The Hunga Tonga-Hunga Ha'apai eruption on January 15, 2022, was the most powerful eruption this century, creating the loudest sound on Earth since Krakatoa erupted in 1883, and sending atmospheric waves higher than the International Space Station. Now scientists studying it have discovered some more incredible data: it dramatically changed 8,000 square kilometers of ocean floor around it and displaced enough rock and ash to fill the Panama Canal.
The eruption shifted 7 cubic kilometers (1.6 cubic miles) of material, scientists from New Zealand’s National Institute for Water and Atmospheric Research (NIWA) say, enough to fill the artificial freshwater Gatun Lake that makes up most of the Panama Canal, with plenty leftover. Put that in a cube, and the material would be as tall as five Empire State Buildings. The eruption changed 8,000 square kilometers (3,088 square miles) of ocean bed surrounding the volcano and buried the seafloor where the Tonga internet cable that broke was located under 30 meters (100 feet) of ash and sediment.
The expedition to study the aftermath is a collaboration between NIWA and Tonga Geological Services. Prof Shane Cronin from the University of Auckland, New Zealand told BBC News that the volcano's caldera dropped by hundreds of meters following the eruption. With a crater that is now 4 kilometers (2.5 miles) across, it dropped from 150 meters (492 feet) deep to 860 meters deep (2,822 feet) – by far the deepest in the world. But the fact that so much of the volcano remains intact was also surprising.
“With an explosion that violent – the biggest ever recorded – you would expect that the whole volcano would have been obliterated, but it wasn’t," NIWA marine geologist Kevin Mackay said in a statement. "While the volcano appeared intact, the seafloor showed some dramatic effects from the eruption. There is fine sandy mud and deep ash ripples as far as 50 kilometers away from the volcano, with gouged valleys and huge piles of sediment.”
The team not only mapped changes to the seafloor but also studied how this has impacted living creatures in the surrounding abyss. The initial release of precious minerals in the ash led to a boom in microalgae, which began feeding a whole ecosystem.
But the team reported that a lot of ash is still suspended in the water and regions of low oxygen are appearing around the volcano. The long-term effects on the area are unknown. The scientists hope that the data and material collects will bring a new understanding of underwater volcanic eruptions to the Kingdom of Tonga and many other nations.
“The eruption sent shockwaves around the world, but the effects were felt most keenly in Tonga. It was a miracle to lose so few lives (God rest their souls), but our streets, crops, air, and waters were devastated," Tonga’s Deputy Secretary for Lands and Natural Resources, Taaniela Kula, said.
“We, along with other nations on the Pacific Ring of Fire, know only too well how at mercy we are to nature. By studying an unprecedented event like this in such detail, we will gain invaluable knowledge and experience so we can recover quickly and be prepared for the next time something like this happens.”
The Tonga Eruption Seabed Mapping Project (TESMaP) is part of the Nippon Foundation-GEBCO Seabed 2030 Project, which aims to map the whole seafloor by the end of the decade.