go out there, find a tiger and get me a story. [ monkeys chattering ] i found myself driving into ranthambhore one morning with salim, who i'd just met -- neither of us tiger experts. salim used to bring tourists into this area but salim didn't have much of a clue, really and i certainly didn't have a clue about tigers. salim: now it's working. johnson: ranthambhore had to teach us about tigers. how fresh do you reckon these pug marks are? salim: they're from the morning.

yeah, coming... [ excited whispering ] [ starts vehicle ] once you see your first wild tiger it's an experience that stays with you. you shouldn't have an apex in evolution but if there was one it's got to be the tiger.

we had to explore the area get to see where the tigers were moving and then choose a tiger. so we started following this tigress that we called "machli." and because we spent every day on her trail she became very tame. let's go, come on, come on let's keep moving. keep it close. i remember coming up to christmas and machli started acting strangely. and we thought, salim and i, she must be looking for a man. on a christmas morning the sun was just coming up beautifully over the hill. machli came walking up with her suitor.

he was a great big male called "bomburam." they spent the next few days together, mating continuously. sure enough, out came these two little bundles. the bundles that we were going to call "broken tail" and "slant ear." broken tail was just special. he was adventurous, exuberant, kind of full of life charismatic, arrogant, fearless --

totally fearless -- he would chase our car some days. we thought he was going to come into the car sometimes. never seen that in a tiger before. for a male tiger, they are normally more reserved. salim and i had the unique -- literally unique experience. i don't think anyone had ever done what we had done before. we spent 600 days in ranthambhore, from dawn till dusk, every day following the one tiger family. i remember my father used to call me "the bee," and that's because i was always as busy as a bee pretty much getting up to no good, things i shouldn't be doing. and in that way, i guess broken tail mirrored me as a child.

broken tail was always the ringleader -- mischievous, playful so confident. i followed them steadily till he was about two-and-a-half. i think i knew broken tail as well as i knew my own daughters.

he was going to become a really important tiger in ranthambhore. you felt like one day he was going to dominate that area, he was going to be "the man." sadly, it wasn't to be the case. something happened after that -- we don't know what. we weren't finding broken tail's pug marks at all. broken tail was gone.

where, broken tail? where is he? i'd love to see him again. i hope we do.

[ train blowing horn ] i couldn't believe it. to see this amazing animal i'd spent so much time with, that this is how it ended up. in the middle of the night

in this god-forsaken barren place where no tiger has a right to be. i went to bed that night... talking to salim the next day, and he said couldn't sleep he just kept thinking about how tragic that this happened. probably only a couple of miles from -- what was he doing there? that's the thing i couldn't understand. how on earth did he get from ranthambhore -- this wonderful sort of tiger paradise, as it were to this place called "darra," that i'd never heard of? how did he -- everyone used to say to me absolutely impossible. and broken tail had done it.

so, immediately, there was a mystery. although his death was sad it opened up lots of questions that i felt i had to answer. we felt we owed it to broken tail in some way to retrace his journey. that's the only thing we could do for him, was to somehow benefit his kind by undertaking this journey. we hoped to fill in what happened on those last days. we didn't know how long that journey had taken him. had anyone witnessed any part of that journey? where did they see him? we felt by doing it we were going to learn something important that could ultimately help in tiger conservation.

the story of broken tail is really the story of the modern indian tiger. all tigers in india are born into these island reserves but they're isolated all over the country. they were once part of this great population that stretched right across india and throughout the subcontinent. human pressure around ranthambhore is massive -- a quarter of a million people living right on its borders, almost like an invading army waiting to come in. every little inch of that land is in use. watch where you put your feet. as soon as you come out, that's what you see.

[ bleating ] all you can hear is goats -- and all those goats, they're eating ranthambhore national park. [ explosions ] we've only been on the road about ten minutes, i'd say and already we've hit this devastated landscape. [ goats bleating explosions in background ] they're blasting these mountains quite openly. not a forest guard in sight. no effort, obviously to control this at all. this is the problem when you have island reserves. as soon as you draw a line on a map people start fraying away at the edges. you have to assert your influence

otherwise year and year, people are just going to move further and further into the park. how on earth did broken tail manage to handle this sort of stuff? he didn't know he wasn't in ranthambhore anymore. he never made a decision to leave. he just wandered. the night, he just crossed. no problem. no problem at all to cross. as we set off on our journey we were thinking why did he leave? was he kicked out of the reserve? was he getting interference from people? poaching?

moghiyas shoot quite a few tigers in this way. we're just paying a surprise visit to a guy called lackan. he belongs to a group, a tribal caste of moghiyas traditional hunters and poachers and we reckon he has killed tigers in the recent past. salim: lackan? oh, lackan?

