The Antarctic is teeming with microscopic life: Mites, water bears, and roundworms squirm around, invisible to the naked eye. In fact, the Antarctic is full of biodiversity hotspots—and they’re thanks to penguin and elephant seal poop.
A new study published Thursday in the journal Current Biology tracked how nutrients from sea make their way onto land by big animals eating fish and then coming ashore to shit. Their poop eventually fuels the cycle that gives life to the frozen continent. Water availability and temperature are factors scientists already know influence life in this desolate ecosystem, but this study is the first to examine the impact good ol’ poo is having on the environment.
Many animals are known to benefit their ecosystems by dropping the occasional deuce—from whales to hippos—but these creatures poop in environments that have, well, a lot more life than the South Pole does. Antarctica’s cold, dry climate isn’t all that amicable to biodiversity.
The authors conducted this study by sending Stef Bokhorst, an ecologist at the VU University Amsterdam, to the Antarctica Peninsula where he sampled three locations near seal and penguin colonies to see how much nitrogen levels were elevated around them. Then, he measured the abundance of living organisms, including tiny invertebrates invisible to the human eye, as well as lichen and moss.
The team found that the lichen and moss were unaffected by poop for the most part, but microarthropods were. These animals were two to eight more abundant in sampled regions tainted by penguin and elephant seal poop than in regions that weren’t. Water bears were barely affected, but springtail and mites benefited. Even predatory nematodes were found, showing a mini food web in action.
One of the coolest findings, perhaps, is that this impact stretched far beyond where colonies were concentrated. You see, the nutrients don’t just stay where the droppings land. The nitrogen can travel some miles away from the coastlines where the penguins and seals hang out because it evaporates as ammonia gas, which the wind blows inland, explained Bokhorst.
Using the data they collected and the locations of other penguin colonies Bokhorst couldn’t get close to, his team mapped out likely biodiversity hotspots across the Antarctica Peninsula. If their analysis is right, well, the peninsula is popping with microscopic critters.
This study shows the important role marine vertebrates like penguins and elephant seals play in their ecosystems. It also shows what’s at risk if we lose them, said Bokhorst. And some populations are facing serious threats.
An entire penguin colony hasn’t recovered since 2016 when a storm wiped out thousands of eggs and chicks. Events like this could become more common as our climate warms, threatening key habitats for large animals in Antarctica. The peninsula, in particular, saw rapid warming in the late 1990s, and if it continues, that’s bad news for the animals that rely on the ice to breed and, well, live.
And if we lose these big, charismatic species, biodiversity hotspots could start to unravel. Still, Bokhorst is hopeful. He imagines climate change will wind up moving these hotspots around, not erasing them entirely. Guess we’ll have to wait and see.
Rivers are the Earth’s arteries, and humans are clogging them with all sorts of junk. In fact, just a little over a third of the planet’s longest rivers remain free from human interference, according to a new study released in Nature on Wednesday. Like the arteries in our bodies, choking rivers could lead to a planetary health crisis.
“We see this biodiversity crisis worldwide and in rivers particularly, the decline in biodiversity is staggering and really concerning,” Günther Grill, a geographer at McGill University who led the study, told Earther.
Left to their own devices, rivers transport all sorts of good stuff around Earth, including freshwater, fish, nutrients, and sand. But humans have turned to dams to regulate those flows and generate electricity, allowing communities to spring up on once unruly banks. Levies, roads, and urbanization have further interfered with the natural course of rivers. This has largely been to the detriment of rivers and the people and ecosystems downstream (and sometimes the people living next to them, for that matter).
In an effort to suss how restricted rivers have become, Grill and an international team of scientists first set out to define what a “free-flowing” river looked like. Their definition of a free-flowing river is pretty simple: any waterways that remain connected in a way that allows ecosystems to function as they normally would. The researchers took stock of how many were left using dam data and river models.
They then analyzed an astounding 7.6 million miles of rivers—enough waterways to go to the moon and back 15 times—broken down into short, medium, long, and very long rivers. The findings show most short and medium-length rivers are still largely free-flowing, though Grill warned that the results likely underestimate dams on them.
“We are more confident looking at patterns from larger rivers,” he said.
There, the results are much more stark. Sixty three percent of very long rivers—those 620 miles or more in length—are no longer free flowing, blocked up by many of the estimated 2.8 million dams globally. Of the 37 percent of mega rivers that remain free-flowing, most are in the Arctic, Amazon, Congo, all areas that are hard to develop and lightly populated.
