Geologists Discover Largest Underwater Volcano, Explain Weird Hum Heard Around the World

A strange seismic event off the coast of Africa has led scientists to a mighty finding: the discovery of the largest underwater volcanic eruption ever recorded.

The eruption also may explain a weird seismic event recorded in November 2018 just off the island of Mayotte, located between Madagascar and Mozambique in the Indian Ocean. Researchers described that event as a seismic hum that circled the world, but no one could figure out what sparked it.

For starters, the hum rang at a single, ultralow frequency, which was strange because seismic waves usually rumble at many frequencies. Moreover, there were hardly any detectable “p-waves” or “s-waves,” which usually accompany earthquakes. And, incredibly, the island of Mayotte moved a few inches south and east after the mysterious event. [Photos: Hawaii’s New Underwater Volcano]

Now, scientists have an idea why. This weird seismic hum was likely the birth announcement of a new underwater volcano, according to Science magazine.

The underwater volcano is enormous, rising nearly a half mile (0.8 kilometers) from the ocean floor. It’s the length of a 3.1-mile (5 km) race and lies about 31 miles (50 km) off Mayotte’s eastern coast. And it came into being in just six months.

“We have never seen anything like this,” Nathalie Feuillet, a leader of an expedition to the site by the research vessel Marion Dufresne, who is with the Institute of Geophysics in Paris (IPGP), told Science magazine.

In addition to the weird “seismic hum,” there were other clues that something big was happening. The inhabitants of the French island of Mayotte reported feeling more than 1,800 little earthquakes almost daily since the middle of last year, including a large magnitude-5.8 earthquake in May 2018, the largest ever recorded in the region, National Geographic reported.

How scientists found it
Finding the newborn volcano took an enormous effort, including work from organizations such as the National Center for Scientific Research (CNRS) in France, the IPGP and the French Research Institute for the Exploitation of the Sea (IFREMER), according to a joint statement released May 16.

Part of that research included six seismometers placed on the ocean floor, close to the seismic activity, Science magazine reported. These instruments revealed a tight cluster of earthquakes deep in Earth’s crust, likely stemming from a deep magma chamber that’s gushing molten rock onto the sea’s bottom.

This magma chamber may also be shrinking, as Mayotte has sunk about 5 inches (13 centimeters) and moved 2.5 inches (10 cm) to the east over the past year, Science magazine reported.

In addition, sonar revealed 1.2 cubic miles (5 cubic km) of magma on the seafloor, as well as plumes of bubble-rich water streaming from the volcano. Rock samples collected from the site may reveal the depth of the magma source, as well as the risk of a volcanic eruption.

A volcano in the Indian Ocean?
Mayotte isn’t a stranger to volcanic eruptions, but it’s been at least 4,000 years since volcanoes last stirred in the area, National Geographic reported. The island is part of the Comoro archipelago, islands created by volcanism. [Sunset Crater: Spectacular Photos of a Cinder Cone Volcano]

As news of the seismic hum and the tiny earthquakes spread, a group of French researchers posted a draft of a research study on EarthArxiv, a non-peer-reviewed site in February 2019, positing that the rumblings might have to do with a draining magma chamber. But researchers still have to publish a peer-reviewed study on the events, and it remains unclear exactly how the weird hum, earthquakes and volcano are related.

It’s also a mystery why volcanoes are found near the tiny island. Unlike Hawaii, which formed because of hotspot volcanism roiling up, the volcano near Mayotte lies within the ancient rift where Madagascar tore away from eastern Africa long ago. It’s possible that fissures from this break are now a cradle for this new volcano. However, it’s strange that the volcano popped up by Mayotte, which is the oldest island in the archipelago, Ken Rubin, a volcanologist at the University of Hawaii at Mānoa, told National Geographic.

It also remains to be seen if this volcano is completely new, or whether it sits on an older volcanic structure, the researchers said. In other words, geologists have a lot of work to do, and they’re eager to get to the bottom of this geologic conundrum.

