Earth's restless crust has buried cities, raised new islands and taught scientists how the planet works. These stories visit volcanoes and earthquakes on Earth and beyond, correct a few stubborn myths, meet the people who learned to measure the shaking, and revisit famous disasters with respect for the lives they took.
Every tile in a Volcanoes and Earthquakes game carries one of these. Open one to read it now, or leave them for the board to hand you.
Volcanoes
nine stories
1The lighthouse of the Mediterranean
On the tile: StromboliSince antiquity
Most eruptions are brief. Of 3,211 historical eruptions studied by Smithsonian volcanologists Tom Simkin and Lee Siebert, 83 percent were over within a year. Then there is Stromboli, an island volcano north of Sicily that has apparently been erupting almost continuously for more than 2,400 years. Several small gas explosions each hour toss glowing cinders tens or hundreds of feet into the air, a show that Greek and Roman sailors knew as the lighthouse of the Mediterranean. Volcanologists now call that style of eruption Strombolian, after the island.
The word volcano comes from a small island, Vulcano, the southernmost of the Aeolian Islands north of Sicily. In Roman myth, Vulcan, the god of fire who forged the weapons of the gods, lived inside it, and the glow of its eruptions came from his forges. The word passed through Italian into English by the 1610s. The island later lent its name to a second term. Its eruption of 1888 to 1890 became the model for Vulcanian eruptions: intermittent explosions that hurl blocks, bombs and ash.
Measured from the deep ocean floor, Hawaii's Mauna Kea stands nearly 33,500 feet tall, well above the 29,029 feet that Mount Everest rises above sea level. Its neighbor Mauna Loa is not quite as tall but is much larger in volume, and the USGS calls it the largest active volcano on the planet. Mauna Loa is so massive that its weight has pressed the seafloor beneath it down about 5 miles. Count that sag, and its summit stands about 10.5 miles above its true base, most of the mountain hidden under water and rock.
Volcanologists around the world describe lava flows in Hawaiian. Smooth, billowy or ropy lava is pāhoehoe, pronounced pah-hoy-hoy. Rough, jagged, clinkery lava is ʻaʻā, pronounced ah-ah. The two words entered the scientific literature in the late 19th century and are now used worldwide, including for flows at Craters of the Moon in Idaho. Pāhoehoe appears related to hoe, to paddle, perhaps for the swirls a paddle leaves in water, while ʻaʻā likely relates to the Hawaiian word for fire. The two can share the same chemistry; temperature and viscosity make the difference.
When gas bubbles burst at the surface of fluid lava, they can stretch the molten skin into threads that cool into golden volcanic glass. The strands are named for Pele, the Hawaiian volcano deity, and can be more than 3 feet long while often thinner than a millimeter. Winds carry them downwind; near Kīlauea's summit they have piled up against curbs and draped ʻōhiʻa trees like tinsel on a Christmas tree. Birds use them too. A nest made of Pele's hair, perhaps built by an ʻapapane, is in the museum collection at Hawaiʻi Volcanoes National Park.
On November 14, 1963, an eruption burst through the sea off Iceland's south coast, and over three and a half years it built a new island, Surtsey, named for a fire giant of Norse myth. In 1965, Iceland made it a nature reserve for scientists only, so they could watch life arrive on its own, and visitors may not bring seeds. Even so, tomato plants once sprouted there, which one researcher blamed on a careless restroom break, and in 1977 boys from the nearby Westman Islands rowed over and planted potatoes. Both were dug up immediately.
In March 1979, Linda Morabito, an astronomer on NASA's Voyager navigation team, was not looking for volcanoes. She was processing a Voyager 1 picture of Jupiter's moon Io, stretching its contrast to bring out a faint background star, part of low-priority work to refine the orbits of Jupiter's moons. Instead, something odd appeared off Io's edge. It was a volcanic plume, the first evidence of active volcanism seen beyond Earth. A week earlier, three scientists had predicted in the journal Science that tidal heating had likely melted much of Io. NASA now calls Io the most volcanically active world in the solar system.
A popular claim says Yellowstone has a giant eruption every 600,000 years and, since the last one was 631,000 years ago, is overdue. USGS geophysicist Michael Poland, writing as head of the Yellowstone Volcano Observatory, answered, "In three words, not even close." Yellowstone's three huge explosions came about 2.08 million, 1.3 million and 631,000 years ago, an average spacing of about 725,000 years, and an average of just two gaps means little anyway. Volcanoes erupt when enough magma and pressure build up, not on a schedule. Yellowstone's most recent eruption was a lava flow 70,000 years ago.
