick steel walls finally after seven years of modifications and  manned test dives no deeper than three and a   half miles the trieste was ready to attempt  the seven miles to the bottom of the trench   the commander of this perilous undertaking  was u.s navy lieutenant and deep sea explorer   don walsh i know the astronauts that go through  this all the time why do you have to be there   why can't we just put up a robot to do things  we've got to be there because that's what we do only a few officers and scientists  knew about the risky mission   which was launched in january 1960  from the western pacific island of guam guam in those days was kind of a backwater was  just right for us because we were trying to do   this project sort of out of sight because  we weren't too sure it was going to work   my navy just didn't want to be embarrassed  by a failed science spectacular accompanying walsh was the son of the trieste  designer engineer and oceanographer jacques picard   the two men would spend the next nine  hours squeezed inside the cramped sphere   and we had 20 cubic feet of space inside that's  about the same as a household refrigerator   and the temperature was almost  that cold inside it was a drama the marianas trench is one of the most  remote inhospitable places on earth in january 1960 two deep-sea explorers   don walsh and jacques picard plunged into its  depths on board the submersible the trieste at a speed of just three miles per hour they  began their slow descent into the twilight zone by three thousand feet the darkness was total   the only illumination was from  the trieste's powerful lights the depths we're operating at it was always black   the only thing that lit up the  abyss was the bioluminescence from   animals and plankton like fireflies they  carry their own light sources with them   encased in their five-inch thick steel  sphere walsh and picard quickly passed   their test dive record of 18 000 feet  everything appeared to be going to plan at the rear of the cabin the crew were  protected by a double layer of glass   but two hours into the dive the outer pane cracked we had a great big bang we didn't know  what it was we were about 20 000 feet   and we looked around and checked everything every square inch of their tiny life-supporting  capsule was fighting back eight tons of pressure with the outer pain broken the only  thing between the men and instant death   was a single pane of glass if the inner window  had cracked we would have been instantly dead   maybe even before we knew it   but incredibly the inner pain remained watertight  walsh and picard decided to continue the descent after a tense claustrophobic four hours and  48 minutes they approached the bottom of the   trench only to be startled by movement on the sea  floor just before we landed we saw a flat fish   about a foot long and that's a bottom dwelling  fish so if you see one there are others nobody expected to see life  at these crushing depths   but it meant the explorers had reached their goal the very bottom of the marianas trench the  depth gauge with a reading of 35 800 feet   nearly seven miles below the  surface confirmed the sonar findings squeezed inside their bubble of  breathable air the two explorers   were closer to the earth's center than  man had ever been we took a self portrait   that's the picture that you see he  said we're gonna do it and we did it but there was work to be done  walsh and picard wanted to   make detailed observations of the enormous trench unfortunately the trieste stirred up a cloud   of fine powdery sediment from the  sea floor that obscured their view it's like being a bowl of milk at that point  so realizing where i could see anything   we decided to go on back up to the surface off  the island of guam and priest surfaces after a   descent into the marianas trench after nine  grueling hours underwater walsh and picard   returned to the surface on january 23 1960 and  officially entered the record books for the   deepest dive of all time to this day their  extraordinary feat has never been repeated the mission was a success   but the mystery remained geologists still didn't  understand what could have formed the immense   trench and if they couldn't find the answer inside  the trench they would have to look elsewhere perhaps there was something somewhere on the ocean  floor that might explain the trench's origins throughout the 50s and 60s a team of  geologists led by princeton's harry hess   compiled sonar data from all of the world's oceans it was as though they had pulled out a giant plug  to drain away all the water and expose the ocean   floor their maps revealed that the marianas  trench is just a tiny fraction of a network   of enormous underwater canyons stretching  right around the planet but that wasn't all   running parallel to the trench on the other  side of the pacific the map showed a giant   underwater mountain range the east pacific ridge  and this too is part of a global network a forty   thousand mile long chain of mountain ranges  that ring the globe like the seams of a baseball   to make the largest geological feature on earth it was a major development in the investigation   one that scientists hoped might  explain the trench's formation the next step was clear investigators  needed to understand whether there was   a connection between the trench  and the east pacific ridge the breakthrough came from  the unlikeliest of sources during the cold war the u.s built a vast network   of underground seismometers to pick up  atomic bomb testing around the world inadvertently the seismometers also  detected naturally occurring earthquakes   when geologists plotted these  on a map a pattern emerged the earthquakes were clustered along  the oceans ridges and trenches it was   a discovery that transformed  our understanding of the earth   geologists realize the friction that causes  earthquakes comes from movements that must be   occurring deep beneath the ridges and trenches  with