How can you hide a large volcano here on Earth? Place it several miles below the surface of the Pacific Ocean.

Researchers, reporting this week in Nature Geoscience, have discovered just that: a hidden volcano so big it can rival some of the largest in the Solar System. (Think Olympic Mons on Mars.) For several million years, Tamu Massif, has been under cover in the northwest Pacific Ocean, about 1,000 miles east of Japan where three tectonic plates meet: the Pacific, the Farallon and the Izanagi.

Scientists knew there were underwater volcanoes in the Shatsky Rise but it was unclear whether Tamu Massif was a single volcano, or a composite of many eruption points. By integrating several sources of evidence, including core samples and data collected on board the JOIDES Resolution research ship, the authors have confirmed that the mass of basalt that constitutes Tamu Massif did indeed erupt from a single source near the center.

Tamu Massif stands out among underwater volcanoes not just for its size, but also its shape. It is low and broad, meaning that the erupted lava flows must have traveled long distances compared to most other volcanoes on Earth.

Although it rivals Olympic Mons in width and sheer area (about 120,000 square miles), it only rises about 13,000 feet above the sea floor. (Mons is about 14 miles tall! You can thank low martian gravity for that.) Tamu Massif’s tallest point rests at about 6,500 feet below the ocean surface.

“It’s not high, but very wide, so the flank slopes are very gradual,” says lead author William Sager, of the University of Houston. “In fact, if you were standing on its flank, you would have trouble telling which way is downhill. We know that it is a single immense volcano constructed from massive lava flows that emanated from the center of the volcano to form a broad, shield-like shape.”

Thankfully, the massive Tamu Massif is an inactive volcano. Sager and his team put the megavolcano at about 145 million years old, and believe it became inactive within a few million years after it was formed.

“Its shape is different from any other sub-marine volcano found on Earth, and it’s very possible it can give us some clues about how massive volcanoes can form,” Sager says. “An immense amount of magma came from the center, and this magma had to have come from the Earth’s mantle. So this is important information for geologists trying to understand how the Earth’s interior works.”

Image: Will Sager

Supervolcanoes here on Earth capture a lot of attention; from doomsday predictions to TV specials to planetarium shows, many folks seem concerned about these phenomena occurring at any moment from far beneath our feet.

But when searching for volcanoes, instead of down, maybe we should look up. We have found many unusual types of volcanoes in space.

A recent photo of Io, one of Jupiter’s moons, has just revealed a massive eruption on the surface of the large moon. The spread of the returning material covers about 30 square kilometers (11.5 square miles), making it one of the largest eruptions humans have ever witnessed and placing it within the top ten eruptions on Io.

Why is Io so active? The most likely explanation is the gravitational tug of war between the tidally locked moon and the massive planet Jupiter. This constant pulling and stretching is keeping the moon warm and fluid.

But why do explosions halfway across the Solar System away interest scientists? What we learn about these volcanic eruptions can help us understand volcanoes here on Earth a bit better and also give us a glimpse “under the hood” of Io.

And perhaps the coolest reason of all? Scientists studying the ice moon next to Io, Europa, have found magnesium salts on the surface of that moon that may have been spread there by Io throwing material into orbit around Jupiter! Some of that volcanic spray may be shared amongst the rest of the great moons of Jupiter as well. Evidence that these worlds have a diverse mix of chemicals is a big step toward determining the kind of primordial soup that could exist upon (or within) them, not to mention the kind of chemistry—or, perhaps, even evolution—that could be occurring there.

Josh Roberts is a program presenter and astronomer at the California Academy of Sciences. He also contributes content to Morrison Planetarium productions.

Image: NASA’s Galileo spacecraft

The conference gave the same opportunity to younger scientists, through the AGU’s Bright STaRS program. “The program began in 2003 to get schools kids to the AGU meeting,” according to Pranoti Asher, manager of education for the AGU. She also reports that the number of middle and high school students attending has grown from 31 in 2003 to 128 this year.

Two teams from the Academy’s Careers in Science (CiS) intern program were among the Bright STaRS participants. The CiS program serves youth from communities traditionally underrepresented in the sciences with opportunities to immerse themselves in the natural world, develop life and job skills, receive college and career mentorship, and learn science and sustainability concepts in an authentic, paid work environment.

In a poster session that included 2,500 posters from professional and young scientists, CiS interns presented two very diverse posters—one on volcanism on the Moon and the other on sand crabs that live on Ocean Beach.

