Hunga Tonga-Hunga Ha'apai eruption - information about the tsunami
At 5:20pm on Saturday 15 January, a large, impulsive eruption at Hunga Tonga-Hunga Ha’apai volcano in Tonga occurred causing tsunami activity on coastlines around the Pacific – observed as widely as the west coast of the USA, Peru, Japan and New Zealand.
A volcanic-source tsunami event is rare but not unprecedented. It’s one of those things scientists always talk about as a possibility, but they are far from common.
It is likely that the earlier 14 January eruption blew away part of the volcano above water, so water flowed into the extremely hot vent. This meant that the Saturday evening eruption initially occurred underwater and exploded through the ocean, causing a widespread tsunami. There are also a few other potential mechanisms that could have contributed to the tsunami. We won’t know for sure until scientists can investigate what happened at the volcano – and right now both ash clouds and limited communications with Tonga mean that we can’t be certain.
As soon as tsunami activity was reported following the eruption, the GNS Science team swung into action to assess the tsunami threat to New Zealand shores. The first sign of unusual activity came when the New Zealand DART buoy closest to Tonga triggered at 5:48pm. Over time, as data was recorded at more of our DART buoys and coastal tsunami gauges, we were able to build a picture of what threat there might be to New Zealand.