NARRATOR: THERE ARE FEW SIGHTS ON EARTH AS COMPELLING AS A VOLCANIC ERUPTION... AND FEW THAT PROVIDE SUCH DRAMATIC INSIGHT INTO HOW OUR PLANET FORMED.

VOLCANOES HAVE THE POTENTIAL TO CHANGE OUR WORLD IN A HEARTBEAT, CAUSING DEATH AND WIDESPREAD DESTRUCTION.

BUT THEY ALSO HAVE THE POWER TO CREATE, AND THE SURFACE OF OUR REMARKABLE PLANET IS WELL-STOCKED WITH NATURAL WONDERS FORGED BY FIRE.

VOLCANIC ACTIVITY HAS HELPED SHAPE THE EARTH OVER BILLIONS OF YEARS.

GASES ESCAPING FROM VENTS AND FISSURES CREATED THE ATMOSPHERE AND OCEANS WHICH THEN ALLOWED LIFE ON EARTH TO EVOLVE.

AS CONTINENTS FORMED AND CONTINUOUSLY SHIFTED, EARTHQUAKES AND VOLCANOES HELPED TO SHAPE AND RESHAPE THE EARTH'S SURFACE, CREATING AND DESTROYING ISLANDS AND MOUNTAIN RANGES.

WHILE MANY OF EARTH'S VOLCANOES ARE THOUGHT TO BE EXTINCT, OVER 1,500 REMAIN, AT LEAST POTENTIALLY, ACTIVE.

SOME ARE DORMANT, SLEEPING GIANTS JUST BIDING THEIR TIME, BUT OTHERS OOZE LAVA ON A DAILY BASIS, OR RANDOMLY HURL ROCK AND ASH THOUSANDS OF FEET INTO THE SKY.

75% OF THE WORLD'S ACTIVE VOLCANOES LIE WITHIN OR AROUND THE RIM OF THE PACIFIC OCEAN, A 25,000-MILE ARC GEOLOGISTS CALL THE RING OF FIRE.

THE SEISMIC ACTIVITY AS WELL AS THE VOLCANIC ERUPTIONS THAT OCCUR HERE INFLUENCE THE GEOGRAPHY OF THE WHOLE PLANET, AND, AT LEAST FOR THOSE LIVING WITHIN THE REGION, EVERYDAY LIFE AND CULTURE.

[CHILDREN CALLING] BEFORE MODERN SCIENTIFIC THINKING, MANY OCEANIC COMMUNITIES HAD SPIRITUAL OR CULTURAL EXPLANATIONS FOR THE NATURAL PHENOMENA ASSOCIATED WITH VOLCANOES, ATTRIBUTING THEIR EXISTENCE TO SUPERNATURAL POWERS, OR THE DEEDS OF THEIR LEGENDARY ANCESTORS.

IN INDONESIA, VOLCANOES ARE STILL WIDELY WORSHIPED, DESPITE THE NATION'S ACCEPTANCE OF MORE ORTHODOX THEOLOGIES.

INDONESIA HAS MORE ACTIVE VOLCANOES THAN ANY OTHER COUNTRY ON EARTH.

76 OF THESE HAVE ERUPTED IN HISTORICAL TIMES, 10 ARE CURRENTLY LETTING OFF STEAM.

[STEAM HISSING] THE WHOLE ARCHIPELAGO IS SITTING ON A GEOLOGICAL TIME BOMB.

THIS IS WHERE FOUR OF THE EARTH'S TECTONIC PLATES MEET, SO TREMORS AND EARTHQUAKES HAPPEN ALL THE TIME.

OCCASIONALLY THEY HELP TO SET OFF HUGE VOLCANIC ERUPTIONS THAT THEN TRIGGER HORRIFIC TSUNAMIS.

THE ERUPTION OF KRAKATOA, IN 1883, WAS ONE OF THE DEADLIEST AND MOST DESTRUCTIVE EVENTS IN RECORDED HISTORY, KILLING MORE THAN 36,000 PEOPLE AND ALMOST COMPLETELY DESTROYING THE ISLAND.

FOUR HUGE EXPLOSIONS RANG OUT ACROSS THE PACIFIC.

THE FIRST BLAST RUPTURED THE EARDRUMS OF SAILORS WHO WERE 64 KILOMETERS OFFSHORE, BUT THE LAST, THE LOUDEST SOUND IN RECORDED HISTORY, WAS HEARD BY PEOPLE LIVING 3,000 KILOMETERS AWAY IN AUSTRALIA.

10,000 TIMES MORE POWERFUL THAN THE ATOMIC BOMB THAT DEVASTATED HIROSHIMA, THE ERUPTION TRIGGERED TSUNAMIS AROUND THE WORLD AND SENT PLUMES OF ASH AND DEBRIS 80 KILOMETERS SKYWARD, DRAMATICALLY AFFECTING THE CLIMATE BY CAUSING TEMPERATURES ACROSS THE GLOBE TO DROP FOR A FULL FIVE YEARS.

INDONESIA'S VOLCANOES ARE JUST AS VOLATILE TODAY AS THEY WERE BACK IN THE 1800s, AND JUST AS WORTHY OF RESPECT.

THE TENGGER PEOPLE, WHO LIVE WITHIN THE REALM OF MOUNT BROMO, A PARTICULARLY ACTIVE VOLCANO ON THE ISLAND OF JAVA, BELIEVE ITS ERUPTIONS ARE A CLEAR INDICATION THAT THEY HAVE MADE THEIR GOD VERY ANGRY.

THEIR RELIGION COMBINES ELEMENTS OF HINDUISM, BUDDHISM, AND ANIMISM, AND EVERY YEAR THEY SET OUT TO APPEASE THE DEITIES OF BROMO, CLIMBING TO THE CRATER TO OFFER GIFTS OF FOOD OR FLOWERS AND THE OCCASIONAL SACRIFICIAL GOAT.