The loss of very long rivers running their natural coursehas huge impacts for downstream areas, and not just on biodiversity. Louisiana, for example, is losing land and its delta ecosystems in part because the Mississippi River that once flowed freely is now under the control of a huge network of dams. Grill pointed to loss of connectivity in the Mekong River basin of Southeast Asia, which reduces the movement of fish, and could exacerbate food security.
“In Cambodia, most protein comes from fisheries products,” he said. “The loss of fisheries to dams could have direct and negative impacts on tens of millions of people.”
Grill said he views the study as a jumping off point for future analysis and decisions. In the electricity realm, those decisions may include weighing whether hydropower is a better option than renewables. And in the ecosystem realm, they may including deciding if a dam on an already impacted river is smarter than clogging a free flowing one, or how and when to release water from dams to mimic the natural world, something water managers have done with the Colorado River in recent years.
“We need smart solutions going into the future,” Grills said. “We need to look at the bigger picture.”
Across the U.S., industrial machinery creates a constant underground hum that sends vibrations through the surface of the Earth. Scientists are now mapping that subterranean humming.
In any experiment, it’s crucial to understand what’s going on in the background—what noise already exists—in or to fully characterize any signals you’re seeing. Scientists have realized that Earth is full of vibrations from turbines, regularly spinning fans that send low-frequency pulses through the ground. Those hums could interfere with some scientific research, including the work done by seismologists and even particle physicists.
The industrial “hum” is much like a hum you hear when you walk into a room where a fan is running—a persistent signal, but much lower in frequency. Wind turbines and turbines in hydroelectric systems can produce these hums, which can get in the way when you’re trying to study earthquakes, scientist Omar Marcillo from Los Alamos National Laboratory said in a press statement. Indeed, the researchers first noticed the hum when it showed up in data about ocean storms. It could even show up in sensitive physics experiments, where even the slightest vibrations can produce false signals.
The researchers started with two seismic stations in Texas. Now, they have added signals from 400 mobile seismic stations called the U.S. Transportable Array, giving them more than 10 years of data, according to a press release from the 2019 Seismological Society of America Annual Meeting.
Crunching all the data from all of those stations has been a challenge, according to a project update from the team published in Eos—analyzing 13 years of data from two stations took over 30 hours. But with updated computing methods, they were able to crunch the numbers from 100 stations in the same amount of time. The researchers are now moving their analysis to data from 1,690 mobile stations, according to the update. This will allow them to create an even more detailed map of the hums across the U.S.
Truly, the entire world is vibrating with the hum of humanity.
A year and a half ago, in the middle of the Antarctic winter, satellite images of the frozen continent revealed something wild: a gaping hole in the middle of Antartica’s sea ice that spanned thousands of square miles. Scientists were fascinated and puzzled by feature, which hadn’t appeared at this scale since the 1970s. Now, a team of researchers think they know what caused it.
The ice hole—known as a polynya in the parlance of sea ice researchers—was likely caused by a powerful cyclone that spun up in Antarctica’s Weddell sea before migrating eastward into the Lazarev sea in mid-September 2017, according to research published Wednesday in the Journal of Geophysical Research: Atmospheres. In an age of human-caused climate change, that’s a valuable insight, because rising temperatures could alter the frequency or intensity of polar cyclones, potentially affecting the occurrence of these polynyas and, in turn, global ocean circulation.
When the polynya was first spotted in mid-September, it spanned about 3,700 square miles—more than twice the area of Rhode Island. It would balloon in size over the weeks to come, reaching 31,000 square miles (roughly the size of Ireland) by late October before it merged with the open ocean as Antarctic sea ice retreated with the onset of summer.
The hole was, in a word, enormous, and it prompted a raft of speculation as to what could have caused it. The site of the polynya—directly above an enormous undersea mountain known as the Maud Rise—made it especially intriguing, as similar giant polynyas had been spotted in the same location in satellite imagery from the 1970s.
That’s likely no accident.As senior study author David Holland of New York University’sAbu Dhabi Research Institute explained to Earther by phone this week, the presence of the Maud Rise seamount—which he described as “the equivalent of the Himalayas” except underwater in a polar ocean—pushes the warm, dense, salty water that typically lingers near the seafloor closer to the ocean’s surface. If a big storm rolls through and clears away the overlying sea ice, it can then cause this warm water to mix with the cooler, fresher water floating atop the Lazarev sea.
