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Current Affairs

Lewotolok volcano eruption

Date: 02 December 2020 Tags: Geography & Environment

Issue

Lewotolok volcano in Indonesia's East Nusa Tenggara province has erupted, spewing ash and smoke as high into the sky.

 

Background

Indonesia has nearly 130 active volcanoes, more than any other country, and while many show high levels of activity it can be weeks or even months before an eruption.

 

Details

  • The area near the volcano is likely to be inundated with hot clouds, lava stream, lava avalanche, and poisonous gas.

  • There are only three other volcanoes with this level. These include the Merapi volcano on the island of Java and Sinabung on Sumatra, which erupted this month.

 

Types of volcanoes

Shield volcano

  • A shield volcano is a type of volcano usually composed almost entirely of fluid lava flows. It is named for its low profile, resembling a warrior's shield lying on the ground.

  • A volcanic mountain having a broad profile is built up over time by flow after flow of relatively fluid basaltic lava issuing from vents or fissures on the surface of the volcano. Many of the largest volcanoes on Earth are shield volcanoes.

  • The largest is Mauna Loa on the Big Island of Hawaii; all the volcanoes in the Hawaiian Islands are shield volcanoes.

 

Composite volcano

  • Composite volcanoes, also called strato-volcanoes, are cone-shaped volcanoes built from many layers of lava, pumice, ash, and tephra.

  • Since they are built of layers of viscous material, rather than fluid lava, composite volcanoes tend to form tall peaks rather than rounded cones.

  • The essential feature of a composite volcano is a conduit system through which magma from a reservoir deep in the Earth's crust rises to the surface.

 

Cinder cones

  • A cinder cone is a steep conical hill of loose pyroclastic fragments, such as volcanic clinkers, volcanic ash, or cinder that has been built around a volcanic vent.

  • The pyroclastic fragments are formed by explosive eruptions or lava fountains from a single, typically cylindrical, vent.

 

Caldera

  • A caldera is a large cauldron-like hollow that forms shortly after the emptying of a magma chamber/reservoir in a volcanic eruption.

  • When large volumes of magma are erupted over a short time, structural support for the rock above the magma chamber is lost.

  • The ground surface then collapses downward into the emptied or partially emptied magma chamber, leaving a massive depression at the surface.

 

Flood Basalt

Flood basalt is formed by an eruption or series of eruptions of large volcanic episodes that cover vast stretches of land or ocean floor with flows of igneous rocks (basalt lava flows).