Scientists are scrambling to monitor the underwater volcano Hunga Tonga-Hunga Ha'apai which erupted last weekend. The volcanic explosion destroyed the sea surface crater and drowned its mass, thus obscuring it from satellite view.
Previously reported, this seismically active volcanic eruption on the Pacific Ring of Fire sent tsunami waves across the Pacific Ocean and was heard some 2,300km away in New Zealand.
"The concern right now is how little information we have and it's scary. It's like when a vent is underwater, no one can tell us what's going to happen next," said Janine Krippner, a New Zealand-based volcanologist with the Program Smithsonian Global Volcanism, quoted by Reuters.
Krippner said observational instruments close to the site were likely to be destroyed by the eruption and the volcanology community was gathering the best data and expertise at their disposal to review the explosion and predict future activity in anticipation.
Saturday's eruption (15/1) was so powerful that space satellites captured not only a huge ash cloud but also an atmospheric shockwave emanating from the volcano at speeds close to the speed of sound.
Photographs and video recording the event showed ash clouds billowing over the South Pacific and one-meter-high waves soaring up the Tonga coast.
There have been no official reports of injuries or deaths in Tonga, but currently internet and telephone communications are very limited and remote coastal areas are cut off.
Experts say the volcano, which last erupted in 2014, appeared to be out of breath for about a month before magma rose. The temperature becomes very hot to about 1,000 degrees Celsius. When magma meets seawater, a large-scale explosion occurs.
"The unusual speed and power of the 'astonishing' eruption suggests a force greater than just magma meeting water," the scientists said.
Very hot magma rises rapidly and encounters cold seawater, as well as large amounts of volcanic gas. This process intensifies the explosion.
Some volcanologists liken the eruption to the 1991 eruption of Pinatubo in the Philippines, the second largest volcanic eruption of the 20th century, which killed about 800 people.
Tonga's Geological Service Agency, which monitors the volcano, was not yet reachable. Most communications to Tonga have been cut off after a major undersea communications cable lost power.
American meteorologist Chris Vagasky studied lightning around the volcano and found that its intensity increased to about 30,000 strikes in the days leading up to the eruption. On the day of the eruption, it detected 400,000 lightning events in just three hours, which dropped to 100 lightning events per second.
He compared it to the 8,000 strikes per hour during the 2018 eruption of Anak Krakatau, which caused part of the crater to collapse into the Sunda Strait and sent a tsunami crashing into western Java, killing hundreds of people.
Vagasky said it was difficult to predict continued activity, and volcanic vents could continue to release gas and other material for weeks or months.
"It's something unusual to witness a few more eruptions, although maybe not as big as Saturday's eruption (15/1). Once the volcano has lost its gas, then the mountain will calm down," he explained.