“And once you do that, you’ve upset the cart, and the warm water’s at the surface, and it’s gonna take months to cool” enough to freeze over again, Holland explained.
Using a combination of satellite observations and climate models, the research team led by NYUAD’s Diana Francis determined that the polynya’s opening coincided with a cyclone— roughly equivalent in strength to a powerful tropical storm—forming over the Maud Rise. The researchers think the cyclone’s winds pushed the ice outward from its center, creating a hole that would continue to expand over the days to come.
Céline Heuzé, a physical oceanographer at the University of Gothenburg, Sweden, told Earther in a phone interview that other recent research has shown 2017 to be “quite an intense year in the Southern Ocean with respect to storm activity.” While Heuzé said that the new study’s findings “make sense,” she’s keen to learn more about the role that the ocean plays, which is why she recently had a student trek out and deploy an “autonomous profiler” to measure temperature and salinity in the Maud Rise area. Heuzé hopes there’s another polynya this winter, so that this instrument can capture any changes taking place in the ocean as it’s opening.
Torge Martin, a meteorologist and climate modeler at the Helmholtz Centre for Ocean Research in Kiel, Germany, told Earther via email that the study’s authors “make a valuable contribution to explaining the occurrence of the polynya, and they are correct in arguing that the atmospheric side has been less studied in the past.”
“This is because the preconditioning in the ocean is essential,” Martin wrote. “The regional atmospheric conditions then can be the trigger in a specific winter season.”
The idea that cyclones can trigger the polynya raises the possibility that it will crop up more often in the future, with rising temperatures expected to intensify polar cyclone activity. Climate change is also warming the oceans, potentially making it harder for the polynya to refreeze once it’s been opened. And this is worth exploring, Holland said, because the polynya’s delivery of ocean heat to the surface, followed by the sinking of that water as it becomes cooler and denser, plays an important role in global ocean circulation.
Changes to the polynya could, in other words, ripple outward across Earth’s oceans. As Heuzé put it, “everything’s connected.”
Update: This article has been updated to clarify that the cyclone in question formed in the Weddell sea, but migrated east over the Lazarev sea where it generated a polynya.
Every several years, magnetic field observatories record quick changes to the position or strength of the planet’s magnetic field, so-called geomagnetic jerks. The cause of these shifts has remained a mystery.
Improvements to ground-based observatories and more magnetic field measurements from satellites have given scientists new insights into the planet’s magnetic behavior. Though we can’t look directly into Earth’s core, these measurements have let scientists build models to help infer what might be going on in there. Most recently, scientists realized that that suddenly released, moving blobs inside the core could explain the geomagnetic jerks.
“The ability to numerically reproduce jerks offers a new way to probe the physical properties of Earth’s deep interior,” researchers Julien Aubert from the University of Paris and Christopher Finlay from the Technical University of Denmark write in a new paper, published in Nature Geoscience.
Earth scientists are pretty sure that the planet generates its own magnetic field thanks to the geodynamo: heat-generated motion of conductive liquid metal inside the core, combined with the planet’s spin. Changes are generally slow—like being on a fancy new train, where you barely perceive the forces of speeding up or slowing down. But sometimes the magnetic field experiences “jerks,” where it unpredictably goes from speeding up to slowing down, similar to the whiplash-inducing jolts you might feel on a rickety old train.
These “jerks” occur over the course of just a few years, and have appeared in 2007, 2011, and 2014, according to observed data. To better understand this, the researchers built a simulation of Earth, in which the outer core is represented as a rotating spherical shell filled with an electrically conducting liquid, and the inner core and mantle as solids sandwiching the liquid later. It’s like a spinning jawbreaker with a layer of goo between the center and the outer shell.
The model revealed that isolated blobs appearing in the liquid could move upward and around the core, creating waves through the liquid’s electrically charged atoms. Once these waves are stopped by the solid mantle, they compress, leading to the temporary disturbances in the magnetic field that cause the geomagnetic jerk. It would take around 25 years from the release of the blob to the observation of a jerk.
This is a model based on what we know of Earth’s interior, and it’s worth taking it (and all models) with a grain of salt. Nor is this the only possible explanation for these jerks—others have suggested they come from a torsional, or twisting, oscillation in the core, though the researchers behind the new paper argue that torsional oscillations are too weak to generate the signals observed in real life.
