Strange waves rippled around the world, and nobody knows why


Instruments picked up the seismic waves more than 10,000 miles away—but bizarrely, nobody felt them.

On the morning of November 11, just before 9:30 UT, a mysterious rumble rolled around the world.

The seismic waves began roughly 15 miles off the shores of Mayotte, a French island sandwiched between Africa and the northern tip of Madagascar. The waves buzzed across Africa, ringing sensors in Zambia, Kenya, and Ethiopia. They traversed vast oceans, humming across Chile, New Zealand, Canada, and even Hawaii nearly 11,000 miles away.

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These waves didn’t just zip by; they rang for more than 20 minutes. And yet, it seems, no human felt them.

Only one person noticed the odd signal on the U.S. Geological Survey’s real-time seismogram displays. An earthquake enthusiast who uses the handle @matarikipax saw the curious zigzags and posted images of them to Twitter. That small action kicked off another ripple of sorts, as researchers around the world attempted to suss out the source of the waves. Was it a meteor strike? A submarine volcano eruption? An ancient sea monster rising from the deep?

“I don’t think I’ve seen anything like it,” says Göran Ekström, a seismologist at Columbia University who specializes in unusual earthquakes.

“It doesn’t mean that, in the end, the cause of them is that exotic,” he notes. Yet many features of the waves are remarkably weird—from their surprisingly monotone, low-frequency “ring” to their global spread. And researchers are still chasing down the geologic conundrum.

Why are the low-frequency waves so weird?

In a normal earthquake, the built-up tensions in Earth’s crust release with a jolt in mere seconds. This sends out a series of waves known as a “wave train” that radiates from the point of the rupture, explains Stephen Hicks, a seismologist at the University of Southampton.

The fastest-traveling signals are Primary waves, or P-waves, which are compression waves that move in bunches, like what happens to an extended slinky that gets suddenly pushed at one end. Next come the secondary waves, or S-waves, which have more of a side-to-side motion. Both of these so-called body waves have relatively high frequencies, Hicks says, “a sort of ping rather than a rumbling.”

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Finally, chugging along at the end come slow, long-period surface waves, which are similar to the strange signals that rolled out from Mayotte. For intense earthquakes, these surface waves can zip around the planet multiple times, ringing Earth like a bell, Hicks says.

However, there was no big earthquake kicking off the recent slow waves. Adding to the weirdness, Mayotte’s mystery waves are what scientists call monochromatic. Most earthquakes send out waves with a slew of different frequencies, but Mayotte’s signal was a clean zigzag dominated by one type of wave that took a steady 17 seconds to repeat.

“It’s like you have colored glasses and [are] just seeing red or something,” says Anthony Lomax, an independent seismology consultant.

Mayotte’s volcanic roots

Based on the scientific sleuthing done so far, the tremors seem to be related to a seismic swarm that’s gripped Mayotte since last May. Hundreds of quakes have rattled the small nation during that time, most radiating from around 31 miles offshore, just east of the odd ringing. The majority were minor trembles, but the largest clocked in at magnitude 5.8 on May 15, the mightiest in the island’s recorded history. Yet the frequency of these shakes has declined in recent months—and no traditional quakes rumbled there when the mystery waves began on November 11.

The French Geological Survey (BRGM) is closely monitoring the recent shaking, and it suggests that a new center of volcanic activity may be developing off the coast. Mayotte was formed from volcanism, but its geologic beasts haven’t erupted in over 4,000 years. Instead, BRGM’s analysis suggests that this new activity may point to magmatic movement offshore—miles from the coast under thousands of feet of water. Though this is good news for the island inhabitants, it’s irksome for geologists, since it’s an area that hasn’t been studied in detail.

“The location of the swarm is on the edge of the [geological] maps we have,” says Nicolas Taillefer, head of the seismic and volcanic risk unit at BRGM. “There are a lot things we don’t know.” And as for the November 11 mystery wave, he says, “it’s something quite new in the signals on our stations.”

Motion in the ocean

Since mid-July, GPS stations on the island have tracked it sliding more than 2.4 inches to the east and 1.2 inches to the south, according data from Institut National de L’information Géographique et Forestière. Using these measurements, Pierre Briole of the Ecole Normale Supérieure in Paris estimated that a magma body that measures about a third of a cubic mile is squishing its way through the subsurface near Mayotte.

The early period of rumbling was also overprinted with what seemed to be the P- and S- waves of tiny tremors, explains Lomax, who spotted the faint pings by filtering out the low-frequency signals. Such pings are commonly associated with magma moving and fracturing rock as it squirts through the crust. But even those signals were a little strange, says Helen Robinson, a Ph.D. candidate in applied volcanology at the University of Glasgow.

“They’re too nice; they’re too perfect to be nature,” she jokes, although she quickly adds that an industrial source is impossible, since no wind farms or drilling are taking place in the deep waters off Mayotte’s shores.

Ekström thinks that the events on the morning of November 11 actually did begin with an earthquake of sorts equivalent to a magnitude 5 temblor. It passed by largely unnoticed, he suggests, because it was what’s known as a slow earthquake. These quakes are quieter than their speedy cousins since they come from a gradual release of stress that can stretch over minutes, hours, or even days.

“The same deformation happens, but it doesn’t happen as a jolt,” Ekström says.

