Axial Seamount, a highly active underwater volcano off the coast of the Pacific Northwest, is heading toward eruption for the first time in a decade, providing scientists with a rare window into oceanic eruptions.
While the ecosystem surrounding Axial Seamount’s hydrothermal vents will be impacted, the eruption will pose no threat to humans. Instead, researchers expect a brilliant display of lava flows, implosions, and “snow blowers,” as warm fluid pushes a stream of microbial life into the surrounding ocean.
Axial Seamount
“Over two-thirds of the Earth’s surface was formed by volcanic eruptions at these mid-ocean ridges,” said Maya Tolstoy, a marine geophysicist and Maggie Walker Dean of the UW College of the Environment. “So the volcano is formed by these really fundamental processes that shape our planet.”
Situated 4,900 feet below the ocean surface and 300 miles from Portland, Oregon, Axial Seamount was born from molten material surging through Earth’s mantle toward the crust in scorching plumes, creating a “hot spot” of volcanic activity in the area. Such long chains of volcanoes appear across the globe, some even developing into island chains such as Hawaii and Samoa.
Axial’s location straddling the Juan de Fuca Ridge, where the Pacific and Juan de Fuca tectonic plates separate, gives the submerged volcano its unique properties.
“It’s pretty unusual,” said marine geophysicist William Wilcock, a professor in the UW School of Oceanography. “It’s a genuine hotspot, and the volcano itself is quite large, rising about 3600 feet above the seafloor. The summit, bisected by the Juan de Fuca Ridge, is marked by a large caldera [a type of crater formed by volcanic eruptions], where the magma chamber has collapsed during multiple eruptions. That combination of features, located right on top of a mid-ocean ridge, is not very common.”
The Study Begins
At the annual American Geophysical Union conference last December, researchers announced that the volcano was building toward eruptions, potentially by the end of 2025, setting off a surge of interest.
The UW College of Environment was already well-positioned to study the events as they unfolded. With its massive underwater observatories, the Ocean Observatories Initiative Regional Cabled Array (RCA), comprised of 150 sensors throughout the water and spread across the sea floor at the Juan de Fuca plate, RCA is capable of collecting not just measurements but high-resolution images and live video.
“Three-quarters of all of the volcanic activity on Earth takes place at mid-ocean spreading centers,” said Kelley. “But people have never directly witnessed an eruption along this mountain chain, so we still have a lot of unanswered questions.”
Previous known eruption events occurred in 1998, 2011, and 2015. However, it wasn’t until that 2015 event that the RCA provided researchers with the proper equipment to adequately monitor one of Axial Seamount’s eruptions for the entire duration. With a decade of research behind them, geologists are looking to continue improving their eruption prediction methodology.
Predicting the Eruption
When the volcano finally erupts, a sudden rise in localized earthquakes will be the first indicator that magma is beginning its journey to the surface.
“That period lasts about an hour, and then the magma reaches the surface,” Wilcock said. “Lava flows spread across the caldera, and lava-filled fissures open up to the north or the south, reaching as far as 40 kilometers [about 25 miles]. The seismic activity dies down pretty quickly over the next few days, but the eruption will continue slowly for about a month.”
Another sign, albeit a less certain one, will be inflation as magma begins to collect under the surface. While inflation is a potential indicator of impending eruption, it isn’t a sure proof, and researchers aim to better understand why that correlation does not always hold true.
“The volcano has already surpassed the inflation we observed in 2015, but the earthquake activity is still quite low,” said Deborah Kelley, a professor in the UW School of Oceanography and director of the Regional Cabled Array. “We’re seeing 200 to 300 earthquakes daily, with some spikes around 1,000 per day due to the tides. If what we learned in 2015 is correct, I would expect to see more than 2,000 per day for a few months before the eruption.”
The researchers who made the December announcement were Bill Chadwick of Oregon State University and Scott Nooner of the University of North Carolina at Wilmington. In their blog, the pair carefully notes that their initial statement was not a certain prediction that the volcano would erupt soon, but that inflation was headed somewhere. They continue to study whether the volcano’s eruptions can be accurately predicted from inflation data.
In their most recent blog post from late April, the pair notes that Axial Seamount has been holding relatively steady on earthquakes and inflation, stating, “it sure doesn’t seem like anything is imminent.”
Cosmic Forces at Play
Another wrinkle in any prediction is that the sun and moon affect the tides.
“Axial is under a state of critical stress now,” explained Tolstoy. “At high tide the weight of the ocean presses down on the crust, and when that weight is ever so slightly decreased at low tide, the number of earthquakes increases. What will be really interesting to see is whether those factors also affect the likelihood of an eruption by putting additional stress on the magma chambers.”
Interestingly, the three previously recorded eruptions occurred under reduced gravitational influence as Earth moved further from the sun between January and May, potentially indicating a prime eruption window.
“Until it happens, we won’t know which of these hypotheses are right,” Wilcock said. “Whatever it does, we’re going to learn something new.”
However, as the event plays out, researchers are excited to collect new data to improve their understanding of sea volcanic prediction methodology.
“The last eruption brought our community together in a really exciting way,” said Tolstoy. “It’s such an amazing opportunity to observe one of our planet’s most important processes, and I think we’re all looking forward to it.”
When the Eruption Hits
On the spectrum of volcanic activity, Axial’s eruptions are relatively tame yet interesting for the unusual conditions they can cause. For instance, as magma hits cold ocean water, it can produce loud noises that can be heard locally by underwater microphones placed in the area.
“When a pocket of seawater gets trapped beneath a lava flow, it heats up and turns to steam,” Wilcock said. “When that steam finally escapes, it forms a bubble which cools very quickly and collapses, causing a loud implosion that we can pick up with our hydrophones.”
The sounds Axial will produce during this active period, between magma hitting water and continual Earthquake rumbles, will likely be audible to some whale species, due to their low-frequency hearing. Despite their potential proximity to the events, scientists expect the whales will remain unharmed and likely unbothered.
Microbial Life and Volcanoes
By comparison, life on the hydrothermal vents will have a different experience. Despite how inhospitable Axial is, extremophile organisms, including microbes and marine animals, make their home within hydrothermal vents. Heated by magma deep underground, mineral-rich water springs erupt through the seafloor in ultrahot blasts.
“In 2011, we saw one of the venting areas become completely covered in lava flows,” Kelley said. “It wiped everything out. But what’s fascinating is that when we came back three months later, there were animals and bacteria colonizing the area again. They’re surprisingly resilient ecosystems.”
Land dwellers have little to fear as the Axial Seamount’s distance and depth leave it incapable of generating earthquakes and tsunamis that could be felt in the Pacific Northwest.
One of the most fascinating elements of these deep-sea events for scientists is the plumes of warm fluid filled with microbes and white masses of their biological waste that eject from under the ocean floor.
“The snowblowers are really astounding, and we’ve only seen them a handful of times,” Kelley said. “You can see billions and billions of microbes and their waste products streaming out from within the volcano.
I think it’s one of the biggest discoveries we’ve made,” Kelley added.
“Life thrives in these inhospitable environments, and volcanoes are probably one of the major sources of life in our oceans.”
Ryan Whalen covers science and technology for The Debrief. He holds an MA in History and a Master of Library and Information Science with a certificate in Data Science. He can be contacted at ryan@thedebrief.org, and follow him on Twitter @mdntwvlf.