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00:01Scientists uncover underwater remains of what could be a long-lost Egyptian city.
00:07But historians could never determine exactly where in Egypt it was supposed to have been.
00:11We've never seen any proof it actually existed.
00:14So could the cities have finally been discovered?
00:18After an extinction-level event that killed the dinosaurs,
00:21new discoveries reveal a thriving ecosystem.
00:25This is strange because you would assume that the closer you are to the impact crater,
00:28the longer it would take for life to rebound.
00:30Workers uncover strange markings left in the wake of a volcanic eruption.
00:35The scoria was lying above a layer of volcanic ash,
00:39which is what protected these strange imprints over the course of thousands of years.
00:45All over the world, incredible discoveries are being revealed by devastating events.
00:51Floods, earthquakes, droughts, hurricanes, volcanic eruptions.
00:59Trails of destruction expose long-lost mysteries.
01:03This is discovered by disaster.
01:15In 140 BCE, a fabled opulent and powerful ancient port in the Nile Delta,
01:22the revered gatekeeper of Egypt's riches, is stricken by a sudden devastating calamity
01:28that sends its greatest monuments tumbling into the shallow waters.
01:33This once legendary city never fully regained its glory.
01:37And as years and centuries passed, it sunk ever deeper into the water and mud
01:40until every trace vanished.
01:45In the late 1990s, a team of archaeologists were hoping to locate the wrecks of late 18th century French warships,
01:52which they had reason to believe sank somewhere in the waters of Egypt's Bay of Aboukir.
01:58Using a nuclear magnetic resonance magnetometer to scan the seafloor, the team gets a hit.
02:05But whatever's there is much bigger than a shipwreck.
02:09The water is only about 20 feet deep.
02:12And on the bottom, baled in silt, is a huge line of massive rectangular limestone blocks.
02:18A wall.
02:20And it's 10 feet thick.
02:22Just the part that's visible at this point is at least 65 feet long.
02:28It's clear there's something significant here.
02:31But what?
02:35A team of divers is sent to investigate, and they find huge pieces of stone scattered about like gigantic dice.
02:43The massive fragments are painstakingly raised and studied.
02:47The results leave the archaeologists stunned.
02:50They're pieces of huge stone statues.
02:53One of them is a male figure about 18 feet tall.
02:57He's in mid-stride and is carrying some kind of tray with four loaves of bread on it.
03:03The forward striding pose signifies he's about to offer something,
03:06while the tray is what's known as an offering table.
03:08So the interpretation is that the statue is offering abundance.
03:11The abundance symbolized by the loaves of bread.
03:13This is likely the Egyptian god Happy, the father of the gods, the source of everything.
03:18The other gods, the world, food, all of humanity.
03:22It makes perfect sense that this towering statue of Happy would have been positioned at the Nile's mouth,
03:28welcoming ships coming to the kingdom of Egypt from the outside world.
03:33The jumble of other colossal stone fragments yields even more potent symbolism.
03:39The rest of the pieces belong to a pair of statues.
03:41A male and a female carved out of pink granite and standing about 16 feet tall.
03:45The pair are dressed in a distinctively Egyptian way.
03:48The woman is wearing the same headdress as the god Isis.
03:51So this has got to be a royal couple.
03:53But who exactly?
03:55As the underwater excavations continue, more sections of wall are found.
04:00And for the archaeologists, something begins to take shape.
04:04This was some sort of building, but of truly impressive proportions.
04:09Larger than 35,000 square yards, built out of huge limestone blocks.
04:16Radiocarbon testing reveals that it was probably erected between 450 and 380 BCE.
04:23For archaeologists well-versed in Egyptian and Greek writings, the presence of the wall in these colossal statues sparks a
04:30realization.
04:33In the 5th century BCE, the Greek historian Herodotus wrote about an amazing city, built on islands in a marsh.
04:40Though he said the city was in Egypt, he simply referred to it as Heraklion, which means the place of
04:47the temple of Heracles.
04:48And Heracles was a Greek god.
04:50But historians could never determine exactly where in Egypt this city with a Greek name was supposed to have been.
04:57The ancient Egyptians had records of an island city as well, somewhere at the gateway to the Mediterranean, the mouth
05:04of the Nile.
05:04But they called it Phonus.
05:07But we've never seen any proof it actually existed.
05:10So could these cities have finally been discovered?