These slow types of quakes are often associated with volcanic activity. At the Mount Nyiragongo volcano in the Democratic Republic of Congo, a similar slow earthquake and low-frequency waves were linked with a magma chamber collapsing. Slow quakes were also stunningly frequent during the most recent fiery run of Kilauea in Hawaii, which produced nearly 60 of these events between May and the end of July, sending seismic waves around the world.

Assembling the geologic puzzle

So what is actually causing the super-slow vibrations at Mayotte? A submarine eruption could produce these low rumblings, but evidence for such an event has yet to materialize.

Most current guesses revolve around resonance in a magma chamber, triggered by some type of subsurface shift or chamber collapse. The resonance itself can be any type of rhythmic motion, like sloshing of the molten rock, or a pressure wave ricocheting through the magma body, Ekström explains. Studying the intricate features of the seismic waves could yield clues to the size and shape of the molten material lurking below.

It is very difficult, really, to say what the cause is and whether anyone’s theories are correct.

Helen Robinson, University of Glasgow

“It’s like a music instrument,” says Jean-Paul Ampuero, a seismologist at the Université Côte d’Azur in France. “The notes of a music instrument—whether it’s grave or very pitchy—depends on the size of the instrument.”

The signal’s odd uniformity could be due, in part, to the surrounding rocks and sediments, Lomax adds. Perhaps the local geology is filtering the sounds and only letting this single 17-second wave period escape.

Robinson agrees with this idea, noting that the geology here is extremely complex. Mayotte sits in a region crisscrossed by ancient faults—including fracture zones from the final breakup of the southern supercontinent Gondwana. What’s more, the underlying crust is somewhat transitional, shifting between the thick continental crusts and the thinner oceanic crusts. Perhaps this complexity drives the simplicity of the escaping waves, Robinson says.

Secrets of the sea

For now, though, the lack of data makes it tough to say more about the wiggly forms. Hicks’ preliminary models hinted that the waves emanated from subsurface inflation, rather than a magma chamber draining or collapsing. But with a little additional data, the model flipped and pointed to chamber deflation instead.

It also could be a bit of both, notes Robinson: “Some collapse mechanisms, you can get inflation and deflation occurring at the same time,” she says. Or sometimes they can alternate, pumping up and down like Earth’s fiery lungs.

“It is very difficult, really, to say what the cause is and whether anyone’s theories are correct—whether even what I’m saying has any relevance to the outcome of what’s going on,” Robinson says.

BRGM plans to do ocean bottom surveys to get more detailed information about the region and investigate the possibility of a submarine eruption. In the meantime, the seismic sleuthing continues with the data that’s available. Whether the cause is ordinary or extraordinary remains to be seen, Lomax says, but the science—and the fun—is in the chase.

“Depending on what field and what time in history, 99.9 percent of the time, it’s ordinary, or noise, or a mistake, and 0.1 percent, it’s something” he says. “But that’s just the way it goes. That’s the way it should go. That’s scientific advance.”

 

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Indonesian Tsunami Was Powered by a Deadly Combo of Tectonics and Geography


The magnitude 7.5 earthquake that touched off the tsunami occurred amid a complex puzzle of tectonic plates.
Indonesian Tsunami Was Powered by a Deadly Combo of Tectonics and Geography
Rubble and debris lie around the ruins of a mosque following an earthquake, on October 02, 2018 in Palu, Indonesia.

Videos circulating on social media show an 18-foot wall of water advancing on the horizon.

The tremendous wave builds to a crescendo when it barrels ashore, submerging buildings already toppled by the deadly magnitude 7.5 earthquake that pummeled the northern part of Indonesia’s Sulawesi island last weekend (and triggered the inundation). The temblor and tsunami have killed well over a thousand people, with the toll expected to rise. The tsunami surprised the local population and, at first, some geologists, because the fault that ruptured was not the type typically associated with tsunamis.

Most big tsunamis, like the series of waves up to 100 feet high that killed more than 200,000 people around the Indian Ocean Basin in 2004, result from a sudden lurch of a subduction zone —a line where one of Earth’s tectonic plates is slowly diving beneath another. This heaving of the seafloor forces ocean water upward and outward. The tsunami that recently devastated the city of Palu on Sulawesi, however, was associated with a “strike-slip” fault, where two plates are sliding past each other. “It’s not something that you would’ve predicted,” says Jim Gaherty, a seismologist at Columbia University’s Lamont–Doherty Earth Observatory.

But strike-slip faults can also generate tsunamis through a couple different mechanisms that geologists have been evaluating for this event, in real time on Twitter and other social media platforms. The event, they say, speaks to the complex tectonic jumble that lies beneath Indonesia’s 14,000-plus islands.

Underwater Landslides

The earthquake’s shaking may have loosened sediment on a slope below the sea’s surface, triggering a submarine landslide that pushed water out of the way and sent it rocketing toward shore. Such occurrences have long been known to cause massive tsunamis; a rockslide triggered by a magnitude 7.8 earthquake set off the mega-tsunami in Lituya Bay, Alaska, in 1958. It sent water roaring up mountainsides to reach elevations of 1,700 feet, and remains the largest tsunami recorded in modern times.

Another possibility is the movement of the fault itself caused the tsunami. Although the fault moved horizontally and not vertically, the steep slopes and other unique features on the floor of Palu Bay could have pushed water in front of them as they moved during the earthquake. “It’s like pushing your hand through a bathtub,” says Chris Rowan, a geologist at Kent State University. Researchers at the Karlsruhe Institute of Technology in Germany have done a preliminary study with a tsunami model, and found the lateral movement of the fault and the topography of the bay would be enough to generate a tsunami the size of the one that hit Palu.

