KINGSTON, R.I. – Jan. 26, 2022 — When the volcano near the island nation of Tonga erupted on Jan. 15, it created a plume of smoke and ash 400 to 500 kilometers high as well as a tsunami that affected land from Hawaii to Peru.

The eruption caused at least two deaths and widespread destruction, according to news reports.

But it also created an opportunity for University of Rhode Island Professor and Fulbright Scholar Stephan Grilli and Ph.D. Ocean Engineering candidate Maryam Muhommadpour to gather an enormous amount of data on the workings of tsunamis.

Grilli, on sabbatical in France at the time, heard about the eruption from scientists in Hawaii posting to bulletin boards. Immediately, warning centers around the world began to calculate the most likely locations to be affected by the tsunami created by the explosion. Social media blew up as people began to post satellite images of the explosion. Other scientists posted global pressure measurements.

“It started with observations made at tide gauges and tsunami buoys called ‘dark buoys’,” Grilli said.

The data indicated that it would hit the coast of California about 10 hours later. 

Muhommadpour first learned of the eruption when she turned on the news that morning. “I woke up, saw the news and I immediately opened my laptop.” What she found was a real-time event that matched her studies perfectly. “I was following up on something that had happened only three hours ago. Professor Grilli began sending me data and forwarding emails from other scientists. I was really excited because I was working on something that was happening right now.”

International news outlets sought out Grilli to provide information on the catastrophe. In an interview with the BBC, Grilli said, “I have been following this event and gathering data since the onset and am assembling an international team of colleagues to address the event and its modeling.”

Tonga is a South Pacific archipelago that 110,000 people call home. The eruption destroyed underwater communications cables, leaving the main island cut off from the rest of the world. A resort owner on the west side of the island called for help on a satellite phone. The person said that he heard the explosion, and 5 minutes later the tsunami hit. Grilli was able to verify the claim and used a formula to estimate that the tsunami that hit the west side of the island was 50 feet tall.

Grilli said that the volcano, called the Hunga-Tonga-Hunga-Ha’apai volcano, has been active since before people began keeping records. It reached a level of intensity that he says occurs once in a thousand years.  Grilli theorizes that vents from the submerged volcano had been sealed by water pressure from the 50 meters of depth. That kept the vents sealed, but pressure inside the volcano continued to build. Eventually, the pressure caused the material sealing the vent to pop, “just like champagne,” Grilli said. There was an 18-kilometer plume of volcanic materials that shot into the atmosphere, along with a mushroom cloud like a nuclear explosion. Eventually, the cloud grew to a size of 4-500 km. At the same time there was a sound wave that could be heard at locations around the Pacific, just like Krakatoa in the Sunda Strait in 1883.

As tragic as the event was, it gave students like Muhommadpour an opportunity to analyze an event in real time. “I had the chance to work on a team. Not just one from URI, but in places like France and Australia, all over the world. It felt really good to be working in a group where we were all focused on the same thing.

“It really helped me to both learn something new and have the experience of working with others. Now, of course, I’m really happy that I’m at URI and working in the Ocean Engineering department.”

When enough data is assembled, Grilli estimates that the energy of Tonga will be hundreds of times the energy of the bomb dropped on Hiroshima. To prove that, Grilli will have to use the data from pressure gauges around the world. His hope is that, with the help of modeling generated from the collected data, people will receive better information that may allow them to prepare for future disasters.

Grilli and his colleagues at URI and the University of Delaware are in the process of creating inundation maps, “like flood maps designed by FEMA for storms but for tsunamis,” Grilli said. Modern technology has made collecting detailed information about the movement of energy in a tsunami far more rapid. This allowed Grilli to conduct a class focused on this event within days of its occurrence.

And while theories regarding Tonga are already being created, Grilli says scientists still have a lot to learn. “We still have to do the hard work of going through the data and creating new models, so it’s going to be a few years of interesting work, publications, and discussions. Then the community will have new tools and more information on making predictions about tsunamis.”

It’s an exciting moment for scientists, Grilli says. “The reason we get excited is that, although this is a very sad human tragedy, if we can learn from that, we can be better prepared. There are other underwater volcanoes currently being studied by graduate students at the (URI’s Graduate) School of Oceanography.

“We are usually well prepared for a tsunami here in the United States, since we have a large number of sensors.” That isn’t true for other locations. “In Tonga’s case, people heard the explosion, but only had 5 minutes before the tsunami hit. They had no time to react, they just had to run. It takes time for people to comprehend when something this unusual is happening.”

Grilli has reached out to colleagues around the world to begin processing the massive amount of new data from the eruption. “We’re starting to assemble a team of people to address the work that will come from this. There are probably a dozen other groups around the world that will do the same thing. There is a lot of work to be done in terms of gathering the data.”

This release was written by Hugh Markey