Volcanic Ash In Antarctica Pins Down Date Of One Of The Most Violent Eruptions In The Past 5,000 Years

Lake Taupō is the largest freshwater lake in Oceania, located in the center of New Zealand’s North Island. It is a caldera lake, filling a large cauldron-like depression that formed shortly after the emptying of a magma chamber in a volcanic eruption.

The Taupō supervolcano produced two of the world’s most violent eruptions in geologically recent times. The Ōruanui supereruption is the world’s most recent supereruption dated at 25,500 years. It coated the North Island in a thick layer of ash and igneous rocks. About 2,000 years ago, the volcano erupted again, with New Zealand’s largest eruption known so far.

Scientists have been hunting for evidence of this eruption for more than a decade, hoping it would help pin down the date of this event, which has been a point of dispute, said Stephen Piva, the study’s lead author and a Ph.D. candidate at Te Herenga Waka—Victoria University of Wellington.

“The Taupō eruption was one of the largest and most powerful volcanic eruptions known to have occurred in the past 5,000 years, devastating an area of about 20,000 kilometers and spreading volcanic fallout throughout the region.”

“But exactly when the eruption occurred has sparked debate. Our discovery of seven geochemically unique volcanic glass shards buried deep within an ice core confirms the likely timing of the eruption in late summer/early autumn in the year 232,” he said.

Volcanic ash consists of rock fragments and quickly solidified lava, forming a bubble -rich and amorphous material. Under a microscope, this material looks like tiny shards of broken glass.

The volcanic glass shards of the Taupō eruption were found at a depth of 279 meters in the Roosevelt Island Climate Evolution ice core, taken from West Antarctica.

Analysis of the geochemical make-up of the shards linked them to the Taupō eruption. Researchers were then able to assess how long the shards had been there based on the modeled age of the ice layers.

Of the seven shards, one was a match for volcanic glass produced by the earlier Ōruanui supereruption. The other six shards had a similar geochemical composition that researchers considered could be confidently linked to the Taupō eruption itself.

“Combined, the seven shards provide a unique and undeniable double fingerprint of the Taupō volcano as the source,” Piva explained.

Detecting the glass shards in Antarctica, which is about 5,000 kilometers away from Taupō, shows the power of the eruption.

“A massive eruption plume would have sent a huge volume of volcanic particles into the air where they would have been widely dispersed by the wind. Confirming the eruption date provides an opportunity to study the volcano’s potential global effects on the atmosphere and climate, which is crucial for better understanding its eruptive history and behavior.”

The Taupō is considered still an active supervolcano.

The study “Volcanic glass from the 1.8 ka Taupō eruption (New Zealand) detected in Antarctic ice at ~ 230 CE” was published in the journal Scientific Reports (2023). Additional material and interviews provided by Victoria University of Wellington.

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