Why this matters now
Volcanoes are tested for their types, landforms and global distribution (Ring of Fire, hotspots), and they connect to plate tectonics and disaster management.
How volcanoes form
Volcanoes form where magma from the mantle reaches the surface — mostly at plate boundaries (subduction zones and mid-ocean ridges) and at hotspots (mantle plumes, e.g. Hawaii). The nature of an eruption depends on the magma’s viscosity and gas content — runny basaltic magma erupts gently, while sticky silica-rich magma erupts explosively.
Types of volcanoes
By activity: active (erupting/likely to), dormant (“sleeping”) and extinct (unlikely to erupt). By form: shield volcanoes (broad, gentle, basaltic — Hawaii), composite/strato volcanoes (steep, explosive — Fuji), cinder cones, and calderas (huge collapse craters).
Volcanic landforms
Eruptions create extrusive landforms (lava plateaus like the Deccan Traps, volcanic cones, craters/calderas) and intrusive landforms where magma solidifies underground (batholith, laccolith, sill, dyke). Volcanic soils (e.g. black regur over the Deccan) are highly fertile.
Global distribution
Most volcanoes lie along the “Pacific Ring of Fire” (subduction zones around the Pacific), the mid-Atlantic ridge, and the Mediterranean belt. India’s only active volcano is on Barren Island (Andaman Sea).
UPSC angle
Distinguish shield (gentle, basaltic) vs composite (explosive) volcanoes, know intrusive vs extrusive landforms (Deccan Traps), the Ring of Fire, and Barren Island as India’s only active volcano.
Frequently asked questions
How do volcanoes form?
Where magma from the mantle reaches the surface — mainly at plate boundaries (subduction zones, mid-ocean ridges) and hotspots.
What is the difference between shield and composite volcanoes?
Shield volcanoes are broad and gentle with runny basaltic lava; composite (strato) volcanoes are steep and erupt explosively with viscous lava.
What is the Ring of Fire?
A zone of intense volcanic and earthquake activity around the Pacific Ocean, associated with subduction at plate boundaries.
Where is India’s only active volcano?
On Barren Island in the Andaman Sea.