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Geologists Find Magma ‘Conveyor Belt’ That Fuelled Earth’s Longest Supervolcano Burst

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A subterranean ‘conveyor belt’ of magma, pushing up to Earth’s surface for millions of years, was responsible for the longest stretch of erupting supervolcanoes ever seen on the planet, according to new research.

 

Shifts in the seabed caused channels to form, through which the magma could flow freely, researchers say. This resulted in an extensive period of eruptions lasting from around 122 million years ago to 90 million years ago; exceptional, considering that typically these types of flows lasted just 1-5 million years.

This all took place on the Kerguelen Plateau, which now sits under the Indian Ocean. It’s what’s known as a large igneous province or LIP, a widespread accumulation of magma and lava. Scientists can use these LIPs to trace volcanic activity back through time.

“Extremely large accumulations of volcanic rocks – known as large volcanic provinces – are very interesting to scientists due to their links with mass extinctions, rapid climatic disturbances, and ore deposit formation,” says geologist Qiang Jiang, from Curtin University in Australia.

Jiang and his colleagues used samples of black basaltic rocks taken from the sea floor, together with an argon isotope dating method to determine the spread and rise of the LIP as it sat on what’s known as a mantle plume, created by rising magma.

 

Across the 30 or so years of intense activity, the Kerguelen Plateau rose by about 20 centimetres (7.87 inches) a year, the researchers say. Across the gigantic size of the LIP – about three times the size of Japan – the outpouring equates to lava filling 184,000 Olympic-sized swimming pools per year.

The Kerguelen Plateau saw such a long and steady run of supervolcano activity because of its unique configuration, the study suggests: a mantle plume combining with slow spreading mid-ocean ridges channelling the magma upwards.

“The volcanism lasted for so long because magmas caused by the mantle plume were continuously flowing out through the mid-oceanic ridges, which successively acted as a channel, or a ‘magma conveyor belt’ for more than 30 million years,” says geologist Hugo Olierook, from Curtin University.

“Other volcanoes would stop erupting because, when temperatures cooled, the channels became clogged by ‘frozen’ magmas. For the Kerguelen Plateau, the mantle plume acts as a Bunsen burner that kept allowing the mantle to melt, resulting in an extraordinarily long period of eruption activity.”

That’s a lot of volcanic eruption activity over many millions of years, but the rate dropped significantly about 90 million years ago, and scientists still aren’t sure why. Associated volcanic activity continues to this day, on a much smaller scale.

It’s a fascinating look at the past history of our planet, and of course it informs our study of volcanic activity in the present day too – the more we know about how these kinds of systems can form and stay active, the better we can understand the interactions taking place under the Earth’s surface right now.

“Finding this long, continuous eruption activity is important because it helps us to understand what factors can control the start and end of volcanic activity,” says geochronologist Fred Jourdan, from Curtin University.

“This has implications for how we understand magmatism on Earth, and on other planets as well.”

The research has been published in Geology.

 



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The World’s Largest Shield Volcano Isn’t What We Thought It Was

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Beneath the cyan and cerulean waters of the Northwestern Hawaiian Islands lurks a leviathan. Its true extent has been hidden for many years, but no more. What geologists have found is a marvel – the biggest, hottest known volcano in the world.

 

Startlingly, it’s more than twice the size of the previous record holder, Mauna Loa on the Island of Hawai’i. And it could change our understanding of the vast Hawaiian-Emperor seamount chain of volcanoes that span the North Pacific Ocean.

The new record-breaker spreads across around 148,000 cubic kilometres (35,507 cubic miles) beneath the waves of the Papahānaumokuākea Marine National Monument, compared to Mauna Loa’s 74,000.

Only relatively small rocky pinnacles known as the Gardner Pinnacles break the surface, giving the volcano its name – Pūhāhonu, the Hawai’ian word for ‘turtle rising for breath’.

“We are sharing with the science community and the public that we should be calling this volcano by the name the Hawaiians have given to it, rather than the western name for the two rocky small islands that are the only above sea level remnants of this once majestic volcano,” said geologist Michael Garcia of the University of Hawai’i at Manoa.

Back in the 1970s, low-resolution bathymetric data suggested Pūhāhonu was around 54,000 cubic kilometres in size, then thought to be the largest volcano before a more extensive survey of Mauna Loa revealed its true size.