IT'S A RITUAL THAT HONORS THE LEGEND OF A PRINCE WHO GAVE HIS OWN LIFE TO SAVE HIS FAMILY, AND INDEED THE WHOLE TENGGER COMMUNITY, FROM DEATH AND DESTRUCTION BY FIRE.

WITH SO MANY VOLCANOES RISING FROM THE PACIFIC RING OF FIRE, BIG ERUPTIONS ARE SOMETHING OF A CERTAINTY IN THIS PART OF THE WORLD, A CASE OF WHEN RATHER THAN IF.

ONE VOLCANO THAT'S BARELY PAUSED FOR BREATH SINCE IT FOUND ITS WAY INTO RECORDED HISTORY IS YASUR ON THE ISLAND OF TANNA IN VANUATU.

RISING JUST 361 METERS ABOVE SEA LEVEL, YASUR IS SMALL BUT VOLATILE, IN A STATE OF CONTINUOUS ACTIVITY, ERUPTING NUMEROUS TIMES EVERY HOUR OF EVERY DAY.

THE MOST ACTIVE VOLCANO ON EARTH.

IT ISN'T KNOWN FOR SURE WHEN THESE ERUPTIONS STARTED, BUT BRITISH EXPLORER CAPTAIN COOK CERTAINLY NOTED THE ACTIVITY WHEN HE VISITED TANNA IN 1774.

SOME VOLCANOLOGISTS BELIEVE IT MAY HAVE BEEN ERUPTING LIKE THIS FOR 800 YEARS.

YASUR IS A STRATOVOLCANO, BUILT UP FROM ALTERNATING LAYERS OF LAVA AND ASH.

ITS SIDES ARE NOT VERY STEEP, AND AS MOST OF ITS ERUPTIONS ARE RELATIVELY SMALL, IT'S RELATIVELY EASY AND SAFE TO ACCESS.

EVERY AFTERNOON, LOCALS GUIDE A STEADY FLOW OF THRILL SEEKERS UP TO THE 400 METER-WIDE CRATER, FOR ONE OF THE GREATEST PYROCLASTIC LIGHT SHOWS ON EARTH.

[LAVA EXPLODING] BECAUSE OF ALL THE MINERALS THAT SPEW OUT OF THIS VOLCANO, TANNA IS BLESSED WITH INCREDIBLY RICH, FERTILE SOILS, PERFECT FOR GROWING JUST ABOUT ANYTHING.

IT'S ONE OF THE GREAT IRONIES OF NATURE THAT THE SAME VOLCANIC ERUPTIONS THAT CAUSE WIDESPREAD DEVASTATION ALSO HERALD NEW LIFE.

IN THE SHORT TERM, VOLCANIC ASH CAN COMPLETELY DESTROY AGRICULTURAL LAND AND CROPS, BUT IN THE LONG TERM, IT'LL MAKE THE SOIL MORE PRODUCTIVE.

VOLCANIC SOILS COVER JUST 1% OF THE EARTH'S LAND SURFACE, BUT THEY ARE SO FERTILE, THEY FEED 10% OF THE WORLD'S POPULATION, CLEARLY A GOOD REASON TO LIVE SO CLOSE TO VOLCANOES, PROCESSING CROPS SUCH AS SAGO, DESPITE THE OBVIOUS RISKS.

LIVING IN VOLCANICALLY ACTIVE AREAS HAS ITS BENEFITS, INCLUDING, IN MANY CASES, ACCESS TO FREE AND ABUNDANT HOT WATER.

GEOTHERMAL SYSTEMS OCCUR AROUND CALDERA-FORMING SUPERVOLCANOES, WHERE LARGE QUANTITIES OF HOT ROCK LIE CLOSE TO THE SURFACE.

NEW ZEALAND HAS A HUGE SUPPLY OF GEOTHERMAL ENERGY, GENERATING OVER 17% OF THE NATION'S ELECTRICITY.

BUT LONG BEFORE STEAM-DRIVEN TURBINE GENERATORS WERE INVENTED, NEW ZEALAND'S ORIGINAL POLYNESIAN INHABITANTS, THE MAORI, WERE COOKING, WASHING, AND WARMING THEMSELVES WITH HEAT SOURCED DIRECTLY FROM THE EARTH'S MOLTEN CORE.

IT DIDN'T TAKE LONG FOR EUROPEAN COLONISTS TO DISCOVER THE THERAPEUTIC BENEFITS OF HOT SPRINGS SUCH AS THESE, SETTING THE TOWNSHIP OF ROTORUA IN THE NORTH ISLAND OF NEW ZEALAND ON ITS FAST-TRACK TO FAME.

AREAS THAT ARE CLEARLY ACTIVE, IN A GEOTHERMAL SENSE, ARE USUALLY LOCATED CLOSE TO THE BOUNDARIES OF TECTONIC CONTINENTAL PLATES.

NEW ZEALAND SITS OVER TWO.

IT ALSO HAS EIGHT VOLCANOES, WITH A HIGH FREQUENCY OF ERUPTIONS.

THE TAUPO VOLCANIC ZONE, WHICH EXTENDS FROM RUAPEHU TO WHITE ISLAND, IS EXTREMELY ACTIVE ON A WORLD SCALE.

INDEED, WHITE ISLAND HASN'T STOPPED VENTING ITS IRE FOR MORE THAN FOUR DECADES!

48 KILOMETERS FROM THE NORTH ISLAND'S BAY OF PLENTY, THE HIGHEST POINT ON UNINHABITED WHITE ISLAND IS 321 METERS.

70% OF THE VOLCANO'S CONE IS UNDER THE SEA, SO THE FLOOR OF ITS CRATER IS LESS THAN 30 METERS ABOVE SEA LEVEL, A BEWITCHING LANDSCAPE THAT IS AS COMPELLING AS IT IS REPELLING.

