Tonga eruption

Subject: Geography

Section: Geomorphology

Context:

Researchers are starting to piece together why the Hunga Tonga–HungaHa’apai eruption in the South Pacific on January 15 was so explosive.
Evidence gathered by two groups suggests that when the Tongan volcano’s centre collapsed, it spewed an enormous amount of magma that reacted violently with water.
Concept :

Tonga

Located in Oceania, Tonga is a small archipelago in the South Pacific Ocean, directly south of Samoa and about two-thirds of the way from Hawaii to New Zealand.
It has 169 islands, 36 of them inhabited, which are in three main groups – Vavaʻu, Haʻapai, and Tongatapu – and cover an 800-kilometer (500-mile)-long north–south line.
The total size is just 747 km2 (288 sq mi). Due to the spread out islands it has the 40th largest Exclusive Economic Zone of 659,558 km² (254,657 sq mi).
Geologically the Tongan islands are of two types: most have a limestone base formed from uplifted coral formations; others consist of limestone overlaying a volcanic base.
Tongan Volcanic Arc was created from the subduction of the westwards-moving Pacific plate under the Australia-India plate at the Tonga Trench.
The eastern islands are not volcanic and sit above the mostly submerged Tonga ridge that runs parallel to the Tongan Volcanic Arc and the Tongan Trench.
In regards to volcanism, Tonga has moderate volcanic activity.
Fonualei has shown frequent activity in recent years, while Niuafo’ou which last erupted in 1985, has forced evacuations; other historically active volcanoes include Late and Tofua.