[ speaking moghiya language ] i suppose the straight question, has he been directly or indirectly involved in killing tigers? [ speaking moghiya language ] salim: he used to be a hunter. he has done a lot of hunting he killed a lot of animals for hunger. but hunger is still there. i stopped that work but hunger is still there. and, did you make a lot of money from killing tigers? he says if i had made good money, i'd have nice buildings here. only i fill my stomach with that money. otherwise, i don't make much money. how much money would he get personally for one animal? sometimes 6,000, sometimes 5,000 rupees.

5,000 rupees? how much, then? $100? yeah, not more than that. you see, these guys, they're not the guys making the big money, obviously. somehow puts things in perspective a little bit, when you meet the guy. you have this preconceived idea, you know they're going to be real nasty kind of people, but of course he's just a bloke who doesn't have any money. you do look at the kids and once you're a father yourself you kind of think, "i'd do anything for my kids." i wouldn't let them go hungry no matter what. something about having kids yourself it just makes you look at other people's in a different light somehow. lovely little kids. even moghiya kids play "ring-a-ring-a-rosie."

it's not just lackan here and this little group -- every village in this entire belt has got moghiyas living there. so every village in this entire area has people who have the knowledge, the capability, and sometimes the opportunity to kill tigers. so broken tail was really threading a fine line walking through here. people have referred to this area in the past as being a killing zone for tigers. tigers don't get through here. if ever they leave the park, this is where they get hammered. so broken tail was an exception to the rule.

i think people sometimes make the mistake of saying, "it's tigers or people." and sometimes you think, well, are there so many human problems in india, that why should they bother about tigers? but the tiger is a human problem. the bottom line is that,

without tigers the forests of india will disappear. the only well-protected forests are those that have tigers. as soon as tigers disappear, the political eye is removed from that forest and it quickly starts to degrade. if you lose those watersheds everyone living along this mountain range is going to have a serious problem. it's not just about saving fluffy animals -- every person who lives along these mountain ranges actually depends on tigers, too. they just don't all realize it yet. salim: he go to graze his goats, he's a shepherd, and he saw tiger. big, big head. quite big? quite big head? and where exactly did you see him? [ salim interpreting ] salim: on the hill. in the daytime he saw. in the daytime?

if ever a tiger is going to walk in the middle of the day in the middle of, you know people around and goat herders that'd be broken tail, huh? salim: this could be broken tail because the time he's saying the time broken tail left ranthambhore. this is exciting, yeah? because we weren't even totally sure if he'd come this way. we were guessing he was coming as far as here. we guessed right. now we have evidence. i've actually got some photographs of broken tail that we took in ranthambhore. this is when he was a little cub. more and more i've come to realize that the people you really have to convert if you want to save tigers are the people who are living with them. people who live in rajasthan never seen the tiger they don't have any books to look at them, they don't have tvs to see them on tv. they're actually just not a part of their lives in any way. we got to know him extremely well as the months went by.

you'd think you could go up and stroke him but you'd be dead if you did. he'd get up to all sorts of mischief. he'd be the one to break cover you know when the tigress goes hunting. it's very important that the cubs stay absolutely quiet. as she would leave she'd make a little noise that would mean, "stay there, shut up be quiet until i come back." give it half an hour, an hour, broken tail would start moving around, and he kind of dragged slant ear into problems.

of course, they had no chance of actually catching anything. the exuberance of youth. great times... great times. [ coughs ] good morning.

i sometimes wonder why he never turned back. you'd think he'd somehow have that sort of homing instinct but there must have been something -- something was driving him forward, maybe something he didn't understand. something compelled him every day to keep moving. that was the smell of a tigress. he was at an age where essentially, all he was thinking about was girls. meeting girls and making babies. the scent of tigers behind him is sort of gone, and so he just sort of kept moving, kept moving

kind of getting into deeper and deeper water, but maybe still hoping that he'd come to a place where he could settle down. broken tail never got that moment... because there was no one else out there. there were no other members of his kind anywhere on that route. do anything like nilgai or wild boar come in the mustard crops? salim: they do. they do? they can eat them too?