ON ANY GIVEN DAY, THE ISLAND SPEWS BETWEEN 2,000 AND 3,000 TONS OF TOXIC GASES INTO THE ATMOSPHERE.

FLYING STRAIGHT INTO THIS SORCERER'S CAULDRON OF TOXIC FUMES AND ACIDIC GASES IS NOT WITHOUT RISK, AND YET, THERE ARE MANY PREPARED TO TAKE IT FOR THE CHANCE TO WITNESS THE RAW POWER OF NATURE FIRST-HAND.

FUMAROLES HISS, STEAM, AND BUBBLE AWAY, CREATING EXQUISITE CRYSTAL GARDENS OF SULFUR.

THE TEMPERATURE OF THE GASES BILLOWING FROM THESE VENTS VARIES WILDLY.

DURING AN ERUPTION IN 2012 THEY HIT 450 DEGREES CELSIUS, BUT IN LESS VOLATILE TIMES THEY CAN BE JUST OVER 100 DEGREES.

THE ENTIRE LANDSCAPE IS CONSTANTLY TRANSFORMING.

IN 2015, AN EXPLOSIVE ERUPTION COMPLETELY CLEARED OUT THE ISLAND'S MAIN CRATER LAKE.

RAINWATER HAS DILUTED A NEW LAKE THAT EVENTUALLY FORMED, BUT IT'S STILL AS ACIDIC AS BATTERY ACID.

ATTEMPTS WERE MADE TO MINE THE SULFUR HERE AROUND THE BEGINNING OF THE 20th CENTURY, BUT TRAGEDY STRUCK IN 1914 WHEN PART OF THE CRATER WALL COLLAPSED, CAUSING A LANDSLIDE THAT KILLED ALL 10 MINERS ON THE SITE.

WHAT REMAINS OF THEIR ENDEAVOR SERVES AS AN EERIE REMINDER TO ALL WHO VISIT WHITE ISLAND OF JUST HOW UNPREDICTABLE VOLCANOES CAN BE.

SCIENTISTS NOW MONITOR WHITE ISLAND CLOSELY FOR ANY INDICATION OF VOLCANIC UNREST, FOR THEY BELIEVE IT MIGHT ACT AS AN EARLY WARNING SYSTEM FOR ERUPTIONS AND EARTHQUAKES ON THE MAINLAND.

THE CONNECTION BETWEEN ALL OF THE VOLCANOES IN THE TAUPO VOLCANIC ZONE IS RECOGNIZED SCIENTIFICALLY AND CULTURALLY.

THE MAORI BELIEVE THEIR ANCESTORS, ON ARRIVAL IN NEW ZEALAND, SET OUT TO EXPLORE THE MOUNTAINS OF THE NORTH ISLAND.

THE LOCAL GODS WERE FURIOUS, AND SENT A FIERCE BLIZZARD TO TURN THEIR LEADER, NGATOROIRANGI, INTO ICE.

THE ANCESTORS APPEALED TO THEIR SPIRIT SISTERS FOR WARMTH, AND THEY RUSHED IMMEDIATELY TO THEIR AID, TRAVELING BENEATH THE LAND AND SEA, CARRYING FIRE FROM THEIR TRIBAL HOMELANDS.

EVERYWHERE THEY SURFACED EN ROUTE TO TONGARIRO, THEY LEFT PART OF THEIR GIFT BEHIND, EFFECTIVELY CREATING ALL THE GEOTHERMAL SYSTEMS AND SUPERVOLCANOES EVIDENT IN THE LANDSCAPE TODAY, INCLUDING MOUNT RUAPEHU.

RISING TO 9,177 FEET, SNOW-CAPPED RUAPEHU IS THE CENTERPIECE OF NEW ZEALAND'S FIRST NATIONAL PARK, TONGARIRO.

THE PARK WAS ALSO THE FIRST CULTURAL LANDSCAPE TO FIND ITS WAY ONTO THE WORLD HERITAGE LIST, RECOGNIZING THE SPIRITUAL SIGNIFICANCE OF TONGARIRO TO THE MAORI PEOPLE.

THE ENTIRE NATIONAL PARK IS A NATURAL WONDER, FULL OF POWERFUL WATERFALLS, THICK FORESTS, RUGGED PLATEAUS, AND VOLCANOES.

FANS OF PETER JACKSON'S "LORD OF THE RINGS" MOVIES MAY RECOGNIZE MANY LOCATIONS, INCLUDING MOUNT NGAURUHOE, WHICH PLAYED A KEY ROLE AS MOUNT DOOM IN LEGENDARY MORDOR.

IF THE ACADEMY OF MOTION PICTURE ARTS AND SCIENCES WERE EVER TO AWARD AN OSCAR FOR BEST SUPPORTING LANDSCAPE IN A MOVIE, NEW ZEALAND'S MIDDLE EARTH WOULD BE A SERIOUS CONTENDER.

BUT THEY'D HAVE SOME FIERY COMPETITION FROM HAWAII, ONE OF THE MOST ISOLATED ARCHIPELAGOS IN THE WORLD.

ALL OF HAWAII'S MAIN ISLANDS ARE VOLCANIC, RISING UP FROM THE PACIFIC OCEAN BASIN.

THE TECTONIC PLATE THAT SITS BENEATH THEM MOVES NORTHWEST AT THREE TO SIX INCHES A YEAR.

AS IT MOVES, IT PASSES OVER A FIXED HOT-SPOT, A POINT WHERE MOLTEN LAVA ESCAPES FROM THE EARTH'S MANTLE.

