Volcanism - UPSC Geography Notes

Volcanism at Stromboli Volcano/Source: Simon

Volcanism refers to the processes and phenomena associated with the eruption of magma, gases, and other substances from the interior of the Earth onto its surface.

Volcanoes are the primary features of volcanism, where magma reaches the surface through vents or fissures.

Types of Volcanoes:

  • Shield Volcanoes: Broad, gently sloping volcanoes with basaltic lava flows. Example: Mauna Loa in Hawaii.
  • Stratovolcanoes (Composite Volcanoes): Steep-sided cones built from layers of lava, ash, and other volcanic materials. Example: Mount Fuji in Japan.
  • Cinder Cones: Small, steep-sided volcanoes formed by the accumulation of pyroclastic material. Example: Paricutin in Mexico.
  • Calderas: Large, basin-shaped depressions formed by the collapse of the ground after a massive eruption. Example: Yellowstone Caldera in the United States.

Volcanic Eruptions:

  • Effusive Eruptions: Characterized by the relatively gentle release of lava onto the surface, forming lava flows.
  • Explosive Eruptions: Involve the violent ejection of fragmented magma, volcanic ash, and gases into the atmosphere.
  • Pyroclastic flows: Fast-moving currents of hot gas, ash, and rocks that flow down the sides of volcanoes.
  • Ash clouds: Volcanic ash and gases can reach high altitudes, impacting air travel and climate.
  • Lahars: Mudflows formed by the mixing of volcanic debris with water, often caused by melting snow or heavy rainfall.

Volcanic Hazards and Impact:

  • Primary hazards: Lava flows, pyroclastic flows, ashfall, volcanic gases, lahars, and volcanic projectiles.
  • Secondary hazards: Tsunamis (if the volcano is in the ocean), landslides, and earthquakes.
Volcanic eruptions have the potential to cause extensive damage to infrastructure, agriculture, and human settlements. However, volcanism also contributes to the formation of fertile soils, geothermal energy resources, and distinctive geological formations.

Volcanic Monitoring and Prediction:

  • Monitoring techniques include seismometers, gas monitoring, ground deformation measurements, and thermal imaging.
  • Volcanologists analyze data to detect changes in volcanic activity and attempt to forecast eruptions.
  • Although progress has been made, accurately predicting volcanic eruptions remains challenging.
Volcanism on Earth:
  • Most volcanic activity occurs along plate boundaries, especially at convergent and divergent boundaries. (Read: Plate Tectonics Theory)
  • Subduction zones often exhibit explosive volcanism due to the release of volatiles from subducting plates.
  • Hotspots, such as those responsible for the Hawaiian Islands, can generate volcanic activity far from plate boundaries.

Volcanism is a potent geological process that shapes the surface of the Earth. It includes diverse volcanic characteristics, eruption types, risks, and monitoring techniques. Understanding volcanism is essential for assessing and mitigating the risks associated with volcanic activity, as well as exploiting its benefits, such as geothermal energy and fertile soils.

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