In 2012, the New Zealand ship HMNZS Canterbury, bound for Raoul Island, heard that a patrol plane had spotted open ocean covered with floating pumice. Soon the ship was sailing through it. The raft was up to two feet thick and, wrote science writer Rebecca Priestley from aboard, "extended sideways as far as the eye could see." No one knew where it came from until earthquake records and satellite images traced it to Havre, an undersea volcano that had erupted that July from more than half a mile down. Researchers later called it the largest deep-ocean eruption in history.
Seismometers left by Apollo astronauts revealed that the Moon has quakes of its own. Some start hundreds of miles down, set off by Earth's gravity tugging and stretching the Moon's interior. Others come from meteoroid impacts, or from rock expanding and contracting as the surface swings between frigid night and very hot day. Another kind, 20 to 30 kilometers down, can reach magnitude 5.5 and last more than 10 minutes. Its cause is surprising: the Moon is shrinking as it cools, and its diameter has shrunk by about 150 feet over the last several hundred million years.
The belief in earthquake weather goes back to Aristotle, who proposed in the 4th century BC that earthquakes were caused by winds trapped in underground caves. With so much air bottled up below, the reasoning went, the weather above would be hot and calm before a quake. The USGS says there is no such thing as earthquake weather. Quakes begin miles below the reach of weather and are spread about equally across cold, hot and rainy days. Each region's earthquake weather is simply whatever it had during its most memorable quake.
California is not going to fall into the ocean. As the USGS explains, the ocean is not a great hole for California to fall into; it is land at a lower elevation with water on top. The real motion is sideways. Along the San Andreas Fault system, the Pacific Plate slides northwest past the North American Plate about two inches a year, roughly the rate fingernails grow. At that pace, Los Angeles and San Francisco will be next-door neighbors in about 15 million years, and some 70 million years after that, Los Angeles would reach Alaska.
Big earthquakes can change the length of a day. By rearranging Earth's mass, the magnitude 9.0 Japan earthquake of March 11, 2011, should have made the planet spin a little faster. NASA scientist Richard Gross first calculated that the day grew shorter by about 1.8 microseconds, then, using an updated model of the fault, revised it to about 1.4. By his estimate, the 2004 Sumatra earthquake took off 6.8 microseconds. Nobody could feel it: a microsecond is a millionth of a second. By his calculations, the Japan quake also shifted the axis around which Earth's mass is balanced by several inches.
When seismic waves from a big earthquake pass through, water in rivers, reservoirs, ponds and lakes can rock back and forth in standing waves called seismic seiches. After the great Alaska earthquake of 1964, seiches were recorded at more than 850 water-gauging stations across North America and at four in Australia. They were most common in states bordering the Gulf of Mexico, where waves as high as 6 feet were reported. The effect was noticed long before. After the Lisbon earthquake of November 1755, a Scottish magazine described seiches in Loch Lomond, Loch Ness and other lochs.
Sheet lightning, balls of light, streamers and steady glows have all been reported around earthquakes, and geophysicists still disagree about how many reports are genuine; some turned out to be power lines arcing as they shook. From 1965 to 1967, a swarm of hundreds of thousands of small earthquakes struck Matsushiro, in central Japan. There a local dentist, Toru Kuribayashi, took the first known photographs of earthquake lights. One glow, shot with a fish-eye lens in September 1966, lasted 96 seconds. Researchers say the processes behind such lights remain largely unexplained.
On June 16, 1964, an earthquake of about magnitude 7.5 struck Niigata, Japan. Destruction was largely limited to buildings standing on loose, water-soaked soil. Near the Shinano River, the ground beneath a group of apartment buildings liquefied, lost its ability to hold them up, and the buildings tilted severely. The strange part was the buildings themselves: despite the extreme tilting, they suffered remarkably little structural damage. The ground had failed, not the structures. Niigata, together with the Alaska earthquake of the same year, brought liquefaction and its effects to the attention of engineers and seismologists.
In the 1960s, fluid wastes pumped deep beneath the Rocky Mountain Arsenal near Denver triggered earthquakes. That raised a bold question: if fluid pressure could start earthquakes, could scientists control them? Beginning in 1969, researchers tried it at an oil field in Rangely, Colorado, where water injected to recover oil had raised the pressure along a fault and small quakes clustered there. By alternately injecting water and pumping it back out, they varied the fluid pressure, and earthquake activity varied with it. They concluded that earthquakes can be controlled wherever the fluid pressure in a fault zone can be.
Tsunamis are often called tidal waves, but scientists avoid the term, because tsunamis have nothing to do with tides, which come from the gravitational pull of the Moon and Sun. A tsunami is set off by a large earthquake near or under the ocean, a volcanic eruption, or a landslide into or beneath the sea. The word, pronounced soo-NAH-mee, comes from Japanese characters meaning harbor wave. In deep water, tsunami waves may travel as fast as jet planes and go unnoticed, slowing down only as they reach shallow water.
