How the Tonga eruption rang Earth like a bell

Date:
Fri, 14 Apr 2023 18:00:00 +0000

Description:
Earth-observing satellites captured the powerful eruption. NASA Earth Observatory A detailed simulation of underwater shockwaves changes what we know about the Hunga Tonga-Hunga Haapai eruption. The post How the Tonga eruption rang Earth like a bell appeared first on Popular Science .

FULL STORY ====================================================================== Earth-observing satellites captured the powerful eruption. NASA Earth Observatory

When the Hunga TongaHunga Haapai volcano in Tonga exploded on January 15, 2022setting off a sonic boom heard as far north as Alaskascientists instantly knew that they were witnessing history.

In the geophysical record, this is the biggest natural explosion ever recorded, says Ricky Garza-Giron , a geophysicist at the University of California at Santa Cruz.

It also spawned a tsunami that raced across the Pacific Ocean, killing two people in Peru. Meanwhile, the disaster devastated Tonga and caused four deaths in the archipelago . While tragic, experts anticipated an event of
this magnitude would cause further casualties. So why didnt it?

Certainly, the countrys disaster preparations deserve much of the credit. But the nature of the eruption itself and how the tsunami it spawned spread
across Tongas islands, also saved Tonga from a worse outcome, according to research published today in the journal Science Advances . By combining field observations with drone and satellite data, the study team was able to recreate the event through a simulation. Satellites captured the explosive eruption of the Hunga Tonga-Hunga Haapai volcano. National Environmental Satellite Data and Information Service

Its yet another way that scientists have studied how this eruption shook
Tonga and the whole world. For a few hours, the volcanos ash plume bathed the country and its surrounding waters with more lightning than everywhere else
on Earthcombined. The eruption spewed enough water vapor into the sky to
boost the amount in the stratosphere by around 10 percent.

[Related: Tongas historic volcanic eruption could help predict when tsunamis strike land ]

The eruption shot shockwaves into the ground, water, and air. When
Garza-Giron and his colleagues measured those waves, they found that the eruption released an order of magnitude more energy than the 1980 eruption of Mount St Helens .

It literally rang the Earth like a bell, says Sam Purkis , a geoscientist at the University of Miami in Florida and the Khaled bin Sultan Living Oceans Foundation. Purkis is the first author of the new paper.

The aim of the simulation is to present a possible course of events. Purkis and his colleagues began by establishing a timeline. Scientists agree that
the volcano erupted in a sequence of multiple bursts, but they dont agree on when or how many. Corroborating witness statements with measurements from
tide gauges, the study team suggests a quintet of blasts, each steadily increasing in strength up to a climactic fifth blast: measuring 15 megatons, equivalent to a hydrogen bomb. Credit: Steven N. Ward Institute of Geophysics and Planetary Physics, University of California Santa Cruz, U.S.A.

Then, the authors simulated what those blasts may have done to the oceanand how fearsome the waves they spawned were as they battered Tongas other islands. The simulation suggests the isle of Tofua, about 55 miles northeast of the eruption, may have fared worst: bearing waves more than 100 feet tall.

But theres a saving grace: Tofua is uninhabited. The simulation also helps explain why Tongas capital and largest city, Nukualofa, was able to escape
the brunt of the tsunami. It sits just 40 miles south of the eruption, and seemingly experienced much shallower waves.

[Related: Tonga is fighting multiple disasters after a historic volcanic eruption ]

The study team thinks geography is partly responsible. Tofua, a volcanic caldera, sits in deep waters and has sharp, mountainous coasts that offer no protection from an incoming tsunami. Meanwhile, Nukualofa is surrounded by shallower waters and a lagoon, giving a tsunami less water to displace. Coral reefs may have also helped protect the city from the tsunami.

Researchers believed that reefs could cushion tsunamis , Purkis says, but
they didnt have the real-world data to show it. You dont have a real-world case study where you have waves which are tens of meters high hitting reefs, says Purkis.

We do know of volcanic eruptions more violent than Hunga TongaHunga Haapai: for instance, Tambora in 1815 (which famously caused a Year Without a Summer ) and Krakatau in 1883 . But those occurred before the 1960s when geophysicists started deploying the worldwide net of sensors and satellites they can use today.

Ultimately, the study authors write that this eruption resulted in a lucky escape. It occurred under the most peculiar circumstances: At the time of its eruption, Tonga had shut off its borders due to Covid-19, reducing the number of overseas tourists visiting the islands. Scientists credit this as another reason for the low death toll. But the same closed borders meant scientists had to wait to get data. Ash over the South Pacific could be seen from space. NASA

Thats part of why this paper came out 15 months after the eruption. Other scientists had been able to simulate the tsunami before, but Purkis and his colleagues bolstered theirs with data from the ground. Not only did this help them reconstruct a timeline, it also helped them to corroborate their simulation with measurements from more than 100 sites along Tongas coasts.

The study team argues that the eruption serves as a natural laboratory for
the Earths activity. Understanding this tsunami can help humans plan how to stay safe from them. There are many other volcanoes like Hunga TongaHunga Haapai, and volcanoes located underwater can devastate coastal communities if they erupt at the wrong time.

Garza-Giron is excited about the possibility of comparing the new studys results with prior studies, such as his own, about seismic activityin
addition to other data sources, likethe sounds of the oceanto create a more complete picture of what happened that day.

Its not very often that we can see the Earth acting as a whole system, where the atmosphere, the ocean, and the solid earth are definitely interacting, says Garza-Giron. That, to me, was one of the most fascinating things about this eruption.

The post How the Tonga eruption rang Earth like a bell appeared first on Popular Science . Articles may contain affiliate links which enable us to share in the revenue of any purchases made.



======================================================================
Link to news story: https://www.popsci.com/science/tonga-volcano-tsunami-simulation/


--- Mystic BBS v1.12 A47 (Linux/64)
* Origin: tqwNet Science News (1337:1/100)