yep. so that's where the moghiyas are going to be? they guard this field. good girl, good girl. how far do you reckon we've come today? 20 ks or so? about 20 k, yeah. didn't you do well? i'm not going to get on you again today, okay? that's some spot. salim: wow! look at this. that was worth the walk, huh? this is the place! this is the place. look at that...

perfect for tonight. salim: you like to have some tea first? i'd love it! no point two people making tea i always say. salim: look at tiger here. it is a tiger. people with bows and arrows, they're chasing away the tiger. look at that -- he's got a cutlass machete, or something, that one.

how old do you reckon these paintings are, salim? these definitely thousands years old. this place must have been full of tigers when these were drawn. tigers are absolutely on the edge. they have reached critically low numbers. and for the most popular animal in the world if we lose them, what a sad indictment that is for the human race. and we have knowledge now, knowledge, easy ways of accessing knowledge around the world. we know this. and to allow it to happen on our watch with that knowledge, how could you possibly explain that to people in the future? how could you sit down a classroom full of kids in 50 years' time and explain to them, "oh, yes, we knew that tigers were on the edge. oh, but we let them go." how could you possibly rationally explain that to anyone in 50 years' time? you just couldn't.

broken tail and slant ear were growing up. we were constantly worried that a male was going to turn up and do damage to the cubs. their father was hardly to be seen and new males were moving in as a result. now, that's a dangerous thing, because if a new male moves into an area he can kill the cubs the female will come back into cycle, and he will father his own cubs. so there was always this tension. and then there was a day when we met machli. she was acting strange again -- she was acting nervous.

and we had seen male prints in the area and we realized the male prints hadn't left the area. so he was still there. this day, obviously, she decided he meant business and they fought. it didn't last very long 'cause they can't last very long because it's very dangerous for both animals. the cubs were safe... she was a great mother great mother.

broken tail must have had a real search for water, particularly summertime. it's a mystery how he even managed to find the water. wouldn't mind jumping in there, myself. [ man speaking native language ] i'm picking up some of it, but i can't get it all. he's saying there about three or four kilometers from that village manak chowk, there's small bridge over the small nala, and there is a water hole. he was coming back from the bundi and he saw a tiger crossing a road, and he gets shocked, you know. it was very close to his motor bike, and -- [ speaking native language ]

this big tiger is walking in the royal style. johnson: like he owns the place. broken tail puts the royal in royal bengal tiger. do you think he stopped at the water hole? [ conversing, interpreting ] he don't see that. he turned around and got out of there! run away! [ continues in native language ] and for ten kilometer he's feeling like he's having a loose motion. [ all laughing ] i'm not surprised! [ exchanging goodbyes ] that's the thing about india people do have a great respect for living things. can you imagine in europe allowing a great predator to wander freely around the country? it wouldn't happen!

it's been great to see what it's like, the india outside the reserves outside the protected areas.

whoops-a-daisy. you going that way? okay, good idea. good idea. this is an old maharajah's place. it must've been a hunting lodge or something. looks like. see the holes everywhere. it's for the gunshots. if broken tail had gotten here and there was a female here, he'd still be alive today -- he'd never have left. why would you want to leave? he could've been the... he could be living happily here now.

empty place. [ birds calling ] just listen to the sounds. this is the quietest place i've ever been to in india. and when you have an area that's remarkably quiet, it means there are few people living there -- and when you have few people living in a place it means you have an opportunity to protect that area for wildlife. and we have to find all the bits of india that still exist that are like this grab them now, grab them quickly, and put the focus on these places. having a little island like ranthambhore, it has no long-term future. you have to connect it to another area -- and broken tail is showing us the way. reporter: tiger hunting in india takes on added pomp and ceremony... this place was owned by the maharajah of bundi and he entertained all sorts of people from you know, errol flynn to lord mountbatten, the queen of england and prince philip. all the hollywood set used to come here. that's what people used to do for fun in those days.

these guys shot so many of them. i mean, they wiped out tens of thousands of tigers all over india. good work! one shot did it! he was a big fella, but all fight was gone out of him now. they would shoot as many tigers as they could lay their hands on. they would blast as many as they could and they'd boast about it. in some areas they drove tigers into local extinction.