Bermuda Volcano Formed In a Way That Has Never Been Seen Anywhere Else On Earth

A volcano beneath Bermuda formed in a way that has never been seen before, scientists have discovered. The volcano appears to have been created by material rising up from a region deep beneath Earth’s surface—the transition zone.

The transition zone is the region between the upper and lower mantle. It extends between 250 and 400 miles beneath the surface of the planet and is rich in water, crystals and melted rock.

Volcanoes normally form when the tectonic plates are pushed together or pulled apart, producing a crack in Earth’s surface where magma can escape. They can also form at “hotspots,” where mantle plumes rise up and melt a hole in the plate—Hawaii is an example of this.

Now, researchers have found volcanoes can also form when material moves up from the transition zone. The team believes there was a disturbance in the transition zone that forced the material in this layer to melt and move up towards the surface. Their findings are published in the journal Nature.

The researchers were analyzing a now dormant volcano beneath the Atlantic Ocean that was responsible for the formation of Bermuda. They were looking at the chemical composition of a 2,600-foot core sample—by understanding its makeup they could build a picture of Bermuda’s volcanic history.

“Before our work, Bermuda has been interpreted as the result of a deep thermal anomaly in the Earth’s mantle, but there was no direct data to support this. This is due to the fact that the volcanic edifice is completely covered by limestone,” Cornell’s Esteban Gazel, one of the study authors, told Newsweek.

In a statement, he said they were expecting to show that the volcano was a mantle plume formation like Hawaii. This was not what they found, however. The measurements taken from the core sample were unlike anything seen before, suggesting the lava came from a previously unidentified source.

The samples contained signatures from the transition zone. Compared to samples taken from subduction zones, there was more water trapped in the crystals. The transition zone is known to contain vast quantities of water—one study calculated there is three times as much water in this region of Earth than is present in all the world’s oceans.

“I first suspected that Bermuda’s volcanic past was special as I sampled the core and noticed the diverse textures and mineralogy preserved in the different lava flows,” lead author Sarah Mazza, from the University of Münster, Germany, said in the statement. “We quickly confirmed extreme enrichments in trace element compositions. It was exciting going over our first results … the mysteries of Bermuda started to unfold.”

Numerical models developed by the team indicate a disturbance in the transition zone forced the material up. This is thought to have taken place about 30 million years ago and provided the foundation that Bermuda sits on today.

“We found a new way to make volcanoes,” Gazel said in the statement. “This is the first time we found a clear indication from the transition zone deep in the Earth’s mantle that volcanoes can form this way.”

The researchers believe there will be other examples of volcanoes being formed in this way. “With this work we can demonstrate that the Earth’s transition zone is an extreme chemical reservoir,” Gazel said. “We are just now beginning to recognize its importance in terms of global geodynamics and even volcanism.”

Speaking to Newsweek, he added: “I think many hotspot locations … are not deeply rooted to the core-mantle boundary probably have past similar to Bermuda’s.”

Australian Scientists Help With Key Volcano Study Using Hawaii’s Kilauea Disaster

Australian scientists have helped shed new light on volcanic eruptions, using Hawaii’s months-long Kilauea disaster which destroyed hundreds of homes. After analysing the eruption on Hawaii’s Big Island beginning in May 2018, researchers from France, the UK, US and Tasmania say changes in the speed of vibrations travelling through a volcano could be used to pinpoint its imminent eruption.

Ten days before the eruption of Kilauea, the University of Tasmania’s Gerrit Olivier says he and his colleagues found these vibrations inside the volcano’s magma chamber changed dramatically.

“The volcano is constantly bulging and contracting as the pressure inside the magma chamber changes,” Dr Oliver said.

“The behaviour of the seismic wave speeds are initially quite predictable.

“When the volcano bulges, the speed at which the vibrations travel through the volcano increase slightly as material is compressed. On the other hand, when the volcano contracts these wave speeds decrease.”

Days before the May 3 eruption, Kilauea was still bulging because of a build-up of pressure, but the vibrations stopped speeding up and instead slowed right down.

