ज्वालामुखी क्या है? विश्व में ज्वालामुखियों का वितरण समझाइए।

Introduction: A Volcano is a vent, fissure, or opening in the Earth's crust through which molten rock material (magma/lava), volcanic ash, pyroclastic debris, steam, and gases ($SO_2, CO_2, H_2S$) are violently or quietly extruded onto the surface. Their global distribution is closely correlated with Tectonic Plate Boundaries.

1. Major Global Volcanic Belts (Distribution):

• 1. Circum-Pacific Belt ("Ring of Fire" - ~68% of World's Active Volcanoes):
  • Follows the convergent (subduction) plate boundaries enclosing the Pacific Ocean where oceanic plates subduct beneath continental plates.
  • Extends across the Andes (Cotopaxi, Chimborazo), Central America, Cascades (Mt. St. Helens, Mt. Rainier), Aleutian Islands, Kamchatka, Japan (Mt. Fuji), Philippines (Mt. Pinatubo, Mayon), and New Zealand.
• 2. Mid-Continental / Mediterranean Belt (~21% of Active Volcanoes):
  • Associated with the convergent collision zone between the Eurasian Plate and the African/Indian Plates (Alpine-Himalayan mountain system).
  • Famous Mediterranean volcanoes: Mt. Vesuvius, Mt. Etna, Mt. Stromboli (Lighthouse of the Mediterranean), and Vulcano; Mt. Ararat (Turkey) and Mt. Damavand (Iran).
• 3. Mid-Atlantic Ridge Belt (Divergent Boundary):
  • Runs along the constructive divergent plate margin where Eurasian/North American and African/South American plates pull apart.
  • Characterized by fissure eruptions creating basaltic oceanic crust (e.g., Iceland - Hekla, Eyjafjallajökull, Azores, St. Helena).
• 4. Intra-Plate / Hotspot Volcanism:
  • Isolated volcanoes formed over deep mantle plumes independent of plate margins (e.g., Hawaiian Islands - Mauna Loa, Kilauea, Reunion Hotspot).

Conclusion: Volcanism is the primary geothermal mechanism of planetary crust formation and mineral concentration on Earth.