 

Pūhāhonu only regains its crown after extensive surveys of the region added high-resolution bathymetric and multibeam sonar data to our existing understanding of the northwest Hawaiian Ridge, from which the volcano rises.

Geologists combined this with petrologic analyses of rock samples retrieved from the volcano, refining volume calculations and modelling based on these parameters.

“It has been proposed that hotspots that produce volcano chains like Hawai’i undergo progressive cooling over 1-2 million years and then die,” Garcia said.

“However, we have learned from this study that hotspots can undergo pulses of melt production. A small pulse created the Midway cluster of now extinct volcanoes and another, much bigger one created Pūhāhonu. This will rewrite the textbooks on how mantle plumes work.”

volc chonk(Garcia et al., EPSL, 2020)

Pūhāhonu is a shield volcano, between 12.5 and 14.1 million years old, formed by a single magma plume surging through the mantle. Over the millennia, this source gradually built the volcano to a height of 4,500 metres (14,764 feet) from its lowest point, spanning an area 275 kilometres (171 miles) long and 90 kilometres (56 miles) wide.

Chemical analysis of rock collected from the volcano revealed a higher concentration of an olivine mineral called forsterite than we’ve ever seen in a Hawaiian volcano. This mineral indicates magma on the higher end of the temperature range.

 

The calcium oxide content in the forsterite allowed the team to infer the depth at which it formed, confirming that it did form in magma. Simulations allowed the team to calculate the pressure at which the forsterite formed, and the temperature.

According to these calculations, the magma clocked in at 1,703 degrees Celsius (3,097 degrees Fahrenheit) – hotter than any other Hawaiian basalt. This extreme temperature is reflected in the volcano’s size, the researchers said.

It’s an impressive beast in its own right. But it also has important implications for our understanding of the processes that create these incredible formations.

“The Hawaiian-Emperor Chain is arguably the world’s best studied surface expression of a mantle plume,” the researchers wrote in their paper.

“Nonetheless, new insights into its magmatic and thermal history continue to be revealed as more of the Hawaiian-Emperor Chain is mapped and sampled. These insights are providing a more complete understanding of the mechanics and thermal evolution of mantle plumes.”

The research has been published in Earth and Planetary Science Letters.

 



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An Ancient Meteorite Is The First Chemical Evidence of Volcanic Convection on Mars

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For many years, we thought Mars was dead. A dusty, dry, barren planet, where nothing moves but the howling wind. Recently, however, pieces of evidence have started to emerge, hinting that Mars is both volcanically and geologically active.

 

Well, the idea of a volcanically active Mars just got a little more real. A meteorite that formed deep within the belly of Mars has just provided the first solid chemical proof of magma convection within the Martian mantle, scientists say. 

Crystals of olivine in the Tissint meteorite that fell to Earth in 2011 could only have formed in changing temperatures as it was rapidly swirled about in magma convection currents – showing that the planet was volcanically active when the crystals formed around 574 to 582 million years ago – and it could still be intermittently so today.

“There was no previous evidence of convection on Mars, but the question ‘Is Mars a still volcanically active planet?’ was previously investigated using different methods,” explained planetary geologist Nicola Mari of the University of Glasgow to ScienceAlert.

“However, this is the first study that proves activity in the Mars interior from a purely chemical point of view, on real Martian samples.”

Olivine, a magnesium iron silicate, isn’t rare. It crystallises from cooling magma, and it’s very common in Earth’s mantle; in fact, the olivine group dominates Earth’s mantle, usually as part of a rock mass. On Earth’s surface, it’s found in igneous rock.

 

It’s fairly common in meteorites. And olivine is also fairly common on Mars. In fact, the presence of olivine on the surface of Mars has previously been taken as evidence of the planet’s dryness, since the mineral weathers rapidly in the presence of water.

But when Mari and his team started studying the olivine crystals in the Tissint meteorite to try to understand the magma chamber where it formed, they noticed something strange. The crystals had irregularly spaced phosphorus-rich bands.

We know of this phenomenon on Earth – it’s a process called solute trapping. But it was a surprise to find it on Mars.

magma olivine(Mari et al., Meteoritics & Planetary Science, 2020)

“This occurs when the rate of crystal growth exceeds the rate at which phosphorus can diffuse through the melt, thus the phosphorus is obliged to enter the crystal structure instead of ‘swimming’ in the liquid magma,” Mari said.