“This is a good indicator that the volcano isn’t able to sustain the pressure inside the magma chamber anymore, that the bulge is too big and it starts breaking the material around the magma chamber which ultimately leads to the eruption,” Dr Oliver said.

These changes have been recorded before, but the study said it was the first time it showed them occurring because of a weakening of material inside the volcano just before an eruption.

Dr Oliver and his colleagues hope this method could be used to help predict when other volcanoes will erupt, after Kilauea spewed out 800 million cubic metres of lava destroying more than 700 homes.

Mysterious Volcanic Ash Layer From 29,000 Years Ago Traced To Volcano In Naples

Researchers from the University of Oxford have traced the origin of a pre-historic eruption that blanketed the Mediterranean region in ash 29,000 years ago to Naples’ lesser-known volcano Campi Flegrei, located immediately to the west of the city.

Since the late 1970s scientists have identified the same pre-historic volcanic ash layer in sediment cores extracted from sites ranging across 150,000 square kilometres of the central Mediterranean. This widespread ash layer, dated at 29,000 years ago, blanketed the region and clearly indicated a large volcanic eruption. Whilst the region is well known for its many active volcanoes, such as Mount Vesuvius which famously destroyed Pompeii in 79 AD, scientists had failed to confidently match this older, far-ranging ash deposit to a specific volcano or eruption.

The research, led by Dr Paul Albert, a Research Fellow in the School of Archaeology, has now identified an ash rich-eruption deposit within the city of Naples which was produced by Campi Flegrei volcano and has a chemical composition that matches the prehistoric ash layer traced across the Mediterranean region. The work was done in partnership with international researchers, including those from the National Institute of Geophysics and Volcanology (INGV), the National Research Council in Italy, the Laboratoire des Sciences du Climat et de l’Environnement in France, and the Berkeley Geochronology Centre in the USA.

“Part of the challenge of reliably attributing this major ash fall event to Campi Flegrei volcano has been that there is limited evidence for a large eruption close to the volcano,” says Albert. “This is in part because a more recent large-scale eruption of the volcano buried the Naples area in a thick ash deposit, largely destroying or concealing the evidence of this older event,” says Albert.

The team used a computer-based ash dispersal model to reconstruct the size of the eruption. “By linking the thickness of the ash deposits found in Naples, to those preserved in cores from across the central Mediterranean, the model was able to demonstrate and provide important constraints on the size of this large magnitude eruption,” says Albert.

This research positions the timing of this previously un-reported large-scale eruption of Campi Flegrei between two well-known large-scale eruptions of the volcano, at 15,000 and 40,000 years ago, drastically reducing the reoccurrence interval of large magnitude eruptions at the volcano.

The research, published today in the journal Geology, also highlights the importance of considering ash fall events preserved well away from the volcano when reconstructing the timing and scale of past explosive eruptions. “Ash fall preserved hundreds of kilometers away from the volcano has been critical here in the identification and reconstruction of this large eruption at Campi Flegrei,” says Albert.

Major Deep Carbon Sink Linked To Microbes Found Near Volcano Chains

Up to about 19 percent more carbon dioxide than previously believed is removed naturally and stored underground between coastal trenches and inland chains of volcanoes, keeping the greenhouse gas from entering the atmosphere, according to a study in the journal Nature.

Surprisingly, subsurface microbes play a role in storing vast amounts of carbon by incorporating it in their biomass and possibly by helping to form calcite, a mineral made of calcium carbonate, Rutgers and other scientists found. Greater knowledge of the long-term impact of volcanoes on carbon dioxide and how it may be buffered by chemical and biological processes is critical for evaluating natural and human impacts on the climate. Carbon dioxide is the major greenhouse gas linked to global warming.

“Our study revealed a new way that tiny microorganisms can have an outsized impact on a large-scale geological process and the Earth’s climate,” said co-author Donato Giovannelli, a visiting scientist and former post-doc in the Department of Marine and Coastal Sciences at Rutgers University-New Brunswick. He is now at the University of Naples in Italy.

