Almost a year on from Tonga's devastating undersea volcanic eruption, volcanologist Shane Cronin asseses the impact and implications for monitoring other Pacific fault lines. The Hunga Tonga-Hunga Haʻapai eruption in January generated a huge tsunami that reached the coasts of Japan and the Americas, claiming six lives, injuring 20 people and causing damage in excess of 100 million dollars. The submarine volcano lies around 65 kilometres north of the Kingdom's main island, Tongatapu, and it was biggest atmospheric explosion recorded on Earth in more than 100 years. It is part of the active Kermadec-Tonga subduction zone and the volcanic arc associated with it extends from New Zealand to Samoa. Since the eruption University of Auckland vulcanologist Shane Cronin has been back to Tonga, leading the local science response and identifying ongoing hazards.