“In the magma chamber that generated the lava that I studied, the convection was so vigorous that the olivines were moved from the bottom of the chamber (hotter) to the top (cooler) very rapidly – to be precise, this likely generated cooling rates of 15-30 degrees Celsius per hour for the olivines.”

 

The larger of the olivine crystals were also revealing. Traces of nickel and cobalt are in agreement with previous findings that they originated from deep under the Martian crust, a depth of 40 to 80 kilometres (25 to 50 miles).

This supplied the pressure at which they formed; along with the equilibration temperature of olivine, the team could now perform thermodynamic calculations to discover the temperature in the mantle at which the crystals formed.

They found that the Martian mantle probably had a temperature of around 1,560 degrees Celsius in the Martian Late Amazonian period when the olivine formed. This is very close to the ambient mantle temperature of Earth of 1,650 degrees Celsius during the Archean Eon, 4 to 2.5 billion years ago.

That doesn’t mean Mars is just like an early Earth. But it does mean that Mars could have retained quite a bit of heat under its mantle; it’s thought that, because it lacks the plate tectonics that help to dissipate heat on Earth, Mars may cool more slowly.

“I really think that Mars could be a still volcanically active world today, and these new results point toward this,” Mari told ScienceAlert.

“We may not see a volcanic eruption on Mars for the next 5 million years, but this doesn’t mean that the planet is inactive. It could just mean that the timing between eruptions between Mars and Earth is different, and instead of seeing one or more eruptions per day (as on Earth) we could see a Martian eruption every n-millions of years.”

We’ll need more research to confidently say this hypothesis checks out. But these results also mean that previous interpretations of the planet’s dryness based on surface olivine may need to be revisited. (Although let us be clear, Mars is still extremely dry.)

The ongoing NASA InSight mission that recently found evidence of Marsquakes, measures – among other things – the heat flux from the Martian crust. If Mars is still volcanically active, we may know more about it really soon.

The research has been published in Meteoritics & Planetary Science.

 



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‘Throat of Fire’ Volcano in Ecuador Shows Early Signs of Collapse, Scientists Warn

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Tungurahua, an active stratovolcano in Ecuador, is an ancient mountain that’s picked up many names over the centuries.

In the indigenous tongue of the Quechua peoples, the name means ‘Throat of Fire’. Others say Tungurahua is Quichua for ‘crater’. One nickname is the Black Giant.

 

Something everybody can agree upon, though, is that this old volcano has been a danger for a very long time – although the latest rumblings may signify a menace greater than any ordinary eruption.

According to a new analysis, Tungurahua may be showing early warning signs of what could be a catastrophic structural collapse, thought to be due to instabilities wrought by the damage of ongoing magma activity inside the volcano.

“Using satellite data we have observed very rapid deformation of Tungurahua’s west flank, which our research suggests is caused by imbalances between magma being supplied and magma being erupted,” says geophysical volcanologist James Hickey from the University of Exeter in the UK.

Tungurahua has been persistently active since 1999, but if 20 years of relatively frequent eruptions seems like a long time, it’s not – at least not in the lifespan of this very long-lived volcano.

Tungurahua is actually on its third life, you might say, having already endured two of these structural collapses triggered by eruptions. The first Tungurahua edifice (Tungurahua I) collapsed sometime around the end of the Late Pleistocene.

 

For thousands of years, the volcano then slowly rebuilt itself inside the remains of its original caldera. Then, about 3,000 years ago, Tungurahua II let forth, with another eruption prompting a partial collapse of the west flank.

When the sides of volcanoes give way like this, massive landslides can result, with avalanches of rock that can travel for up to tens of kilometres.

The collapse 3,000 years ago is thought to have unleashed a debris avalanche laying ruin to an area of some 80 square kilometres (over 11,000 football fields in size).

Given a single eruption in 1999 forced the evacuation of over 25,000 people in nearby areas, it’s hard to understate the threat an actual flank collapse could pose to Tungurahua’s living neighbours.

Nonetheless, according to Hickey and his team’s modelling, significant surface deformation on Tungurahua’s west flank (involving temporary uplift of about 3.5 cm, resulting from recent volcanic activity), is suggestive that a collapse could perhaps occur if the stresses do not abate.

“Shallow and rapid pressurisation from this inclined deformation source can generate shear stress along the collapse surface, which increases with greater volumes of magma,” the authors write in their paper.

 

“This may contribute to slope instability during future unrest episodes and promote flank failure, with general application to other volcanoes worldwide displaying asymmetric deformation patterns.”

