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Volcanic eruption creates new island in Tonga

Date: 07 November 2019 Tags: Geography & Environment

Issue

An undersea volcanic eruption in the Tongan archipelago has sunk one island and created another three times larger, according to a report by geologists.

 

Background

The formed new Lateiki island is estimated to be about 100 metres wide and 400 metres long, and is situated about 120 metres west of its submerged predecessor.

The upheaval followed an 18-day undersea eruption last month in an area prone to earthquakes and volcanic activity.

 

Details

  • Tonga is located on the notorious Ring of Fire, an area of frequent seismic activity in the Pacific Ocean and which is responsible for about 90% of the world's earthquakes.

  • In late 2014 the eruption of an undersea volcano created another Tongan island that is now home to plants and birdlife.

Tonga

  • Tonga, officially named the Kingdom of Tonga, is a Polynesian sovereign state and archipelago comprising 169 islands, of which 36 are inhabited.

  • Tonga stretches across approximately 800 kilometres (500 mi) in a north-south line.

  • It is surrounded by Fiji and Wallis and Futuna (France) to the northwest, Samoa to the northeast, Niue to the east, Kermadec (part of New Zealand) to the southwest, and New Caledonia (France) and Vanuatu to the farther west.

  • Capital: Nuku’alofa

  • Currency: Pa’anga

Pacific ring of fire

  • The Pacific Ring of Fire is an arc around the Pacific Ocean where many volcanoes and earthquakes are formed. 

  • The area is also called the Pacific Rim, a term which refers to the coastal areas of the countries round the Pacific.

  • About three quarters of the world's dormant volcanoes and active volcanoes are here. The ring is 40,000km long, and there are 452 volcanoes.

  • About 90% of the world's earthquakes and 81% of the world's largest earthquakes occur along the Ring of Fire.

Illustration

Volcanic eruption creates new island in Tonga

Types of Volcanoes

Composite volcanoes

  • Composite volcanoes, sometimes known as strato volcanoes, are steep sided cones formed from layers of ash and lava flows.

  • Eruptions are explosive due to the thick, highly viscous lava that is produced by composite cone volcanoes.

  • This viscous lava has a lot to do with why they are shaped the way they are. The thick lava cannot travel far down the slope of the volcano before it cools and hence creates steep slopes.

  • Composite volcanoes are usually found at destructive plate margins.

  • Examples of composite volcanoes include Mount Fuji (Japan), Mount St Helens (USA) and Mount Pinatubo (Philippines).

Shield volcanoes

  • Shield volcanoes are low with gently sloping sides and are formed from layers of lava. Eruptions are typically non-explosive.

  • Shield volcanoes produce fast flowing fluid lava that can flow for many miles. Eruptions are frequent but gentle.

  • Shield volcanoes are usually found at constructive boundaries and sometimes at volcanic hotspots.

  • Examples of shield volcanoes include Mount Kilauea and Maunaloa on Hawaii.

Caldera

  • Magma is stored beneath a volcano in a magma chamber. When a very large explosive eruption occurs which empties the magma chamber, the roof of the magma chamber can collapse forming a depression, or bowl on the surface which has very steep walls. These are calderas and can be tens of miles across.

  • An example of a caldera is Yellowstone in North America.

Spatter cones

When magma contains too much gas to form an effusive lava flow, but too little to form an explosive eruption, it erupts from the volcano as blobs of magma which fall close to the vent forming a low, steep-sided cone that is called a spatter cone.

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