Giovannelli is a principal investigator for the interdisciplinary study, which involves 27 institutions in six nations. Professor Costantino Vetriani in the Department of Marine and Coastal Sciences and Department of Biochemistry and Microbiology in the School of Environmental and Biological Sciences is one of the Rutgers co-authors. The study covers how microbes alter the flow of volatile substances that include carbon, which can change from a solid or liquid to a vapor, in subduction zones. Such zones are where two tectonic plates collide, with the denser plate sinking and moving material from the surface into Earth’s interior.

The subduction, or geological process, creates deep-sea trenches and volcanic arcs, or chains of volcanoes, at the boundary of tectonic plates. Examples are in Japan and South and Central America. Arc volcanoes are hot spots for carbon dioxide emissions that re-enter the atmosphere from subducted material, which consists of marine sediment, oceanic crust and mantle rocks, Giovannelli said. The approximately 1,800-mile-thick mantle of semi-solid hot rock lies beneath the Earth’s crust.

The Earth’s core, mantle and crust account for 90 percent of carbon. The other 10 percent is in the ocean, biosphere and atmosphere. The subduction zone connects the Earth’s surface with its interior, and knowing how carbon moves between them is important in understanding one of the key processes on Earth and regulating the climate over tens of millions of years.

The study focused on the Nicoya Peninsula area of Costa Rica. The scientists investigated the area between the trench and the volcanic arc – the so-called forearc. The research reveals that volcanic forearc are a previously unrecognized deep sink for carbon dioxide.

Volcano In Indonesia’s Bali Erupts, Triggering Rains Of Ashes

Mount Agung volcano in Bali resort Island of central Indonesia on Sunday spewed a column of ashes by up to two km onto the sky, leaving rains of ashes, a disaster agency official said.

Thousands of masks have been distributed to the communities amid the fears of the ashes impacting human respiratory, spokesman of national disaster management agency Sutopo Purwo Nugroho said.

The eruption occurred at 08:23 a.m. local time with belching of ash and smoke heading southwest of the crater, he said.

No halt of flight however took place at the I Gusti Ngurah Rai International Airport, said the official.

Rains of ashes with an intensity ranging from thin to thick have been pouring down in the districts of Karang Asem, Klungkung and Bangli, he added.

No report of casualty has so far been reached after the eruption, said Sutopo.

Mount Agung alert status’s remains at the second highest level with no-go zone at four km from the crater.

Mount Agung is situated in Karangasem district and about 70 km from tourist hub Kuta. In its last eruption in 1963, more than 1,100 people were killed.

Scientists Monitor Increased Activity At Big Island Volcano

HILO, Hawaii – Scientists in Hawaii are monitoring increasing activity surrounding one of the Big Island’s volcanoes.

The Hawaii Volcano Observatory is closely monitoring Mauna Loa because conditions have risen to levels comparable to a more active period between 2014 and 2017, The Hawaii Tribune-Herald reported Sunday.

It is too early to predict possible outcomes of Mauna Loa’s activity, according to Tina Neal, the observatory’s scientist-in-charge.

“An eruption could be anywhere from months to years away,” Neal said. “But we do know that it’s not days or weeks away.”

There have been increased earthquakes and ground deformation around Mauna Loa’s summit, she said.

Earthquakes on Mauna Loa dropped to less than five per week in early 2018, but there have been up to 90 earthquakes weekly since August, with most considered mild at 2.0 or less on the Richter scale, Neal said.

Gas monitoring equipment at Mauna Loa’s summit has not detected any emerging fumes, she said.

“The most important thing is that there is no cause for alarm,” Neal said.

An eruption last year by Hawaii’s Kilauea volcano destroyed more than 700 homes from May through August. Kilauea’s current alert status is “Normal.”

The Kilauea eruption came shortly after a decrease in volcanic activity at Mauna Loa, but Neal said there is no “perfect correlation” between the volcanoes indicating one always becomes active as the other falls silent.

However, there is some geological basis to suggest a pattern, and Mauna Loa’s increased activity “would test that hypothesis,” Neal said.