That said, the researchers acknowledge that their study is no prediction of certain doom. If anything, the findings could help us monitor these processes, so we can try to anticipate ahead of time what future conditions might trigger catastrophe.

“Magma supply is one of a number of factors that can cause or contribute to volcanic flank instability, so while there is a risk of possible flank collapse, the uncertainty of these natural systems also means it could remain stable,” Hickey says.

Let’s hope so. If not, the throat of fire may be about to speak again, and it won’t be good news for anyone close enough to hear.

The findings are reported in Earth and Planetary Science Letters.

 



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The Biggest Volcano on Io May Be About to Erupt, And Scientists Are Watching Closely

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The biggest volcano on Jupiter’s moon Io could be about to blow. Decades of observation have revealed a periodic cycle in the volcano’s eruptions; according to past behaviour, it’s due for the next one any day.

 

That potential burst of activity – or lack thereof – could help us to better understand the volcano and Io itself, the most volcanically active object in the Solar System.

The massive volcano, called Loki, was originally discovered to have a cycle of around 540 days. This was based on years of observations between 1988 and 2000, described in a 2002 paper led by physicist and planetary scientist Julie Rathbun of the Planetary Science Institute.

At the start of the eruption, Loki would brighten, and remain bright for around 230 days before falling darker again. Then, the cycle would repeat. This was happening like clockwork until 2001, when the volcano stopped brightening and dimming.

Then, in 2013, Loki started up again, but on a slightly shorter cycle – 475 days, instead of 540. It’s been on a 475-day cycle ever since.

“If this behaviour remains the same, Loki should erupt in September 2019,” Rathbun said. “We correctly predicted that the last eruption would occur in May of 2018.”

Rathbun and her team interpreted Loki as a lake of lava in a crater-like depression called a patera about 200 kilometres (124 miles) across. As the cooling crust on the surface of the lake becomes gravitationally unstable and collapses into it, the pool “overturns”, flooded by fresh lava.

 

This was supported by observations reported in 2017 that saw waves of lava slowly rolling across the patera – a process that can take up to 230 days.

What caused the hiatus in this cycle between 2001 and 2013 is not yet known, but one possible explanation could implicate changes in the volatile content in the magma, which affects the density of both magma and crust. Even a small change can produce large variations in how long the crust takes to sink.

The last eruption started sometime between 23 May and 6 June 2018. That means the 475-day window is between 9 and 24 September. It may have already started.

“Volcanoes are so difficult to predict because they are so complicated. Many things influence volcanic eruptions, including the rate of magma supply, the composition of the magma – particularly the presence of bubbles in the magma, the type of rock the volcano sits in, the fracture state of the rock, and many other issues,” Rathbun said.

“We think that Loki could be predictable because it is so large. Because of its size, basic physics are likely to dominate when it erupts, so the small complications that affect smaller volcanoes are likely to not affect Loki as much.”

Rathbun presented her findings at the EPSC-DPS Joint Meeting 2019 in Geneva.

 



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Scientists Have Found a Way to Better Predict Where Volcanoes Will Erupt Next

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Not every volcanic eruption is a Mount Vesuvius-like catastrophe, with rivers of fire and flying rock that rains down on unsuspecting Pompeiians.

Sometimes, volcanoes’ summits collapse, forming miles-wide depressions called calderas, which are peppered by eruptive vents. When rivulets of magma force their way out of these vents, those small eruptions can spew dangerous amounts of lava and gas.

 

But the locations and threat levels of these vents are difficult to predict – eruptions can sometimes occur miles from the caldera’s center. That leaves cities located on or near volcanic fields, like Naples, Italy, facing a constant risk of poisonous volcanic gas, ash, and explosive bursts of lava.

Now, however, a group of scientists have figured out how to accurately pinpoint where on a volcano’s surface or in a caldera’s volcanic fields these damaging vent eruptions are likely to occur.

“Calderas have fed some of the most catastrophic eruptions on Earth and are extremely hazardous,” the scientists wrote in a new study published Wednesday in the journal Science Advances. That hazard is often underestimated by local populations, they added.

Mount Kilauea in Hawaii, which erupted last year, is speckled with such vents. The eruptions forced nearly 1,500 people to flee their homes, CBS News reported.

“These vents have lava coming out of them like fountains, which then leaks across the landscape like a slug,” Eleonora Rivalta, the lead author of the study, told Business Insider.