Still, models are crucial for better understanding how motion deep in our planet manifests here on the surface, and understanding the jerks might help scientists predict them in the future. You might be aware that the magnetic field protects us from solar rays that would otherwise make the planet unlivable. So it’s nice to be able to understand it better.
Beneath the waves some 130 miles southeast of Cape Cod, there’s a hidden world of giant canyons and extinct volcanos home to a stunning array of life forms, from sharks to sea turtles to sperm whales. Now, scientists have discovered what appear to be two new species of deep-sea corals thriving in this undersea jungle.
In September 2018, scientists at the Woods Hole Oceanographic Institution, with the support of Bloomberg Philanthropies and OceanX, embarked on a two-week expedition to Lydonia Canyon, one of three huge chasms located inside the Northeast Canyons and Seamounts National Monument. Using OceanX’s submarine Nadir, they traversed the ravine and collected nearly thirty samples of corals at depths down to almost 3,000 feet. An ongoing analysis of the samples in the lab has now revealed what is, likely, at least two new, genetically-distinct species of bubblegum coral, fan-shaped creatures with bundles of polyps reminiscent of wads of gum.
“This part of the Atlantic, a hundred miles off Cape Cod, this area is heating three times faster than any other place in the Atlantic,” Shank said. “It’s sort of a canary in the coal mine location.”
The team is still analyzing the data from its recent expedition, so more findings could be forthcoming. And the researchers are hoping to get out to these waters at least one more time this year. Prior to this research the monument was already known to harbor at least 54 species of deepwater corals as well as sponges and anemones, which provide spawning grounds and shelter for numerous fishes and marine invertebrates. But each new species represents an opportunity to learn more about what makes this delicate ecosystem tick. Shank explained that oftentimes, certain animals will only live in association with certain species of coral.
“We want to understand how these relationships have formed and are maintained before we destroy them,” he said.
By trapping bubbles of atmosphere as it freezes, ice imprisons the climate secrets of Earth’s past. The trick is knowing how to find, and then recover, this buried treasure beneath miles of thick ice sheets in the first place.
Having made stunning gains in the last few decades, ice core hunters are now poised to drill further down, and go further back in time, than ever before. Announced this week at the annual gathering of the European Geosciences Union in Vienna, a team of scientists from 10 different countries is about to start drilling a 1.68-mile long ice core out of East Antarctica, one which will chronicle changes in Earth’s climate going back a record-breaking 1.5 million years.
James Lea, a lecturer in glaciology at the University of Liverpool who is not involved in the project, told Earther that should the researchers successfully obtain a complete core, the implications will be huge. It will give climate scientists “an unprecedented insight into how the Earth’s climate has changed over multiple ice ages,” he said, something that has clear implications for understanding our future.
Forward-looking climate models can be tested by looking at previous warm periods, like the last interglacial. So with this new library of icy information, we will be able to compare the natural fluctuations in the climate of the past to the anthropogenic perturbations we are seeing in the present, and untangle the two with more precision than ever before.
“Understanding past change is crucial to predicting our collective future,” said Chris Fogwill, a professor of glaciology and paleoclimatology at Keele University.
For Robert Mulvaney, the science leader of the Ice Dynamics and Paleoclimate team at the British Antarctic Survey and member of the project, it’s more about solving an ancient puzzle than anything else.
Prior to 1.2 million years ago years ago, he told Earther, the switch between frigid glacial and warm interglacial periods was ruled by a 41,000-year cycle, one that is extremely clear in marine sediment records. From 500,000 years ago to the present, though, a 100,000-year cycle completely dominates. So, what caused that switchover?
These cycles are dependent on the way Earth orbits the Sun, with variations in how it wobbles, for example, causing planet-wide changes in glacial extent. These orbital variations likely haven’t differed in billions of years, so it’s clear that something else is contributing to major changes and exacerbating the temperature swings. Among other interlinked factors, Mulvaney strongly suspects greenhouse gases are playing a major role, and this new ice core will likely provide some answers.
“For me, that is where the excitement is,” he said. There are snapshots of carbon dioxide from that cycle switchover period, but this new ice core will be the first continuous record, from modern times through the transition period and beyond, allowing us to see how the cycles evolved and perhaps what drove these changes.