this great investment in seismology   it became possible to locate very precisely where  earthquakes had occurred and it was these things   the precise location the depth and the motion  that really gave the outlines of plate tectonics it was the birth of an extraordinary new theory  the solid layer of rock the crust on which the   land and ocean sits is broken up into a series of  vast slabs that geologists call tectonic plates   it's these plates that are moving grinding  past each other and triggering earthquakes   the underwater ridges and trenches sit on  the boundaries between tectonic plates the   east pacific ridge and the marianas trench  lie on opposite edges of the pacific plate the journey to discover what formed the marianas  trench is accumulating additional evidence   the trieste dive to the bottom of the trench  and confirmed that it is the deepest point   on the planet sonar maps then revealed the east  pacific ocean ridge running parallel to the trench to solve the mystery of the  marianas trench investigators   needed to find out exactly what was  happening at the east pacific ridge   and that meant exploring these vast  mountains 8 000 feet underwater the pieces of the marianas trench puzzle  are falling into place with the knowledge   that it lies on the western edge  of the pacific tectonic plate   on the opposite side of the plate lies the east  pacific ocean ridge part of an enormous chain   of underwater mountain ranges that ring the globe  to create the largest geological feature on earth   scientists had a hunch that this colossal ridge  might help explain how the trench was formed and they found a major clue  halfway around the globe   where the ridge passed beneath  the middle of the atlantic ocean during the cold war the u.s navy developed  a new technique to spot soviet submarines   they scanned the seas with a tool called mad   a magnetic anomaly detector which could  pinpoint steel hulls lurking in the deep but they stumbled across something else running  parallel on either side of the ridge they found   strange stripes of magnetic rocks alternating  positive and negative away from the ridge's peak   here's the mid-atlantic ridge coming down through  here almost perfectly symmetric on either side   of that are these white and black stripes  these have often been called zebra stripes geologists know that the earth is like a giant  magnet with a north and a south pole but the   magnetic poles aren't fixed every 300 000 years or  so the magnetic field suddenly flips 180 degrees when the field flips a compass that was previously  pointing north will swing to the south this   reversing of the earth's magnetic field is   a very interesting and exciting but very  puzzling phenomenon for geophysicists to explain scientists think this reversal explains  the stripes either side of the ocean ridge   in the 1960s geologists discovered  that molten volcanic rock known as   magma swelled up from deep underground to  create the ridges in the atlantic and pacific as magma wells up between the tectonic plates   it pushes the sea floor up and forms the  colossal mid-ocean ridge thousands of feet high when the rock is hot and molten its magnetic  minerals line up with the north-south direction   of the earth's magnetic field as the magma  cools the minerals are locked in position   these rocks act as a permanent record of the  magnetic poles location when the rocks were formed as more and more magma is forced  up the old crust is pushed away   from the ridge and records the reversals  in the earth's magnetic polarity   if you have reversals of magnetic polarity then  the seafloor acts sort of like a tape recorder   and records these changes in magnetization then  the pattern of magnetic stripes allows people to   calculate the speed at which  the plates are moving apart the zebra stripes are proof that over time the  sea floor in both the atlantic and the pacific   is spreading away from the ridges at  a rate of more than two inches a year but geologists needed proof that magma  created the ridge if red-hot molten rock   is forming the enormous mountain range in the  pacific the surrounding water should be warm in 1977 a team of scientists set out to  discover whether this warm water really existed dudley foster was the pilot for these  historic dives it's been an exciting   occupation because you're on the cutting  edge of science new discoveries all the time   every cruise there's a new group of scientists  with new scientific objectives and there's the   exploration and the discovery and that's  really what puts the thrill in the job for weeks the crew scanned the undersea mountains  without success and then they hit the jackpot a bizarre pillar of rock spewing  hot toxic gas and we saw the water   was sort of shimmering sort of like a  bubbling in a glass teapot or something we stuck the temperature probe in there and  measured 38 39 degrees fahrenheit which was   really amazing because the  the ocean is a huge heat sink   so to see something warm like that was  kind of startling in these pillars of rock   the expedition had found the heat from the  magma surging up from deep inside the earth it wasn't warming the water evenly along the ridge   it was channeled up through  strange hydrothermal vents when you make these discoveries you don't  know how significant they are the true   significance of them maybe takes several years  to appreciate and this was one of those times   for the investigation into the marianas trench  these vents are a decisive piece of evidence they confirm that magma is continually  creating new crust at the pacific ocean ridge   and magnetic zebra stripes prove  that old crust is pushed away from   the ridge towards the other side of the  pacific plate towards the marianas trench but this presents scientists with a puzzle if  new crust is being created at the ocean ridge   and the earth isn't expanding then the old  crust must be disappearing somewhere else   the reason that there's not getting