VOLCANIC MOUNDS FORM, WHICH OVER MILLIONS OF YEARS, REACH SEA LEVEL AND GROW INTO ISLANDS.

A STRING OF ISLANDS EVENTUALLY EMERGE, MAPPING THE TECTONIC PLATES' MOVEMENT OVER A VAST PERIOD OF TIME.

KAUA'I IS THE OLDEST OF HAWAII'S CHAIN OF VOLCANIC ISLANDS, AND BIG ISLAND, WELL, IT'S STILL FORMING, FOR IT NOW SITS DIRECTLY OVER THAT HOT-SPOT THAT'S BEEN OOZING LAVA FOR 70 MILLION YEARS.

THE YOUNGEST OF THE FIVE VOLCANOES THAT OVERLAP ON THE BIG ISLAND IS KILAUEA, HOME OF PELE, THE HAWAIIAN GODDESS OF FIRE, SHE WHO SHAPES THE SACRED LAND, OR MORE OMINOUSLY, DEVOURS IT.

THE CRATER OF KILAUEA CONTAINS ONE OF THE LARGEST LAVA LAKES ON THE PLANET.

THE LAVA STAYS CONTAINED WITHIN THE LAKE, FLOWING UP AND BACK INTO THE EARTH, CAUSING THE LAKE TO RISE OR FALL UP TO 30 FEET IN A MATTER OF DAYS.

VOLCANOLOGISTS MONITOR ITS EVERY MOVE TO ENSURE THE SAFETY OF EVERYONE LIVING ON THE ISLAND, ISSUING WARNINGS IF AND WHEN THEY FEEL BIG ERUPTIONS ARE IMMINENT.

PELE'S HAIR IS AN ALMOST MYSTICAL CURIOSITY CREATED BY KILAUEA.

FRAGILE STRANDS OF VOLCANIC GLASS THAT FORM WHEN MOLTEN LAVA IS THROWN INTO THE AIR AND SMALL DROPLETS, CAUGHT BY THE WIND, ARE STRETCHED INTO THIN GOLDEN THREADS.

KILAUEA IS STILL IN THE THROES OF A LONG ERUPTION THAT BEGAN IN 1983.

BUILT ALMOST ENTIRELY FROM SLOW-FLOWING LAVA, KILAUEA HAS A BROAD, LOW PROFILE.

SCIENTISTS CALL THIS A SHIELD VOLCANO, AND THE FIVE HERE ON BIG ISLAND ARE THE LARGEST VOLCANOES ON EARTH.

THE WAY LAVA BEHAVES IS INFLUENCED BY ITS TEMPERATURE AND COMPOSITION.

IF LAVA MOVES AND COOLS SLOWLY, IT FORMS A SMOOTH, ROPY LAVA CALLED PAHOEHOE.

AND IT'S RELATIVELY SAFE, AND MESMERIZING, TO WATCH UP CLOSE.

KILAUEA IS CURRENTLY OOZING SOME 200,000 TO 500,000 CUBIC METERS OF LAVA A DAY, MORE THAN ENOUGH TO RESURFACE A 32-KILOMETER STRETCH OF ROAD, WHICH IS WHAT IT QUITE LITERALLY TRIES TO DO FROM TIME TO TIME.

THIS PARTICULAR TRAFFIC-STOPPING FLOW OCCURRED IN 2002.

BUT ON THE OTHER SIDE OF KILAUEA, MORE RECENT FLOWS HAVE FOUND THEIR WAY TOWARDS THE SEA, AND THE REACTION WHEN 2,000-DEGREE LAVA HITS 26-DEGREE WATER CAN BE EXPLOSIVE.

LAVA CAN SHATTER INTO FRAGMENTS SMALLER THAN A GRAIN OF RICE, OR BIGGER THAN A BREAD BOX.

THE HARDENING LAVA COOLS QUICKLY, BUT THE WATER IT PLUNGES INTO HEATS UP, PRODUCING STEAM.

THE LAVA ADDS LAYERS OF RUBBLE TO THE FLANK OF THE VOLCANO, ABOVE AND BELOW THE WATERLINE, STEADILY INCREASING THE SIZE OF THE ISLAND.

SINCE KILAUEA BEGAN ITS CURRENT ERUPTION IN 1983, AROUND 200 HECTARES OF NEW LAND HAVE BEEN ADDED TO BIG ISLAND.

KAUA'I LIES AT THE OTHER END OF THE HAWAIIAN ARCHIPELAGO, AND IT'S THE OLDEST OF THE MAJOR ISLANDS IN THE CHAIN.

FIVE MILLION YEARS HAVE PASSED SINCE MOLTEN LAVA PETRIFIED TO FORM THESE EXTRAORDINARY, CORRUGATED CLIFFS ON THE NAPALI COAST.

THEY SOAR 1,219 METERS ABOVE THE OCEAN, LIKE A GIANT FORTRESS WALL, PROTECTING AN IMPENETRABLE WORLD FULL OF HIDDEN VALLEYS AND JAW-DROPPING WATERFALLS, INCLUDING MANAWAIOPUNA, ALSO KNOWN AS JURASSIC FALLS.

PRIOR TO ITS APPEARANCE IN STEVEN SPIELBERG'S "JURASSIC PARK" MOVIE, ONLY A FEW LOCALS KNEW OF ITS EXISTENCE, BUT NOW THE SECRET IS OUT.

FOUR MILLION YEARS AGO, A PORTION OF THE VOLCANO THAT CREATED KAUA'I COLLAPSED, ALLOWING WAIMEA CANYON TO FORM.

IT'S A SPECTACULAR GEOLOGICAL WONDER THAT CHANGES CONTINUOUSLY, THANKS TO THE STEADY PROCESS OF EROSION.

