Just beyond the tip of the Antarctic Peninsula lies an iceberg graveyard.

There, in the Scotia Sea, many of the icebergs escaping from Antarctica begin to melt, depositing sediment from the continent that had been trapped in the ice onto the seafloor. Now, a team of researchers has embarked on a two-month expedition to excavate the deposited debris, hoping to discover secrets from the southernmost continent’s climatic past.

That hitchhiking sediment, the researchers say, can help piece together how Antarctica’s vast ice sheet has waxed and waned over millennia. And knowing how much the ice melted in some of those warmest periods, such as the Pliocene Epoch about 3 million years ago, may provide clues to the ice sheet’s future. That includes how quickly the ice may melt in today’s warming world and by how much, says paleoclimatologist Michael Weber of the University of Bonn in Germany.
Weber and Maureen Raymo, a paleoclimatologist at Lamont-Doherty Earth Observatory in Palisades, N.Y., are leading the expedition, which set sail on March 25.

“By looking at material carried by icebergs that calved off of the continent, we should be able to infer which sectors of the ice sheet were most unstable in the past,” Raymo says. “We can correlate the age and mineralogy of the ice-rafted debris to the bedrock in the section of Antarctica from which the bergs originated.”
Icebergs breaking off from the edges of Antarctica’s ice sheet tend to stay close to the continent, floating counterclockwise around the continent. But when the bergs reach the Weddell Sea, on the eastern side of the peninsula, they are shunted northward through a region known as Iceberg Alley toward warmer waters in the Scotia Sea.

Because so many icebergs from all around the continent converge in one region, it is the ideal place to collect sediment cores and take stock of the debris that the bergs have dropped over millions of years.

“That area in the Scotia Sea is so exciting, because it’s a focus point between South America and the Antarctic Peninsula where the currents flow through, and there are a lot of icebergs,” says Gerhard Kuhn, a marine geologist at the Alfred Wegener Institute in Bremerhaven, Germany. “You get a picture of more or less [all of] Antarctica in that area,” says Kuhn, who has studied the region but is not aboard the current cruise.
The expedition, known as leg 382 of the International Ocean Discovery Program, plans to drill at six different sites in the Scotia Sea. At three sites, the team plans to penetrate about 600 meters into the seafloor. “That would likely bring us back to the mid-Miocene, which could translate into 12 million to 18 million years back in time,” Weber says.

At another site, the team plans to drill even deeper, 900 meters, to go further back in time, in hopes of finding sediments that date to the opening of the Drake Passage about 41 million years ago. That passage, a body of water that now lies between South America and Antarctica, opened a link between the Atlantic and Pacific oceans and may have played a role in building up Antarctica’s ice sheets at different times in its history.

A graveyard turned crystal ball
How much a melting Antarctica might have contributed to global sea-level rise following the last great ice age, which ended about 19,000 years ago, has been a subject of debate. Seas rose by about 130 meters from 19,000 to 8,000 years ago, Weber says, and much of the melting happened in the northern hemisphere.

But Antarctica may have played a larger role than once thought. In a study published in Nature in 2014, Kuhn, Weber and other colleagues reported that ice-rafted debris from that time period, as recorded in relatively short sediment cores from Iceberg Alley, often occurred in large pulses lasting a few centuries to millennia. Those data suggested that the southernmost continent was shedding lots of bergs much more quickly during those times than once thought.

Now, the researchers want to see even further into the past, to understand how quickly Antarctica’s ice sheet might have melted during even warmer periods, and how much it may have contributed to episodes of past sea-level rise.

The new drilling expedition targets several periods when the climate is thought to have warmed dramatically. One is a warm period in the middle Pliocene about 3.3 million to 3 million years ago, when average global temperatures were 2 to 3 degrees warmer than today; another is the ending of an older ice age about 130,000 years ago, when sea levels rose by about 5 to 9 meters.

Such periods may serve as analogs to the continent’s future behavior due to anthropogenic global warming. Currently, global average temperatures on Earth are projected to increase by between about 1.5 degrees and 4 degrees Celsius relative to preindustrial times, depending on greenhouse gas emissions to the atmosphere over the next few decades (SN: 10/22/18, p. 18).

“The existing [ice core] record from Iceberg Alley taught us Antarctica lost ice through a threshold reaction,” Weber says. That means that when the continent reached a certain transition point, there was sudden and massive ice loss rather than just a slow, gradual melt.