[ calling ] i remember the last time that the family were together. [ calling ] machli had left the cubs and she had gone hunting. [ calls ]

a couple of hours later she came back and she started roaring. she was calling the cubs. then we heard a rustle in the bushes behind us, and she lay down on the road. and broken tail and slant ear both came out of the bush and then started suckling from her. of course she hadn't had milk for well over a year. this was some sort of amazing bonding behavior that no one had ever seen before. extraordinary to see these two male tigers bigger than her, suckling from her.

that was the last time we saw the family unit together. was there an incident, a natural incident with a male tiger? was there an incident with a poacher? maybe slant ear was shot and that's why the family split up. we'll just never know.

how the heck did he get across here? how long does this gorge run for, do you know? salim: this gorge is four kilometers. i'd say he got here, went down some sort of river bed, tracked along it and came to some shallow area. there must be some shallow areas. we should go and see that. poor old horses, though. they haven't enjoyed this rocky ground. wouldn't want to push them too much more. either we can walk and... you can walk? i've only ever seen you walk to your car!

and does he remember the tiger being killed by the train here? [ salim interpreting ] said there is old lady in the village, darra village. they might have seen tigers when they come to collect wood. is she still around or can we find out -- [ salim interpreting ] [ woman speaking native language ] i think i can understand. she was out wood-cutting picking sticks off the ground and when she cracked one -- she crack one of the sticks and tiger hear that, because tiger was not expecting this

lady, so suddenly he heard sound and he's shocked to see them so he run away and she run away. [ all chuckling, woman continues ] they say "we really felt very bad when we get to know about the tiger being killed because he never make any harm and is such a beautiful animal." she says, "we trust the tiger like we can trust a human in the house." can these ladies put a date on when they last saw him? [ speaking native language ] salim: she knows when the tiger killed by the train here. in the daytime she saw him and the next morning they found him dead. so you were the last person to see broken tail alive, probably. this is the same chain of hills

that stretches all the way to ranthambhore. 200 miles long. and this is where broken tail ended up. every so often you can hear a train. it's quite a busy train track. he was born to the sounds of train. even in the middle of ranthambhore, you can hear train horns in the distance. kind of poignant. he knew that sound so well but he didn't know to avoid them. he hadn't learned that lesson. traveled so far, he must've learned so much, and even for me, it was quite a journey. but he sort of did it all by himself. he had no mate. that's kind of sad. but to have made it this far he was some tiger. really was some tiger.

what number did that guy say? he said this was between 870 and 871. this could have been the very spot where he came down. this was the place, colin. he jump out from here and fall down here. why didn't he just jump up there? he tried to save himself. maybe he don't have enough time or... i've seen tigers jump walls that high many times. they do that. just think, after all he went through,

after his journey, after all the hardships he must have faced generally in life... pity that it all ended here. i shall do some puja at memory of... it's satisfying to solve the mystery. it's more than that. we feel like his life has... we've kind of put a full stop on it. didn't want to just leave it hanging.

i'd hate to have heard of this you know, emaciated tiger being found 200 miles away that kind of wandered into a village because he, you know hadn't found water. and that would've been an awful thing to kind of hear about. but that's not what i heard about. i heard about a tiger that had been killed by a train. and when he died, he was the weight he should've been his coat was in perfect condition he was a perfect, confident, arrogant male tiger. and that gives me a lot of comfort, i suppose. and, although broken tail didn't make it

his mother lives on in ranthambhore to this day. machli, after all these years, is still having cubs. and for me she symbolizes the resilience of her kind. if we could just give tigers limited amounts of protection, they'll take full advantage of that, and they will thrive. i think broken tail's death, in the end will be one of the most important things he ever did the way he died and where he died. broken tail has shown us the way. this is what tigers do. this is what they need. this is where they move to. they need zones, whole areas that they can wander through.

we need prey in those zones. and i think broken tail might end up being an extremely important tiger that we look back on in years to come and say, "that's the one who started all this. "that's the one who changed our mind about how we should protect tigers." isolated by embargo. frozen in time. rich with wildlife.

cuba. conservation here isn't easy. man #1: a cuban biologist doesn't make more than $25 a month. man #2: this expedition requires signatures from the army. and as pressure to develop builds, cuba could sacrifice this accidental eden. don't miss a single moment. now you can watch "nature" online. go to pbs.org to screen complete episodes from this season and seasons past. visit "nature" online for production updates from the field. well, here we are on the alaska coast. go behind the scenes with our filmmakers. we also used a borescope lens and that allowed us to put the lens right into a flower. and get connected with "nature"'s online community. all at pbs.org. "nature" is made possible in part by...