bigger  with sea floor spreading is because the same   amount of seafloor is being destroyed in  the pacific something in the pacific ocean   is devouring the sea floor and all the  evidence points to the marianas trench in the hunt to discover what formed the  marianas trench scientists now know crust   created at the ocean ridge is being devoured  somewhere and by something in the pacific ocean they suspect the marianas trench is involved but the proof would come not  from the trench but from these the mariana islands a chain of volcanoes that  break through the ocean's surface 200 miles west   of the trench scientists noticed the island  chain mirrors the trench's exact shape   this led them to think the trench was  responsible for the island's creation if you see pictures of the  marianas trench it's curved   and the line of volcanoes that it  generates is curved exactly parallel to it geologists believe that the trench formed  the volcanoes via a process called subduction subduction occurs where  two tectonic plates collide   as they grind past each other the heavier  plate is pushed beneath the lighter plate   the descending plate is forced down into the  earth's intensely hot interior called the mantle   it takes with it water and sediment built up  over millions of years volcanoes form above   subduction zones not because the earth is hotter  there but because this is where we're taking the   water that once was in the ocean it's taken  into the mantle and gets sweated out causes   the mantle to melt and this magma is what then  rises and erupts explosively out these volcanoes the water in the sediment forces magma to swirl  up and push through the plate above and when it   breaks the surface it creates volcanoes like  the volcanoes that form the mariana islands it was subduction that formed  the islands west of the trench   and gave investigators the  breakthrough they'd been looking for because here at last was a process powerful  enough to create the marianas trench   as the descending plate dives  down it digs into the mantle   here the colliding plates form a trench  a giant crease in the ocean floor it seemed that scientists had finally  explained how the trench was formed there was just one problem a very large problem   around the world subduction zones cause  violent earthquakes and catastrophic tsunamis we know subduction is happening because of  the active earthquakes and these are the   most devastating earthquakes this is the  earthquake that generated the tsunami in sumatra also the other very large  earthquakes in alaska and chile but the marianas trench the deepest  subduction zone in the world   hasn't caused the devastating earthquake  since records began in the 17th century   investigators needed to know why ah  that's that's a thousand dollar question they hope the trench's shallower  western edge might provide the answer   here they found an intriguing chain of underwater  hills two miles below the surface of the sea engineers drilled down into the  hills and collected core samples and when the scientists analyzed the samples  they discovered the hills were actually volcanoes   and they spewed out not lava but mud the fine  powdery mud is made up of a soft type of rock   that has been ground up in the  subduction zone it seemed this   soft rock might explain why there have been  no major earthquakes at the marianas trench everybody has a sense of what a volcano is but  not all volcanoes erupt igneous rocks there's some   volcanoes that erupt mud and a certain  kind of unusual kind of mud in the marianas   is made out of serpentine and serpentine is a very   weak rock and it can be scratched  with a knife or something like that investigators realize the grinding  plates crush the soft rock to form   a lubricating mud that prevents large earthquakes then the mud bubbles up to the  ocean floor where it forms the strange mud   volcanoes found along the trenches western edge  other parts of the world like the andes or maybe   indonesia you've got two plates that are grinding  together and one of the plates is quite strong   and it takes a big earthquake to rupture  that plate interface but if these rocks   are weak like they are in the marianas where  you've got these cerpentinites those are very   weak and it doesn't take much energy at all to  get the two plates to glide one past the other at last geologists had discovered  what created the marianas trench 50 million years ago the pacific plate  slipped under the edge of the philippine plate   as it bent and dived into the earth's mantle  it formed the colossal marianas trench and the plate is still moving  like a giant conveyor belt   the earth's crust travels slowly across  the pacific plate from its birthplace in   the east pacific ridge to its graveyard  10 000 miles away in the marianas trench   today the pacific plates movement  can be tracked in real time confirmation has come from gps technology where  we can actually put a transmitter on an island and   come back year after year and actually follow it  moving a few centimeters a year towards the trench it's devouring the crust at a rate of three inches  a year about as fast as a human fingernail grows every four million years it swallows  an area the size of the united states   by consuming the crust created  at the pacific ocean ridge   the ravenous marianas trench is  the world's largest recycling plant but there was one remaining and  major piece of the puzzle to find   scientists still didn't know why it is the  deepest trench on earth they suspected the   age of the sea floor at the bottom of the  trench may provide the answer it turns out   there's a really strong relationship between the  age of the sea floor and its depth in the water in 1999 a team of deep sea drillers returned  to the trench to collect core samples one great thing about drilling station  crust is we actually got pieces of it   so we're holding in our hands here the material  that's actually getting subducted at the