OVER TIME, THE BASALT, OR VOLCANIC, ROCK HERE HAS WEATHERED FROM ITS ORIGINAL BLACK TO A STRIKING DEEP RED.

THE HIGHEST POINT ON THE ISLAND HAS A REPUTATION FOR BEING ONE OF THE WETTEST PLACES ON EARTH, RECEIVING OVER 10 METERS OF RAINFALL PER YEAR, HELPING TO SUSTAIN KAUA'I'S TROPICAL FORESTS, WHICH GROW ON ALL BUT THE MOST SHEER-SIDED CLIFFS.

THEY GIVE THE WHOLE PLACE A PRIMORDIAL FEEL, AND WITH IT, A GREAT DEAL OF MYSTIQUE, WHICH ONLY SERVES TO HEIGHTEN THEIR WONDER.

ICELAND STRADDLES THE MID-ATLANTIC RIDGE, AN UNDERWATER CHAIN OF MOUNTAINS AND RIFT VALLEYS RUNNING ALONG THE NORTH-SOUTH AXIS OF THE ATLANTIC OCEAN.

THE RIDGE SEPARATES THE EURASIAN AND NORTH AMERICAN TECTONIC PLATES, FORCING THEM OVER TIME TO DRIFT FURTHER AND FURTHER APART, TRIGGERING EARTHQUAKES, LEAKING LAVA, AND SPEWING FORTH GEYSERS AND HOT SPRINGS.

THIS IS EARTH UNDER CONSTRUCTION, AND IT'S ABOUT AS DYNAMIC AS IT GETS!

A HOT-SPOT, OR UPWELLING PLUME OF MAGMA, JUST BELOW VATNAJOKULL, ONE OF THE LARGEST ICECAPS IN EUROPE, HAS CONTRIBUTED TO THE ISLAND'S FORMATION AND COULD, AT ANY TIME, ERUPT WITH SUCH FORCE IT WOULD DESTROY THE COUNTRY COMPLETELY.

YOU WOULD THINK THAT LIVING WITH THAT POTENTIAL THREAT WOULD KEEP THE POPULATION OF ICELAND ON EDGE, BUT THE OPPOSITE APPEARS TO BE TRUE.

THEY PRIDE THEMSELVES ON THEIR LONG LIVES, RESILIENCE, AND GOOD HUMOR.

IN THIS EXTRAORDINARY LAND OF FIRE AND ICE, LOCALS JOKE THAT THEY HAVE ONE TAP IN THEIR HOMES CONNECTED TO A GLACIER AND THE OTHER TO THE DEPTHS OF HELL.

VOLCANOES THAT ERUPT BENEATH ICECAPS, SUCH AS THOSE HERE IN ICELAND, ARE OFTEN DOUBLY DANGEROUS.

THEIR ERUPTIONS ARE MORE EXPLOSIVE AND CONTAIN A GREAT DEAL OF ASH, BUT SOMETIMES, MORE SIGNIFICANTLY, THEY CAUSE THE ICECAP AND ITS OUTLET GLACIERS TO MELT, TRIGGERING CATACLYSMIC FLOODS.

WHEN ICELAND'S INFAMOUS SUBGLACIAL STRATOVOLCANO, EYJAFJALLAJOKULL, ERUPTED IN 2010, THE MASSIVE PLUME OF ASH BILLOWING FROM ITS SUMMIT FORCED THE LARGEST AVIATION SHUTDOWN IN EUROPE SINCE WORLD WAR II, DISRUPTING THE JOURNEYS OF AN ESTIMATED 10 MILLION TRAVELERS OVER THE COURSE OF A MONTH.

THE FLASH FLOODING OF GLACIAL MELTWATER WAS NOTHING SHORT OF BIBLICAL, LEAVING THIS BARREN VALLEY IN ITS WAKE.

THE ICECAP THAT CROWNED EYJAFJALLAJOKULL WAS ONE OF THE SMALLEST IN THE COUNTRY, BUT AS IT LIQUEFIED, IT WASHED DOWN THE SIDE OF THE VOLCANO, FORCING EVACUATIONS AND CAUSING WIDESPREAD DESTRUCTION.

130 MILLION CUBIC METERS OF ICE WERE EITHER VAPORIZED OR LIQUEFIED, AS NEARLY 23 BILLION LITERS OF LAVA FLOWED FROM THE VOLCANO.

IT WAS THE FIRST TIME IT HAD ERUPTED IN 180 YEARS, AND THE ASH THAT WAS EJECTED, WIDELY DISPERSED.

NONETHELESS, MANY AIRBORNE PARTICLES LANDED ON THE SOUTH AND SOUTHEAST SIDE OF THE VOLCANO, BLANKETING WHAT WAS LEFT OF THE GLACIERS IN A THICK LAYER OF SOOTY ASH.

ACCORDING TO THE WORLD ENERGY COUNCIL, SOME 40 COUNTRIES COULD POTENTIALLY PRODUCE ALL THE ELECTRICITY THEY NEED THROUGH HARNESSING THE HEAT TRAPPED BELOW THE SURFACE OF THE EARTH.

ICELAND IS A PIONEER IN THIS FIELD, CURRENTLY CREATING ONE OF THE WORLD'S DEEPEST GEOTHERMAL WELLS, DRILLING MORE THAN 4,500 METERS TOWARDS HEAT-PRODUCING MAGMA.

AN ADDED BONUS FROM THIS PARTICULAR POWER PLANT IN ICELAND IS THE BLUE LAGOON SPA, AN ENORMOUS COMMUNAL BATH WITH A WEALTH OF THERAPEUTIC BENEFITS.

THE LAGOON CONTAINS NINE MILLION LITERS OF WATER THAT IS NATURALLY SELF-CLEANSING, RENEWING EVERY 40 HOURS.