leave it untouched by your presence capture its image and preserve it forever. canon -- living and working together to appreciate today and care for tomorrow. additional funding provided by... the corporation for public broadcasting. and by contributions to your pbs station from viewers like you. this "nature" program is available on dvd and blu-ray. to order, call...

to learn more about what you've seen on this "nature" program, visit pbs.org. woman: i think you see the role of women changing most obviously in the girls, because they're the young generation that's going to seize on the new opportunities

that are provided for women. the fashions for women started to loosen a little. we didn't have to wear corsets which was a luxury you know. and anyone else who was wearing them we just couldn't talk about it, 'cause it's... ha ha ha! the change in fashion has freed women. they can move. they can breathe. dockery: the waists have dropped. the ankles are showing a little and there's more of a freedom in the structure of the costumes. women were being much more practical. it says a lot about women's liberation and that kind of starting to take place socially. and there's designers that have admitted to being influenced by the fashions in the show. it's wonderful.

narrator: a volcano awakens in iceland. a mountain erupts, belching millions of tons of ash into the sky. airlines soon feel the effect. a hundred thousand flights are cancelled... around 10 million passengers stranded. chaos, aircraft grounded airlines going out of business. it had an enormous impact for aviation brought europe to a standstill. narrator: the impact quickly spreads. freight movement around the globe is crippled costing the world's already fragile economy billions of dollars. and now scientists are discovering volcanoes in iceland that can dwarf this eruption of ash in 2010...

volcanoes that produce killer clouds of sulfuric acid. and most alarming of all a giant ice-covered volcano that's overdue to erupt and that could threaten the entire planet. anja schmidt: nowadays we are very vulnerable to volcanic eruptions. it's not a matter of if, it's when. volcanoes can be considered a ticking time bomb. i would predict that we would see death tolls running into the hundreds of thousands. narrator: how threatening could the next eruption from iceland be? "doomsday volcanoes"-- right now on nova. major funding for nova is provided by the following:

supporting nova and promoting public understanding of science. and by the corporation for public broadcasting. and by contributions to your pbs station from: additional funding is provided by millicent bell through: narrator: reykjavík, the world's most northern capital city... home to most of iceland's 320,000 inhabitants. over a thousand years ago, the vikings settled this frozen land. today, tourists flock here to marvel at iceland's explosive geysers... and boiling pools.

but this abundant thermal energy has a darker side-- its volcanic threat. in 2010, the volcano eyjafjallajokull nicknamed eyja explodes into life. the eruption lasts for over two months. icelanders head for shelter as the ash rains down. but eyja's effects are soon felt globally when the ash cloud spreads into the busy routes of trans-atlantic aircraft. airports around the globe are gridlocked as thousands of flights are cancelled. but scientists are concerned much worse could come from iceland. i think we dodged a bullet with the 2010 eruption.

in the future there are going to be eruptions in iceland much bigger than the 2010 event. narrator: these scientists are uncovering the devastating effects of past volcanic eruptions and trying to predict how widespread the deadly consequences of the next eruption could be. thor thordarson is a volcanologist. he knows iceland's volcanic threat well, having spent almost 30 years mapping its complex geology. the amazing thing about iceland is that it has 30 active volcanic systems. narrator: iceland is about the size of kentucky. with so many live volcanoes in such a small area it's one of the most volcanically active places

on earth. but while eyja sleeps again, three nearby volcanoes are cause for concern. narrator: eyja's volcanic neighbors-- hekla, katla and laki-- are clustered in a zone of intense volcanism in the south of the island. each has a distinct personality. laki-- a fissure volcano that tears across the landscape for 17 miles. she last erupted in 1783 wiping out a fifth of iceland's population. hekla-- a menacing peak almost 5,000 feet high. historically she has erupted violently, without warning

belching vast amounts of ash. and katla-- a giant volcano 18 miles across hidden under 2,000 feet of ice. katla is decades overdue for an eruption. she's currently rumbling so volcanologists are most worried about her. so, why does iceland have so many threatening volcanoes packed into such a small area? it's a result of its unique location. iceland lies in the north atlantic, between north america, greenland and europe. here, two of the earth's crustal plates are being pulled apart and iceland straddles their boundaries. below is a hot spot-- a huge upwelling of hot rock from deep within the earth.

