By Mary Lyn Fonua

An explosive volcanic eruption shooting ash and pyroclastic material up to 350 metres above sea level was captured on camera yesterday by a Tonga Navy crew, sailing close to the Hunga Tonga-Hunga Ha'apai active volcano.

Taaniela Kula, leading the Tonga Geological Service volcano monitoring, said the important video, uploaded to Instagram by a crew member late yesterday, helped Tongan geologists understand the nature of the explosive basal surge eruption.

The Ministry of Lands & Natural Resources has been relying on satellite imagery analysis, since an explosive ash eruption at Hunga Ha'apai on Monday sent ash and dust 18km above sea level, followed by clouds of gaseous emissions over following days.

“We couldn't see the emissions sideways, until the video came in and it helped us understand it,” he told Matangi Tonga.

Taaniela said while the ash rose and fell down, the steam vapor went higher and travelled further across Tonga.

“These pyroclastic explosives fired up to only 350m tops and fell back down. Only the gaseous materials plumed all the way up to 8-14km altitude.”

Video: Tonga Navy (videographer unidentified)

Taaniela said the ash was not detected at the height of aviation.

“This is a point of discussion with the authorities,” he said today. “They don't mind the steam vapor but not the ash.”

He said the satellite data says there's no ash, only sulfur detected in the drifting clouds.

Latest report

At 5:30pm today TGS said the eruption had reduced this afternoon from pyroclastic to gaseous emissions rising to 14km above sea level. The wind direction  at 12km was predominantly North. (TGS report 18)

This week, most of the staff of the Ministry of Lands and Survey is on leave for the government Christmas holidays, and will not return to work until the first week of January.

Taaniela said he had been contacted by Massey University in Wellington, New Zealand, today and he welcomed the assistance they had offered in managing the data, coming in daily from the continuing eruption.