Photos: Tonga Navy

Eruption of tephra at 600m (~2,000ft) altitude. Hunga Tonga on the right has no activity. The ash extends just over 2km over the sea surface eastward. 6 January 2015. Photo: Tonga Navy.

Eruption of ash and tephra is slowing down, while sulphuric gas and steam continues to be emitted from Hunga Ha‘apai, Tonga's Ministry of Lands and Natural Resources said yesterday.

An advisory on the volcanic activity located about 65km northwest of Nuku‘alofa, included photographs of a dramatic eruption shooting tephra to 1,300m (4,300ft) on January 6, taken by the Tongan Navy.

The volcanic activity began about December 20 from a submarine vent 3 km south of Hunga Tonga and 3.2km SW of Hunga Ha‘apai, an area that is known for periodic eruptions.  

“The photographs by the Tonga Navy from the eastern side of the region on 6 January 2015 confirms the eruption of tephra and ash to be from Hunga Ha‘apai...There was no indication of further steam emission from the submarine vent,” the advisory stated.

There appeared to be no activity from the nearby Hunga Tonga volcanic island.

A Tonga Navy boat on its way back to Nuku‘alofa from the northern islands captured images of the changing nature of the eruption, which cycles between emissions of water vapour to tephra and ash. The images were taken a couple of minutes apart.

“The eruption of tephra and ash lasted around three and a half minute’s total,” the advisory stated.

The pilot flying over the region at 10:17am on January 13 had reported no tephra and ash eruptions. “The forecasting of volcanic ash was predicted to be clear by 6:00pm today,” said the advisory.

All international flights on 13 January were cancelled, while the domestic airline was operational.

Above, The ash and tephra shoots out violently in dense grey to 200m (~1,000ft) altitude. 6 January 2015. Photo: Tonga Navy.

An eruption of thick black ash and tephra material shoots northerly up to 400m (~1,000ft) altitude. The ash expands just over 1km over the sea surface eastward from Hunga Ha‘apai. 6 January 2015. Photo: Tonga Navy.

Eruption of tephra at 750m (2,500ft) altitude, only a minute after initial eruption. 6 January 2015. Photo: Tonga Navy.

The next cycle emission of gas and vapour (white part rising from the middle) builds up a couple minutes after the tephra eruptions lifted. Hunga Tonga, right, is isolated by the ash and steam cover in a matter of minutes. 6 January 2015. Photo: Tonga Navy.