as the rock rises, it produces magma. the magma forces through cracks in the crust until it erupts at the surface forming active volcanoes. thordarson: one of the reasons why it is difficult to predict volcanic eruptions is that we're trying to predict the behavior of something that we can't see. we can't see the magma that actually is the source of these events. narrator: above ground, eyja, laki hekla and katla appear to be separate volcanoes. but some scientists are starting to wonder if they might be linked underground, and that eyja's recent eruption could have disturbed one of its neighbors. now there's an astonishing place that helps reveal how volcanoes are linked.

it's exciting to be here. it's quite unique to be able to go down into the crater. narrator: these geologists are about to take an incredible journey into the heart of a volcano. 70 miles west of eyja is thrihnukagigur crater. it's a unique location that gives a tantalizing insight into how iceland's volcanoes work. sigmundsson: as we go down here this is quite narrow here; we just make it. sigrun hreinsdóttir: this is really, really neat. narrator: after squeezing through the neck they're confronted with an amazing sight. hreinsdóttir: whoa, look at that! sigmundsson: yeah, it's beautiful. narrator: a vast chamber dropping 450 feet below the surface.

4,000 years ago, when the magma drained the chamber remained remarkably intact. it's the only place on earth where scientists can study a volcano from the inside. hreinsdóttir: really impressive. narrator: freysteinn sigmundsson is looking for evidence of how volcanoes like this are fed by molten rock. it's been something of a mystery until now. sigmundsson: look at this. can you see the fracture? hreinsdóttir: wow. it's actually really cool how it goes up. sigmundsson: this is an absolutely unique place. it is fantastic. we can see the fissures that fed magma into this volcano. this black line in the wall here it's a crack that delivered magma to the eruption. now the magma is solidified in this fissure. narrator: this fissure acted like a giant vein pumping magma into the chamber horizontally

as well as from deep below. sigmundsson: what is so special is we can clearly see it both sides. narrator: the fissure sliced right through the chamber and out the other side. and freysteinn is working out which direction it took. if you trace it you can get the orientation of this crack. narrator: by lining up the fissure on either side of the chamber the team finds the exact route it took and make an important discovery. sigmundsson: what we have found out is that they can go on for many miles, they're like thin sheets. they can link different volcanoes. narrator: so although volcanoes appear isolated on the surface, fissures carrying magma can link them underground. and that's an important consideration

in trying to predict which of iceland's volcanoes might erupt next. historically, katla has erupted shortly after eyja on more than one occasion, suggesting hidden underground fissures could link them. if so, could eyja's recent 2010 eruption be the trigger that sets off the giant ice-covered katla again? or one of her other volcanic neighbors? and what would be the consequences? volcanoes are some of nature's biggest killers. they threaten us with torrents of molten lava... clouds of choking ash... mists of toxic gas.

and in the past, iceland's inhabitants have suffered more than most. (bell tolling) in 1783, an eruption kills over 10,000 locals. it's one of the deadliest ever recorded. a killer that atmospheric scientist anja schmidt knows all about. 50 miles northeast of eyja lies the volcano anja's interested in-- the fissure called laki. we are standing on the laki lava flows. so as far as the eye can see we can see the moss-covered lava flows from the 1783 laki eruption. just to give you a feeling for this scale the area that these lava flows cover is actually ten times the size of

manhattan. narrator: why laki produced so much lava is due to her volcanic character. laki has a very special personality. it's very different in terms of eruption style how it erupts, from other volcanoes. it's a so-called fissure eruption which means it erupts along a linear vent system. narrator: a linear vent system works like this. instead of erupting from a single crater lava gushes along a line where the fissure breaches the surface. in the united states fissure eruptions are common on the big island of hawaii, like this one in kilauea. in 1783, laki also erupted from a fissure but on a vast scale. the earth opened up along a 17-mile fissure...

spraying molten rock skywards. schmidt: just imagine the earth's crust zips open along a line. if we were standing here in 1783 witnessing the laki eruption it must have been a pretty frightening sight. the sky would have been black and dark because the first volcanic ash fall had come down. and looking towards the actual eruption site people could see fire fountains glowing red into the sky rising up to one mile high into the sky. and then you would have these lava flows slowly advancing so you see incandescent red glowing lava flows in this darkened landscape. narrator: it sounds like a vision from dante's inferno. but surprisingly it wasn't lava that was the killer.