Neither possibility precludes the other. “I think the most likely [scenario] is there’s a combination of both going on,” says Austin Elliott, a geologist at the University of Oxford. Whatever the cause was, Palu’s location at the end of a narrow, V-shaped bay “is the worst place for a tsunami,” Elliott says, because the steadily narrowing channel funnels the water into an ever-narrower space, making the waves even higher.

Tectonic Jigsaw Puzzle

The Palu–Koro Fault Zone, the system that ruptured during this quake, is in the middle of a geologic tangle where multiple tectonic plates come together. Below western Indonesia the Indo–Australian Plate is shoved below the Eurasian Plate, occasionally creating the classic megathrust earthquakes that can generate huge tsunamis (just as the magnitude 9.1 temblor did in 2004). But in eastern Indonesia, where Sulawesi is located, the Indo–Australian Plate is topped by continental crust that does not subduct —so it is simply ramming headlong into the crust of the Eurasian Plate, fracturing it. “You’ve kind of got this jigsaw of little plates,” Rowan says, creating a complex environment with “lots of active, dangerous faults.”

Credit: Amanda Montañez; Source: USGS

The dangers of the Palu–Koro Fault have been known since the 1970s, Elliott says. Work in the 1990s and 2000s showed the plates on either side of the fault were moving in opposite directions “faster than the San Andreas Fault,” he says, meaning considerable stress was building up along the fault. A 2017 paper identified this fault as the most dangerous in the area, and suggested a future rupture was most likely to occur in the center of the valley where Palu is situated.

Being situated in this spot exacerbated the damage in Palu because the valley is filled with “flat, weak, soft, wet sediment,” says Robert Hall, a geologist at Royal Holloway, University of London who co-authored the 2017 paper. “Building on top of that is like building on jelly,” because this loose ground intensifies the shaking, he says. (The same thing occurred with the Mexico City earthquake of 1985.)

Surveys of the bay floor will need to be done to confirm the cause of the Sulawesi tsunami. They can look for signs of a landslide, and clues as to how much the fault moved. However it was triggered, the event makes it clear that coastal communities in seismically active regions should not only be worried about tsunamis from subduction zones —and this needs to be better communicated to local communities, Elliott and other experts say. The bottom line, he adds, is: “If you’re at the coast and you feel such a large earthquake, you just should assume there was a tsunami.”

Incredible ‘Lost World’ of Underwater Volcanoes Discovered Deep in The Ocean


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And it’s teeming with life.

Hidden below the waves off the east coast of Australia, scientists have discovered a ‘lost world’ of epic volcanic peaks buried under the Tasman Sea, never before seen with human eyes.

This range of volcanic seamounts – underwater mountains formed by ancient, extinct volcanoes – towers some 3 kilometres (1.9 miles) above the ocean floor. Despite the immense height, it has never been previously detected, since even the highest peaks are concealed 2 km (1.2 miles) below the surface of the South Pacific.

“Our multibeam mapping has revealed in vibrant detail, for the first time, a chain of volcanic seamounts rising up from an abyssal plain about 5,000 metres (16,400 ft) deep,” explains marine geoscientist Tara Martin from Australia’s CSIRO.

“This is a very diverse landscape and will undoubtedly be a biological hotspot that supports a dazzling array of marine life.”

https://player.vimeo.com/video/293879340

The researchers say the volcanic terrain varies in size and shape, including both sharp peaks and broad plateaus punctuated with smaller conical hills.

The discovery, made aboard the CSIRO research vessel Investigator, occurred during a voyage led by scientists from Australian National University.

The team was examining the relationship between nutrient levels and phytoplankton behaviour in the East Australian Current when their seafloor mapping detected the dramatic, uncharted contours, produced in another era of history.

“We’re pretty sure that these seamounts were related to the break up of Australia and Antarctica. It was about 30 million years ago,” Martin explained to ABC News.

“As Australia and Antarctica and Tasmania all broke up, a big hotspot came in under the earth’s crust, made these volcanoes, and then helped the Earth’s crust break so that all of those areas could start to drift apart.”

Future research is already being planned to study the terrain and its marine life later in the Australian summer, but already the researchers think these volcanic valleys might serve as a kind of navigational hub for creatures who live in the deep.

051 volcanic seamounts 3

“These seamounts may act as an important signpost on an underwater migratory highway for the humpback whales we saw moving from their winter breeding to summer feeding grounds,” one of the team, zoologist and bird researcher Eric Woehler from the University of Tasmania, said in a statement.

“We expect that these seamounts will be a biological hotspot year round, and the summer visit will give us another opportunity to uncover the mysteries of the marine life they support.”

In addition to the humpbacks, the researchers found increased ocean productivity over the seamounts, including spikes in phytoplankton activity, plus numerous sightings of other marine life, such as a giant pod of 60-80 pilot whales, and seabirds (four species each of albatross and petrels).

051 volcanic seamounts 3Humpback whale

Given how new this discovery is, we don’t fully understand yet how this lost world and its ocean-dwelling inhabitants interact.

But there’s no doubting we’ve uncovered a vibrant and diverse ecosystem here – a convenient place to stop for food or directions, whether you’ve got scales, feathers, or mere plankton bits.

051 volcanic seamounts 3Black-browed albatross

“These seamounts act to change the oceanography in these areas,” Woehler told ABC News.

