What is a volcano?
A volcano is a geological feature through which molten rock, gases and particles can reach the surface. Molten rock at the surface is lava; below ground it is magma. Volcanoes are not limited to cone-shaped mountains.
Formation and eruption styles
Magma commonly forms under conditions associated with plate boundaries or hotspots. Its composition, temperature, gas content and viscosity influence the eruption. Runny lava may produce relatively gentle flows, while gas-rich viscous magma may drive explosive ash and rock ejection. Lava spreading from fissures can cover broad areas; a caldera may form after some eruptions. Everyday labels such as active, dormant and extinct do not offer a certain prediction of future behavior.
Hazards and monitoring
Lava flows, ashfall, harmful gases and hot pyroclastic flows are distinct hazards. Volcanic mudflows can travel rapidly down valleys after rain or ice melt. Ash may disrupt aviation and water systems far away. Scientists monitor tremors, ground swelling, gas emissions and temperature to assess change. These signs may warn of rising risk but cannot determine every event’s exact timing or size. Preparation depends on local hazard maps and evacuation plans.