The scientists hope that insights from their new model could help communities like Hawaii’s better prepare for and anticipate future eruptions.

 

Magma’s fickle pathways

Magma, the liquid or semi-liquid rock under the Earth’s crust, makes up most of our planet’s mantle (its intermediary layer). When magma pushes its way to the surface, that causes a volcanic eruption.

Magma likes to take the path of least resistance as it surges upward. So figuring out what that path is can enable scientists to predict where it will next breach our planet’s surface. That’s what Rivalta’s team set out to do.

The easiest path, the researchers found, is for magma to move through rocks that are more “stretched out” than their nearby counterparts – less compressed, in other words.

Although many geologists thought the path of least resistance would be through an existing pathway or fault, Rivalta’s team found that vents are often “single-use only”, meaning magma erupts through them once and never again.

Rivalta and her colleagues used these discoveries to make computer models of future magma paths to the surface. They compared the predictions of their model to the known eruptive behaviour of vents across Italy’s Campi Fleigrei, outside of Naples.

 

This 8-mile-wide active volcanic field – known as the “burning fields” – first erupted almost 50,000 years ago, though the most recent major eruption was in 1538.

Rivalta’s model accurately mapped Campi Flegrei’s 70 eruptions over the past 15,000 years, including the highly damaging Monte Nuovo eruption in 1538.

Predicting the next Yellowstone eruption

Between 1600 and 2017, 278,880 people around the world were killed by volcanic activity and the consequences of those eruptions, like starvation or tsunamis.

Since the 1980s, deaths related to volcanic eruptions have been rather limited, as geographer Matthew Blackett reported in The Conversation. This isn’t because scientists have gotten better at predicting eruptions – it’s a matter of chance, since recent eruptions have been far from heavily populated areas.

So Rivalta hopes to leverage her group’s new research to give cities like Naples more information about impending eruptions. She also wants to apply this new model to Mount Etna in Sicily, and use it to examine the supervolcano under Yellowstone National Park.

That enormous volcano last erupted more than 640,000 years ago. If it were to erupt again, the supervolcano would spew ash across thousands of miles of the US.

Following the Yellowstone volcano’s last eruption, it collapsed on itself, creating a 1,500-square-mile caldera that’s ripe for new appearances of magma.

“Yellowstone is a caldera with tons and tons of vents,” Rivalta said. “The question of where the next one might appear is very relevant to this caldera.”

This article was originally published by Business Insider.

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We Just Learned The Moon Could Be Much Older Than We Thought

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The most comprehensive and widely-held theory of how the Moon formed is called the ‘giant impact hypothesis.’ That hypothesis states that about 150 million years after the Solar System formed, a roughly Mars-sized planet named Theia collided with Earth.

 

Though the timeline is hotly-debated in the scientific community, we know that this collision melted Theia and some of Earth, and that molten rock orbited around Earth until it coalesced into the Moon.

But now a new study, though not contradicting the giant impact hypothesis, is suggesting a different timeline, and an older Moon.

New research from scientists at the University of Cologne’s Institute of Geology and Mineralogy suggests that the Moon is older than the giant impact hypothesis says it is.

Their research is based on chemical analyses of Apollo lunar samples and it shows that the Moon formed only 50 million years after the Solar System, rather than 150 million years. This ages the Moon by 100 million years.

This is important work because understanding the age of the Moon helps us understand the age of the Earth. And this type of study can only be done with Moon rocks because they’re largely unchanged since the time of formation.

Earthly rocks have been subjected to geological processes for billions of years and don’t provide the same type of pristine record of formation that Moon rocks do.

 

The study is titled “Early Moon formation inferred from hafnium-tungsten systematics,” and is published in Nature Geoscience.

The evidence stems from the relationships between two rare elements: halfnium (Hf) and tungsten (W; it used to be known as wolfram.) It’s focused on the amounts of the different chemical elements that are in rocks of different ages.

640px Hafnium bits(Deglr6328/Wikimedia Commons)

“By comparing the relative amounts of different elements in rocks that formed at different times, it is possible to learn how each sample is related to the lunar interior and the solidification of the magma ocean,” said Raul Fonseca, from the University of Cologne.

Together with his colleague, and co-author of the study Felipe Leitzke, they do laboratory experiments to study the geological processes that occurred in the Moon’s interior.

After Theia struck Earth and created a swirling cloud of magma, that magma cooled and formed the Moon. After the collision, the newly-born Moon was covered in magma. As the magma cooled, it formed different types of rocks.