We might even be surprised by what we find. While carbon dioxide is crucial to the warming we’re seeing today, other greenhouse gases, like methane and nitrous oxide, “may prove crucial” to understanding the changing climate, Fogwill explained. Although relatively short-lived in the atmosphere compared to carbon dioxide, “they may have a disproportionate effect during periods of rapid transition.”
The project is essentially a sequel to the original multinational effort, the European Project for Ice Coring in Antarctica, or EPICA. This drilling, from the mid-1990s to mid-2000s, pulled out an ice core spanning 800,000 years of history, at the time a remarkable feat.
The drill spot, dubbed Dome C, was essentially chosen by a logistics expert driving a tractor train full of base camp-building tech up to the highest point in that region of the frigid continent. Deciding somewhat randomly where to stop, they offloaded the equipment, started drilling, and rather serendipitously came across very old ice. They drilled a core just over two miles long, which although longer than the proposed new core doesn’t contain older ice, as the older ice at the base had already melted away.
For the sequel, dubbed Beyond EPICA-Oldest Ice, a lot more work needed to be done first to ensure a 1.5-million-year-old record could be obtained. The researchers had to find a spot where the lowermost ice wasn’t melting, which depends on a huge range of factors including, but not limited to, the ice thickness, the mean annual temperature, the depth of the ice and the flow of heat from various sources in Earth’s crust.
Subglacial melting is pretty common underneath Antarctic ice, so finding that unthawed deep ice was quite the challenge. Calculations and models were used to find areas in which so-called basal ice wasn’t melting. Then, radar measurements and borehole measurements, which took place during three field seasons between 2015 and 2018, were deployed. Altogether, these techniques ascertained where the ice was just the right thickness at the right depth to reliably record such a long span of time. Three places were earmarked as having potential, and one–dubbed Little Dome C–was ultimately chosen.
Mulvaney explained that they will soon use a prototype radar system to try to see if there are well-defined internal layers near the base of the ice, just to confirm their suspicions that this is the best spot to drill. If everything looks good, drilling will then commence within the year. The drilling is expected to take three to four years to complete.
“Finding such old ice is an absolutely monumental scientific and logistical challenge,” said Lea. Aside from making sure the ice is likely to preserve that precious, exceedingly ancient climate record, the team is “working in one of the most harsh, remote locations on the planet. If anything goes wrong the nearest place to get spare parts for the drill rigs can be at least a couple of thousand miles away.”
Winter in Antarctica features temperatures of -112°F, which is nearly as cold as boiling kettle water is hot. With temperatures of around -13°F austral summer is comparatively balmy, which allows the team to drill between 16 and 24 hours per day from December to January. Unlike full-blown Antarctic bases, the Beyond EPICA team members will mostly be living in tents and converted shipping containers.
Mulvaney, in what is surely an understatement, described working in the field as “quite intense.”
As well as the terrifically cold conditions, the drills themselves don’t always work as planned. On the original EPICA project, a drill got stuck at one point, and the team had to move the rig to another location and start all over again. “Every time you send the drill down, your heart’s a little bit in your mouth. Is this the last I’m ever going to see it?” Mulvaney said. “Sometimes the ice decides that you’re not getting your drill back.”
Helle Astrid Kjær, an assistant professor and ice core researcher at the Niels Bohr Institute of the University of Copenhagen–which is also part of Beyond EPICA–told Earther that the troubles don’t end when the drilling stops. Some of the lowermost ice core layers, containing millennia of climate records, will be incredibly thin. With such small samples, it will be a challenge for researchers to measure the greenhouse gases trapped within them.
The ice core community has experienced leaps forward in the experimental methods and technology it uses to retrieve this precious data in recent years, “but another leap is needed to resolve the thin layers towards the bottom” and to see the transitions between the two different glacial cycles. Such advances will likely require more funding for Beyond EPICA, which already has an estimated $34 million price tag, funded by the European Union’s science budget.
That might sound like a lot, but it isn’t when you consider that it will help chronicle a key change in our planet’s climate, the variable that seems to matter over all else when it comes to habitability of our world.
Scientists think they’ve figured out how pyroclastic flows, fast-moving bringers of death during volcanic events, can travel such incredible distances and speeds despite the friction between the volcanic material and the ground.
Pyroclastic flows are searing-hot mixtures of volcanic material and gas that travel explosively down the slopes of volcanoes, sometimes traversing tens of miles at hundreds of miles per hour. They’re responsible for some of the deadliest volcanic events, like the 1883 Krakatoa eruption and the 79 AD Vesuvius eruption that destroyed Pompeii. Though the spewed rocks should slow due to friction, new research from scientists in New Zealand, Australia, and the United States seems to show that the flows travel on cushion of lubricating air.