“They change the way the water flows around them. They change the dynamics of the system.”

What Ancient African Huts Reveal About Earth’s Magnetic Flips


Minerals in clays from the Iron Age may help scientists better understand how and why the magnetic poles swap places.

Auroras, products of Earth’s magentic field, dance over the planet in an image captured from the International Space Station in 2017.

 

For the last 170 years, a mysteriously weak patch of Earth’s magnetic field has grown in size, causing some geologists to think that the planet is gearing up to flip its magnetic poles. Now, buildings that were ritually burned down in Africa more than a thousand years ago are adding vital new clues to the case.

Clay fragments baked in the fires contain minerals that preserve the orientation of Earth’s magnetic field during the Iron Age, pushing back our records of these changes and offering some much-needed data from the Southern Hemisphere.

The discovery, described recently in the journal Geophysical Research Letters, also offers support for a theory about what causes the poles to flip—linking the weird weak spot in the magnetic field with an oddly dense region some 1,800 miles underneath Africa, at the boundary between Earth’s mantle and its outer core. The work will help geologists better understand how and why Earth’s magnetic poles occasionally reverse, and perhaps even aid predictions for when they will next make a flip.

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Locked in Position

Our planet has a solid inner core surrounded by a swirling outer core of molten iron. This churning region of hot rock creates a dynamo that generates our magnetic field, which acts as a protective bubble enveloping the entire Earth.

Among other benefits, this long-lived magnetic bubble deflects streams of charged particles constantly flowing from the sun, which would otherwise strip away our atmosphere and pummel the surface with damaging radiation. (The dynamic core is one of six big things that help make life possible on Earth.)

The dynamo is also what creates magnetic poles at each axis that roughly track with the geographic North and South Poles. But minerals in rocks that respond to magnetic cues show that—unlike the physical poles—the north and south magnetic poles have swapped places regularly over Earth’s 4.54 billion years of existence.

During the age of dinosaurs, Earth’s magnetic poles flipped about once every million years. More recently, pole reversals have happened once every 200,000 to 300,000 years or so. It’s been about 780,000 years since the last magnetic pole reversal, which suggests that one is geologically imminent.

Ever since the 1840s, scientists have also noticed that Earth’s magnetic field is getting weaker. The feeblest spot is an area straddling South America and southern Africa that researchers call the South Atlantic Anomaly.

To study the last few millennia—younger than ancient rocks, but older than direct scientific monitoring—scientists can measure magnetic orientations in certain archaeological artifacts. But this record is heavily biased toward the north. More than 90 percent of the data about the last 2,000 years of Earth’s magnetic field come from above the Equator.

To track the South Atlantic Anomaly, researchers are searching for more sites in the Southern Hemisphere. In 2015, scientists announced a fascinating new data source: burned huts in the Limpopo River Valley, an area that falls within modern-day Botswana, South Africa, and Zimbabwe.

About a thousand years ago, a group of Bantu-speaking people living in the valley ritually cleansed their villages during droughts by burning down huts and grain bins. These fires, which could reach temperatures hotter than 1,800 degrees Fahrenheit, wiped the villages’ slates clean—but inadvertently left geomagnetic records.

“When you burn clay at very high temperatures, you actually stabilize the magnetic minerals, and when they cool from these very high temperatures, they lock in a record of the Earth’s magnetic field,” study coauthor John Tarduno, a University of Rochester geophysicist, said in a statement.

Turbulent Core

Building on those results, the researchers have now found evidence that during the fifth and eighth centuries A.D., the region’s magnetic field was rapidly changing direction, much like it is today. These similarities, the researchers argue, mean that the South Atlantic Anomaly is just the latest version of a phenomenon that has long recurred in the area.

What’s more, the anomaly may have something to do with Earth’s shifting magnetic poles. The eastern half of the magnetic weak spot seems to correspond with a dense, steep-sided region of rock deep below Africa, at the core-mantle boundary.

Just as rocks in a stream can create eddies, this dense region—called the African Large Low Shear Velocity Province—may cause the outer core to circulate in unusual ways, expelling lines of the core’s magnetic field and diluting the planetary field above.

Since this region has been in place for more than a hundred million years, some scientists argue that it may have seeded past pole reversals. In rare circumstances, the expelled field lines may have created a regional magnetic field that was the opposite of Earth’s as a whole, triggering a planet-wide flip.

That said, the researchers caution that they still need more data and better models before they figure out precisely how and why Earth’s poles reverse.

“We now know this unusual behavior has occurred at least a couple of times before the past 160 years, and is part of a bigger long-term pattern,” study coauthor Vincent Hare, a postdoctoral researcher at the University of Rochester, said in a statement. “However, it’s simply too early to say for certain whether this behavior will lead to a full pole reversal.”

There’s Mounting Evidence The African Continent Is Splitting in Two


A huge crack has appeared in Kenya, and it’s growing.

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A large crack, stretching several kilometres, made a sudden appearance recently in south-western Kenya.

The tear, which continues to grow, caused part of the Nairobi-Narok highway to collapse and was accompanied by seismic activity in the area.

The Earth is an ever-changing planet, even though in some respects change might be almost unnoticeable to us. Plate tectonics is a good example of this.

But every now and again something dramatic happens and leads to renewed questions about the African continent splitting in two.

The Earth’s lithosphere (formed by the crust and the upper part of the mantle) is broken up into a number of tectonic plates.

These plates are not static, but move relative to each other at varying speeds, “gliding” over a viscous asthenosphere.

