Tonga volcanic eruption registered in Lancaster

Shockwaves from a massive volcanic eruption in Tonga have been registered by scientists at Lancaster University’s weather station.

A barograph measuring atmospheric pressure at Lancaster University’s Hazelrigg Weather Station registered two shockwaves around 14 hours after the volcanic eruption on the opposite side of the world.

The eruption of the underground volcano ‘Hunga Tonga-Hunga Ha’apai’, near Tonga, in the South Pacific, happened at around 4.10am UK time on January 15th (5.10pm local time). The shockwaves were registered at Hazelrigg at around 7.30pm on Saturday, January 15th, and 2am on the Sunday and were noticed by Dr James Heath, who takes readings from the various weather-recording instruments at Hazelrigg.

Dr Heath said: “When I went to change the barograph chart I was wondering what might have caused the sudden fluctuations in the readings, but before I had chance to think about it, one of our volcanologists, Hugh Tuffen, emailed to ask if we had picked it up here. It certainly makes it seem like a very small planet we live on.”

Dr Hugh Tuffen, a Volcanologist at Lancaster Environment Centre, said: “This is unusual (for a volcanic eruption to be registered so far away) and reflects the particularly violent explosion that occurred at Hung Tonga-Hunga Ha-apai, which has caused extensive hazards with a tsunami spreading through much of the Pacific Ocean.

“The violent eruption was due to runaway explosive interactions between magma and seawater, in what is called fuel-coolant interaction. Volcanologists are puzzled why this particular explosive event was so powerful as Hunga Tonga-Hunga Ha’apai, and many other submarine volcanoes, have recently erupted without anything like this violence. Further research is required to better understand the factors that control this type of eruption and identify which other submarine volcanic systems, particularly in the Pacific, are capable of similar eruptions, in order to assist with hazard mitigation.”

Dr Tuffen explained that the shockwave registered at Hazelrigg was generated by a dramatically sudden vaporisation of seawater in contact with magma at the eruption.

“This generated a pressure front that moved outwards at supersonic speeds, pushing on the surrounding air and creating a ring of pressure perturbation that expanded outwards around the entire globe the speed of sound,” he said. “As the shockwave spread out symmetrically from Tonga, it hit the UK twice, when each side of the expanding wave hit us.”

Dr Tuffen said the jury is still out as to whether this was the largest eruption of the 21st Century so far.

“Despite its remarkable intensity, the eruption was short-lived,” he said. “The largest eruption of the century to date by far, of the little-known submarine volcano Mayotte, near Madagascar, in 2018, involved at least 6.4 cubic kilometres of lava erupted over many months, beneath more than three kilometres of seawater, and failed to reach the ocean surface. The volume erupted at Hunga Tonga-Hunga Ha’apai is unlikely to match this, but the intensity of the eruption and global impacts were far greater.”

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