Volcanic material has a static friction of around 35-45 degrees, meaning it wouldn’t slide until it were placed on a 35- to a 45-degree slope, according to the paper published today in Nature Geoscience. And yet, pyroclastic flows can travel for tens to hundreds of miles down slopes with angles of just 8 to 9 degrees. How the material can move so far, for so long, has remained a mystery—after all, it’s hard to mathematically model a speeding death column.
The researchers explored the question using an experiment called PELE, the Pyroclastic flow Eruption Large-scale Experiment. The experiment is essentially a large, heated container with a literal ton of aerated, natural volcanic particles which are then dropped onto a 40-foot-long, 1.5-foot-wide, high-friction chute that leads down to a concrete pad. It’s a sandpaper slide at the theme park of death.
During the experiments, which the researchers recorded with a high-speed camera, the mixture separates into a denser underflow below and a 6-to-15-foot ash cloud above. The cloud would run to 115 feet, while the underflow would run up to 87 feet. The researchers performed a number of calculations and numerical modeling with the data and reviewed the footage. The saw that areas with fewer particles developed near the ground. They hypothesized that in these flows, faster-moving materials higher up generate higher-pressure regions closer to, but not quite on, the ground. This would cause gas particles to travel toward the lower-pressure region closer to the ground and inflate an air pocket on which the flow can slide nearly frictionlessly.
There’s more work to do, as Alain Burgisser, scientist at the Université Savoie Mont Blanc in France wrote in a Nature Geoscience commentary: “The exact conditions under which this layer appears remain to be determined with precision.” But the effect is an exciting one to discover experimentally, and the researchers’ numerical modeling demonstrates that air lubrication could explain these pyroclastic flows in nature.
But these air cushions might not just describe pyroclastic flows. Perhaps, the authors write, avalanches and landslides are also propelled by similar air cushions. That’s physics for you. It can help you understand the mysteries of the Universe, but it won’t stop your near-instant death if you’re standing in the way of a pyroclastic flow.
At one of the most important ancient graveyards on Earth in North Dakota, paleontologists unearthed the fossilized remains of fish seemingly killed by the effects of the asteroid that ended the Cretaceous.
We know that a large asteroid struck the Earth 66 million years ago, and around the same time, the dinosaurs went extinct. We’re not completely sure whether the asteroid was solely responsible for the mass extinction, but you might ask, “Shouldn’t we see remnants of animals killed by the asteroid’s effects?” Well, now we have found some.
“This is the last day of the Cretaceous,” David Burnham, professor in the Department of Geology at the University of Kansas and one of the study’s authors, told Gizmodo.
When a giant meteorite strikes, you’d expect chaotic effects, like rocks altered by the impact’s high pressures and temperatures, enormous earthquakes, and tsunamis. But Earth’s rocks don’t directly preserve single days of the planet’s several billion-year-old history. You’ve got to get creative when it comes to teasing apart the geologic record. For example, around the world, layers of rock 66 million years old seem to contain excess iridium, presumably deposited by the Chicxulub impactor that struck near what is today the Yucatán Peninsula of Mexico. Then there are tektites, small, glassy spheres of compressed and heated rock. Theoretically, there should also be fossilized evidence of animals killed by the asteroid’s effects.
This is what makes the new research, led by Robert DePalma at the University of Kansas, so exciting—the description of a pair of sediment layers at the Tanis site of the The Hell Creek Formation in southwestern North Dakota. Both layers contain an excess of iridium, but only the lower level contains glass pieces that seemed to have been deposited from an inland-moving force. They take this to mean that they’re observing two events: The upper layer is the settling dust from after the impact. The lower is a large deposit of sediment from the hours following the impact.
But if the rocks alone don’t convince you, perhaps the fossils in the event deposit will. A large swath of ocean traveled up the interior of the United States during the late Cretaceous, terminating not far from the Tanis region. But the rocks at Tanis preserve a mixture of both freshwater fish, like paddlefish and sturgeon, and marine mollusks called ammonites—implying that around this time, the ocean had mixed with freshwater rivers. And lodged inside the fossilized paddlefish’s gills were more of the glass spherules. It appeared that waves containing shocked glass from the impact over 3,050 kilometers (1,895 miles) away had inundated the area, and in their dying breaths, the fish had inhaled some of them.