Exactly what mechanism or mechanisms are behind their movement is still debated, but are likely to include convection currents within the asthenosphere and the forces generated at the boundaries between plates.

These forces do not simply move the plates around, they can also cause plates to rupture, forming a rift and potentially leading to the creation of new plate boundaries.

The East African Rift system is an example of where this is currently happening.

The East African Rift Valley stretches over 3,000 km from the Gulf of Aden in the north towards Zimbabwe in the south, splitting the African plate into two unequal parts: the Somali and Nubian plates.

Activity along the eastern branch of the rift valley, running along Ethiopia, Kenya and Tanzania, became evident when the large crack suddenly appeared in south-western Kenya.

Why does rifting happen?

When the lithosphere is subject to a horizontal extensional force it will stretch, becoming thinner. Eventually, it will rupture, leading to the formation of a rift valley.

AfricaSplit1(Shutterstock)

This process is accompanied by surface manifestations along the rift valley in the form of volcanism and seismic activity.

Rifts are the initial stage of a continental break-up and, if successful, can lead to the formation of a new ocean basin.

An example of a place on Earth where this has happened is the South Atlantic ocean, which resulted from the break up of South America and Africa around 138m years ago – ever noticed how their coastlines match like pieces of the same puzzle?

AfricaSplit2(Snider-Pellegrini/Wikimedia)

Continental rifting requires the existence of extensional forces great enough to break the lithosphere.

The East African Rift is described as an active type of rift, in which the source of these stresses lies in the circulation of the underlying mantle.

Beneath this rift, the rise of a large mantle plume is doming the lithosphere upwards, causing it to weaken as a result of the increase in temperature, undergo stretching and breaking by faulting.

AfricaSplit3(Snider-Pellegrini/Wikimedia)

Evidence for the existence of this hotter-than-normal mantle plume has been found in geophysical data and is often referred to as the “African Superswell”.

This superplume is not only a widely-accepted source of the pull-apart forces that are resulting in the formation of the rift valley but has also been used to explain the anomalously high topography of the Southern and Eastern African Plateaus.

Breaking up isn’t easy

Rifts exhibit a very distinctive topography, characterised by a series of fault-bounded depressions surrounded by higher terrain. In the East African system, a series of aligned rift valleys separated from each other by large bounding faults can be clearly seen from space.

AfricaSplit4(James Wood/Alex Guth, NASA)

Not all of these fractures formed at the same time, but followed a sequence starting in the Afar region in northern Ethiopia at around 30m years ago and propagating southwards towards Zimbabwe at a mean rate of between 2.5-5 cm a year.

Although most of the time rifting is unnoticeable to us, the formation of new faults, fissures and cracks or renewed movement along old faults as the Nubian and Somali plates continue moving apart can result in earthquakes.

However, in East Africa most of this seismicity is spread over a wide zone across the rift valley and is of relatively small magnitude. Volcanism running alongside is a further surface manifestation of the ongoing process of continental break up and the proximity of the hot molten asthenosphere to the surface.

A timeline in action

The East African Rift is unique in that it allows us to observe different stages of rifting along its length. To the south, where the rift is young, extension rates are low and faulting occurs over a wide area. Volcanism and seismicity are limited.

Towards the Afar region, however, the entire rift valley floor is covered with volcanic rocks.

This suggests that, in this area, the lithosphere has thinned almost to the point of complete break up. When this happens, a new ocean will begin forming by the solidification of magma in the space created by the broken-up plates.

Eventually, over a period of tens of millions of years, seafloor spreading will progress along the entire length of the rift.

The ocean will flood in and, as a result, the African continent will become smaller and there will be a large island in the Indian Ocean composed of parts of Ethiopia and Somalia, including the Horn of Africa.

Dramatic events, such as sudden motorway-splitting faults or large catastrophic earthquakes may give continental rifting a sense of urgency but, most of the time, it goes about splitting Africa without anybody even noticing.

Scientists Just Discovered a Strange New Type of Ice Inside Deep-Earth Diamonds


We’ve never seen ice-VII in nature before.

Thanks to the discovery of water trapped inside diamonds from deep underground, geologists are thinking our planet could have much more water inside than we ever knew.

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Not only would this require a slight recalculation of the total amount of water our planet happens to hold, it would change how we model everything from the way heat moves through the crust to models predicting the frequency of earthquakes.

Researchers made the find by analysing the way X-rays diffracted through diamonds collected from southern Africa, China, Zaire, and Sierra Leone.

The water molecules found in these diamonds were squeezed into a solid form of ice, but they represent briny pools of liquid water that would be trapped in rocks far, far down – below a section of the mantle called the transition zone.

While there have been previous estimates on how much water could be contained by the hot, pressurised rocks at those depths, the only way to be confident in any of the guesses is to acquire a sample.

Since we’re talking more than 600 kilometres (roughly 400 miles) underground, you can forget digging down to grab a handful of magma.

Luckily there’s a solution in nature’s own tiny glass elevator – the diamond.

Only recently flecks of a mineral called calcium silicate perovskite (CaSiO3) were discovered inside a diamond. Despite the mineral’s predicted prevalence in our planet’s geology, it had never been seen – because it forms so far underground.

Similarly, the water molecules from below the transition zone were held under pressure inside flaws in the diamond crystal’s matrix of carbon atoms.

Squeezing water molecules together forces them to arrange themselves into different structures, effectively turning them into forms of ice – and it’s not like the simple stuff you can find in your freezer.

