When it struck early last Tuesday in the Gulf of Alaska, a magnitude 7.9 earthquake caused a small tsunami, triggering middle-of-the-night alerts along shores from British Columbia through California and sending residents fleeing to high ground and huddling in shelters. It was the U.S.’s biggest quake of the year so far, at a time when geologists say the Earth may be primed for more. By the time the waves arrived on land, however, they never reached more than three to eight inches, leading to some confusion among those who received alerts and those who didn’t.
But no alerts were sent to the typically tranquil Devil’s Hole, a shallow, 18-foot-long pool in Death Valley National Park, which straddles California and Nevada. A few minutes after the quake began, the water at Devil’s Hole began sloshing around. Along the western coast of the United States, the tsunami’s waves were pathetic; here, 1,800 miles from the epicenter, the waves reached over a foot tall, park rangers said.
Within an hour of the quake, groundwater 3,500 miles away in Fort Lauderdale yo-yoed by up to an inch and a half. Up the coast in Florida’s marshy Big Bend, water levels rose two inches in wells in Madison.
Back at Devil’s Hole, watchful park rangers noticed something else as the waves dissipated: The pool’s most famous inhabitants, a group of critically endangered desert pupfish, appeared to be spawning out of season. One telltale sign: the males glow an iridescent blue.
Pupfish spawning typically happens in the spring and fall, but it can also occur when their habitat is disturbed. In this case the culprit wasn’t a tsunami but what hydrologists call a seiche: when a standing wave appears on a river, reservoir, pond, or lake, as a result of strong winds, changes in air pressure, or, in this case, seismic waves from an earthquake passing through the ground.
“It’s crazy that distant earthquakes affect Devils Hole,” said Kevin Wilson, Aquatic Ecologist for Death Valley National Park in a statement. “We’ve seen this a few times before, but it still amazes me.”
When a seiche (pronounced say-ch) hit Devil’s Hole following an earthquake in Qaxaca, Mexico, in 2012, that, too, triggered a spawning event among the pupfish. “Environmental disaster, it seems, acted as an aphrodisiac,” Peter Byrne wrote in Scientific American. (It also spawned a viral video, below.)
With a population at last census of 115 fish, the Devil’s Hole pupfish, or Cyprinodon diabolis, are considered by some to be the world’s rarest fish. Devil’s Hole is their only natural habitat, and is the tiniest habitat of any endangered vertebrate species. For thousands of years the fish have relied on the pool’s steady oxygen concentrations and a constant temperature of 93 degrees Fahrenheit.
Their population had long hovered around 400 to 600 fish, until water levels in the pool dropped due to nearby irrigation (the pool is fed by the Nevada aquifer). After the pupfish became one of the first fish to be protected by the U.S. Endangered Species Act in 1973, local landowners, complaining that the protection curtailed their right to draw water, appealed all the way to the Supreme Court. The justices upheld the government’s water rights, and the pupfish won.
The fish are up against weirder threats, too: In 2016, three men broke into the protected Devil’s Hole area, waded into the water, vomited near it, destroyed scientific equipment, sprayed gunfire, and killed a pupfish. Last week, two of the intruders pleaded guilty to violating the Endangered Species Act and now face a maximum penalty of one year in prison and/or a fine of up to $50,000.
The earthquake-induced spawn will be a temporary boon to the pupfish’s fluctuating population (in 2006 there were only 28 of them), but the seiche may have also temporarily disturbed a key part of their diet: the algae that grows on a shallow sunlit shelf at the top of Devils Hole. “The pupfish’s food source will probably be a little reduced for a bit, but it is expected to rebound,” said Ambre Chaudoin, a Biological Science Technician at Death Valley.
A seiche like the one at Devil’s Hole can occur in any enclosed body of liquid, including your bathtub or your coffee cup. As the liquid’s waves hit the edges of that body, they bounce backwards; as they do they can interfere with other incoming waves, producing an even larger wave, and so on. Bigger seiches can happen on lakes that are vulnerable to strong winds, like Lake Erie. It was there, in 1848, that a 22-foot seiche reportedly breached water defense walls, created an ice dam that temporarily stopped water flowing over Niagara Falls, and killed 78 people.
Last week’s earthquake, about 175 miles off the coast, happened in the Alaska subduction zone, part of the Ring of Fire that marks where the Pacific ocean plates are sliding into continental crust, and a place that’s no stranger to massive quakes: In 1964, Alaska was also the site of the most powerful quake in recorded American history, a 9.2 megathrust earthquake that caused about 139 deaths.The Ring of Fire is home to 90 % of the world’s earthquakes, and recent weeks have seemed particularly active, especially if you follow the all-caps headlines and news alerts.
We may be entering a particularly harsh period, seismically speaking. The reason may have to do with a periodic slowing of the Earth’s rotation, according to a recent study of earthquake data published in Geophysical Research Letters by Roger Bilham and Rebecca Bendick. It turns out more sloshing is involved here: The Earth’s 1,200-mile thick outer core, composed mostly of liquid iron and nickel, tends to slosh about, and like water in a bucket, these oscillations slightly change the planet’s rate of spin, which adds to or subtracts from the 24-hour day by about a millisecond and sends more energy outwards toward the crust, meaning more seismic activity, especially around the equator, they hypothesize.
While geologists say the recent seismic hubbub isn’t out of the ordinary, they aren’t in agreement about how, or even if any, of these events are related. Some say one event can trigger another—but as researchers in Mexico observed last year after a pair of earthquakes two weeks apart, it’s still hard to know. Better instrumentation and wider deployments of seismic sensors are helping researchers keep a literal ear to the ground as they seek to better understand how quakes behave and to better warn people.
In the U.S. some of that research is being devoted to the next Big One. To Californians, that would be a rupture of the legendary San Andreas Fault, along which a string of small earthquakes have occurred in recent weeks. To Pacific Northwesterners, the Big One is what the headline of Kathryn Schulz’s Pulitzer-winning New Yorker piece called “the very Big One“: the 9.0 magnitude megathrust earthquake that’s expected along the Cascadia Subduction Zone, a 620-mile-long fault that stretches from northern Vancouver Island to Cape Mendocino, California. (It’s an area that recent audits have said is unprepared for earthquakes and tsunamis.) With an estimated impact of 7 million people across a region of 140,000 square miles, this would be “the worst natural disaster in the history of North America.”
See more photos of the Devil’s Hole pupfish at the National Parks Conservation Association.