marianas   trench and it turned out to be 170 million years  old so we can say with confidence that's the   oldest ocean floor before it's getting swallowed  up in the mantle at the trench but why is this   piece of rock the oldest on the ocean floor the  seafloor at the marianas trench is so old because   it's been so long since it was born so it was born  in the equivalent of the eastern pacific today and   it's just been going on longer than any other  place in the oceans before it's been subducted the pacific plate is the  planet's largest tectonic plate   covering an area 11 times  the size of the united states when crust bubbled up at the ridge 170 million  years ago it was light and buoyant but as it   traveled 10 000 miles across the plate  it cooled and became compact and dense   over millions of years the dense crust got  heavier and began to sink into the mantle below   scientists realize that because the crust at  the marianas trench is the oldest ocean crust   it's also the heaviest and so has sunk deeper  into the mantle than any other area of ocean crust   here at last was the explanation  for the trench's extraordinary depth   the picture of the marianas  trench is almost complete the investigation into the marianas  trench has one final puzzle to solve at the trench's southern end the sea  floor plummets a further ten thousand feet   into a seven mile deep chasm called the challenger  deep it's the lowest point on the planet   but so far scientists have been unable to explain  why this one section of the trench is so deep   now they believe the shape of  the descending tectonic plate   may hold the answer the challenger deep  in addition is a little bit deeper because   of some peculiarities relating to how  the slab that's going down is behaving a narrow slab of crust has torn away  from the pacific plates descending edge   well it's basically got to do with how  the slab pushes the mantle out of the way   where you have a narrow slab like you have  at the challenger deep it can sink almost   vertically because the mantle that it's trying  to displace can move around out of the way investigators have finally unraveled  the mysteries of the marianas trench and in the process they've made a  discovery with implications that stretch   far beyond the trench itself studying the ocean ridges  led geologists to believe   that magma welling up at the  ridges was pushing the plates apart but the exploration of the marianas trench has  changed this idea forever people used to think   that maybe the magma would kind of push the plates  apart and that idea is largely discounted now as the ocean crust travels from the  pacific ocean ridge to the trench   it changes from a buoyant red-hot magma  into a colder denser and heavier crust the plate's leading edge becomes so heavy that  it drags the rest of the plate along behind it the heavy cold plates at the trenches are sinking  down into the mantle and pulling the plates apart   at the ridges and the magma  just passively fills in the gaps the investigation into the marianas  trench has revolutionized our   understanding of how the earth's plates move we now know a worldwide network of subduction  zones drag tectonic plates around the globe   powering the movement of continents over millions  of years and moving the very earth we stand on the plates that are moving fastest on the  earth are the ones that have all the trenches   the pacific plate is the fastest moving  of the nine major plates on the planet   because it is surrounded by dozens of  destructive trenches like the marianas   they are consuming the ocean crust faster than  the ocean ridge can produce it over millions of   years the pacific plate will shrink until sometime  in the distant future the largest ocean on earth   will disappear australia will crash into  the united states reshaping our planet perhaps one day downtown seattle will compete  for real estate with a suburb of sydney australia   and all because of subduction  zones like the marianas trench but for all its significance man has only  ever dived to the bottom of the trench   once and there are no immediate plans  to return imagine asking someone what is the flora and fauna of  california and saying that someone spent   10 minutes there picked up two ants come  back and said they've sampled california   that's probably how well  we know the marianas trench to date less than five percent of  the world's oceans have been explored   but only by returning to the  ocean's very deepest reaches   will we fully comprehend the incredible  forces that recycle and rebuild our world the way i like to think of it is that  ocean exploration leads to new research   questions and if we don't have exploration  we don't even know the right questions to ask   it is now known what a geological  wonder the marianas trench is since this deep chasm in the earth's  crust was first discovered with a   length of rope and a lump of lead more  than a century ago evidence has piled up   a record-breaking dive to the lowest point on  earth giant undersea mountain ranges with bizarre   magnetic zebra stripes proof that the ocean crust  is spreading towards the hungry marianas trench   lined with slippery mud volcanoes which prevent  devastating earthquakes and the planet's oldest   ocean crust the reason that the marianas  trench is the deepest point in the oceans   in the darkest and most remote place  in the world scientists have added to   their knowledge about the powerful forces that  contribute to the dynamic story of our planet you

Channel: HISTORY

Views: 367,111

Rating: 4.7963066 out of 5

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, full episodes, How the Earth Was Made season 1 episode 2, How the Earth Was Made se1 ep2, How the Earth Was Made s1 e2, How the Earth Was Made s01, How the Earth Was Made 1X2, How the earth was made series, The Deepest Place on Earth, Deepest Place, Marianas

Id: JRZ1AvGpbI8

Length: 43min 51sec (2631 seconds)

Published: Sat Dec 19 2020