Other researchers were impressed by the work. “When I first read it, I kept saying ‘wow, wow, wow,’” H. Jay Melosh, distinguished professor of Earth, atmospheric, and planetary science at Purdue University, told Gizmodo. “I think this is one of the most spectacular paleontological discoveries of the century. It’s a snapshot of the moment at which major deaths were occurring right after the impact.”
The researchers point out that there are other scenarios that might have brought the glass particles up to Tanis. Maybe there were meteorological events like gale-force winds, or landslides, the authors write in the paper, which will be published on Monday in PNAS.
But the observations have far-reaching implications. The authors write:
“Observations at Tanis expand our knowledge of the Chicxulub impact’s damaging effects and their far-reaching scope. The highly probable link between impact-induced seismic shaking and the onshore inundation surge at Tanis reveals an important additional mechanism by which the Chicxulub impact could have caused catastrophic conditions in the Western Interior, and possibly worldwide, far from the impact site.
It’s amazing to imagine how abruptly life on Earth changed in the hours and days after the Chicxulub asteroid hit. And it’s equally amazing that we could find direct evidence from that time locked away in the remains of the creatures who experienced it.
On November 11, 2018, a deep rumble ricocheted around the world, one that humans couldn’t feel but that registered quite clearly on seismometers. A new pre-print paper about the event is now suggesting that it was caused by the largest offshore volcanic event in recorded history.
Originating 30 miles east of the island of Mayotte, near Madagascar, the mid-November signal immediately caught the attention of a disparate group of geoscientists. They subsequently took to Twitter to express their fascination over this mysterious event—one even joked about a “giant prehistoric sea monster.”
The rumble formed part of a prolonged seismic sequence that had started in the area back in May 2018, but the very low-frequency, potent growl in November stood out because it wasn’t immediately obvious what caused it. These scientists eventually agreed that it could only have originated from a volcanic event, one involving the movement of a vast volume of magma beneath the seafloor, causing the ground there to significantly deflate.
Now, a new paper by researchers at the French Geological Survey and France’s Ecole Normale Supérieure has been uploaded to the public server EarthArXiv. Although there are plenty of unanswered questions, this first-order estimation of what happened between May and mid-November matches up with the calculations of those geoscientists that took to social media. In fact, the volume of magma involved is so huge that this is certainly one of the largest offshore volcanic events to be spotted by modern scientific instrumentation.
There is a major caveat to all this, however. Compared to land-based monitoring, there’s a huge lack of offshore monitoring happening around the world today, and there are likely plenty of offshore events that have taken place since modern records began that scientists haven’t picked up on.
Make no mistake, though: The recent event offshore from Mayotte, which is still ongoing, is colossal.
According to the data from the onshore GPS stations, as well as the seismic signals—including the weird November 11 event—the rumbling is definitely being generated by volcanic activity of some sort. The way the ground on Mayotte is moving implies that the seafloor off its eastern shoreline is sinking at a rate of around 0.4 inches per month. At the same time, Mayotte itself is shifting eastward at a rate of 0.63 inches per month. Both indicate something huge underground is on the move, causing some serious deflation.
The nature of these tremors suggest that the magmatic source is centered at a depth of 16 miles beneath the seafloor. In the first six months of the sequence alone, at least 0.24 cubic miles of magma has shifted around. That’s roughly equivalent to 385 Great Pyramids of Giza.
Helen Robinson, a geothermal expert and PhD candidate at Glasgow University, compared it to volumes of other submarine eruptions. From the 1998 Axial Seamount eruption offshore from Oregon, to the Havre paroxysm north of New Zealand on the Kermadec arc, “it certainly seems this is the largest submarine event in terms of volume on record,” she told Gizmodo.
Samuel Mitchell, an expert in underwater eruptions at the University of Hawaii at Mānoa, and who worked on the Havre eruption, agreed that the amounts of volcanic material involved are definitely comparable. “The 2018 event at Mayotte does appear to show a substantial volume of magma leaving a deep storage region which, if erupted, would make this indeed one of the largest recent submarine eruptions documented,” he said.
That’s a big “if,” though. As Robinson also points out, and as the new pre-print paper acknowledges, what’s happening near Mayotte is not necessarily an eruption.
