Day 44 – 5. What is volcanism? What are the factors that lead to volcanism? What role do volcanoes play in the climate?
5. What is volcanism? What are the factors that lead to volcanism? What role do volcanoes play in the climate?
ज्वालामुखी क्या है? वो कौन से कारक हैं जो ज्वालामुखी का निर्माण करते हैं? जलवायु में ज्वालामुखी क्या भूमिका निभाते हैं?
Volcanism is the phenomenon of eruption of molten rock (magma) onto the surface of the Earth or a solid-surface planet or moon, where lava, pyroclastics and volcanic gases erupt through a break in the surface called a vent.
Movement of molten rock in the mantle, caused by thermal convection currents, coupled with gravitational effects of changes on the earth’s surface (erosion, deposition, even asteroid impact and patterns of post-glacial rebound) drive plate tectonic motion and ultimately volcanism.
Factors that lead to volcanism:
- Plate Tectonics: The majority of volcanoes occur where two lithospheric plates converge and one overrides the other, forcing it down into the mantle to be reabsorbed.
- Ocean floor spreading: A major site of active volcanism is along the axis of the oceanic ridge system, where the plates move apart on both sides of the ridge and magma wells up from the mantle.
- Weak Earth Surface: Because of high pressure in the earth’s interior, the magma and gases escape with great velocity as the pressure is released through eruptions where opportunity is provided by weak zones along the earth’s surface.
- Faults: Whenever extreme pressure builds in the mantle, along fault lines an eruption is likely to happen next. The earthquakes, for instance, may expose fault zones through which magma may escape.
- Magma crystallization: Decreasing temperatures can cause old magma to crystallize and sink to the bottom of the chamber and this movement can force fresh liquid magma up and out – similar to dropping a brick in a bucket of water.
- A decrease in external pressure: A decrease in external pressure can trigger an eruption as it may minimize the volcano’s ability to hold back by increasing the pressures inside the magma chamber
- Plate movement: Volcanism may occur because of plate movement over a “hot spot” from which magmas can penetrate to the surface. Ex. Islands of Hawaii
The gases and dust particles thrown into the atmosphere during volcanic eruptions have effects on climate.
Negative effects: Volcanic eruptions produce hazardous effects for the environment and climate,
- Ashes can stay in the stratosphere for about two to five years, and within this period, there are chemical reactions that destroy the stratospheric ozone molecules.
- Volcanoes contribute about 18%-20% of Chlorine entering the atmosphere, this also destroys ozone.
- Volcanoes also cause global warming by releasing greenhouse gases such as water vapour and carbon dioxide into the atmosphere.
- Lava can kill plants and animals. This also contributes to global warming by reducing carbon sink.
Positive effects: Unlike other natural disasters such as floods, wildfires and earthquakes, volcanoes can have some positive effects.
- Most of the particles spewed from volcanoes cool the planet by shading incoming solar radiation. The cooling effect can last for months to years causing cooling over large areas of the Earth.
- Some ash and lava breakdown become soils that are rich in nutrients and become good areas for crop planting activities and growth of the forest.
Volcanism helps in the formation of various landforms on the earth’s surface and bears both positive and negative effects on the climate, environment and human life. With scientific studies, one can predict the volcanic eruption to much extent. Preparedness for this natural disaster can protect human life and environment to a larger extent.