The first team worked with a scientist at NASA/JPL, using data and images gathered by the Lunar Reconnaissance Orbiter (LRO). The high schoolers decided to look at a volcanic structure on the far side of the Moon called the Compton-Belkovich Feature (CBF). Their question: How similar or different is CBF to volcanoes on the near side of the lunar surface?

The young researchers looked at albedo, elevation, radioactive thorium concentration and the surrounding geology. The youth found that Compton Belkovich is very different from other lunar volcanoes. Next, the team will attempt to identify potential sites that will yield the safest landing location and most scientific benefit.

A little closer to home, the second team looked at the influence of wastewater effluence on the population of sand crabs on San Francisco’s Ocean Beach. The Oceanside Treatment Plant lies just south of the beach and deposits copper, zinc and ammonia into the ocean.

The interns wondered what effect these chemicals have on the native Pacific mole crabs (Emerita analoga), which are a big part of the local ecosystem. Looking at previous studies on marine invertebrates, the team hypothesized that all three chemicals would negatively affect the abundance of these sand crabs.

The CiS interns have been studying the Pacific mole crabs on Ocean Beach for the past ten years. Using the data they collected between 2007 and 2010 and studying EPA data for the same four years, these young scientists found that while copper and zinc were bad for the populations, ammonia actually increased the abundance of these crustaceans.

Both teams enjoyed presenting to other researchers and their own Bright STaRS peers. Professional scientists seemed to thoroughly enjoy the presentations and gave the youth advice on where to take their research next.

And the high schoolers?

“My favorite part of AGU was presenting our research,” says senior Mollie. “Just like when teaching a lesson on the public floor of the museum, Angel and I had to gauge our visitor’s level of interest, and previous scientific knowledge. By tailoring our presentations and focusing on clearly and succinctly communicating our research, I felt I became more familiar with our project and its subtleties. Additionally, visitor’s suggestions and critiques of our project invigorated my interest in taking our Pacific mole crab research further in future years.”

“It was my first time at AGU and I had a wonderful time meeting scientists and presenting the research on lunar volcanoes to all,” says senior Rabiya. “It was definitely an amazing experience to be in a place where everyone is excited and curious about the same thing—the sciences!”

Image: Careers in Science Interns (from left to right) Mollie, Angel, Joseph, Reina, and Rabiya

Don Swanson of the USGS Hawaiian Volcano Observatory calmly told us to be afraid—be very afraid—of the gentle-appearing Kilauea volcano on the island of Hawaii. Well, he may not have sounded so dire. But he did want us to know that Kilauea had very long-term explosive periods in the past and will likely again, threatening the local population and the 5,000 daily visitors to Hawaii National Park.

The Big Island’s volcanoes are known for their beautiful lava flows, and Kilauea is no exception. But looking at the past using carbon-dating techniques, Swanson and his team have found that for the last 2,500 years, Kilauea had been more explosive (60%) than gentle lava flowing.

The first explosive period lasted for about 1,200 years—from 200 BCE to 1000 CE. The second, more recent period, for the 300 years from 1500 to 1800, exhibited “scores” of explosive events, according to Swanson.

Pele, the ancient Hawaiian goddess of volcanoes, displayed her temper by throwing rocks—perhaps causing these explosions, Swanson mused.

The most lethal eruption known from an American volcano occurred at Kilauea in 1790. Most likely, several hundred people died, but contemporary accounts vary. A battle at the time, between the warriors of Keoua and Kamehameha, put several men near the summit at the time of the eruption. According to Swanson’s presentation, “the conditions of the bodies suggests that a pyroclastic density (known as a “PDC,” but often just called a surge) engulfed the victims.” PDCs are a mixture of hot gas and volcanic ash that travel at hurricane velocities.

Footprints were found in the muddy volcanic ash, and in Swanson’s dramatic fashion, his presentation reported, “They could record someone’s last footsteps.”

Swanson wants us to be aware that it could happen again and without much warning. And not just as little blips: Kilauea could be explosive for very long periods of time, as the historic record shows. While Swanson and other scientists are unable to predict the occurrence of damaging eruptions well in advance, small earthquakes and rock-fall are likely to precede the events, allowing time for evacuation.

Moral of the story: Don’t be fooled by the gentle beauty of Hawaii’s lava-flowing volcanoes. Pele still has some rocks up her sleeve!