THE GEOTHERMAL WATER IN BLUE LAGOON ORIGINATES 2,000 METERS BELOW THE SURFACE, WHERE EXTREMELY HOT FRESHWATER AND SEAWATER COMBINE, BUT BY THE TIME IT REACHES THE POOL, COLLECTING SILICA AND OTHER MINERALS EN ROUTE, IT'S A VERY PLEASANT 37 TO 40 DEGREES.

IT'S MILKY WHITE IN COLOR, BUT THE SILICA REFLECTS LIGHT, SO IT APPEARS TO BE BLUE, A COLOR THAT INSPIRES RELAXATION AND A DEEP SENSE OF CALM.

ANOTHER PLACE WHERE FIRE AND ICE COME TOGETHER TO CREATE A LANDSCAPE OF GREAT BEAUTY IS THE KAMCHATKA PENINSULA IN RUSSIA.

ROUGHLY THE SIZE OF GERMANY, AUSTRIA, AND SWITZERLAND PUT TOGETHER, THIS HALF A MILLION SQUARE KILOMETER WILDERNESS WAS ONCE OFF-LIMITS EVEN TO RUSSIAN CITIZENS LIVING BEYOND THE REGION, FOR IT WAS AN IMPORTANT MILITARY ZONE, REPLETE WITH SECRET COLD WAR INSTALLATIONS.

NOW THIS VAST SANCTUARY THAT BOASTS ONE BEAR FOR EVERY HUMAN INHABITANT IS OPEN TO THE WORLD.

THE PROMISE OF CLOSE ENCOUNTERS WITH WILDLIFE DRAWS MANY VISITORS TO THE REGION, BUT IT'S THE LANDSCAPE THAT LEAVES THE BIGGEST IMPRESSION, FEATURING MANY NEAR-PERFECT SYMMETRICAL CONES THAT RISE OVER 4,000 METERS.

THERE ARE 160 VOLCANOES HERE, AND 29 OF THEM ARE VERY MUCH ALIVE, MAKING KAMCHATKA ONE OF THE MOST ACTIVE VOLCANIC REGIONS IN THE WORLD.

THE TOLBACHIK LAVA FIELDS COVER A HIGH ALTITUDE PLATEAU IN THE FAR NORTH.

THEY LOOK LIFELESS AND UNINVITING, BUT REMAIN A SOURCE OF GREAT FASCINATION AMONG GEOLOGISTS.

AT THIS LATITUDE AND ALTITUDE, THE COLD CLIMATE DOESN'T ALLOW LAVA TO BREAK DOWN INTO SOIL, SO THE FIELDS CONTAINS A PERFECTLY PRESERVED RECORD OF PAST ERUPTIONS THAT HAVE OCCURRED IN THE REGION.

BY WAY OF CONTRAST, THE MOST COLORFUL GEOTHERMAL FEATURE ON THE ENTIRE PENINSULA IS THE VALLEY OF THE GEYSERS.

NOURISHED BY ONE OF THE LARGEST CONCENTRATIONS OF GEYSERS IN THE WORLD, IT'S A LUSH AND FERTILE OASIS IN AN OTHERWISE LUNAR-LIKE WORLD.

ONE OF THE MOST VOLCANICALLY AND TECTONICALLY ACTIVE AREAS IN AFRICA LIES IN THE MIDDLE OF THE EAST AFRICAN RIFT.

BENEATH THE SURFACE OF THE LAND HERE, THE TECTONIC PLATES ARE TEARING APART, CAUSING ERUPTIONS AND EARTHQUAKES THAT OVER TIME HAVE FORCED THE VALLEY FLOOR TO SINK, CREATING ONE OF THE GREAT NATURAL WONDERS OF OUR WORLD.

HEAT BENEATH THE EARTH'S SURFACE FUELS THE VALLEY'S 22 ACTIVE VOLCANOES AND ITS GEOTHERMAL POWER PLANTS, WHICH ARE HELPING NATIONS SUCH AS KENYA TO REDUCE THEIR DEPENDENCY ON EXPENSIVE, IMPORTED FOSSIL FUELS.

LAKES ARE ANOTHER NATURAL FEATURE IN THE RIFT VALLEY LANDSCAPE THAT WERE SHAPED BY EARTH'S VIOLENT RUMBLINGS.

LAKE BOGORIA STILL BUBBLES AWAY WITH ITS HOT SPRINGS AND ACTIVE GEYSERS.

BUT TWO OF THE BETTER-KNOWN LAKES IN THE REGION ARE NAKURU AND NAIVASHA.

10,000 YEARS AGO THESE RIFT LAKES FORMED A SINGLE, DEEP BODY OF FRESHWATER, BUT ALL THAT GEOLOGICAL AND GEOTHERMAL ACTIVITY IN THE REGION, TOGETHER WITH A CHANGING CLIMATE, HAVE BROUGHT ABOUT A DRASTIC CHANGE.

[FLAMINGOS CALLING] LAKE NAKURU IS NOW A SODA LAKE.

IT'S SHALLOW, AND FULL OF SALTS AND MINERALS THAT KEEP MOST OF AFRICA'S WILD ANIMALS AT BAY.

BUT FLAMINGOES?

WELL, THEY CAN'T SEEM TO GET ENOUGH OF THE PLACE!

EQUIPPED WITH SPECIAL GLANDS IN THEIR HEADS TO REMOVE SALT FROM THE WATER WHEN THEY'RE DRINKING, THEY FEAST ON THE BACTERIA THAT GROWS WITHIN THE LAKE.

THEY ARE ONE OF ONLY A FEW SPECIES THAT CAN TOLERATE SUCH A HIGHLY TOXIC MEAL, BUT THE PAYOFF IS QUITE EXTRAORDINARY.

