Tonga

Subject – Places in News

Context – U.S. coast on tsunami alert after Pacific volcano

Concept –

Tonga is a Polynesian country and also an archipelago consisting of 169 islands, of which 36 are inhabited.
In 2010, Tonga took a decisive step away from its traditional absolute monarchy and towards becoming a fully functioning constitutional monarchy, after legislative reforms paved the way for its first partial representative elections.
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.

Why are the volcano’s eruptions so highly explosive, given that sea water should cool the magma down?

If magma rises into sea water slowly, even at temperatures of about 1200 degrees Celsius, a thin film of steam forms between the magma and water. This provides a layer of insulation to allow the outer surface of the magma to cool.
But this process doesn’t work when magma is blasted out of the ground full of volcanic gas. When magma enters the water rapidly, any steam layers are quickly disrupted, bringing hot magma in direct contact with cold water.
Volcano researchers call this ‘fuel-coolant interaction’ and it is akin to weapons-grade chemical explosions. Extremely violent blasts tear the magma apart. A chain reaction begins, with new magma fragments exposing fresh hot interior surfaces to water, and the explosions repeat, ultimately jetting out volcanic particles and causing blasts with supersonic speeds.