05:15Near the ruins of the wall, archaeologists discover a large cabinet-like structure, nearly six feet tall, masterfully carved from
05:24a single block of pink granite.
05:26The roof is pyramidal in shape, and at the corners of the top and bottom edges of the front opening,
05:32there are holes, almost like pivot holes for hinges.
05:37That tells us this cabinet once had double doors.
05:42That, along with where it was found, suggests that it was a naos.
05:48A naos is a kind of shrine that would have held a statue or other religious artifacts.
05:52So is this huge wall part of a temple?
05:54Further examination of the inside surfaces of the naos reveals faint remains of chiseled writing and hieroglyphics.
06:03The hieroglyphics contain the name of the god in whose temple this naos would have resided.
06:09It's the temple of Amun-Garab.
06:11According to the inscription, the god Amun-Garab would bequeath to each new pharaoh everything in their earthly and heavenly
06:18kingdom.
06:19Basically, making them a king entitled to own everything.
06:25In 1866, archaeologists excavating the ancient town of Tanis, just a hundred miles east, discovered two copies of a stone
06:33slab bearing Egyptian hieroglyphic writing.
06:37It's known as the degree of Canopus, and it talks about the god Amun-Garab and his temple.
06:44And it names the town in which his temple stood, Heraklion.
06:49So now we know conclusively, the lost city that Herodotus wrote about did exist.
06:54And this is it right here. This is Heraklion.
06:58And this massive temple of Amun-Garab would have been at the heart of it.
07:04As the underwater excavation progresses, more walls are found, but not all of them seem to belong to the temple.
07:12Some form a network of large trenches surrounding the building.
07:16Samples of the silt between the walls reveal that these are canals running around the temple,
07:22which would have been accessed from other buildings by way of ferries and bridges.
07:29Heraklion was like an ancient Egyptian Venice.
07:35In the area where the canals used to be, a great number of wrecked ships and boats are discovered,
07:41as well as many artifacts, including coins, attesting to the city's great wealth.
07:47Interestingly, a disproportionate number of the coins found are identified as being minted between the 6th and the 4th centuries
07:54BCE.
07:55This must have been when Heraklion was at the peak of its prosperity and power.
08:02The discoveries keep coming, including one found within the grounds of the Temple of Amun-Garab that astounds the archaeologists.
08:11It's an inscribed stone tablet known as a stele, 6 1⁄2 feet tall and in excellent condition.
08:16The hieroglyphics card into its face are completely legible.
08:20It turns out this stele bears a royal decree by the pharaoh Nektenebo I.
08:24This decree even bore a date, which in our modern calendar equates to 380 BCE.
08:28The decree states that this stele should be erected at the entrance to the Sea of the Greeks.
08:33That would be the Mediterranean, in a town by the name of Syse.
08:38This is amazing. We already know that another Egyptian name for Syse is Thonis.
08:44The stele confirms once and for all that Thonis and Heraklion were the same legendary port city.
08:50So what happened that made it disappear?
08:54Buried deep under 16 feet of hard-packed clay alongside the ruins of the Temple of Amun-Garab,
09:01and under heavy limestone blocks, the archaeologists discover the wreck of an 80-foot-long wooden ship.
09:08The ship's hull dimensions made it fairly sleek.
09:11So it might have been a warship or possibly a vessel used by customs officials to police the Nile Delta
09:18and keep money flowing into the royal coffers.
09:23At the time of the ancient cataclysm, this vessel was likely moored alongside the Temple.
09:27When disaster struck and the Temple collapsed, some of its huge limestone blocks smashed down onto the ship
09:32and immediately pressed its remains deep into the mud.
09:36But what was this cataclysm?
09:39Magnetic mapping of the area reveals the presence of a number of faults or rifts that cross the Temple grounds.
09:46These rifts likely resulted from a soil liquification event,
09:50which is when water-saturated soil, like you might find in a river delta,
09:54is subjected to vibrations, like an earthquake.
09:58Vibration causes the soil to momentarily behave like a viscous substance,
10:02incapable of supporting any weight.
10:05The ground turned suddenly and briefly into a muddy soup.
10:09The Temple of Amun-Garib collapsed.
10:12Some of its enormous limestone blocks pinned that moored ship to the bottom,
10:17along with artifacts from the temple, preserving a snapshot of that moment in time.
10:23From approximately the year 140 BCE on, it's clear from the archaeological record
10:29that the flow of coins into the city of Thonus Heraklion all but stopped.