IN A WORLD WHERE YOU ARE WHAT YOU EAT, THAT BACTERIA IS WHAT GIVES THESE FLAMINGOS THEIR COLOR.

60 KILOMETERS FROM LAKE NAKURU IS LAKE NAIVASHA, AND IT'S CLEARLY RETAINED ITS FRESHWATER APPEAL, ATTRACTING A MUCH WIDER VARIETY OF ANIMALS.

HIPPOS WALLOW IN COOLING WATER, WHILE ZEBRAS AND GIRAFFES GRAZE ALONG ITS BANKS, FEASTING ON ALL THAT LOVELY VEGETATION SUSTAINED BY THE RICH VOLCANIC SOILS.

WHILE THE HAWAIIAN ISLANDS IN THE UNITED STATES FORMED OVER A HOT-SPOT IN THE OCEAN, YELLOWSTONE'S SUPERVOLCANO IS TERRESTRIAL, SITTING OVER A FIXED HOTSPOT IN THE MIDDLE OF THE NORTH AMERICAN PLATE.

IT HASN'T ERUPTED IN 631,000 YEARS, BUT NONETHELESS, IT CONTINUES TO ACTIVELY FUEL ALL THE GEOTHERMAL ACTIVITY IN YELLOWSTONE.

10,000 HYDROTHERMAL FEATURES ARE FOUND WITHIN THE PARK.

A WHOPPING 60% OF THE WORLD'S GEYSERS AND HOT SPRINGS ARE LOCATED HERE, INCLUDING OLD FAITHFUL, POSSIBLY THE MOST FAMOUS GEYSER ON THE PLANET.

IN 1872, YELLOWSTONE BECAME THE WORLD'S FIRST NATIONAL PARK, AND SINCE THEN, OLD FAITHFUL HAS ERUPTED MORE THAN A MILLION TIMES.

THE TEMPERATURE OF THE WATER AS IT EXITS THE VENT IS 95.6 DEGREES CELSIUS, BUT THE STEAM TEMPERATURE CAN REACH MORE THAN 176 DEGREES.

YELLOWSTONE IS ONE OF THE DESIGNATED SEVEN WONDERS OF NORTH AMERICA... SHAPED BY WATERFALLS THAT THUNDER THROUGH DEEP VALLEYS.

THE WILDLIFE IS SECOND TO NONE.

THERE ARE MORE WILD ANIMALS HERE THAN ANYWHERE ELSE IN THE U.S.

SEEING BISON ROAMING THROUGH GEOTHERMAL AREAS IS A COMMON SIGHT, PARTICULARLY IN WINTER.

THE GROUND SURROUNDING GEYSERS AND FUMAROLES IS GENERALLY WARM AND WILL THEREFORE HAVE LESS SNOW COVER, MAKING IT FAR EASIER FOR THE BISON TO FORAGE.

THE GRAND PRISMATIC SPRING IS THE LARGEST HOT SPRING IN AMERICA.

HOT SPRINGS FORM WHEN HEATED WATER EMERGES THROUGH CRACKS IN THE EARTH'S SURFACE, THEN FLOWS, UNOBSTRUCTED, ACROSS THE TERRAIN.

THE VIVID COLORS BEYOND THE BLUE IRIS OF THE GRAND PRISMATIC SPRING COME FROM A HEAT-LOVING BACTERIA THAT'S MADE A HOME FOR ITSELF IN THIS SEEMINGLY HOSTILE ENVIRONMENT-- TRILLIONS OF MICROORGANISMS USING CAROTENOIDS, OR PIGMENTS, TO PROTECT THEMSELVES FROM THE HARSH, ULTRAVIOLET RAYS OF THE SUN.

IT'S THE MOST PHOTOGRAPHED NATURAL WONDER IN ALL OF YELLOWSTONE.

THE SAME FORCES THAT CREATE VOLCANOES GIVE RISE TO HOT SPRINGS, AND THE FORMATIONS THEY SPAWN ARE INVARIABLY SPECTACULAR.

BUT THE TRAVERTINE TERRACES IN TURKEY ARE TRULY IN A LEAGUE OF THEIR OWN.

THE LOCALS SAY THEY'RE THE EIGHTH WONDER OF THE WORLD, AND YOU'D BE HARD-PRESSED DENYING THEM THE CLAIM.

CALCITE-LADEN WATERS SPILL FROM A 650-FOOT-HIGH CLIFF OVERLOOKING THE PLAIN OF CURUKSU, CREATING A FAIRYTALE LANDSCAPE OF PETRIFIED WATERFALLS, STALACTITES, AND POOLS WITH STEP-LIKE TERRACES, APTLY NAMED PAMUKKALE, WHICH MEANS COTTON CASTLE.

PEOPLE HAVE BEEN COMING HERE TO RELAX IN THE SOOTHING, THERAPEUTIC WATERS FOR THOUSANDS OF YEARS, BELIEVING THE POOLS OFFER RELIEF FROM SUCH ILLNESSES AS ASTHMA AND ARTHRITIS.

AT THE END OF THE 2nd CENTURY BC, THE KINGS OF PERGAMON ESTABLISHED THE THERMAL SPA TOWN OF HIERAPOLIS NEARBY, BUILDING DIRECTLY OVER THE TOP OF THE GEOTHERMAL FIELD.

CEDED TO ROME IN 133 BC, IT WAS LATER DESTROYED BY AN EARTHQUAKE, BUT REBUILT TO INCLUDE A NUMBER OF MONUMENTS, A NECROPOLIS, AND A THEATER.

IN ITS HEYDAY, THE RESORT TOWN AND WARM POOLS OF PAMUKKALE ATTRACTED PEOPLE FROM ALL OVER THE ROMAN EMPIRE.