“We have rather firm evidence that this threshold is passed once the ice sheet loses contact with the underlying ocean floor,” he says, adding that at that point, the shedding of ice becomes self-sustaining, and can go on for centuries. “With mounting evidence of recent ice-mass loss in many sectors of West Antarctica of a similar fashion, we need to be concerned that a new ice-mass loss event is already underway, and there is no stopping it.”

For 40 years, they’ve held the front line in Florida’s fight against mosquito-borne diseases. And it turns out that the chickens standing sentinel in cities, marshes, woodlands and residential backyards are clucking good at their job.

Last year, chickens in 268 coops in over a third of Florida’s counties provided scientists weekly blood samples that revealed whether the birds had been bitten by mosquitoes carrying West Nile virus or the Eastern equine encephalitis or St. Louis encephalitis viruses.
If a chicken’s blood tests positive for antibodies to one of those viruses, authorities know that the pathogen is circulating. And if enough birds have the antibodies, state officials can ratchet up mosquito-killing measures such as pesticide spraying to help halt disease spread.

The sentinel chicken surveillance programs are “a really good way of monitoring” for certain virus activity, says Thomas Unnasch, a biologist who studies vector-borne diseases at the University of South Florida in Tampa. The birds “are sampling literally hundreds or thousands of mosquitoes every day,” he says. (The chickens can’t keep tabs on dengue or Zika; the mosquitoes carrying those viruses prefer to bite people rather than birds.)
In 2018, 833 chickens tested positive for West Nile virus antibodies in Florida, but only 39 people did, according to data from the state’s health department. For Eastern equine encephalitis virus, 154 chickens tested positive in 2018, compared with only three people.
Chickens that test positive for the viruses being surveyed don’t transmit them, and people don’t either. Both are considered “dead-end hosts,” meaning that the viral concentration in the blood doesn’t get high enough to infect another mosquito after it bites. Infected cardinals, robins and other backyard birds are the animal reservoirs that help keep the three viruses spreading in the area.
Sentinel chickens, by detecting where and when disease-carrying mosquitoes are buzzing, are also providing valuable data on how a virus can spread. Data from 2005 to 2016 revealed that Eastern equine encephalitis virus is active year-round in the Florida panhandle, making the area a source from which the virus moves elsewhere in the state and along the eastern United States, Unnasch and his colleagues report online March 11 in the American Journal of Tropical Medicine and Hygiene.

In people, the viral diseases monitored by the chickens are relatively rare, but can be deadly. The chickens don’t get especially sick, though. “You don’t usually see any symptoms at all,” Unnasch says.

Any chicken whose blood tests positive for the antibodies is removed from the coops since that bird can no longer alert authorities to a new infection. For these chickens, retirement may be spent on a farm, with school or 4-H clubs, or in a backyard coop, depending on the county. The sentinel chicken programs are ready with replacements, raising chicks to supply new birds to signal “where we have a threat to human health,” Unnasch says.

This is what a black hole looks like.

A world-spanning network of telescopes called the Event Horizon Telescope zoomed in on the supermassive monster in the galaxy M87 to create this first-ever picture of a black hole.

“We have seen what we thought was unseeable. We have seen and taken a picture of a black hole,” Sheperd Doeleman, EHT Director and astrophysicist at the Harvard-Smithsonian Center for Astrophysics in Cambridge, Mass., said April 10 in Washington, D.C., at one of seven concurrent news conferences. The results were also published in six papers in the Astrophysical Journal Letters.

“We’ve been studying black holes so long, sometimes it’s easy to forget that none of us have actually seen one,” France Córdova, director of the National Science Foundation, said in the Washington, D.C., news conference. Seeing one “is a Herculean task,” she said.
That’s because black holes are notoriously hard to see. Their gravity is so extreme that nothing, not even light, can escape across the boundary at a black hole’s edge, known as the event horizon. But some black holes, especially supermassive ones dwelling in galaxies’ centers, stand out by voraciously accreting bright disks of gas and other material. The EHT image reveals the shadow of M87’s black hole on its accretion disk. Appearing as a fuzzy, asymmetrical ring, it unveils for the first time a dark abyss of one of the universe’s most mysterious objects.

“It’s been such a buildup,” Doeleman said. “It was just astonishment and wonder… to know that you’ve uncovered a part of the universe that was off limits to us.”

