It’s clear that Hunga contains some very explosive recipes that may not be easily reproducible. For about a month, the eruption proceeded as expected. It was moderately violent, producing gas and ash, but manageable. Then everything went sideways. That’s the result of at least two factors, he says, Cronin. One was the mixing of magma sources with slightly different chemical compositions underground. As these interacted, gas was produced, expanding the volume of magma within the rock. Under tremendous pressure, the rocks above began to crack and seep cold seawater. Massive explosions occurred, two of which were actually he, and trillions of tons of material were blown off the top of the caldera, some of it apparently into space.
Both of these explosions caused large tsunamis. But the biggest wave came later. Cronin thinks it may have been caused by flooding a hole several kilometers deep that was suddenly dug from the seafloor. “This is very new to us,” he says. It’s a new type of threat that should be considered elsewhere. Until now, scientists thought that this type of volcano could only generate large tsunamis if the caldera’s flanks collapsed. The bottom line is that submarine volcanoes are more diverse than anyone thought, and in some cases can take extreme actions.
But the process of stitching together the eruptions has also highlighted the challenges of studying submarine volcanoes. A typical mapping expedition includes a large, fully manned research vessel equipped with multi-beam sonar to map seafloor changes and an array of water-sampling instruments to look for chemical signatures of ongoing activity. It is included. But boating over a potentially active caldera is dangerous, not because the volcano could erupt, but because gas bubbles could form and sink the ship. . In Tonga, researchers have solved that problem with small ships and autonomous ships.
Even Tonga, which has been visited four times in the past year, is unlikely to acquire another large manned mission in the next few years, Cronin says, due to the influx of research funding into groups studying the eruption. The cost is very high. It could take decades to study all the volcanoes in the Tonga Arc alone in detail. It’s a shame, says Walker. Because this kind of expedition is one of the few ways scientists can get close enough to actually see how volcanoes work. The ideal scenario would be to provide more funding for these missions and to invest in improving new technologies such as automated ships that are difficult to operate in dangerous open seas.
Without them, scientists would be watching from afar. This is difficult, but not impossible, to do if you are trying to observe an underwater event. Satellite technology can spot objects known as pumice rafts (sheets of buoyant volcanic rock that rise to the surface of the water), and algal blooms that are nourished by minerals ejected from volcanoes. The USGS and its Australian counterparts are also in the process of installing a network of sensors around Tonga that can more accurately detect volcanic activity, combining seismic stations with acoustic sensors and web cameras to monitor active explosions. . Lowenstern said the challenge is to keep the system connected to data and power so that Tonga can staff the facility. He adds that Tonga is just one of many Pacific nations that can take advantage of this assistance. But it’s just the beginning.
One of the benefits of studying Hunga Volcano in detail is that it has identified new volcanic features that researchers should be aware of. Cronin foresees the process of identifying which volcanoes need more attention over the next few years. On his final Hunga voyage in 2022, Cronin’s team visited two of his other submarine volcanoes in the region on board. One of them, he, was about 100 miles north and had a mesa-like terrain similar to Hunga before the eruption. The maps will serve as a baseline for future surveys that can go above water as a way for researchers to get an idea of how much activity is happening under the sea and rocks. Cronin reports that the sea has been calm so far.