10:34So that strongly supports an estimated date of 140 BCE for the cataclysm.
10:40But the city wasn't completely destroyed at that time.
10:43There's evidence that people lived there for the next eight centuries.
10:46However, over the years the sea level continued to rise
10:49and the buildings of Thonus Heraklion sank under their own weight,
10:52deeper and deeper into the mud.
10:54By 800 CE, following a series of earthquakes and tidal waves,
10:58all trace of the once legendary city was gone.
11:03Few people today have heard of Thonus Heraklion, but chances are that will change.
11:09As we learn more about this great doomed city,
11:12we'll be forced to rethink what we know of the past,
11:15and perhaps to reevaluate our thoughts regarding the permanence of humanity's great port cities.
11:3566 million years ago, the mother of all disasters tore the entire Earth apart.
11:41Not a single corner of the planet was left untouched as the energy from an asteroid impact set the world
11:48on fire.
11:52This asteroid measured six miles in width.
11:54Think about that, that's like something bigger than Mount Everest as tall,
11:57smashing into the Earth at 150,000 miles per hour.
12:03It hit the Earth in and around what is today Mexico's Yucatan Peninsula.
12:07And when it did hit, the result was apocalyptic, in the truest sense of the word.
12:13It generated an enormous tsunami, the size of which is difficult for us to quantify.
12:17Then an unbelievable amount of energy created by the impact set off a chain reaction of hell,
12:23triggering earthquakes as far south as Argentina.
12:27To put how big of an explosion this was into perspective,
12:31take the biggest nuclear explosion ever created by humans,
12:34the Tsar Bomba, set up by the Soviets in the 1960s.
12:39It measured 50 megatons, while the impact created by this asteroid
12:45would have been equivalent to a 20 million megaton explosion.
12:50Basically, what this meant was the equivalent of a one megaton hydrogen bomb
12:54going off every six kilometers all across the planet.
12:59It was like the gods poured gasoline over the Earth and put a match to it.
13:04Everything, absolutely everything was on fire.
13:09With all the debris that was launched into the atmosphere,
13:13the fallout from the blast created an impact winter,
13:16which blotted out the sun for at least a year.
13:19This meant that everything that relied on sunlight for life also died.
13:25This is what we call an extinction-level event.
13:27Actually, it's the extinction-level event of the past 66 million years.
13:32This is the asteroid that killed off the dinosaurs.
13:35As a result of the asteroid's impact, 75% of all of the Earth's species died.
13:40We know about the extinction of the dinosaurs,
13:42but what about the 25% of species that survived?
13:46How did life on Earth not just continue, but continue evolving
13:51when the planet was one massive ashtray?
13:57The 20-mile-deep and 100-mile-wide crater created by the asteroid's impact
14:02is known as the Chicxulub Crater.
14:06In 2016, a team of scientists were taking sediment samples from the crater
14:11in the hope of learning more about the planet in the years following the impact event.
14:16So in these sediment samples taken from deep down in the crater,
14:20roughly 2,000 feet below the seafloor,
14:21there are tiny little burrows as well as the fossils of a very particular organism.
14:26These are the tiny little sea creatures like plankton and foraminifera,
14:30a shelled microorganism populating the world's oceans.
14:34The thing is, there are a lot of them.
14:37They're diverse and seem to have been flourishing.
14:39The sediment cores represent a time from only 30,000 to 200,000 years after impact.
14:46So how on Earth did life in the ocean rebound so quickly?
14:50This is strange because you would assume that the closer you are to the impact crater,
14:54the longer it would take for life to rebound.
14:56When an asteroid hits the Earth like this, a lot of things are killed and decomposed.
15:00And when they do, they consume oxygen.
15:02So if the oxygen isn't replenished somehow, life suffers.
15:07The 35-million-year-old Chesapeake Bay crater was formed by a much smaller asteroid than the Chicxulub,
15:14at only two to three miles wide.
15:16Nevertheless, it still would have had a serious impact on the surrounding environment when it hit.
15:21Following this impact event, the area of the crater became anoxic,
15:26meaning the ocean was without sufficient oxygen to sustain life as diverse as that of Chicxulub.
15:33The Chicxulub crater is massive, but its northeastern section is and was open to the Gulf of Mexico.
15:39This means that there could be circulation of seawater in the crater,
15:43which in turn would allow for life to rebound.