NOW IT ATTRACTS VISITORS FROM ALL OVER THE WORLD.

ANOTHER WHIMSICAL ARTIFACT CREATED BY VOLCANIC ACTIVITY IN TURKEY CAN BE FOUND IN CAPPADOCIA ON THE STARK ANATOLIAN PLAINS.

THESE FORMATIONS, OR FAIRY CHIMNEYS AS THEY'RE POPULARLY KNOWN, EVOKE A SENSE OF THE SUPERNATURAL, BUT THEIR EXISTENCE IS BEST EXPLAINED BY SCIENCE.

MILLIONS OF YEARS AGO, VOLCANIC ERUPTIONS RAINED ASH ACROSS THIS REGION OF TURKEY, WHICH HARDENED INTO A POROUS ROCK CALLED TUFF.

WIND AND RAIN OVER MANY MILLENNIA ERODED THE LANDSCAPE INTO A WONDERLAND OF PILLARS AND SPIRES.

HUMANS HAVE BEEN EXCAVATING THESE STRUCTURES SINCE THE 4th CENTURY, TURNING THEM INTO DWELLINGS AND SANCTUARIES, TAKING THE CONCEPT OF LIVING IN THE REALM OF VOLCANOES TO A WHOLE NEW LEVEL.

ARENAL, IN THE CENTRAL VOLCANIC MOUNTAIN RANGE OF COSTA RICA, IS RELATIVELY YOUNG IN GEOLOGICAL TERMS, FOR IT'S ESTIMATED TO BE ABOUT 5,000 YEARS OLD.

FOR CENTURIES IT WAS A NEAR-PERFECT CONE SHAPE COVERED IN RAINFOREST.

MOST PEOPLE THOUGHT IT WAS EXTINCT, BUT IN 1968, IT SUDDENLY ERUPTED... [LAVA EXPLODING] SPEWING MASSIVE AMOUNTS OF LAVA AND ASH THAT KILLED 87 PEOPLE, AND TOTALLY DESTROYED THREE VILLAGES.

SINCE THEN, SEISMOLOGISTS AND GEOLOGISTS FROM AROUND THE WORLD HAVE STUDIED ARENAL'S EVERY BREATH, VENTURING INTO ITS NEWLY-FORMED CRATERS TO MONITOR CHANGES IN ITS GEOTHERMAL BEHAVIOR.

THE LURE OF ADVENTURE, OF EXPLORATION AND DISCOVERY, IS AN IRRESISTIBLE FORCE THAT DRAWS SCIENTISTS AND THRILL-SEEKERS INTO THE REALM OF EARTH'S RESTLESS VOLCANOES.

BUT MANY HAVE PAID FOR THE PRIVILEGE WITH THEIR LIVES.

DESPITE 24/7 MONITORING, THE 2014 ERUPTION OF ONTAKE, JAPAN'S SECOND HIGHEST VOLCANO, CAUGHT EVERYONE BY SURPRISE, PARTICULARLY THOSE WHO WERE INNOCENTLY TREKKING TO THE SUMMIT THAT DAY.

56 DIED, AND SEVEN WERE OFFICIALLY DECLARED MISSING, AS THEIR BODIES WERE NEVER RECOVERED.

IT WAS THE NATION'S WORST VOLCANIC DISASTER IN LIVING MEMORY, AND IT RAISED FEARS THAT MORE OF JAPAN'S VOLCANOES COULD SPRING TO LIFE WITH LITTLE OR NO WARNING, INCLUDING SACRED MOUNT FUJI, ONE OF THE MOST RECOGNIZABLE VOLCANOES ON THE PLANET.

100 KILOMETERS SOUTHWEST OF TOKYO, RISING 3,776 METERS, MOUNT FUJI IS JAPAN'S TALLEST MOUNTAIN.

THE LAST TIME IT ERUPTED, IN 1707, THE PROFILE OF THE PEAK WAS ALTERED, AND THE NATION'S CAPITAL WAS BLANKETED IN ASH.

IT'S BEEN DORMANT EVER SINCE, BUT COULD POTENTIALLY BLOW AT ANY TIME.

MOUNT FUJI WAS DECLARED A WORLD HERITAGE SITE IN 2013, RECOGNIZING IT AS A SACRED SITE AND A SOURCE OF ARTISTIC INSPIRATION.

FOLLOWERS OF TAOISM, A RELIGIOUS PHILOSOPHY THAT DEVELOPED IN CHINA, BELIEVE THAT THE VOLCANO HARBORS THE SECRET OF IMMORTALITY, WHILE SHRINES AROUND THE BASE OF THE MOUNTAIN AND ALONG THE PATHWAY TO THE SUMMIT, HONOR KAMI, THE SUPERNATURAL DEITIES OF THE SHINTO FAITH.

THE NEAR-PERFECT, GEOMETRICAL SHAPE OF MOUNT FUJI IS AN ENDURING NATIONAL SYMBOL, SOME WOULD SAY, IT DEFINES THE SOUL OF JAPAN... A MOTIF THAT SEEKS TO EXPRESS THE REGARD THEY ALL HAVE FOR NATURE AND BEAUTY.

EVERY VOLCANO ON EARTH IS A MARVEL, SHAPED IN NATURE'S FORGE.

FORMIDABLE AND UNPREDICTABLE, THEY HAVE THE POWER TO CREATE AND DESTROY.

VOLCANIC ERUPTIONS CAUSE WIDESPREAD DESTRUCTION THAT FILL US WITH AWE AND FEAR.

BUT THEY ALSO GIVE RISE TO NEW LIFE, OFFERING A MEASURE OF HOPE.

AND WITH EVERY RUMBLING, BELCHING MOVE THEY MAKE, THEY IGNITE OUR SENSE OF WONDER.