Different pressures can push the water molecules into a range of configurations, and this particular structure is called ice-VII. While it has been produced in the laboratory using containers pressurised to tens of thousands of atmospheres, this is the first time ice-VII has been shown to exist in the natural world, officially making it a bona fide mineral.

Based on the team’s analysis of the diamonds, the water molecules must have become trapped as liquid when crystals formed around 610 to 800 kilometres (400 to 500 miles) beneath the surface.

Only as they ascended did the changing pressure push them into a form that allowed them to stick in place as ice-VII.

The good news is the inclusions provide the first hard evidence that unbound water exists at such depths, most likely as a salty fluid.

Unfortunately it doesn’t say how much water there is inside such pockets, or how common these aqueous zones would be.

Knowing more about them would help inform our understanding of how soluble radioactive particles flow beneath the crust, which in turn would affect how we calculate the transfer of heat from the core to the surface.

Nailing down the distribution of water could also alter predictions on how sections of the crust sink beneath one another.

The mineral constitution of tectonic plates makes a significant difference to their density and the temperature at which they melt, factors that could help improve earthquake models.

Having confirmation that flowing water does indeed exist at these depths is a good start, and makes you wonder what other secrets might be lurking inside the world’s favourite gem.

A Mysterious Anomaly Under Africa Is Radically Weakening Earth’s Magnetic Field


This could be precursor to Earth’s poles swapping places.

Above our heads, something is not right. Earth’s magnetic field is in a state of dramatic weakening – and according to mind-boggling new research, this phenomenal disruption is part of a pattern lasting for over 1,000 years.

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Earth’s magnetic field doesn’t just give us our north and south poles; it’s also what protects us from solar winds and cosmic radiation – but this invisible force field is rapidly weakening, to the point scientists think it could actually flip, with our magnetic poles reversing.

As crazy as that sounds, this actually does happen over vast stretches of time. The last time it occurred was about 780,000 years ago, although it got close again around 40,000 years back.

When it takes place, it’s not quick, with the polarity reversal slowly occurring over thousands of years.

Nobody knows for sure if another such flip is imminent, and one of the reasons for that is a lack of hard data.

The region that concerns scientists the most at the moment is called the South Atlantic Anomaly – a huge expanse of the field stretching from Chile to Zimbabwe. The field is so weak within the anomaly that it’s hazardous for Earth’s satellites to enter it, because the additional radiation it’s letting through could disrupt their electronics.

“We’ve known for quite some time that the magnetic field has been changing, but we didn’t really know if this was unusual for this region on a longer timescale, or whether it was normal,” says physicist Vincent Hare from the University of Rochester in New York.

One of the reasons scientists don’t know much about the magnetic history of this region of Earth is it lacks what’s called archeomagnetic data – physical evidence of magnetism in Earth’s past, preserved in archaeological relics from bygone ages.

One such bygone age belonged to a group of ancient Africans, who lived in the Limpopo River Valley – which borders Zimbabwe, South Africa, and Botswana: regions that fall within the South Atlantic Anomaly of today.

Approximately 1,000 years ago, these Bantu peoples observed an elaborate, superstitious ritual in times of environmental hardship.

During times of drought, they would burn down their clay huts and grain bins, in a sacred cleansing rite to make the rains come again – never knowing they were performing a kind of preparatory scientific fieldwork for researchers centuries later.

“When you burn clay at very high temperatures, you actually stabilise the magnetic minerals, and when they cool from these very high temperatures, they lock in a record of the earth’s magnetic field,” one of the team, geophysicist John Tarduno explains.

As such, an analysis of the ancient artefacts that survived these burnings reveals much more than just the cultural practices of the ancestors of today’s southern Africans.

“We were looking for recurrent behaviour of anomalies because we think that’s what is happening today and causing the South Atlantic Anomaly,” Tarduno says.

“We found evidence that these anomalies have happened in the past, and this helps us contextualise the current changes in the magnetic field.”

Like a “compass frozen in time immediately after [the] burning”, the artefacts revealed that the weakening in the South Atlantic Anomaly isn’t a standalone phenomenon of history.

Similar fluctuations occurred in the years 400-450 CE, 700-750 CE, and 1225-1550 CE – and the fact that there’s a pattern tells us that the position of the South Atlantic Anomaly isn’t a geographic fluke.

“We’re getting stronger evidence that there’s something unusual about the core-mantel boundary under Africa that could be having an important impact on the global magnetic field,” Tarduno says.

The current weakening in Earth’s magnetic field – which has been taking place for the last 160 years or so – is thought to be caused by a vast reservoir of dense rock called the African Large Low Shear Velocity Province, which sits about 2,900 kilometres (1,800 miles) below the African continent.

“It is a profound feature that must be tens of millions of years old,” the researchers explained in The Conversation last year.

“While thousands of kilometres across, its boundaries are sharp.”

This dense region, existing in between the hot liquid iron of Earth’s outer core and the stiffer, cooler mantle, is suggested to somehow be disturbing the iron that helps generate Earth’s magnetic field.

There’s a lot more research to do before we know more about what’s going on here.

As the researchers explain, the conventional idea of pole reversals is that they can start anywhere in the core – but the latest findings suggest what happens in the magnetic field above us is tied to phenomena at special places in the core-mantle boundary.

If they’re right, a big piece of the field weakening puzzle just fell in our lap – thanks to a clay-burning ritual a millennia ago. What this all means for the future, though, no-one is certain.