The much-anticipated big reveal of the image “lives up to the hype, that’s for sure,” says Yale University astrophysicist Priyamvada Natarajan, who is not on the EHT team. “It really brings home how fortunate we are as a species at this particular time, with the capacity of the human mind to comprehend the universe, to have built all the science and technology to make it happen.” (SN Online: 4/10/19)

The image aligns with expectations of what a black hole should look like based on Einstein’s general theory of relativity, which predicts how spacetime is warped by the extreme mass of a black hole. The picture is “one more strong piece of evidence supporting the existence of black holes. And that, of course, helps verify general relativity,” says physicist Clifford Will of the University of Florida in Gainesville who is not on the EHT team. “Being able to actually see this shadow and to detect it is a tremendous first step.”

Earlier studies have tested general relativity by looking at the motions of stars (SN: 8/18/18, p. 12) or gas clouds (SN: 11/24/18, p. 16) near a black hole, but never at its edge. “It’s as good as it gets,” Will says. Tiptoe any closer and you’d be inside the black hole — unable to report back on the results of any experiments.
“Black hole environments are a likely place where general relativity would break down,” says EHT team member Feryal Özel, an astrophysicist at the University of Arizona in Tucson. So testing general relativity in such extreme conditions could reveal deviations from Einstein’s predictions.

Just because this first image upholds general relativity “doesn’t mean general relativity is completely fine,” she says. Many physicists think that general relativity won’t be the last word on gravity because it’s incompatible with another essential physics theory, quantum mechanics, which describes physics on very small scales.
The image also provides a new measurement of the black hole’s size and heft. “Our mass determination by just directly looking at the shadow has helped resolve a longstanding controversy,” Sera Markoff, a theoretical astrophysicist at the University of Amsterdam, said in the Washington, D.C., news conference. Estimates made using different techniques have ranged between 3.5 billion and 7.22 billion times the mass of the sun. But the new EHT measurements show that its mass is about 6.5 billion solar masses.

The team has also determined the behemoth’s size — its diameter stretches 38 billion kilometers — and that the black hole spins clockwise. “M87 is a monster even by supermassive black hole standards,” Markoff said.

EHT trained its sights on both M87’s black hole and Sagittarius A, the supermassive black hole at the center of the Milky Way. But, it turns out, it was easier to image M87’s monster. That black hole is 55 million light-years from Earth in the constellation Virgo, about 2,000 times as far as Sgr A. But it’s also about 1,000 times as massive as the Milky Way’s giant, which weighs the equivalent of roughly 4 million suns. That extra heft nearly balances out M87’s distance. “The size in the sky is pretty darn similar,” says EHT team member Feryal Özel.
Due to its gravitational oomph, gases swirling around M87’s black hole move and vary in brightness more slowly than they do around the Milky Way’s. “During a single observation, Sgr A* doesn’t sit still, whereas M87 does,” says Özel, an astrophysicist at the University of Arizona in Tucson. “Just based on this ‘Does the black hole sit still and pose for me?’ point of view, we knew M87 would cooperate more.”

After more data analysis, the team hopes to solve some long-standing mysteries about black holes, such as how M87’s behemoth spews a bright jet of charged particles thousands of light-years into space.

This first image is like the “shot heard round the world” that kicked off the American Revolutionary War, says Harvard University astrophysicist Avi Loeb who isn’t on the EHT team. “It’s very significant; it gives a glimpse of what the future might hold, but it doesn’t give us all the information that we want.”
Hopes are still high for a much-anticipated glimpse of Sgr A*. The EHT team was able to collect some data on the Milky Way’s behemoth and are continuing to analyze that data, in the hopes of adding its image to the new black hole portrait gallery.

Since the appearance of that black hole changes so quickly, the team is having to develop new techniques to analyze the data. “We’re very excited to work on Sgr A*,” Daniel Marrone, an astrophysicist at the University of Arizona in Tucson, said in the Washington, D.C., news conference. “We’re doing that shortly. We’re not promising anything but we hope to get that very soon.”

Studying such different environments could reveal more details of how black holes behave, Loeb says. “The Milky Way is a very different galaxy from M87.”
The next look at the M87 and Milky Way behemoths will have to wait.

Scientists got a lucky stretch of good weather at all eight sites that made up the Event Horizon Telescope in 2017. Then bad weather in 2018 and technical difficulties, which cancelled the 2019 observing run, stymied the team.

The good news is that by 2020, there will be more observatories to work with. The Greenland Telescope joined the consortium in 2018, and the Kitt Peak National Observatory outside Tucson, Ariz., and the NOrthern Extended Millimeter Array (NOEMA) in the French Alps will join EHT in 2020.