Those rocks contain a record of that cooling scientists are trying to recover.

“These rocks recorded information about the formation of the Moon, and can still be found today on the lunar surface,” says Dr. Maxwell Thiemens, former University of Cologne researcher and lead author of the study.

Simple model(Citronade/Wikimedia Commons)

There are black regions on the surface of the Moon called mares, which means ‘seas’ in latin. They’re large formations of basaltic, igneous rock.

The scientists behind the study used the relationship between uranium, halfnium, and tungsten to understand the melting that created the Moon’s mares. Because of the precision of their measurements, they identified distinct trends among the different suites of rocks.

Clementine albedo simp750(US Geological Survey/Wikimedia Commons)

Halfnium and tungsten provide scientists with a natural clock contained in the rock itself, because over time the hafnium-182 isotope decays into tungsten 182.

But that decay didn’t go on for ever; it only lasted for the first 70 million years of the Solar System’s life. The team compared the Apollo samples with their laboratory experiments and found that the Moon already started solidifying as early as 50 million years after solar system formed.

Wolframite from Portugal(Alchemist-hp/Wikimedia Commons)

“This age information means that any giant impact had to occur before that time, which answers a fiercely debated question among the scientific community regarding when the Moon formed,” adds Carsten Münker from the UoC’s Institute of Geology and Mineralogy, senior author of the study.

Peter Sprung, co-author of the study, adds: “Such observations are not possible on Earth anymore, as our planet has been geologically active over time. The Moon thus provides a unique opportunity to study planetary evolution.”

 

It’s amazing that the rocks collected during Apollo 11 fifty years ago are still yielding evidence like this. The team’s extremely precise measurements are based on inductively coupled plasma mass spectrometry, something that wasn’t possible in Apollo’s time.

The astronauts that collected the samples couldn’t have known this, but those rocks are still teaching us not only about the Moon, but about the age of the Earth itself.

This article was originally published by Universe Today. Read the original article.

 



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Stunning Sonar Image Just Revealed Largest Underwater Volcano Eruption Ever Detected

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In November last year, geologists announced they’d picked up something really weird: a huge seismic event originating in the island of Mayotte in the Indian Ocean, felt all across the globe, source unknown. A few months later, scientists used modelling to produce an answer – hypothesising a giant underwater volcanic eruption.

 

And now it seems that is pretty likely to be the case. Scientists travelled out to where they think the swarm’s epicentre is located, and they found a large active volcano, rising 800 metres (2,624 feet) from the seafloor, and sprawling up to 5 kilometres (3.1 miles) across.

A large active volcano that wasn’t there six months prior.

If these volcanic birth pains didn’t produce the detected seismic activity, that would be a pretty amazing coincidence. But more research is still needed to make absolutely sure.

The seismic rumbles actually started on 10 May 2018. Just a few days later, on 15 May, a magnitude 5.8 quake struck. Since that time, hundreds of seismic rumbles have been detected, most on the smaller side, with the notable exception of the Earth-rattling low-frequency November event.

swarm(BGRM)

All those events pointed to a spot around 50 kilometres from the Eastern coast of Mayotte, a French territory and part of the volcanic Cormoros archipelago sandwiched between the Eastern coast of Africa and the Northern tip of Madagascar.

To find out what was going on, a number of French governmental institutes sent a bunch of scientists aboard the Marion Dufresne research vessel to investigate the area.

 

Starting in February, the team began monitoring the region. They placed seismometers on the seafloor, 3.5 kilometres deep, and used a multibeam sonar to map the seafloor. They dredged up rocks from far below.

The researchers combined this with data collected from Mayotte to build a comprehensive picture of what was occurring down in the dark depths of the lower bathypelagic.

new volcano(MAYOBS – CNRS/IPGP/IFREMER/BRGM)

It’s a fascinating one. Data from the seismometers suggests the existence of a large magma chamber between 20 to 50 kilometres below the surface. This could have been seeping hot magma to the seafloor, where it met the cooler water and contracted, causing the crust to crack.

The plume of volcanic material produced only reached about 2 kilometres upwards, which explains why nothing was visible on the surface. The rocks pulled up from the seafloor were popping – a sign, according to Science, of high-pressure gas escaping from volcanic material.

But that’s not all. GPS data from Mayotte has revealed that the island is both shifting and sinking. It’s moved 10 centimetres eastward and sunk 13 centimetres since May of last year. This suggests the magma chamber that produced the volcano is collapsing and shrinking.