15:45On the other hand, the shape of the Chesapeake Bay crater probably made this very difficult,
15:49meaning that the ocean water remained stagnant.
15:52So despite the entire world being devastated,
15:56the ocean environment in the impact crater actually rebounded extremely quickly,
16:01which is really incredible.
16:02But what about life on land?
16:04How long did it take for ecosystems and animal life to recover?
16:09To find out, we need to look at the fossil record from the years before and after the event.
16:14We know that the biggest mammals that existed during the time of the dinosaurs
16:17were only as big as your average rat.
16:18But we have almost no evidence of what animals survived or evolved
16:23in the thousands of years following the Chicxulub impact event.
16:27A few decades ago, a group of paleontologists were out hunting for fossils in a known hotspot for dinosaur bones,
16:34Colorado's coral bluffs,
16:36when one of them stumbled upon a fossil embedded in a curious rock.
16:41It was the pallet of a mammal that was set in a concretion,
16:44which is a rock that over time forms around organic material, which in this case is bone.
16:50The find alerted scientists to the idea that maybe, just maybe,
16:54more such fossils could be found encased in concretions.
16:57So they began scouring the coral bluffs, quickly discovering several fossils encased in concretions from around the time after the
17:06apocalypse.
17:09One fossilized skull has these sharp, jagged teeth in the front of its mouth,
17:13whereas in the back, the teeth are broader and blunter.
17:16This indicates that it could eat both meat and plants.
17:18If the ecosystem of the entire world has been nearly destroyed,
17:23it would be beneficial if you could eat everything,
17:26which it appears this animal, named the Loxolophus, could do.
17:30It also has a hole underneath its eye.
17:32This was a passage through which nerves could travel,
17:34so it probably had very sensitive whiskers.
17:37And the shape of the skull also indicates that a big portion of it was dedicated to smell.
17:41What we're looking at here is maybe an omnivorous, highly adaptable, raccoon-like creature
17:46that could scavenge what little food was available.
17:48So quite early on, only around 100,000 years after the event,
17:52we're seeing bigger animals than rats living in the post-apocalyptic world.
17:57Mammals that were more specialized, like plant eaters,
18:00wouldn't have been able to survive the catastrophe
18:02and would have been among the 75% that went extinct.
18:07As the scientists continue searching the coral bluffs for more fossils,
18:11they discover a much larger skull than that of the Loxolophus,
18:15dated to around 300,000 years after the asteroid impact.
18:20This mammal has huge teeth that would be used more for grinding than for tearing,
18:25which means that it was a vegetarian.
18:27What this tells us is that in the intervening 200,000 years
18:31between the Loxolophus and this plant eater,
18:34mammals had become specialized.
18:37On an evolutionary timeline, this is very fast.
18:40But in order for this to have happened, the environment would have to support such a diet.
18:45There likely would have been a wide variety of plants available.
18:49Otherwise, it simply wouldn't have enough food to have been so highly specialized.
18:54So after 300,000 years, the forest environment appears to have recovered fully,
18:59and along with it, the mammal population began to explode.
19:04Two more skull fossils dating to 300,000 years after the impact event are discovered in the coral bluffs.
19:11One has large incisors, whereas another has very flat back teeth.
19:17The shape of their teeth shows us that they each had different plant-based diets.
19:20And judging by the size of their skulls,
19:22the mammal with large incisors would have weighed around 80 pounds,
19:26whereas the one with the broad teeth would have been even bigger
19:28and could measure up to 170 pounds.
19:31This is incredible.
19:33Because their size relative to the size of the mammals living only a few hundred thousand years earlier,
19:38prior to the extinction event, were way smaller.
19:42We have seen this before, mammals growing significantly in size,
19:46but we've seen it over a 30 million year timeframe,
19:49not one of less than a million years.
19:51It's pretty rapid.
19:53So how did they get so big so fast?
19:56Again, we have to look at their diet and the food available to them.
20:00The existence of these mammals tells us that the ecosystem had rebounded quite well,
20:05as only a healthy, diverse environment would be able to support such large animals.
20:10Without protein-rich foods, they could never attain such a size.
20:16Still working in Colorado's coral bluffs, scientists unearth another concretion.
20:21This time, inside the rock is a rounded oblong fossil.
20:25This is the fossil of a bean pod, and it's dated to about 700,000 years following the asteroid's impact.