“We now know this unusual behaviour has occurred at least a couple of times before the past 160 years, and is part of a bigger long-term pattern,” Hare says.

“However, it’s simply too early to say for certain whether this behaviour will lead to a full pole reversal.”

Earth’s Magnetic Poles Are Overdue For a Switch And We’re Not Prepared


Earth’s magnetic field is pretty adept at flipping polarity. The poles have swapped, reversing north and south, many times over the planet’s history.

Within the last 20 million years, Earth has fallen into the pattern of pole reversal every 200,000 to 300,000 years, and between successful swaps, the poles sometimes even attempt to reverse and then snap back into place.

About 40,000 years ago, the poles made one such unsuccessful attempt, and the last full swap was about 780,000 years ago, so we’re a bit overdue for a pole reversal based on the established pattern.

The planet’s magnetic field is already shifting, which could signify the poles are preparing to flip, and while we can’t yet confirm that a reversal is on the near horizon, it is well within the realm of possibility.

While a pole reversal isn’t entirely uncommon when you consider Earth’s history, this time it could have serious implications for humanity.

To try to determine whether or not a flip is imminent, scientists have begun using satellite imagery and complex calculations to study the shifting of the magnetic field.

They’ve found that molten iron and nickel are draining energy from the dipole at the edge of the Earth’s core, which is where the planet’s magnetic field is generated.

They also found that the north magnetic pole is especially turbulent and unpredictable. If the magnetic blocks become strong enough to sufficiently weaken the dipole, the poles will officially switch.

Again, while it is not a certainty that the switch will happen soon, this activity at the Earth’s core suggests that it is possible in the near future. So, how might a pole switch impact our lives?

The Earth’s magnetic field protects the planet from solar and cosmic rays. When the poles switch, this protective shield could diminish to as little as one-tenth of its typical ability.

The switching process could take centuries, and the entire time, radiation would be able to get closer to the planet than usual.

Eventually, this radiation could reach the surface of the Earth, rendering some regions uninhabitable and causing entire species to go extinct.

Before that happened, though, a weakened magnetic field would likely impact orbiting satellites, which have suffered from memory failure and other damage when exposed to such radiation in the past.

Damage to satellites caused by decreased protection from the magnetic field could affect the satellite timing systems that control electric grids.

These grids could fail, leading to worldwide blackouts that experts predict could last for decades.

Without functioning electric grids, we couldn’t use cell phones, household appliances, and so much more. The sudden blackouts would have hospitals scrambling for backup power sources, putting countless lives at risk.

GPS technology would also be compromised, affecting everything from military operations to our ability navigate our cars.

Additionally, we are becoming more reliant on technology by the day, with autonomous vehicles, artificial intelligence (AI), and other innovations all advancing rapidly.

By the time a pole switch did take place, these innovations could be a regular part of our daily lives, furthering the potential for disruption.

It’s true that we live in an age where data rules all. From how we communicate to how we get around to how our governments and critical facilities run, it all comes down to how we send and store data, so if the world’s satellites are damaged or rendered nonfunctional, life as we know it could forever change.

But this isn’t a doomsday prediction. While the poles will inevitably flip again at some point, our ability to recognise this possibility in advance allows us to prepare for it.

For starters, satellite companies can begin to collaborate, sharing ideas with one another on how to equip satellites to deal with a pole reversal.

Government and university researchers can focus their efforts on developing new satellites specifically designed to withstand extreme radiation and space weather.

Governments, businesses, and communities can come together to form action plans.

They can find ways to store energy and ensure the public is educated on the subject of pole reversal, so that when it happens, the situation won’t cause widespread panic.

Earth’s poles have been switching for millions of years, and they will continue to do so for the foreseeable future. The best thing we can do is prepare now so we’re ready the next time it happens.

We All Nearly Missed The Largest Underwater Volcano Eruption Ever Recorded


She was flying home from a holiday in Samoa when she saw it through the airplane window: a “peculiar large mass” floating on the ocean, hundreds of kilometres off the north coast of New Zealand.

 

The Kiwi passenger emailed photos of the strange ocean slick to scientists, who realised what it was – a raft of floating rock spewed from an underwater volcano, produced in the largest eruption of its kind ever recorded.

“We knew it was a large-scale eruption, approximately equivalent to the biggest eruption we’ve seen on land in the 20th Century,” says volcanologist Rebecca Carey from the University of Tasmania, who’s co-led the first close-up investigation of the historic 2012 eruption.

The incident, produced by a submarine volcano called the Havre Seamount, initially went unnoticed by scientists, but the floating rock platform it generated was harder to miss.

467 underwater volcano havre 1High-resolution seafloor topography of the Havre caldera (Rebecca Carey, University of Tasmania/Adam Soule, WHOI)

Back in 2012, the raft – composed of pumice rock – covered some 400 square kilometres (154 square miles) of the south-west Pacific Ocean, but months later satellites recorded it dispersing over an area twice the size of New Zealand itself.

Under the surface, the sheer scale of the rocky aftermath took scientists aback when they inspected the site in 2015, at depths as low as 1,220 metres (4,000 feet).

“When we looked at the detailed maps from the AUV [autonomous underwater vehicle], we saw all these bumps on the seafloor and I thought the vehicle’s sonar was acting up,” says volcanologist Adam Soule from the Woods Hole Oceanographic Institution.