In AD 132, the Chinese scholar Zhang Heng built what the USGS calls the earliest seismoscope. It was a large urn ringed by eight dragon heads facing the principal directions of the compass. Below each dragon sat a toad with its mouth open. When an earthquake struck, a dragon released a ball into the toad beneath it, and the direction of the shaking determined which dragon let go. The instrument is reported to have detected an earthquake 400 miles away that was not felt where it stood. What was inside is unknown; most guesses involve a pendulum.
John Milne, an English geologist, reportedly suffered so badly from seasickness that in the 1870s he traveled to a teaching post in Japan overland, a long trek across Europe and Asia that included crossing Mongolia by camel. After an earthquake struck Yokohama on February 22, 1880, he spurred British and Japanese colleagues to form the Seismological Society of Japan, the first organization devoted solely to earthquakes and volcanoes. Known as Earthquake Milne, he later set up an observatory on England's Isle of Wight and linked stations around the world, the beginnings of today's global seismograph network.
Charles Richter took his idea from astronomy. Developed in 1935 at the Seismological Laboratory in Pasadena with Beno Gutenberg, his earthquake scale was modeled on the stellar magnitude scale for star brightness, a logarithm that turns hugely varying values into easy single-digit numbers. It was built for southern California earthquakes: one 100 kilometers away that made a one-millimeter trace on the Caltech seismometer was defined as magnitude 3. As stations spread worldwide, the method proved valid only for certain distances and frequencies, and for very large earthquakes seismologists now rely on moment magnitude.
An earthquake has one magnitude, but its intensity depends on where you are. Magnitude is based on seismic records; intensity describes the shaking and damage actually experienced at a particular place. In the United States, intensity is rated on the Modified Mercalli scale, developed in 1931 by American seismologists Harry Wood and Frank Neumann and written in Roman numerals, from imperceptible shaking to catastrophic destruction. The lower numbers depend on how people felt the quake. The USGS website Did You Feel It? collects reports from people who felt an earthquake and turns them into maps of what they experienced.
5The seismologist who found a core within the core
On the tile: Inge Lehmann1936
If Earth had only a mantle and a liquid core, some earthquake waves should never reach certain shadow zones on the far side of the planet. Yet newer seismographs kept detecting faint ones there, and many geophysicists treated them as errors. After a massive New Zealand earthquake in 1929 made them hard to dismiss, Danish seismologist Inge Lehmann proposed an answer: an inner core within the liquid one, where the waves travel faster. She published it in September 1936 in a paper titled simply P′. Later work showed that inner core is solid. Lehmann lived to 104 and won the Bowie Medal, the American Geophysical Union's highest honor.
The father of continental drift was an astronomer turned meteorologist. Alfred Wegener studied the upper air with kites and balloons, and in 1906 he and his brother Kurt set a world endurance record by staying aloft in a balloon for more than 52 hours. On January 6, 1912, he startled a geological meeting in Frankfurt by arguing that the continents had moved. Most geologists came to dismiss it as mere geopoetry. Wegener died on the Greenland ice sheet during an expedition in 1930. Plate tectonics later showed he was right in most of his major concepts.
Croatian scientist Andrija Mohorovičić began his career studying weather. In 1909 his new seismographs recorded the Kupa Valley earthquake of October 8, and by analyzing those records with seismograms from across Europe, he proved there is a boundary between Earth's crust and mantle, now called the Moho. Project Mohole was launched to drill a hole to it, and its first test drilling came in 1961 from the CUSS I, a converted Navy barge that John Steinbeck said had the "sleek race lines of an outhouse standing on a garbage scow." The project was canceled in 1966 for lack of funding.
During World War II, Princeton geology professor Harry Hess commanded the assault transport Cape Johnson in the Pacific. Between battles in the Marianas, Leyte and Iwo Jima, he and his crew ran echo-sounding surveys of the ocean floor. His research led to a landmark 1962 paper, History of Ocean Basins: molten rock rises along mid-ocean ridges, forms new seafloor, and spreads toward deep trenches, where old crust sinks. That solved the problem that had plagued Wegener's continental drift: continents did not plow through the ocean floor but rode along with it. Unlike Wegener, Hess lived to see his idea largely accepted.
Nuclear test-ban talks in 1958 led a U.S. panel to study how to detect and identify underground nuclear explosions. One recommendation was standardized seismographs, with accurate clocks, at 100 to 200 existing stations. The first system of the new World-Wide Standardized Seismograph Network went in at Albuquerque in October 1961, and more than 100 more followed by 1967. The network was not meant for surveillance of nuclear tests; its role was to supply data for basic research in seismology. The research paid off: data from the network played a pivotal role in developing plate tectonics in the 1960s.
