Answer in brief
Explain the types of volcanoes on the basis of periodicity of eruption with examples.
Solution
Volcanoes are mountains that result from volcanic eruptions. Volcanic eruptions occur when either plates sink below another plate (subduction), heating and creating magma, or plates pull apart, allowing magma to rise to the surface. In both these conditions, the magma reaches the surface or is thrown out to the surface through vents and fissures. Periodicity refers to the period between which eruptions occur from a particular volcano. On the basis of periodicity, volcanoes are of three types –
1) Active Volcanoes -
• A volcano that is erupting or shows signs of future eruptions like emission of gas, muds, etc. is called active.
• Any signs of unrest including unusual earthquake activity or significant new gas emissions makes a volcano active by nature.
• Most volcanoes are situated on the Pacific Ring of Fire are considered active. Mt Fujiyama in Japan, Mt. Stromboli in Mediterranean Sea are also considered as active volcanoes.
2) Dormant Volcanoes –
• Dormant volcanoes are those that have not erupted for thousands of years, but are likely to erupt again in the future.
• Mt. Vesuvius in Italy, Mt. Katmai in Alaska, and Barren Island, India are considered to be examples of dormant volcanoes.
3) Extinct Volcanoes –
• Any volcano that shows no magma supply and has not erupted in recorded history is considered as an extinct volcano.
• Mt. Kilimanjaro in Tanzania is an extinct volcano.
