Rare Mega-Eruption That Lasted For Six Months Leaves Earth's Biggest Caldera Formation

On September 2014, Iceland's Bardarbunga volcano made headlines after it continued to emit hot molten lava for six months after it began erupting. The official end of the eruption, which started in the region of Holuhrau, was declared on February 28, 2015.

Gizmodo notes that the eruption was the strongest in Europe in more than 240 years, spewing large volumes of sulphur dioxide that caused poor air quality in Iceland and as far away as Dublin in Ireland.

After the eruption that covered 85 square kilometers, the site was monitored closely and it was discovered that a caldera was formed from the mega-eruption.

A caldera is defined by Science Daily as a feature formed by the collapse of a volcano into itself, making it a large, special form of volcanic crater.

The geologic phenomenon is rare. In fact, since the formation of the Katmai caldera in 1912, during the 20th century's largest eruption, only five caldera collapses are known to have occurred before that at Bardarbunga.

Unlike other massive eruptions where the caldera was formed quickly, the caldera in Bardarbunga was formed slowly. This gave scientists a once-in-a-lifetime opportunity to study the hole more.

A group from GFZ German Research Centre for Geosciences and Magnus T. Gudmundsson from the University of Iceland lead the study recently published in journal Science.

Using satellite images, seismological and geochemical data, GPS data and modelling, they were able to come up with the explanation as to why the eruption lasted that long and how it started.

According to the report, the eruption started when pressure was felt with the buildup of magma in the chamber. The caldera collapse began a few days later, when "12 to 20 percent of the total magma intruded and erupted had flowed from the magma reservoir. "

Dr. Gudmundsson told New York Times that if the collapse has not incurred, the eruption might have already ended. The collapse put further pressure on the chamber which resulted in continuous lava flow.

The study further revealed that Bardarbunga produced the largest caldera formation ever observed, covering about 40 square miles and sank about 200 feet during the eruption.

"With an area of 110 square kilometers, this is the largest caldera collapse ever monitored. The results provide the clearest picture yet of the onset and evolution of this enigmatic geological process," said Dr. Eoghan Holohan, who led the modelling part of this work at the GFZ, in a statement published by Science Daily.

The study helps in proving more in-depth insight to the rare and unexplored world of caldera formation.