Adding more telescopes could allow the team to extend the image, to better capture the jets that spew from the black hole. The researchers also plan to make observations using light of slightly higher frequency, which can further sharpen the image. And even bigger plans are on the horizon: “World domination is not enough for us; we also want to go to space,” Doeleman said.

These extra eyes may be just what’s needed to bring black holes into even greater focus.

Black holes have been beguiling from the very beginning.

Hinted at as early as the 1780s and predicted by Einstein’s general theory of relativity, they didn’t get the name we know today until the 1960s. Bizarre beasts that squash gobs of matter into infinitely dense abysses, black holes were once thought to be merely a mathematical curiosity.

But astronomers tallied up evidence for black holes’ existence bit by bit, puzzling over where these behemoths live, how they gulp down matter and what their existence means for other physics theories.

For more than a decade, a team of researchers has been engrossed in an ambitious effort to snap a picture of a black hole for the very first time. And now they’ve done it. What better time to think back to black holes’ origins and the journey so far?

WASHINGTON — In 2021, wildfires pillaged the world’s carbon-rich snow forests.

That year, burning boreal forests released 1.76 billion metric tons of carbon dioxide, researchers reported March 2 in a news conference at the annual meeting of the American Association for the Advancement of Science.

That’s a new record for the region, which stores about one-third of the world’s land-based carbon. “It’s also roughly double the emissions in that year from aviation,” said earth system scientist Steven Davis of the University of California, Irvine. The trend, if it continues, threatens to make fighting climate change even more difficult.
Boreal forests are part of the taiga, a vast region that necklaces the Earth just south of the Arctic Circle. Blazes in tropical forests like the Amazon tend to garner more attention for their potential to contribute large amounts of climate-warming gases to the atmosphere (SN: 9/28/17). But scientists estimate that on a per area basis, boreal forests store about twice as much carbon in their trees and soils as tropical forests.

Climate change is causing the taiga to warm about twice as fast as the global average. And wildfires are growing more widespread in the region, releasing more of the trapped carbon, which in turn can worsen climate change (SN: 5/19/21).

Davis and his colleagues analyzed satellite data on carbon emissions from boreal regions from 2000 to 2021. In 2021, emissions from boreal wildfires made up a whopping 23 percent of all the CO2 emitted by wildfires around the world, the researchers report in the March 3 Science. In contrast, CO2 emissions during an average year from 2000 to 2021 were about 10 percent.

The record-breaking emissions coincided with widespread heat waves and droughts in Siberia and northern Canada, probably fueled by human-caused climate change.

There’s no data yet to show if 2022 saw a similar surge in emissions. But, Davis said, “there’s not actually that much evidence that this record will stand for long.”

Full-grown snapping shrimp were already known to have some of the fastest claws under the waves. But it turns out they’re nothing compared with their kids.

Juvenile snapping shrimp produce the highest known underwater accelerations of any reusable body part, researchers report February 28 in the Journal of Experimental Biology. While the claws’ top speed isn’t terribly impressive, they go from zero to full throttle in record time.

To deter predators or competitors, snapping shrimp create shock waves with their powerful claws. The shrimp store energy in the flexing exoskeleton of their claw as it opens, latching it in place much like a bow-and-arrow mechanism, says Jacob Harrison, a biologist at Georgia Tech in Atlanta.
Firing the claw and releasing this elastic energy produces a speeding jet of water. Bubbles form behind it and promptly implode, liberating a huge amount of energy, momentarily flashing as hot as the sun and creating a deafening crack (SN: 10/3/01).

But it was unclear how early in their lives the shrimp could use this weaponry. “We knew that the snapping shrimp did this really impressive behavior,” Harrison says. “But we really didn’t know anything about how this mechanism developed.”

While a grad student at Duke University, Harrison and his adviser, biomechanist Sheila Patek, reared bigclaw snapping shrimp (Alpheus heterochaelis) from eggs in the laboratory. At 1 month old, the tiny shrimp — less than a centimeter long — began firing their claws when disturbed. The researchers took high-speed video footage of these snaps and calculated their speed.

The wee shrimp could create the collapsing bubbles just like adults. Despite being a tenth the adults’ size or smaller, the juveniles’ claws accelerated 20 times as fast when firing. This acceleration — about 600 kilometers per second per second — is on “the same order of magnitude as a 9-millimeter bullet leaving a gun,” Harrison says.
Dracula ants (Mystrium camillae) and some termites produce more explosive bites but aren’t pushing against water. The stinging cells of jellyfish launch their venomous harpoons about 100 times as fast, but their firing mechanism is inherently single use. Snapping shrimp, on the other hand, can fire their claws again and again.
The juveniles’ firing and bubble creation weren’t very reliable at the smallest sizes, but the shrimp routinely tried snapping anyway. The team wonders if the young shrimp could be practicing and training the necessary musculature.