20:31Lagoons are incredibly nutritious.
20:34Even today, they are an essential food source for billions of people.
20:38And because they provide such a good amount of calories,
20:40eating them would also be highly advantageous for mammals living millions of years ago.
20:45Eating these plants led to the evolution of mammals the size of a modern-day wolf,
20:49weighing roughly a hundred pounds.
20:51These creatures were a hundred times larger than those that survived the mass extinction a few hundred thousand years earlier.
20:59The speed at which all this happened is remarkable and entirely unexpected.
21:03It shows us how life always finds a way, even in the hardest of circumstances.
21:12The collapse triggered by the Chicxulub impact was one of five mass extinctions that occurred in the last 450 million
21:20years.
21:21And the frightening reality is that this kind of natural apocalyptic event could happen at any time.
21:27And who knows if the planet will rebound next time.
21:44In 1431, after years of unprecedented drought,
21:49Angkor, Cambodia, the capital of the mighty Khmer civilization, was experiencing high levels of instability.
21:56This enormous city with its beautifully ornate temples and highly sophisticated urban infrastructure
22:01was attacked by its number one enemy, the people of the Ayutthaya kingdom,
22:05who arrived from their homelands to the west.
22:07The Ayutthaya burned Angkor, anarchy reigned, and the population fled en masse.
22:13Their invasion also disrupted critical supply and trade into the city,
22:18which contributed to its total abandonment.
22:22The collapse of Angkor, one of the greatest cities the world has ever seen, has long been a mystery.
22:27The site has been studied for over a hundred years,
22:30yet there has been little concrete historical evidence to truly explain why it collapsed.
22:35So there must be more to the story.
22:38Almost 600 years after the fall of Angkor,
22:41a team of researchers from the Tree Ring Lab at Columbia University
22:45are trying to create a holistic picture of the time period.
22:49Working in Vietnam's Badoop Nui Ba National Park,
22:52they begin drilling holes in old trees in order to extract a core sample.
22:57Trees are incredible bookkeepers.
22:59Their growth rings contain a detailed record of the environmental conditions
23:03they've experienced over their lifetime.
23:05Each ring corresponds to one year of growth.
23:09Generally speaking, if one year the rings are spaced further apart,
23:13it indicates that conditions were optimal for growth and the tree grew more.
23:17If they're spaced closer together, it means conditions weren't as good,
23:21and so the tree grew less.
23:23This remote section of the park is pristine,
23:26and the trees that were sampled are over 1,000 years old,
23:29some of them dating back to when Angkor was at its peak.
23:32And it's relatively close,
23:34so historically it would have experienced the same environmental conditions.
23:38A sample taken from a cypress tree revealed an environmental record starting in 1030 CE and ending in 2008.
23:45The extremely narrow spacing between specific tree rings showed that a severe drought hit the area between 1362 and 1392,
23:53and then again from 1415 to 1440, which is more or less the exact time when Angkor collapsed.
23:59So was there more to it than just an invasion by a regional rival?
24:05Founded in 802 CE, the Khmer Empire grew to cover much of present-day Cambodia, Laos, Thailand and Vietnam.
24:13It was enormously influential in the region and shaped much of its political and artistic character.
24:20At its peak, the Khmer capital of Angkor boasted what to this day remains one of the world's largest religious
24:27structures,
24:27sophisticated urban infrastructure, as well as a population of over a million people.
24:33The city spanned an area about the size of Los Angeles.
24:37And for comparison's sake, even an important European city like London only had a population of about half a million
24:44people in the late 1600s.
24:46So you can only imagine how high-functioning and well-built Angkor's infrastructure had to be to support such a
24:52population.
24:57The infrastructure was centered around a resource vital to human survival, water.
25:02Because water is as much an asset as it was a potential threat, water management was integral to Khmer culture
25:08and was treated as a religious duty.
25:12Even today, the water that feeds the agricultural plains is considered sacred and Cambodians blessed themselves with it for good
25:18luck.
25:19It was this very advanced water management system that allowed Angkor to grow to its incredible size.
25:24The city was crisscrossed with an endless network of canals, dikes, irrigation and overflow channels.
25:29An entire river was diverted into a reservoir.
25:32All this water fed one of the greatest inland fisheries in the world, the Tonle Sap Lake.
25:38And the land surrounding this lake is incredibly fertile, very well suited for rice crops.