“It turned out that each bump was a giant block of pumice, some of them the size of a van. I had never seen anything like it on the seafloor.”

The investigation – conducted with the AUV Sentry and the remotely operated vehicle (ROV) Jason – reveals that Havre Seamount’s eruption was more complex than anyone topside ever knew.

The caldera, which spans nearly 4.5 kilometres (about 3 miles), discharged lava from some 14 vents in a “massive rupture of the volcanic edifice”, producing not just pumice rock, but ash, lava domes, and seafloor lava flows.

It may have been (thankfully) buried under an ocean of water, but for a sense of scale, think roughly 1.5 times larger than the 1980 eruption of Mount St. Helens – or 10 times the size of the 2010 Eyjafjallajökull eruption in Iceland.

The researchers say that of the material erupted, three-quarters or more floated to the surface and drifted away – tonnes of it washing up onto shorelines an ocean away.

The rest of it was scattered around the nearby seafloor, bringing devastation to the biological communities who called it home, and are only now rebounding.

“The record of this eruption on Havre volcano itself is highly unfaithful,” says Carey.

“[I]t preserves a small component of what was actually produced, which is important for how we interpret ancient submarine volcanic successions that are now uplifted and are highly prospective for metals and minerals.”

With samples collected by the submersibles yielding what the scientists say could amount to a decade’s worth of research, it’s a huge, rare opportunity to study what takes place when a volcano erupts under the sea – a phenomenon that actually accounts for more than 70 percent of all volcanism on Earth, even if it’s a bit harder to spot.

“Underwater eruptions are fundamentally different than those on land,” says one of the team, geophysicist Michael Manga from UC Berkeley.

“There is no on-land equivalent.”

Ocean Levels Aren’t Just Rising, the Sea Floor Is Sinking, Too


Sea levels are rising as a result of accelerating climate change, but it turns out we might be underestimating just how rapidly it’s occurring. Get ready for your world to crumble, because a new geological study is saying that’s precisely what’s happening.

sunrise.floor.otherraw0036

In a paper published December 23 in the journal Geophysical Research Letters, Dutch and Australian geologists outline how the increasing mass of seawater has deformed the bottom of the ocean, making sea level rise in some regions appear less drastic than it really is, and as a result distorting current assessment of global ice melt. The researchers argue we’ve been underestimating annual sea level rise from 1993 to 2014 by 0.13 millimeters.

In some regions of the world this number is even bigger. For instance, the study’s authors say previous estimates of sea level rise in the Arctic Ocean have been off by up to a whole millimeter each year. A millimeter might not sound like a whole lot, but spread over millions of square miles of ocean, we’re talking about a massive amount of water.

Sea Ice Patterns
The Arctic Ocean may have risen up to a millimeter more per year than previous estimates showed.
Why the disparity in how we’re tracking sea level rise? These measurements come down to the difference between geocentric sea level and barystatic sea level. Geocentric sea level refers to sea level as measured from the center of the Earth, whereas barystatic sea level refers to the actual mass of water in the sea. The issue that arises here is that measuring sea level rise by satellite, as NASA has done for the last 25 years, only captures geocentric sea level, since satellites measure altitudes. This is a really useful way to track the effects of climate change across the globe, but it fails to gauge how a sinking seafloor can mask the actual increase in ocean water mass.

“Because satellite altimetry observes sea level in a geocentric reference frame, global mean sea level estimates derived from altimetry will not observe the increase in ocean volume due to ocean bottom subsidence, and hence, they may underestimate GMSL rise,” write the study’s authors.

The Earth has had basically the same amount of water for billions of years, so it may sound odd that the seafloor is sinking due to increased ocean water mass. The explanation for this is pretty simple, though: Water is denser than ice, so when sea-based ice masses melt and mix with the ocean, they increase the average density of the ocean. In addition, land-based glaciers and ice-masses are melting into the ocean, exacerbating the ocean’s mass, and increasing the weight ocean floors have to withstand.

seafloor
Geologists say we’ve underestimated the true extent of sea level rise because sea floors are dropping under the pressure of increased water mass.
It’s like if your cereal bowl somehow got deeper, but the milk stayed at the same level. From the surface, it would look the same, but in fact, the mass of the milk has actually increased. This is what geologists say is happening with Earth’s oceans.

It’s not totally clear what a sinking seafloor means for humans, but if these geologists’ measurements are correct, then we’ve been underestimating the true rate of sea level rise for over 20 years. The biggest risk is posed to people who live on coasts and island nations — areas already being inundated by rising waters. Further research will show just how severe the underestimate has been.

Abstract: Present-day mass redistribution increases the total ocean mass and, on average, causes the ocean bottom to subside elastically. Therefore, barystatic sea level rise is larger than the resulting global mean geocentric sea level rise, observed by satellite altimetry and GPS-corrected tide gauges. We use realistic estimates of mass redistribution from ice mass loss and land water storage to quantify the resulting ocean bottom deformation and its effect on global and regional ocean volume change estimates. Over 1993–2014, the resulting globally averaged geocentric sea level change is 8% smaller than the barystatic contribution. Over the altimetry domain, the difference is about 5%, and due to this effect, barystatic sea level rise will be underestimated by more than 0.1 mm/yr over 1993–2014. Regional differences are often larger: up to 1 mm/yr over the Arctic Ocean and 0.4 mm/yr in the South Pacific. Ocean bottom deformation should be considered when regional sea level changes are observed in a geocentric reference frame.

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