Pierre Briole, a geophysicist at France’s Ecole Normale Supérieure and one of the authors of the pre-print, told Gizmodo that the indirect evidence means that he’s “pretty sure it’s an eruption.” But as there is currently no direct evidence of an eruption having taken place, “there is a significant probability that no lava reached the surface.”
Failing to breach into the sea, the migrating magma might have injected itself into thick sediments in the seafloor and spread itself around. Mitchell explained that this has been observed elsewhere, when the magma is denser than the surrounding sediment.
Although the overall volume of magma involved is comparable to the 2012 Havre eruption, the two are likely to be quite different events. The former definitely involved plenty of eruptive material, whose huge pumice raft was first spotted from a plane. At the same time, large, gloopy volcanic domes formed on the seafloor.
In Mayotte’s case, if an eruption did take place, Mitchell explained, it’s more likely to be some sort of fissure effusion involving more fluid lava, a bit like an underwater version of what happened on the slopes of Hawaii’s Kīlauea in 2018.
Jean Paul Ampuero, a seismologist and director of research at France’s Research Institute for Development, told Gizmodo that “this whole sequence is record-breaking in many aspects.” Along with the huge volume of magma, the November 11 signal was also easily one of the largest low-frequency tremors of its kind.
That the low-frequency rumble spread across the world was probably due to a “perfect storm,” according to Stephen Hicks, a seismologist at the University of Southampton.
In this case, that meant having both a very large source and vibrations at the exact right pitch to carry them across a considerable distance.
The November 11 signal’s individual elements still remain deeply puzzling. In particular, its repeated high-frequency bursts, which are similar (but aren’t related to) industrial activity, are difficult to explain. Ampuero said that they fall into a timing pattern that indicates they are strongly connected to the low-frequency pulses, indicating the two components “are talking to each other in some way.”
One highly speculative explanation is that the high-frequency events are related to the collapse of the rocky walls surrounding the magmatic monster. This disturbs the magma reservoir, causing it to oscillate or ‘hum.’ At the same time, waves bouncing back and forth hit other flanks and trigger more collapses, generating more high-frequency events. This all happens, Ampuero suggests, in a way that causes the low- and high-frequency events to synchronize, forming the November 11 signal.
It’s very difficult to say for sure. Some smaller tremors in the sequence also had a similar signal, Ampuero added, so “perhaps they’ll catch another one” like the big tremor and take it apart to see what it’s made of.
The geological setting is also pretty weird. This major volcanic event is taking place on the eastern end of the island chain, whereas the youngest volcanic islands are to the west. So it appears to be happening in the ‘wrong’ place.
It’s also unclear what’s responsible for the volcanism in the first place. It could be caused by action along a tectonic plate boundary, an upwelling plume of superheated mantle material, or even an extension of the East African Rift, a major tectonic event that’s slowly tearing the continent apart, said Hicks.
There is even an ecological element to the story that’s currently unexplained: the emergence of lots of dead fish offshore from Mayotte. Volcanic gases can suffocate sea life during eruptions, but the pre-print reports that the gases remained trapped in the magma.
Briole has heard unverified reports that the fish that died were deep-sea fish. The magmatic activity might have scared them up to the surface, where they experienced low pressures that they couldn’t survive in. Robinson said that the magma, which may have intruded into seafloor sediments, cooked those sediments and released carbon dioxide into the water column, which could also have asphyxiated those deep-sea fish.
Like much about the event, this remains speculative for now. Clearly more instrumentation is required, and the French National Centre for Scientific Research—with help from the BRGM and other authorities—are now deploying plenty. This includes equipment on Mayotte, at the site of the activity, and on the Glorioso Islands to the east, so that they can ‘listen’ to the disturbances from the other side.
That still won’t solve all the enigmas. Mitchell pointed out that underwater drones and ship-based radar surveys will be required to determine how much lava erupted at the surface, if any, and Hicks suggested that numerical simulations and laboratory work may be required to better comprehend what’s going on beneath the surface.
As Ampuero emphasizes, this isn’t just about scratching a scientific itch, but helping out the local communities, too. “The people in Mayotte really want to know what’s going to happen next,” he said. As a recent report on the situation notes, there is often an atmosphere of confusion and distrust on the island. The more research that’s conducted, the better off everyone will be.
Correction: This article has been corrected to note that the rate of eastward drift of Mayotte is 0.63 inches per month, not 6.3 inches.
