Trying to watch over a hidden giant
The recent event and all its oddities underscore how little is known about underwater volcanoes, says Jackie Caplan-Auerbach, a seismologist at Western Washington University. Many of these submerged giants linger in the depths of the ocean, and their blasts are usually not lethal. Yet this weekend’s explosion is a stark reminder of the hazards of lingering volcanoes just below the waves.
For now, Hunga Tonga-Hunga Ha’apai seems to have fallen silent. The inhabitants are help each other pick up the mess and clean the streets. Although communications remain largely cut off, information on the current situation is finally starts to sink. Three deaths have been confirmed among residents of Tonga, including two additional deaths in Peru of the tsunami.
The damage on some of the islands is severe. The homes of the 36 inhabitants of Mango Island were destroyed. Only two houses remain on the island of Fonoifua, and extensive damage extends to the island of Nomuka, which has a population of 239. Damage to the largest and most populous island, Tongatapu, home to around 75,000 people, was mainly concentrated on the western side. The Tonga Red Cross Society estimates that a total of 1,200 “affected households”.
Ash contaminated the islands’ drinking water supplies and aircraft delayed from landing with additional supplies. The New Zealand Navy has deployed two supply ships which are due to arrive on January 21.
And there is always a risk that the volcano has more explosive explosions in store. Tonga Geological Surveys rely on visual and satellite observations to track the activity of the many volcanoes in the region. But with the Hunga Tonga-Hunga Ha’apai volcanic tip now below the surface, scientists have lost sight of any signs that could help understand the volcano’s activity. The potential for additional activity also prevents scientists from flying nearby for closer examination.
Even when the volcano is not actively erupting, monitoring largely submarine volcanoes is a complex task. GPS, which is frequently used to track surface changes as magma moves underground, does not work on the seafloor. And getting real-time data from seismometers on the ocean floor is technologically difficult and expensive. Caplan-Auerbach says she often compares working in the oceans to seismology on another planet.
Instruments known as hydrophones can listen to the grunts of undersea volcanoes as the sound travels across vast swaths of the ocean. But these are not easy to deploy in emergency situations and require connection to undersea cables for real-time data.
The situation in Tonga underscores the need for better international efforts to fund volcano monitoring around the world, Krippner said. She and other volcanologists have all pointed out how Tonga’s geological surveys are doing a nearly impossible job. “They don’t have a lot of money. They don’t have a lot of staff,” Kilgour says. “But we ask them to do a lot.”
In the days leading up to the January 15 explosion, based solely on visual and satellite information, the agency constantly warned of future eruptions and a possible tsunami, asking residents to stay away from the beaches. “Because of that, I think they probably saved thousands of lives,” Barker says.
“We often learn from those really terrible times,” adds Caplan-Aurbach. Perhaps by studying the consequences of this volcanic explosion closely, “we will have a better idea of what is to come”.