 

This could help explain how the volcano formed: it’s consistent with a mantle plume formation, where a rising plume of hot rock in Earth’s mantle creates melting at shallow depths. Cormoros is a mantle plume hotspot – the islands were formed by volcanic activity – but, again, this is yet to be confirmed by detailed study.

That research is currently underway.

Meanwhile, the French government is also taking steps to ensure the safety of the residents of Mayotte, where tremors and sinking continue.

“The government is fully mobilised to deepen and continue understanding this exceptional phenomenon and take the necessary measures to better characterise and prevent the risks it would represent,” the French Ministry of the Interior wrote in a press release.

In the meantime, a mission to support civil safety and security has been dispatched to the island.

 



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Geologists May Have Traced The Source of Last Year’s Unexplained Massive Earth Shake

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Last November, a huge seismic event that shook the planet left experts wondering about its possible source. Researchers now think they know what might have caused it: an offshore volcanic event unlike any other in recorded history.

 

If the hypothesis is right, and there has been a massive movement of magma underneath the sea floor, that has implications for nearby Mayotte and the neighbouring Comoros islands off the coast of Africa.

Mayotte has already started to sink (by around 9 mm or 0.35 inches per month) and move eastward (by around 16 mm or 0.63 inches per month) – movements that would tally with an underground chamber getting deflated as magma flows out.

“We believe that the 2018 crisis is associated to an eruption, despite the fact that we do not have direct observations so far,” write the researchers behind the new study.

“It might be the offshore eruption with the largest volume ever documented.”

Based on the seismic readings taken in the area over six months leading up to the November tremor that was spread across the world, the team suggests more than a cubic kilometre (0.24 cubic miles) of magma has been shifted from an eruption point some 28 kilometres (17.4 miles) below the surface.

The thinking is that all this magma may not have reached the seafloor but instead flowed into the surrounding sediments, with volcanic gas remaining trapped inside the magma. That would explain why nothing has been observed yet above the surface.

 

“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,” geologist Samuel Mitchell from the University of Hawaii at Mānoa, who wasn’t involved in the study, told Gizmodo.

As the tremors continue, scientists are scrambling to get more instruments and equipment to the area, to get a better idea of what’s actually going on. For the time being, the idea of a major volcanic event fits the existing data pretty well.

There are still lots of unanswered questions though: why is the event happening at the eastern end of the Comoros island chain, when the newer volcanic islands in the area are to the west? And if the magma remains trapped underground, why are schools of dead fish appearing in the water?

Also, what caused the high frequency pulses that occurred alongside the low frequency tremor in November? Waves of magma crashing against each other as a chamber collapsed could be one explanation, but until more data from the area becomes available this is only speculation.

Experts are similarly uncertain over what’s causing the volcanic activity in the first place. Seismologist Stephen Hicks from the University of Southampton in the UK, who wasn’t involved in the latest study, told Gizmodo that tectonic plate movements, a region of superheated mantle, or the ongoing East African Rift event could be responsible.

The new research paper hasn’t yet been peer-reviewed, and the authors behind it say other scenarios are still possible – but volcanic activity seems to fit what we know so far.

What’s clear is that we need a lot more investigation of the events, even though scientists think they’ve now got a promising hypothesis. If more quakes are on the way, people living on Mayotte – already worried by what’s going on around them – need to be well prepared.

“Improving the knowledge of the distribution, alignment and ages of the offshore volcanic features, especially around the main islands, may lead to a better understanding of the behaviour, evolution, and related hazard of this peculiar area,” write the researchers.

The research is available to view on the pre-print server EarthArXiv.

 



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We Just Got Evidence That Mars Could Have Volcanic Activity

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A new study shows that Mars may very well be volcanically active. Nobody’s seen direct evidence of volcanism; no eruptions or magma or anything like that. Rather, the proof is in the water.

 

In the past, Mars was a much warmer and wetter place. Now, Mars is still home to lots of water, mostly as vapor and ice. But in August 2018, a study published in Science showed a 20-km-wide (12-mile-wide) lake of liquid water underneath solid ice at the Martian South Pole.

The authors of that study suggested that the water was probably kept in liquid state by the pressure from above, and by dissolved salt content.

But this new research shows that pressure and salt couldn’t have prevented that water from freezing. Only volcanic activity could have kept it warm enough.

