Two of history’s most terrifying volcanic eruptions took place in August: Mount Vesuvius, on August 24-25 in 79 A.D., and Krakatoa, on August 26-27 in 1883. Each blasted colossal volumes of burning ash and rock high into the atmosphere and killed thousands of people for miles around. Vesuvius buried the ancient towns of Pompeii and Herculaneum under a deep layer of compacted ash, thereby preserving them intact; their rediscovery and excavation since the 17th century helped give rise to modern scientific archaeology. Krakatoa’s cataclysmic 1883 boom was the loudest sound ever recorded, clearly audible some 3000 miles away in Australia; the eruption caused massive tsunamis that wiped out tens of thousands of lives. As Simon Winchester writes in Krakatoa: The Day the World Exploded, it was one of the first natural disasters to be reported rapidly around the world, thanks to recently laid transoceanic submarine telegraph cables, thereby setting the template for modern disaster news coverage. The Krakatoa eruption may even have helped catalyze Muslim uprisings in Indonesia that eventually drove out the repressive Dutch East Indian government. Both volcanoes have erupted several times since on a smaller scale, and are still dangerously active; Vesuvius smolders just above Naples, which since the most recent eruption in 1944 has grown into one of the most populous urban centers in Europe.
Both Vesuvius and Krakatoa are stratovolcanoes; steep conical volcanoes built up by millennia of eruptions into hardened composite layers of lava and rock, often with a collapsed summit crater called a caldera. The stiff layers of rock trap volatile gases in the underlying magma, which can explode out when a break occurs that causes the pressure to release rapidly, launching pulverized rock and steam miles into the sky. Pyroclastic flows of lava, superheated ash, and gases race down the mountainsides and wipe out all life below. Since the 1960s, the development of plate tectonic theory has shown that volcanoes are crucial features of the movement of the plates that form the Earth’s crust; most volcanoes are underwater, and the aboveground ones are almost always at the edge of a moving plate, such as the ‘Ring of Fire’ around the Pacific Rim. The volcano-rich Indonesian archipelago, home to Krakatoa and others, curves along the subduction zone where the Indo-Australian plate is dragged down beneath the Eurasian plate. Here the crust is weaker and molten material from the Earth’s mantle can bubble up.
In 79 A.D., the Roman Empire was thriving, and several towns bustled at the foot of Mount Vesuvius, cultivating the fertile soil there. As Peter Francis recounts in Volcanoes, it had not erupted for centuries previously and was presumed to be long dormant. A series of earthquakes beginning in 62 rattled walls, but no one thought they might portend the reawakening of the mountain. On August 24 in 79, the deadly eruption began; by the end of August 25, the destruction and burial of Pompeii, Herculaneum, and other nearby towns was complete. The only surviving eyewitness account was written by Pliny the Younger many years after the event, in a pair of letters to the historian Tacitus. The younger Pliny was 17 at the time, staying with his family at Misenum, across the Bay of Naples. Pliny first describes an ominous plume rising high into the sky, then spreading out laterally like a Mediterranean pine. His uncle, the admiral Pliny the Elder, wanted to sail over and take a closer look; as they prepared to leave, urgent pleas for help began to arrive and it became a rescue mission. As his ship approached the coast, the rain of ash and rock became too violent, and the crew was forced to make landfall south of Pompeii. There as night fell they observed the baleful eruption, with fires caused by falling pyroclasts lighting up the heavy ash-cloud red from below. By morning the rain of rock and ash was threatening their departure, and the dawn was so darkened they needed torches to light their way. Pliny’s shipmates made their way back to the shore, but the aged and overweight Pliny became unwell and had to lie down. He tried to join the rest, but rose and then fell dead. His companions later told the events to his nephew.
Back in Misenum, although upwind from the volcano, the sky darkened and tremors shook the ground. Pliny the Younger fled to the countryside with his mother, where progressively heavier ash clouds overwhelmed them and finally snuffed out the sun into total darkness, through which they could only hear the terrified screams of fellow evacuees. This lightless rain of ash continued for several hours until eventually, the sun began to peek through again. As Peter Francis writes, “where once the smooth cone of Vesuvius had risen, only an awful stump now remained…there now stretched an unbroken grey carpet of ash, mantling everything as uniformly as a dirty snowfall. Amidst it all, not a bird or an insect stirred.”
Many of the 20,000 or so residents of Pompeii and Herculaneum apparently had time to flee; the blanket of hardened ash many meters thick preserved the structures in a perfect time capsule, with food still on the table and tasks half-finished. Those who were unable to leave or who tried to return perished horribly. Around a thousand impressions of contorted bodies have been excavated in Pompeii so far, the organic remains having decomposed but the petrified ash forming perfect empty molds, from which casts can be made. Pompeii was farther away but directly downwind from the ash-fall; Herculaneum was leeward but closer, and thus many of its residents were incinerated in the radius of a gale-force blast wave of superheated ash and gas. Some 300 carbonized bodies have been recovered from boathouses on what would have been the shoreline at the time.