If so, that training might ultimately be crucial to the claw’s function, says Kate Feller, a visual ecologist at Union College in Schenectady, N.Y., who studies similarly ultrafast mantis shrimp and was not involved in the new study. “If you were to somehow manipulate the claws so that they couldn’t properly close and they couldn’t snap,” she wonders, “would that affect their ability to develop these mechanisms?”

Understanding the storage of elastic energy in biological materials and how it flows through them is “tricky,” Harrison says. Figuring out how such tiny claws store so much energy without fracturing may help researchers illuminate this superpower.

A surprise ingredient may explain how lemon juice puts the squeeze on kidney stones.

Lemons contain nanoparticles that, when fed to rats, block stone formation, scientists report in the Feb. 22 Nano Letters. If the tiny sacs do the same for humans, the nanoparticles might one day offer a way to prevent kidney stones in people, says pharmaceutical scientist Hongzhi Qiao of Nanjing University of Chinese Medicine.

Lemon juice is a well-known home remedy for kidney stones, which form when minerals crystalize and clump up inside the kidney (SN: 9/21/18). These rocky lumps can knock around in the urinary tract, slicing and dicing tissues as they eventually pass out of the body (SN: 10/31/16). “It’s so, so, so painful,” says Jingyin Yan, a nephrologist at Baylor College of Medicine in Houston who was not part of the new study. Patients may feel sharp pain in their back, side or lower abdomen when they pass a stone, she says. “People describe it as worse than delivering a baby.”
Though some medications can help treat kidney stones, many people end up needing surgery to remove them, says Thomas Chi, a urologist at the University of California, San Francisco, also not part of the study. People often imagine kidney stones as tiny pebbles, but sometimes they bulk up like boulders, he adds. “I’ve taken out stones the size of your fist.”

That’s why prevention is key. Scientists already knew that citric acid, which gives lemons their sour power, may do the trick by binding to the minerals that make up stones. But drinking mouth-puckering lemon juice is not so comfortable for patients, Qiao says.

A 2022 clinical trial found that kidney stone patients had trouble downing 120 milliliters — about a half cup — of lemon juice per day. Swilling loads of lemonade can cause dental problems, too. Chi has had patients drink so much that the acidic liquid ate away at their teeth.

So Qiao and colleagues looked for other, more palatable lemon-derived ingredients that might help prevent kidney stones. Inside edible and medicinal plants like ginseng, grapefruit and dandelion, his team has found extracellular vesicle-like nanoparticles, tiny sacs stuffed with molecules including fat, protein and DNA.
These nanoparticles exist in lemon juice, too­­ — and the team fed them to rats that had also ingested a substance that promotes kidney stone growth. The zesty particles slowed stone formation, Qiao and colleagues found. The finding suggests these particles curb development of calcium oxalate crystals, the most common culprit of kidney stones. The particles can also soften the stones and make them less sticky, the team showed.

The new work challenges the conventional wisdom on how lemon juice works to combat kidney stones, Chi says. Using lemon nanoparticles to treat people is still a long way off, but the team’s results hold promise, he says. “The faster you can bring a finding like this towards a human clinical trial, the better.”

It took just a 9-volt battery and a little brain zapping to turn science writer Sally Adee into a stone-cold sharpshooter.

She had flown out to California to test an experimental DARPA technology that used electric jolts to speed soldiers’ sniper training. When the juice was flowing, Adee could tell. In a desert simulation that pit her against virtual bad guys, she hit every one.

“Getting my neurons slapped around by an electric field instantly sharpened my ability to focus,” Adee writes in her new book, We Are Electric. That brain-stimulating experience ignited her 10-year quest to understand how electricity and biology intertwine. And she’s not just talking neurons.
Bioelectricity, Adee makes the case, is a shockingly under­explored area of science that spans all parts of the body. Its story is one of missed opportunity, scientific threads exposed and abandoned, tantalizing clues and claims, “electroquacks” and unproven medical devices — and frogs. Oh so many frogs.

Adee takes us back to the 18th century lab of Luigi Galvani, an Italian scientist hunting for what gives animals the spark of life. His gruesome experiments on twitching frog legs offered proof that animal bodies generate their own electricity, an idea that was hotly debated at the time. (So many scientists repeated Galvani’s experiments, in fact, that Europe began to run out of frogs.)