25:43But when you're that reliant on immense quantities of water, what happens when it all dries up?
25:50The researchers conclude that the years of drought left the region highly vulnerable to flooding.
25:56So when the monsoons finally did return to their regular force, catastrophic flooding would have ensued.
26:04Flooding obviously causes a lot of problems for anyone experiencing it, but how could it have weakened the Khmer power
26:11to such an extent that they were left on the verge of collapse and just needed an invasion to push
26:16them over the edge?
26:19Archeologists wondering how flooding might impact the urban infrastructure dig into the soil underneath the ancient temples.
26:26The city of Angkor was built using a very interesting and advanced technique.
26:30All the city's buildings and temples were built on an artificial layer of sand and water.
26:37On top of this, a moat was built around the temples.
26:40This combination provided enough support for the huge temples while simultaneously allowing the moats to collect runoff water from monsoons.
26:50But during the drought, the consistency of this sand and water foundation changed. It got weaker.
26:56When the monsoons returned, the dry earth couldn't absorb the water fast enough.
27:01And although there were moats around the temples, they couldn't handle the runoff.
27:05This caused massive damage to the urban infrastructure while also making it hard, impossible, to cultivate crops.
27:12This might have contributed to a crisis for the Khmer rulers.
27:15When you have collapsing buildings and bridges, widespread hunger, and then you add an invasion into the mix,
27:21it's not a surprise that things didn't go so well for them.
27:23We know that Angkor returned to nature after its abandonment.
27:27But what happened to all those people?
27:29One million people can't just disappear.
27:33Just to the south of the Tonle Sap Lake, roughly 150 miles from the ruins of Angkor,
27:40archaeological excavations have been taking place at a site known as Longvek,
27:44with the remains of a city dating to the years after the collapse of the capital have been found.
27:50Longvek was the site of the Khmer capital after Angkor was abandoned.
27:53But from what has been found so far, there weren't many people,
27:57and there wasn't much going on here in the years it was occupied.
28:01But the farmers working the rice fields of Longvek keep unearthing an abundance of ceramics,
28:06which seems to contradict what the archaeologists thought they knew.
28:10Considering the volume of ceramics that have been found in these fields,
28:13it's clear that a lot of people lived here.
28:15You would need a substantial population to generate this kind of volume.
28:19So have we been wrong in our assumptions about the city?
28:22It seems like maybe we were. Some of these ceramics are truly magnificent.
28:26There's a piece of pottery with a brown glaze, incised with a coin motif and good luck symbols.
28:32It used to be the lid of a ceramic jar, and it's incredibly rare.
28:37Very few lids like this have ever been found outside of China.
28:41In fact, only in Japanese archaeological sites dating to the 16th and 17th centuries,
28:47has anything remotely similar been found.
28:50So what this indicates is Longvek's participation in extensive trade networks
28:55that link China, Japan, and Southeast Asia in the 16th and 17th centuries.
29:00Having these kinds of things when you've just been chased out of your empire's capital,
29:05that's pretty impressive.
29:08As excavations continue, archaeologists again and again discover rare, exquisite pottery.
29:14There are these green, yellow, and purple glazed dishes featuring waterfowl on a lotus pond.
29:21This kind of pottery goes by the very original name of tricolored dishes.
29:26The artwork on here is truly delicate and would have required considerable skill to produce.
29:31They also date to the same period as the jar lid,
29:34and coming from southeastern China would have been very, very expensive to acquire.
29:39These ceramics were by no means meant for everyday use.
29:42They're far too beautiful for that.
29:43They likely would have been in the possession of high-ranking bureaucrats
29:46or those occupying positions in the Khmer court.
29:49Beginning to question their assumptions,
29:51archaeologists decide to employ the use of LIDAR to survey the area,
29:56in the hope they may learn something new.
29:58Putting it simply, what LIDAR does is essentially use a laser
30:02to measure the distance between the machine emitting the laser and the ground.
30:07This then creates a very detailed 3D digital map,
30:11which has become an incredible tool for archaeologists.
30:14And what these LIDAR scans reveal is incredible.
30:17A series of earthen embankments forming an almost three-square-mile rectangular citadel.
30:23Not only was it well-built, but judging by the wealth of ceramics,
30:26it was thriving economically.
30:28But if the Khmer had seemingly lost everything with the abandonment of Angkor,
30:32how could this have been the case?
