Scientists Discover Even More Underwater Volcanos
We're talking thousands of them.
Hiya!
You likely know that oceans make up 70 percent of Earth’s surface and that the ocean depths are more inhospitable to us than outer space is. Both of these facts make it challenging for scientists to study at length and explain why only about a quarter of the global ocean has been fully mapped.
But modern technology and sciences have finally advanced enough to explore further and make incredible discoveries in the process. Some are curious, others are bizarre, and then there are the ones that make us a smidge nervous. Today’s topic falls into all three categories.
Underwater Volcanoes
They have many names, including Submarine volcanoes and Seamounts, but I prefer underwater volcanoes because it’s simple and self-explanatory — volcanoes that are underwater. The primary difference between underwater volcanoes and volcanoes on land is their eruptions.
Unlike land volcanoes, which can erupt in firey displays, underwater volcanoes have the weight of the ocean pushing down on them. This means any lava that comes out is more passive and drips down the sides, ultimately shaping the volcano itself and the ocean floor rather than spewing toward the ocean surface. That said when an underwater volcano is just the right distance from the ocean surface, an eruption can create a tsunami.
Beyond this, all volcanoes whether on land or the seabed, are born the same way. The Global Foundation for Ocean Exploration (GFOE) explains — the bolding is mine:
“Volcanoes are common occurrences along the boundaries of Earth’s tectonic plates. These boundaries allow super-heated molten rock called magma, along with ash and gases, to rise through Earth’s crust and emerge on the surface, often dramatically. Since many plate boundaries are submerged, around three-quarters of all volcanic activity on Earth actually occurs underwater.”
Volcanoes, like the ocean, contain many mysteries, and scientists still don’t fully understand them. Considering only about 25 percent of the global ocean is mapped, that last sentence adds urgency to the situation — especially since scientists recently linked rising sea levels with increased volcanic activity.
Remarkably, an international team of oceanographers, along with radar satellite data, identified over 19,000 new underwater volcanoes to add to the growing list.
New Research
In April 2023, the journal Earth and Space Science published new research by an international team of scientists from the Chungnam National University in South Korea, the Scripps Institution of Oceanography at the University of California San Diego, Chungnam National University in South Korea, and the University of Hawaii that identified 19,325 new underwater volcanoes.
The team describes in the study that they “used the latest vertical gravity gradient maps to update and refine a global seamount catalog,” finding thousands in the process. The vertical gravity gradient (VGG), they explain, “is the curvature of the ocean surface topography derived from satellite altimeter measurements.”
The VGG was previously used in research published in 2011 by Geophysicists Seung-Sep Kim at Chungnam National University, South Korea, and Pål Wessel at the School of Ocean and Earth Science and Technology at the University of Hawaiʻi at Mānoa.
Kim and Wessel’s research started the Global Seamount Database, which previously mapped 24,643 seamounts. With the new study, however, the number of mapped underwater volcanoes has increased to 43,454.
While the satellites couldn’t photograph the seamounts, they could provide the differences in gravitational pull and altitudes. A research data analyst at The Scripps Institution of Oceanography and co-author of the study, Julie Gevorgian, told Newsweek:
"There have been a handful of studies that predicted there could be thousands of seamounts on the ocean floor. Even then, ~19,000 new seamounts is still incredible to think about.
"Especially when you realize just how big these seamounts are and how they were previously unknown. It really is all due to the improvement in the gravity data from satellite altimetry throughout the last few years which has allowed scientists to better understand the topography of the seafloor."
Over time, underwater volcanos can grow to between 2 and 6 miles high (3 to 10 km), but smaller ones, just over a mile high (2 km), are more challenging to detect. And those are the ones the team was most interested in identifying.
Of the over 19,000 new seamounts the team found, they mostly focused on 739 smaller seamounts between 1,381 feet (421 meters) and 8,202 feet (2,500 meters).
Larger underwater volcanoes are easier to spot thanks to their size, but scientists need to identify the smaller ones, too — which are routinely hazardous for submarine navigation. More than one submarine has crashed into an undocumented seamount, even as recently as 2021.
Separate from this research, a different international group of scientists recently identified another three underwater volcanoes. All of which are just off the coast of Sicily, and experts believe tens of thousands more will likely be discovered as efforts to map the seafloor continue.
Still Mapping
Discovering 43,454 seamounts in just over a decade is wild, but experts believe there are likely many, many, more. The global ocean has a surface area of about 139 million square miles (360 million square km) — and only a quarter has been mapped.
An international project known as Seabed 2030 involving industries, governments, philanthropy, research, civil society, and NGOs is working to collect high-resolution sonar data and complete a map of the entire seabed by 2030.
In addition to Seabed 2030, NASA teamed up with the French space agency Centre National d’Études Spatiales (CNES) to launch a Surface Water and Ocean Topography satellite in December 2022, which can measure the ocean’s water surface height within a couple of centimeters.
Perspective Shift
Who knows how many more underwater volcanoes will be found before the project is finished? Could there be tens of thousands more? A million? How expansive are the magma chambers and tunnels within the planet? I imagine them running beneath the Earth’s surface like blood vessels spread below our skin.
Considering the amount of effort going into learning about the global ocean, there will no doubt be several more remarkable discoveries made by 2030. I think it’s fantastic that so many fields, including governments, civilians, and industries, are working together on this project. Just imagine what we might accomplish if such cooperation occurred within other areas that need our attention.
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Thank you for this overview Katrina; pretty fascinating stuff. Hard to imagine a more compelling story than our world's genesis and evolution. Sadly, there is one: the impending climate-change-induced catastrophe of the Seas rising A LOT - and the inevitable human conflicts to survive will likely kill more than all of our previous wars combined.