it was something far more lethal. something that if repeated in the 21st century could affect millions around the globe. in the heart of the english countryside lies the disturbing evidence for this possible disaster. here in church records, forensic geoscientist john grattan is uncovering clues that reveal just how far laki's deadly eruption reached. grattan: this is a parish record, and it contains the dates and names of people who have been buried here, which is what i'm particularly interested in. using books like this, we can reconstruct patterns of mortality. narrator: deaths normally occur in winter when the old and ill succumb to cold weather. but john's uncovered a period of time in 1783

where the records don't appear to make any sense. we can see an intriguing change to that pattern where people are dying in significant numbers in the summertime when the weather is good when there is plenty of food. so we are interested as to why that might be. narrator: other accounts describe how the villagers are dying. they read like a horror story. "in the foul, hot weather in the beginning of summer "ulcerated mouths and eruptions on the lips "and also pains in the face became epidemical. "burning fevers were accompanied by pleurisy "and inflammation of the lungs. "the burning fever and dysentery "immediately came on us in the center of england "and became epidemical in london and there were some remarkable instances of sudden deaths." narrator: the killer's not only devastating the population it's ravaging across the land. "the barley became brown and weathered at the extremities "as did the leaves of the oats.

"all the different species of grain appeared to have had "all their leaves withered exactly as if a fire had been lighted near them." and the occurrence of a tremendous thunderstorm seems to bring together everybody thinking "this is it, this is the end of the world." narrator: but it isn't just england suffering. vast areas of europe experience the same calamity, as recorded by a founding father living in paris at the time. grattan: this is what benjamin franklin noted: "there existed a constant fog over all of europe. "this fog was of a permanent nature-- "it was dry and the rays of the sun seem to have little effect "towards dissipating it as they easily do on moist fog arising from water." and what this tells us is that this fog is not water vapor, it's something completely different. narrator: the killer is acting on a continental scale. the question is, what is it?

edinburgh, capital city of scotland. in the university labs geologist chris hayward examines lava from laki. he's looking for chemical clues that might identify laki's killer. one of the most interesting things we can see in these lavas are these very tiny crystals. and what these do is they record the chemistry of the magma at different times in its evolution from the time when it formed very deep under the ground until it was erupted so they're like little time capsules. narrator: as the crystals grew they entombed tiny pockets of laki's magma inside them, along with its chemistry. hayward: so here is one of the crystals this dark area.

and you can see one of the little pockets of magma. and if i zoom in, this is the thickness of a sheet of paper, just to give you some idea of how small these things are. narrator: using a sophisticated electron microprobe, chris teases out their chemistry and finds something intriguing. hayward: we've discovered something very interesting. the material inside the crystals these pockets of magma that were trapped early on, contain large amounts of sulfur. narrator: the crystals formed miles underground when laki's magma was relatively rich in sulfur. but when chris analyzes the solidified lava surrounding them formed much later on during laki's eruption, he makes a remarkable discovery. the final magma that froze in the lava when it was erupted

contains almost no sulfur at all. narrator: so where did the sulfur go? it escaped from the rising magma as a gas into the air. we estimate that around 120 million tons of sulfur was released during the eruption. narrator: so could laki's sulfur be responsible for the deaths in europe and iceland in 1783? if so, how might it kill? chemist andrea sella has the answer. sella: sulfur is actually really very abundant. it's kind of up there in the top 20 elements in the earth's crust. and native sulfur actually often comes out of the ground in volcanic areas to give this wonderful lemon yellow material.