30:36Tonle Sap Lake is connected to a river of the same name,
30:38and it drains into the Mekong River, which is one of the longest on the Asian continent.
30:42To this day, the Mekong remains essential to the economies and cultures of the countries it flows through.
30:49And it would have been the same around 600 years ago.
30:51It connects Cambodia with central China, roughly 2,500 miles to the north.
30:56So you can imagine how many people would have relied on it for commerce,
31:00and how many people it would have connected trading in all kinds of different commodities.
31:05By maintaining their capital close to an essential river and its tributaries,
31:10the Khmer managed to thrive despite the incredible pressures that would have been exerted on them by invading forces.
31:17But despite the Khmer Kingdom's resilience in the face of powerful outside forces,
31:22its new capital at Longvek was eventually sacked and looted by their long-time enemy,
31:28the people of the Ayutthaya Kingdom.
31:31With the collapse of Longvek, Khmer's sovereignty suffered a serious blow.
31:36The royals were taken into captivity,
31:38and what was once a mighty kingdom was never to rise again to its past heights.
31:56A quarter of a million years ago, Western Turkey's 2,500-foot Çakalar volcano began to erupt.
32:03It sent lava flows cascading down its slopes, while ash rained down thousands of feet from its vent.
32:10The area where this volcano field sits today is known as the Kula region,
32:14and it's fair to say that this landscape would have been severely impacted back then.
32:19Thick layers of ash coated the land, creating a ghostly landscape
32:24that would have terrified both humans and animals, forcing them out of the area.
32:29In terms of a human timescale, this is a long time ago.
32:32Back then, Homo sapiens, our ancestors, are only found in Africa.
32:36But Neanderthals, our cousins, have spread north into Europe and Asia.
32:42In 1968, just a few hundred feet from the volcano,
32:46workers building an embankment dam were digging through the ancient layers of scoria,
32:51dark, pocketed volcanic rock that had been deposited 250,000 years earlier,
32:57when suddenly they observed abnormal features in the terrain.
33:00The scoria was lying above a layer of volcanic ash,
33:05which is what protected these strange imprints over the course of thousands of years.
33:10And it's important to note that there are little bulges around the rim of the holes,
33:14rising up above the surface about a centimeter.
33:17This indicates that at the time they were made, the ash was wet and coherent,
33:24meaning that these little pockets were made at the same time the volcano was erupting.
33:32The ash layer itself measures two inches, while the little oblong pockets are about an inch in depth.
33:37Some of these features are wider and longer than others,
33:40while there are also small little round holes in the hardened ash.
33:43But what are these things?
33:46Now they could be the result of ejecta,
33:48basically just shrapnel that comes flying out of the volcano during the eruption,
33:52but the shapes of the pockets are far too similar for that to be the case.
33:57Each hole has one or several corresponding similar sized holes placed at an angle diagonal to it.
34:04All of them follow this pattern.
34:06Except for the very small holes, there are four of them.
34:09But each of them is at a diagonal to the other.
34:11It may not seem so at first, but these shapes are actually very familiar.
34:16We see them all the time at the beach.
34:18They're footprints.
34:20They're from adults and from human children,
34:22but also what appear to be some kind of canid footprints, like a wolf or something like that.
34:28And that's super weird because humans only domesticated dogs 40,000 years ago,
34:33and this is six times older than that.
34:36It seems like these are footprints of people, or a family of Neanderthals maybe,
34:40possibly running away from the eruption.
34:43Since their discovery, the age of the footprints has remained a curiosity for scientists
34:48because of the difficulty in getting an exact date for when they were created.
34:52This is because the volcanic rock in which they were found is relatively young basalt.
34:58And younger basalt is very hard for geologists to date.
35:03So the assumption has been that the prints are hundreds of thousands of years old,
35:07but it hasn't been certain.
35:09But in 2019, armed with new state-of-the-art techniques,
35:14scientists decided to reassess the footprints,
35:16hoping to obtain a more accurate date for when they were created.
35:20It's a pretty complicated process, but two things are measured.
35:24First of all, the decay of the elements uranium and thorium creates another element, helium.
35:31This helium is present in little crystals embedded in the ancient ash.
35:35Second, the radioactive levels of the element chlorine
35:39can show us just how long volcanic rocks have been situated on or near the Earth's surface.
35:45So this brand-new dating technique tells us something entirely unexpected.
