Volcano and its Types

Why in News?

Lava flows from a volcano in Iceland were slowing down recently, although new vents could open at short notice, according to the Icelandic Meteorological Office.

What are volcanoes?

• According to the US Geological Survey, volcanoes are openings, or vents where lava, tephra (small rocks), and steam erupt onto the Earth’s surface.

• Occurrence – It can be on land and in the ocean in Earth.
• Scientific evidences also show their presence in other planets like Mars and Venus.
• Formation – They are formed when material significantly hotter than its surroundings is erupted onto the surface of the Earth.
• Earth Core – Earth’s interior has outer crust, middle mantle and inner core layer.
• Mantle is denser than that of the crust and contains a weaker zone called asthenosphere from which the molten rock materials find their way to the surface.
• Liquid rock is known as magma when it is underground and called as lava when it breaks through the surface.
• 3 ways of magma rise
  1. Divergence of tectonic plates – Here, the magma rises up to fill in the space and when this happens underwater volcanoes can form.
  2. Convergence of tectonic plates – When this happens, part of Earth’s crust can be forced deep into its interior, which under high heat and pressure melts, and rise as magma.
  3. At hotspots – They are hot areas inside of the Earth, where magma gets heated up and it becomes less dense, leading to its rise.

The Pacific Ring of Fire includes New Zealand, Southeast Asia, Japan and the western coast of the Americas, is a region in which about 90% of all earthquakes worldwide strike.

• Erupted material – It includes lava flows, pyroclastic debris, volcanic bombs, ash and dust and gases (nitrogen, sulphur and minor amounts of chlorene, hydrogen and argon).

What are the different types of volcanoes?

• According to the British Geological Survey, the type of volcano depends
  • On the viscosity of the magma
  • On the amount of gas in the magma
  • On the composition of the magma
  • On the way the magma reaches the surface
  • On basis of their activity – Active  dormant and extinct
• Shield Volcanoes – They form very large, gently sloped volcanoes with a wide base. Example: Mauna Loa in Hawaii.
• Cinder cones – They are the smallest volcanic landform, formed from accumulation of many small fragments of ejected material.
• Composite Volcanoes (Stratovolcanoes) – They are characterised by eruptions of cooler and more viscous lavas than basalt and have steep sides and are more cone-shaped than shield volcanoes.
• Caldera – These are the most explosive of the earth’s volcanoes.
• When they erupt, they collapse on themselves rather than building and this collapsed depressions are called calderas.
• Flood Basalt Provinces - They outpour highly fluid lava that flows for long distances. Example: The Deccan Traps from India.
• Mid-Ocean Ridge Volcanoes – They occur in the oceanic areas where the central portion of this ridge experiences frequent eruptions.

• Active volcano – It is called so if the materials mentioned are being released or have been released out in the recent past.
  • Iceland, a volcanically active regions on the Earth witnesses an eruption every 4 to 5 years but since 2021, it has spiked to almost 1 eruption per year.

What are impacts of volcanic eruptions?

• Advantages – They help to stabilize the heat of the core part of our planet.

• They form new land forms after the drying process of liquid lava.
• The lava contains different minerals which enriches the existing soil.
• It lead to the formation of geysers which are sources of geothermal electricity which help in domestic and industrial use.
• It facilitate moderation of climate and receive higher rainfall than flat areas.

• Disadvantages - It leads to lot of destruction to life and property.
• It can create other natural hazards like Tsunami.

• It can produce harmful gases and the lava heat act as a booster for the global warming.
• The lava flow often cause wild fire in the nearby forestlands.

References

1. The Indian Express| Volcanoes and its types
2. The Indian Express| The activeness of volcano