Both towns were forgotten as the Roman Empire fell and the Dark Ages began; later eruptions buried them even deeper. Evidence of Pompeii, at last, came to light in 1595 during the digging of an aqueduct. In the 16th and 17th centuries, looters and treasure hunters dug pits haphazardly looking for bronzes, coins, jewelry, and other valuables, with no idea of historic preservation. Nascent archaeological method arrived in the 19th century with Guiseppe Fiorelli, who mapped out the streets and dug stratigraphic layers carefully from the top down to preserve the structures beneath, as well as pioneering the method of injecting plaster into the human-shaped molds. Frescoes and mosaics were still stripped and carted off to Naples, but eventually, a large portion of the town was excavated which in recent years has become a popular tourist destination and a UNESCO World Heritage site, where visitors can duck in and out of ancient Roman houses in the shadow of the ragged summit of Vesuvius.
In 1883 Krakatoa was a forested island cluster with three volcanic peaks, rising from the Sunda Strait between Java and Sumatra (west of Java, contrary to the geographically challenged 1968 disaster movie Krakatoa, East of Java). A series of eruptions began in May, periodically expelling smoke and ash clouds high into the sky with heavy rumbling. Simon Winchester notes that tourists crowded onto steamships from Batavia (now Jakarta) in the months leading up to the cataclysm to steam over and take a closer look. Many among the Javanese locals thought the volcanic activity a distressing omen that the fiery spirit of the mountain was displeased.
On August 26th, a series of earth-shaking explosions began sounding regularly, along with an ominous black vent rising some 20 miles into the atmosphere. Nearby ships in the strait reported artillery-like thunder, smoky clouds with eerie sheet lightning, and a ceaseless rain of pumice and ash that had to be shoveled off the decks. Things seemed to quiet down a little in the early hours of the 27th, but then came four titanic blasts of doom as the mountain met its end, the most ear-shattering one at 10:02 a.m.as noted on instruments and barometers around the world. Still, the loudest sound ever recorded, it traveled around the world several times and was heard distinctly in parts of Australia and India over 3,000 miles away. The big eruption had four times the destructive force of the most powerful thermonuclear bomb ever exploded and launched six cubic miles of earth into the sky.
All was darkness and chaos on the islands, but the worst was yet to come; as the mountain broke and slumped into the sea, a series of gigantic tsunami waves began radiating outwards, reaching heights of 100 feet by the time they slammed into the shores and demolished coastal villages. Almost all of Krakatoa’s reported 36,000 casualties were caused by these tsunamis, which swept away structures and drove large steamships at anchor far into the inland jungle. It took months to sort out the damage and the timeline of events, but just hours for the recently established Reuters news service in Batavia to cable the news via undersea telegraph lines to the home office in London, where newspaper readers the next day could read hair-raising accounts of the volcanic eruption with their morning tea.
The drifting haze of ash and dust lowered temperatures around the world for several years and caused strange atmospheric effects, like blue-tinted suns and fantastical sunsets. Edvard Munch was struck by the phantasmagoric skies over Oslo in 1883, and ten years later depicted them in the swirling colors of his iconic painting The Scream. Krakatoa’s aftereffects inspired novels like M.P. Shiel’s 1901 sci-fi classic The Purple Cloud, and verse by many poets including Tennyson, in “St. Telemachus”:
Had the fierce ashes of some fiery peak
Been hurl’d so high they ranged about the globe?
For day by day, thro’ many a blood-red eve,
In that four-hundredth summer after Christ,
The wrathful sunset glared against a cross...
Could a volcano erupt from beneath our own city streets, like the one in the 1997 blockbuster film Volcano? Los Angeles has been destroyed repeatedly in the movies by everything from giant ants to earthquakes, aliens, tidal waves, very tall women (Attack of the 50 Foot Woman, 1958), diseases, zombies from space, and of course, sharknadoes. In Volcano, lava erupts and a cinder cone grows from beneath the La Brea Tar Pits; hardworking crisis manager Tommy Lee Jones saves the day with the help of Anne Heche and Don Cheadle by diverting the lava flow into a concrete storm drain to the Pacific. Fans of local 90s minutiae will enjoy the billboard of Angelyne toppling from the roof of an apartment building, and one of filmmaker Dennis Woodruff’s over-decorated station wagons melting in a pool of magma. The screenwriters took inspiration from the rapid formation in 1943 of the Parícutin volcano in Michoacán, which began as a sulfurous fissure in a flat cornfield and grew into a 1,400-foot summit, but few volcanologists today think the L.A. scenario likely. Our nearest volcanic area is the Coso Volcanic Field over a hundred miles north past Ridgecrest, which is estimated to have last erupted around 30,000 years ago, although it is now used to produce geothermal power.
Perhaps more troubling is the possibility of a Yellowstone supervolcano. In the 1970s, a field of prehistoric camelid and rhinoceros fossils was discovered in Nebraska, preserved in volcanic ash—but there was no volcanic crater nearby. It took geologists many years and large-scale observations that to realize that the bubbling geysers of Yellowstone National Park are in fact the center of a massive caldera formed by an ancient supervolcano, fueled by a magma hotspot that has been migrating slowly across what is now Idaho and Wyoming for millions of years. That would be a volcano big enough to wipe out everything in at least a thousand-mile radius, rating an 8 or above on the VEI or Volcanic Explosivity Index; Krakatoa had a VEI of 6, Vesuvius was a 5. It’s a logarithmic index, so this would not just be a bigger volcano, it would be a volcano that makes Krakatoa look like a science fair project with vinegar and baking soda. Experts are divided on whether we are overdue for the next Yellowstone eruption, which seems to go off every 700,000 years or so. Let’s just hope Tommy Lee Jones is still around when it does.
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