35:49The volcanic eruption and the prints are only 4,700 years old.
35:55So now the dog footprints make a lot more sense.
35:58But it means we were off by almost a quarter of a million years.
36:02And a lot has happened in that time.
36:04Not only did Neanderthals go extinct some 40,000 years ago,
36:08but Homo sapiens began spreading across the face of the Earth.
36:12Considering the timescale we're looking at here,
36:144,500 years ago is quite recent.
36:17It puts us into the Bronze Age.
36:18So this means that these footprints aren't Neanderthal, but human.
36:25Modern human footprints.
36:27Seeing as we were wrong about the age of these prints
36:30and the species of human that made them
36:33makes you wonder what else we could have been wrong about.
36:38Spurred on by these unexpected finds,
36:40scientists scan the footprints using the structure from motion method.
36:44The structure from motion method is a technique that involves photographing the object,
36:49in this case an ancient footprint,
36:51from a few different angles to create a three-dimensional image of that same object.
36:57The results are surprising.
36:58The images reveal which direction the big toe is pointing.
37:02And that, of course, tells you which way the feet are going.
37:05And it turns out they're going in the opposite direction of what we thought.
37:08We'd assumed they were going away from the volcano,
37:10but this means they were going from west to east towards the Chakalar volcano.
37:16And they were walking either while the ash was falling or immediately after.
37:21So it could be that they were observing the eruption as they approached the volcano.
37:29The footprints are also only about two and a half feet apart,
37:32which indicates that they were walking at a relatively relaxed pace.
37:35If they were running, the footprints would be spaced even further apart.
37:39So they definitely weren't panicking,
37:41but were rather calmly walking together towards this volcano as it was blowing up.
37:47As the scientists are working at the site,
37:50local reports emerge of a discovery of some rock art a little over a mile from where the footprints are
37:56located.
37:57The rock art has long been known by locals, who call the boulder it's painted on bloody rock.
38:02But it's only recently become known to scientists.
38:05The boulder is huge, far bigger than the size of a man.
38:10And it leans out at a 45 degree angle from the ground.
38:14So it was probably a good place for shelter from the elements, whether it was rain or the sun.
38:22You can see with your naked eye, three handprints above a circle that looks like it's bleeding.
38:27The circle has a bunch of little dots in it.
38:30There are also what looks like four smudges around the circle, followed by a longer, broader one at the base
38:36of the painting that definitely seems to have faded over time.
38:39Other than the handprints, what could this represent?
38:42What was their intention?
38:44In order to enhance the faded sections of the painting and obtain a better understanding for what it might represent,
38:50scientists apply a technique known as saturation stretching.
38:54This is basically a process that uses algorithms to make the faded areas more intense in colors.
38:59And that allows them to digitally reconstruct what this painting would have looked like when it was initially created.
39:05A much more complete picture emerges from the rock.
39:09When it was originally painted, the faded line at the bottom of the picture was actually thick and bold, and
39:15the remaining lines and handprints were far more defined.
39:19The circle now looks like it's at the top of a triangular shape.
39:22But what's more interesting is what we thought was maybe blood running down from underneath it.
39:28Considering the location, right in the shadow of the Chakalar volcano, I wonder if this blood could actually be lava,
39:36and if this is a depiction of when it erupted some 4,700 years ago.
39:42It's definitely possible.
39:43The boulder is so close to the footprints.
39:46And for anyone, let alone a person living in the Bronze Age, observing such a natural phenomenon up close would
39:54inevitably leave quite the impression.
39:56So what we're looking at here is maybe their reaction to the event.
40:02This is pretty special.
40:04Not only does it highlight the deeply human characteristic of recording our experiences in art, but it's also unique in
40:13an archeological context.
40:15There are some other examples of rock art depicting what appears to be a volcanic eruption.
40:19But there aren't any this close to the volcano, and to the footprints the artists may have made on their
40:25way to creating the painting.
40:27The rock art by the Chakalar volcano makes it possible to follow in the footsteps of the people of the
40:33Bronze Age in Turkey.
40:34To walk where they walked.
40:36To imagine what they saw.
40:37And realize that the desire to memorialize such a magnificent event is what connects us across time.
40:49All right.
40:50Have a great day.
40:50Bye.
40:51Bye.
40:52Bye.
40:53Bye.
40:54Bye.
40:54Bye.
40:55Bye.
40:55Bye.
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