Tonga eruption yields surprising scientific discoveries

Scientists who've been on a month-long expedition to Tonga to map the impact of January's record-breaking volcanic eruption have made some surprising discoveries.

The researchers expected to find dramatic changes to the volcano because of the power of the explosion, but instead found it largely intact.

There's also evidence the volcano might still be erupting.

We spoke to NIWA's Oceans Chief Scientist Dr Mike Williams.