narrator: it also has a very distinctive odor. sella: if we take a sample of commercial powdered sulfur and take the lid off and give it a quick sniff, it's got a delicate, almost evocative smell. it's something a little bit like a freshly sliced hardboiled egg. it's the kind of smell you often get near hot springs or thermal baths-- something you associate with volcanism. narrator: throughout history sulfur has long been associated with boiling mud volcanoes and hell. sella: it was brimstone, the devil. it was clearly a dangerous and powerful substance. and in order to show this,

what i think we should do is to heat a little bit of sulfur up and see the incredible things that it does. as we warm it, it soon begins to melt. we're gradually getting this deep, dark liquid. this is a little bit like traveling ever deeper into the bowels of the earth. and if we go down far enough deep down in the magma the temperatures are so high the sulfur's actually transformed to a gas. narrator: and as the magma rises the gas escapes explosively as sulfur dioxide. this is among the most dangerous stuff that a volcano can produce. narrator: climate scientist mike

rampino understands the threat from sulfur dioxide only too well. he's come to one of iceland's major attractions-- the thermal pools at geyser-- where water is volcanically heated in spectacular fashion. we are sitting in front of a hot pool, which is giving off water vapor and steam. but i can also smell and even taste an acrid gas, and that is the big problem with volcanoes-- the amount of sulfur gases that they release into the atmosphere. narrator: the sulfur dioxide gas given off by these pools is nasty enough, but when it's pushed into the atmosphere during an eruption it can become a far more lethal chemical compound. the problem is that when the sulfur dioxide reacts with water vapor it forms a little droplet

of the acid sulfuric acid. and so up in the upper atmosphere if enough sulfur is released by the volcano you get this mist of sulfuric acid droplets. narrator: it's the same acid found in your car battery, and it's dangerous stuff. sulfuric acid at lab strength is a really, really potent acid. in fact, it's really something of a tiger. and if we were to take some flesh a piece of meat like this, and then we can take some concentrated sulfuric acid and pour it on top the results are going to be really unpleasant. narrator: andrea's using concentrated sulfuric acid to show the grizzly effects it has on tissue. sella: within seconds you start to see changes in the color

in the surface of the flesh. and you can see it going from that happy dark red color to something much more sort of beigy brown. so what the acid does is it actually reacts with the protein in the flesh. it's a little bit like cooking. what we've done, in effect is that we've used the acid as a kind of tenderizer. wow, look at this! here we've got some meat which has been in the acid for about ten minutes. whoa! and really we can now pull it apart. what we're ending up with is something truly horrific. narrator: sulfuric acid formed from volcanoes is far more dilute forming fine mists. even so, it's something you wouldn't want to breathe. your lungs have some very, very delicate exposed tissue.

they haven't got skin over the top and the result is that anyone inhaling this mist is going to initially suffer some quite serious irritation. but there's going to be very very long-term cumulative damage if this goes on for any period of time. narrator: in 1783, laki's fissure eruption lasted for eight months. iceland's inhabitants didn't stand a chance against laki's acidic cloud. and this cloud also killed hundreds of thousands more in europe, according to john grattan. but how could an eruption in iceland affect people across such a vast area so far away? grattan: how on earth can these gases be concentrated sufficiently that you can taste them and smell them that they will burn your eyes over a thousand miles away?

narrator: the answer to that lies not with laki's eruption, but with the weather. during the last week of june 1783 high pressure sweeps over northwest europe, bringing fine summer weather. but it also allows something foul high in the atmosphere to sink downwards. that's where the volcanic gases are. now they are being sucked down dragged down to the earth's surface, and it's like a blowtorch devastating the environment below it. narrator: the high pressure acts like a vast funnel. air spiraling down from the upper atmosphere brings with it laki's poisonous gases. if we were standing here in 1783, the view behind us would have disappeared. what we would see instead would be a blue haze across the landscape.

the color green would disappear because the acids burned into the trees. the crops would have been burned, people dying the birds dying, fish floating to the top of the ponds because they've been killed as well. really, a view of armageddon. narrator: it's the final link in the chain of events that triggers a volcanic catastrophe over europe. grattan: one thing we do know from the geological record that events that have happened in the past will happen in the future. so the events of 1783, they will be repeated again. narrator: what nightmare scenario awaits us if that happens? if laki's cloud reached europe in 1783 how far could one stretch today? anja schmidt has taken laki's sulfur output from the 1783 eruption and, using a computer model, ejects it into today's atmosphere.

it's a disturbing picture. so the eruption starts in iceland and then, as you can see in the model, the sulfur cloud spreads. it crosses britain, germany, france and spain. it's not only affecting europe but also into north america. so over the course of eight months, the entire northern hemisphere is filled with the sulfurous cloud from one eruption in iceland. narrator: so how could that affect us? already many cities generate pollution that causes premature deaths from asthma heart and lung disease. could a toxic cloud from iceland prove to be the tipping point? combining today's pollution with laki's 1783 pollution anja estimates the extra deaths