The eruption of Vesuvius that buried Pompeii is traditionally dated to August 24, AD 79. That date comes from the only eyewitness account known to survive, letters by Pliny the Younger, but his words reached us through centuries of hand-copied manuscripts, and a few copies point to a date in the fall. Fall fruits found at Pompeii, such as pomegranates, figs and walnuts, and a charcoal inscription uncovered in 2018 that refers to an October date fed the doubts. Then tests showed charcoal writing lasts longer than thought, and the Pompeii park now calls every other date pure invention.
On November 1, 1755, All Saints' Day, an earthquake struck Lisbon. Within the hour a tsunami swept the waterfront, and fires grew into a five-day firestorm. Afterward, the minister of state later known as the Marquis of Pombal sent a questionnaire, through the bishops, to every parish in Portugal, asking when the shaking began, how long it lasted, and whether anything odd happened at sea or in rivers and springs. Strikingly for its time, it made no mention of God. Centuries later geophysicist Maria Ana Baptista used the replies to model how the tsunami swamped Lisbon.
In the summer of 1783, a dry, sulfur-smelling fog hung over Europe for months, and the sun rose and set blood red. Benjamin Franklin suggested it might have come from Iceland's famous volcano Hekla or a new island rising off Iceland, though in the same paragraph he also floated "great burning balls," meaning meteors. The real source was Laki, a 17-mile line of vents in Iceland's highlands that erupted for eight months. In Iceland the toll was grave: half the livestock died after eating grass tainted with fluorine, and 20 percent of the people starved in the famine that followed.
At 10:02 a.m. on August 27, 1883, the biggest explosion of Krakatoa's eruption, between Java and Sumatra, made a sound heard about 3,000 miles away on the Indian Ocean island of Rodrigues. It arrived roughly four hours later, "like the distant roar of heavy guns." Even after it faded below hearing, the pressure wave kept going. For as many as five days, barometers in 50 cities around the globe recorded it returning about every 34 hours as it circled the planet three to four times in each direction. The eruption and the tsunami it created killed more than 36,000 people.
At 8:02 a.m. on May 8, 1902, a ground-hugging cloud of glowing volcanic particles and searing gas swept down Mount Pelée on Martinique and reached the city of Saint-Pierre at hurricane speed. Almost everyone in the city, about 26,000 people, died, and some counts of the eruption's toll exceed 29,000. Only two people within the city are known to have survived. The devastation moved Thomas Jaggar, a 31-year-old Harvard instructor sent to study the aftermath, to devote his life to protecting people through science. In 1912 he founded the Hawaiian Volcano Observatory, the first in the United States.
The USGS calls the name San Francisco earthquake somewhat misleading. The quake that broke loose just after 5:12 a.m. on April 18, 1906, ruptured 296 miles of the San Andreas Fault, and shaking damage was just as severe in many other places along it. The city's name stuck because of the fire that followed. The often quoted toll of 700 deaths is now believed to be three or four times too low. Studying how the ground had shifted, geologist H. F. Reid devised elastic rebound theory, still the principal model of the earthquake cycle.
At 11:58 a.m. on September 1, 1923, an earthquake of estimated magnitude 7.9 struck Tokyo and the surrounding Kanto region. Because it hit at lunchtime, when people were cooking over fires, many fires broke out and spread into huge blazes. About 105,000 people died or went missing, most of them in the fires. Japan has not forgotten the date. The Cabinet designated September 1 as Disaster Preparedness Day, and every year during the week around it, drills, including the national government's comprehensive disaster management drill, are held in many places.
On May 22, 1960, José Argomedo, a farmer outside Maullín, Chile, was riding his horse when the ground began to shake. With the Cold War near its height, he first thought a nuclear war had begun. It was the start of a magnitude 9.5 earthquake, the largest ever instrumentally recorded. Its tsunami crossed the Pacific, killing 61 people in Hawaii and reaching Japan's coast almost a day after the quake. Deaths in Chile are uncertain, with estimates from 490 to 5,700. The disaster led to the creation of the Pacific Tsunami Warning and Mitigation System in 1965.
Mount St. Helens did not simply blow its top on May 18, 1980. At 8:32 a.m., a magnitude 5.1 earthquake struck, and within seconds the volcano's bulging north side and summit slid away in the largest debris avalanche on Earth in recorded history, about 2.5 cubic kilometers of rock. With the pressure inside suddenly released, the volcano blasted sideways through the gap. Fifty-seven people died. Among them was USGS volcanologist David Johnston, 30, who was watching the mountain from an observation post called Coldwater II. It has since been renamed Johnston Ridge in his honor.