3D perspective of the caldera and summit of Havre Volcano. Credit: ©Woods Hole Oceanographic Institution 2018
While on a flight across the Pacific Ocean, a woman spotted a giant floating rock. It turned out she had discovered a massive underwater volcano. Adam Soule, Chief Scientist for Deep Submergence with the Woods Hole Oceanographic Institution talks about the discovery.
In July 2012, a passenger in a commercial airplane flying across the Pacific happened to look down at exactly the right moment. From the window, they saw a gray mass floating on the surface of the ocean. It was something that many wouldn’t give a second thought.
But the mass turned out to be a giant pumice raft roughly the size of Philadelphia — a product of an eruption from an underwater volcano. The Havre volcano off the coast off New Zealand is one of over 10,000 submarine volcanoes in the world — and that’s not counting the mid-ocean ridge, an underwater mountain system and hotbed of volcanic activity. In fact, “most of the volcanism on our planet occurs in the oceans, but we know so little about it,” says Adam Soule, Chief Scientist for Deep Submergence with the Woods Hole Oceanographic Institution, in a phone call to Science Friday. He’s part of the University of Tasmania and WHOI team that studied the Havre eruption.
“The ocean is this sort of veil that we can’t really see through,” says Soule. He notes that the number of terrestrial volcanoes documented is somewhere in the thousands. For underwater volcanoes — where an estimated 70 percent of all volcanic activity occurs — that number is in the tens.
Why the discrepancy? Part of it has to do with the “serendipitous” ways that we discover submarine volcanoes, Soule says. Researchers typically rely on satellites to spot volcano hotspots on land, and use seismometers to detect earthquakes associated with eruptions — methods that don’t work underwater. “An airplane flying over a pumice raft has probably happened a thousand times before this particular case where someone noticed it and got in touch with the right people,” says Soule.
The challenges don’t stop at detection. While this particular pumice raft was spotted in 2012, researchers weren’t able to make it to the site until 2015. Delays in research are never ideal, but they pose a particular challenge when materials are prone to floating away — pumice, even when produced thousands of meters beneath the oceans, is still buoyant.
“Once [these materials] are at the sea surface, they can float for a really long time — years and maybe even a decade or more,” says Soule. “They washed up on shore in Australia and people were finding them.”
While most of the material had floated away by the time researchers arrived at the Havre site, the residue still indicates this was no small eruption. In fact, researchers estimate that the eruption was about 1.5 times larger than the eruption of Mount St. Helens in 1980. It produced more than a cubic kilometer of material, an estimated 75 percent of which floated away.
Soule argues that we need to find better ways of monitoring these underwater volcanoes, and more efficient means of getting to sites.
“There’s this huge and vast region of the earth’s mantle that dwarfs every other part of the planet,” he says. “But it’s hard to get too excited because you don’t really see it. But a volcano is a place where you kind of see the earth breathing.”
Soule discusses the Havre eruption and unpacks the challenges facing researchers who study underwater eruptions.
- What initial evidence led to the discovery of this massive submarine volcano, and how did researchers verify the discovery?
- Based on the description of the pumice raft that led to the discovery of the submarine volcano, in what ways do you think that pumice is different from most other kinds of rock?
- Dr. Soule says that submarine volcanic explosions are observed much less frequently than volcanic eruptions on land. Identify two pieces of evidence that Dr. Soule uses to support this claim.
- Why do you think that volcanic eruptions on land are observed more frequently than submarine eruptions?
- Why did it take three years for researchers to get out to study the pumice raft and volcano in the ocean? What challenges had to be overcome in order conduct research on this submarine volcano?
- Look at the image above of the underwater volcano that was discovered in 2012 and compare it to an image of a volcano on land. Based on your observations, decide whether you agree or disagree with Dr. Soule’s comparison of submarine volcanoes to land volcanoes.
(Left) The Remotely Operated Vehicle (ROV) Jason II collecting the largest pumice sample ever recovered from a deep-sea volcano. (Right) Credit: Remotely Operated Vehicle (ROV) Jason II traversing across the deep ocean. ©Woods Hole Oceanographic Institution 2018
- Go hunting for submarine volcanoes! Google Earth includes submarine as well as terrestrial maps making it almost as easy to find seamounts as mountains on a map. Search Google Earth for “submarine volcano” or “seamount” to find named examples of other submarine volcanoes, and use the internet to search for more information about them, how they were discovered, and when they may have last erupted. Next, try exploring regions near tectonic plate boundaries (e.g. the “Ring of Fire”) to find areas of the ocean floor where not-yet-named submarine volcanoes might exist. Can you find any candidate regions for submarine volcanoes that are ready for exploration?
- Curious which volcanoes could pose a risk to the United States? The USGS operates a volcano hazards program which generates a map of volcanic risks for the United States and Canada. Explore the risk map: Are there any volcanic risks anywhere near the United States? Click on any of the volcano icons on the map that aren’t green — where are the volcanoes located? What makes them a risk to the people in those regions? Has the status of the volcano changed over time? How? Use the information that USGS provides for one of the risky volcanoes to write an e-mail to an imaginary friend in the area near the volcano, indicating what they should be aware of and what actions they should take (is the risk lava or just ash? Should they evacuate or just avoid going outdoors?).
- Dive into this virtual geology field trip to search for evidence of volcanic activity through geologic time in the Columns of the Giants, a geologic formation in California. How does evidence of a volcano on land look different from one underwater? How would the types of volcanic rocks found at Columns of the Giants differ from those surrounding an underwater volcano? Why? Use the graphic below to help you.
- Learn more about igneous rocks in this open textbook chapter on igneous rocks by Ck-12
- How do you know if a volcano is going to erupt? Try listening to it. “Volcano ‘Screams’ Before Eruption” Science Friday, July 19, 2013
- Volcanic eruptions are pretty rare, but in some places where volcanoes are active, it’s important to be prepared if a nearby volcano erupts. Learn about volcano safety at Ready.gov’s volcano site
Vocabulary: Pumice, serendipitous, volcanism, aerial volcanoes, submarine volcanoes, deep submergence vehicles
Next Generation Science Standards: ESS2.A: Earth’s Materials and Systems, ESS1.C: The History of Planet Earth, CCC1: Patterns, SEP 4: Analyzing and Interpreting Data. Can be used to build towards 4-ESS2–2 and MS-ESS2–3.