On 15 January, at about 5 pm (Italian time), the Hunga Tonga-Hunga Ha’apai volcano erupted, spewing a huge amount of ash into the atmosphere. The volcano is part of Tonga, the Polynesian kingdom in the South Pacific that has over 170 islands, many of which are small and uninhabited. These include Hunga Tonga and Hunga Ha’apai, the two rocky cliffs about a hundred metres high that give the volcano its name, and which represent only a tiny summit of the volcano. In fact, the two islands are only part of the edge of the caldera, the crater of an enormous submerged volcano about 1800 m high and 20 km wide. The Tonga archipelago is located in a very active seismic zone, coinciding with the junction between the Pacific and Indo-Australian plates, which are among the largest on the planet. It is an area where enormous forces are concentrated and developed, which become evident with volcanic activity.