But around the same time, Galvani critic Alessandro Volta, another Italian scientist, invented the electric battery. It was the kind of razzle-dazzle, history-shaking device that stole the spotlight from animal electricity, and the fledgling field fizzled. “The idea had been set,” Adee writes. “Electricity was not for biology. It was for machines, and telegraphs, and chemical reactions.”
It took decades for scientists to pick up Galvani’s experimental threads and get the study of bioelectricity back on track. Since then, we’ve learned just how much electricity orchestrates our lives, and how much more remains to be discovered. Electricity zips through our neurons, makes our hearts tick and flows in every cell of the body. We’re made up of 40 trillion tiny rechargeable batteries, Adee writes.

She describes how cells use ion channels to usher charged molecules in and out. One thing readers might not expect from a book that illustrates the intricacies of ion channels: It’s surprisingly funny.
Chloride ions, for example, are “perpetually low-key ashamed” because they carry a measly -1 charge. Bogus medical contraptions (here’s looking at you, electric penis belts) were “electro-foolery.” In her acknowledgements, Adee jokes about the “life-saving powers of Voltron” and thanks people for enduring her caffeine jitters. That energy thrums through the book, charging her storytelling like a staticky balloon.

Adee is especially electrifying in a chapter about spinal nerve regeneration and why initial experiments juddered to a halt. Decades ago, scientists tried coaxing severed nerves to link up again by applying an electric field. The controversial technique sparked scientific drama, but the idea of using electricity to heal may have been ahead of its time. Fast-forward to 2020, and DARPA has awarded $16 million to researchers with a similar concept: a bio­electric bandage that speeds wound healing.

Along with zingy Band-Aids of the future, Adee describes other sci-fi–sounding devices in the works. One day, for example, surgeons may sprinkle your brain with neurograins, neural lace or neural dust, tiny electronic implants that could help scientists monitor brain activity or even help people control robotic arms or other devices (SN: 9/3/16, p. 10).

Such implants bring many challenges — like how to marry electronics to living tissue — but Adee’s book leaves readers with a sense of excitement. Not only could bioelectricity inspire new and improved medical devices, it could also reveal a current of unexpected truths about the body.

As Adee writes: “We are electrical machines whose full dimensions we have not even yet dreamed of.”

The April 25 Nepal earthquake killed more than 8,000 people and caused several billion dollars in damage, but new research suggests the toll could have been a lot worse.

GPS readings taken during the quake indicate that most of the tremors vibrated through the ground as long shakes rather than quick pulses. That largely spared the low-lying buildings that make up much of Nepal’s capital, Kathmandu, geophysicists report online August 6 in Science. Those same low-frequency rumbles, though, toppled Kathmandu’s handful of larger buildings, such as the historic 62-meter tall Dharahara Tower.

Understanding why the fault produced a quake at such low frequencies could help seismologists better identify future seismic hazards, says Jean-Philippe Avouac of the University of Cambridge. “This could be some good news not only for this major fault, but also potentially for similar faults around the world.”

Nepal sits over a tectonic boundary where the Indian Plate slips under the Eurasian Plate. At places, the two plates snag together, building stress that abruptly releases as an earthquake (SN: 5/16/15, p. 12).
Earthquakes stronger than April’s magnitude 7.8 shakedown have hit Nepal before, including a magnitude 8.0 quake in 1934. Despite the recent quake’s feebler intensity, its trembles somehow destroyed large buildings that had previously endured mightier earthquakes.

Avouac and colleagues monitored April’s quake using a network of 35 solar-powered GPS stations, the first time such an accurate system was in place during a major quake on this type of fault. The stations measured ground movements five times each second. The earthquake shook most intensely at 0.25 hertz, or one full wave every four seconds, with only moderate shaking above 1 hertz, or one or more complete waves each second.

A building is most vulnerable when shook near its resonance frequency, a range where even small outside forces can result in big vibrations in the structure. Because taller structures have lower resonance frequencies, the April quake’s low-frequency rumbles caused larger buildings to sway and crumble while largely sparing smaller dwellings, the researchers found.

The low frequencies resulted from the smooth and relatively long duration of the tectonic slipping that initiated the quake, the researchers propose. The low-frequency waves then echoed across the region and produced protracted violent shaking.

Determining where future low-frequency quakes will strike could save lives by identifying which building types are most vulnerable to collapse, says geologist Kristin Morell of the University of Victoria in Canada. “These are things that should be built into building codes.”