Why Tonga volcanic eruption was so big and what’s likely to come next

Experts offer explanations for the power of the Hunga Tonga Hunga Ha’apai volcanic eruption, which ranks among the world’s biggest in 30 years.

SHARE Why Tonga volcanic eruption was so big and what’s likely to come next
This satellite image provided by Maxar Technologies shows an overview of Hunga Tonga Hunga Ha’apai volcano in Tonga on Jan. 6 before a huge undersea volcanic eruption.

This satellite image provided by Maxar Technologies shows an overview of Hunga Tonga Hunga Ha’apai volcano in Tonga on Jan. 6 before a huge undersea volcanic eruption.

©2022 Maxar Technologies via AP

WELLINGTON, New Zealand — Looking on in awe at the satellite images of an undersea volcano erupting in a giant mushroom cloud in the Pacific Ocean, it was hard not to wonder why the Tonga blast was so big.

Shane Cronin, a volcanology professor at the University of Auckland, and Emily Lane, a tsunami expert at the National Institute of Water and Atmospheric Research, offer these explanations.

EXPLOSIVE BUT BRIEF

The eruption was incredibly explosive but relatively brief. The plume rose more than 19 miles, but the eruption lasted only about 10 minutes, unlike some eruptions that can last hours. Cronin said the power of the Hunga Tonga Hunga Ha’apai volcanic eruption ranks among the world’s biggest in 30 years, and the height of the ash, steam and gas plume was comparable with the 1991 Mount Pinatubo eruption in the Philippines, which killed several hundred people.

WHY SO BIG?

The magma in the volcano was under enormous pressure, with gases trapped inside. A fracture in the rock likely induced a sudden drop in pressure, allowing gas to expand and blast the magma apart. Cronin said the crater was about 650 feet below the sea surface, a kind of Goldilocks depth for a big explosion in which seawater pours into the volcano and instantly turns to steam, adding to the expansion and energy of the explosion. Any deeper, and the extra pressure of the water would have helped contain the eruption.

FARFLUNG TSUNAMI

Many scientists were surprised an eruption could produce a Pacific-wide tsunami of about three feet that smashed boats in New Zealand and caused an oil spill and two drownings in Peru. Lane said oceanwide tsunamis usually are triggered by earthquakes that extend across huge areas rather than from a single volcano. She said other factors might have been at play, such as an underwater flank of the volcano collapsing, displacing water.

NO GLOBAL COOLING

Huge eruptions can cause temporary global cooling as sulfur dioxide is pumped into the stratosphere. But satellite measurements indicated the amount of sulfur dioxide released in the Tonga eruption would have only a tiny effect of perhaps 0.02 Fahrenheit global average cooling, said Alan Robock, a Rutgers University professor.

WHAT’S NEXT?

Cronin envisions two main scenarios. The first: that the volcano has exhausted itself for now and will go quiet for 10 to 20 years. The second: that new magma rises quickly, which might mean ongoing eruptions. He thinks the cracks and rifts caused by the explosion will allow more gas to escape, and subsequent eruptions won’t be as big.

The Latest
Meanwhile, downstate U.S. Rep. Mary Miller told Illinois delegates: “If just gun owners would come out and vote ... we could flip the state red.” And at a downtown Milwaukee news conference, Democrats slammed the Heritage Foundation’s Project 2025 as the Trump agenda for a second term.
A partir de las 9:45 p.m., el servicio meteorológico informó de 10 tornados activos en el área de Chicago, según los meteorólogos de ABC7 y WGN-TV. Era demasiado pronto para evaluar los posibles daños, pero poco después de las 10 p.m., ComEd informó de 2,226 fallos que afectaron a 201,217 clientes.
The National Weather Service is investigating more than 25 possible tornadoes, though it’s unlikely the number of confirmed twisters will be that high.
Today’s Sun-Times was not printed due to issues at our vendor’s printing facility. We’ve made the e-paper available for free today and we hope Tuesday’s paper will be delivered with Wednesday’s.
Sean Grusd pleaded guilty last year to stealing $23 million from investors in Chicago and elsewhere. With the latest allegation, prosecutors now want him locked up until sentencing.