Specifically, a magma chamber formed in the last few hundred years is the only way that that water could’ve been prevented from freezing.

The 2018 study focused on an area at Mars’ south pole called the Planum Australe, or Southern Polar Plain. Radar data from the ESA’s Mars Express orbiter. It showed a 20 km wide lake of liquid water at what they call the south pole layered deposits (SPLDs).

But that study just presented the sub-surface radar data showing the liquid water and suggested that pressure and salt kept the lake from freezing. The authors didn’t quantify the conditions required to sustain that liquid water.

 

The new study, published in the AGU journal Geophysical Research Letters, pours water on the salt and pressure idea. The authors go further, and state that without a magma chamber under the south pole, there is likely no water there at all.

“Different people may go different ways with this, and we’re really interested to see how the community reacts to it,” said Michael Sori, an associate staff scientist in the Lunar and Planetary Laboratory at the University of Arizona and a co-lead author of the new paper.

The debate around water on Mars has been ongoing for a long time. We’ve confirmed the presence of water, but now the debate is around how much, where, and in what form. And it’s not all about whether or not we could somehow use the water on missions to Mars.

It’s more about understanding how planets form and evolve. It’s also about how life might survive on other worlds.

“We think that if there is any life, it likely has to be protected in the subsurface from the radiation,” said Ali Bramson, a postdoctoral research associate at the Lunar and Planetary Laboratory at the University of Arizona and a co-lead author of the new paper.

 

“If there are still magmatic processes active today, maybe they were more common in the recent past, and could supply more widespread basal melting. This could provide a more favorable environment for liquid water and thus, perhaps, life.”

Mars and Earth both have giant polar ice sheets. On Earth, it’s common for liquid water to persist under ice sheets. Earth is volcanically active, and that heat prevents the sub-surface water from freezing.

The 2018 paper drew a parallel between Terrestrial ice sheets and Martian ice sheets, and the liquid water under them, but didn’t answer the question of how the water got there.

“We thought there was a lot of room to figure out if [the liquid water] is real, what sort of environment would you need to melt the ice in the first place, what sort of temperatures would you need, what sort of geological process would you need? Because under normal conditions, it should be too cold,” Sori said.

To begin with, Bramson, Sori, and the other authors of the new study assumed that the detection of liquid water under the south pole was correct. Then they figured out what parameters would be necessary to create that water.

 

They modelled the necessary salt content and the necessary heat flow from the planet to create all that water. They found that salt alone wouldn’t be sufficient.

They proposed that additional heat would have to be coming from the planet’s interior, and the only obvious source of heat would be a magma chamber. (Incidentally, the Heat Flow and Physical Properties Probe on the InSight lander should help answer this question.)

Mars was clearly volcanic in the past. Olympus Mons, a shield volcano on Mars, is the largest volcano in the Solar System, dwarfing anything on Earth. In fact, Mars is home to many volcanoes.

There’s also Tharsis Montes, a group of three other shield volcanoes near Olympus Mons.

In the paper, the authors argue that about 300,000 years ago, magma from Mars’ interior rose to the surface. Rather than break through surface, forming another volcano, it was trapped in a magma chamber under the south pole.

The magma chamber would’ve cooled, releasing enough heat to melt the underside of the polar ice sheet. It would still be there today, slowly releasing heat and preventing the sub-surface lake from freezing.

300,000 years ago isn’t that long in geological terms. The authors say that if there was volcanic activity as recently as 300,000 years ago, it could still be happening today.

“This would imply that there is still active magma chamber formation going on in the interior of Mars today and it is not just a cold, sort of dead place, internally,” Bramson said.

This new paper definitely places some constraints on the findings in the 2018 paper. The authors don’t take a position on whether or not the findings in the 2018 paper are true or not.

They just looked at what physical parameters would be required for the water to be there, under the polar ice sheet. In doing so, it adds to the debate, and will likely lead to further study.

Hopefully, the InSight lander’s heat probe will help us understand the whole issue more clearly.

“I think it was a great idea to do this type of modeling and analysis because you have to explain the water, if it’s there, and so it’s really a critical piece of the puzzle,” said Jack Holt, a professor at the at the Lunar and Planetary Laboratory at the University of Arizona, who was not involved in the new research.

“The original paper just left it hanging. There could be water there, but you have to explain it, and these guys did a really nice job of saying what is required and that salt is not sufficient.”

This article was originally published by Universe Today. Read the original article.

 



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