Context: Indonesia's Marapi volcano in West Sumatra erupted on Sunday, spewing volcanic ash as high as 3,000 m into the air.
VOLCANISM & VOLCANICITY
- A volcano on Earth is a vent or fissure in the crust through which lava, ash, rock and gases erupt.
- Sometimes they can be preceded by emissions of steam and gas from small vents in the ground.
- Nuée ardente, or pyroclastic flow is a fluidized mixture of hot gas and incandescent particles that sweeps down a volcano’s flanks, incinerating everything in its path.
VOLCANO ANATOMY
When volcanoes erupt, magma moves upward from a magma chamber and into a vent or conduit. It flows out from a crater at the top, or sometimes emerges at a secondary site on the side of the volcano resulting in a flank eruption. Erupted materials accumulate around the vent forming a volcanic mountain.
The accumulated material might consist of layers of solidified lava, called lava flows, but it might also include fragments of various sizes that have been thrown from the volcano.
MECHANISM & CAUSES OF VULCANISM
Mechanism of volcanism is closely associated with several interconnected processes.
- Average increase of temperature with increasing depth at the rate of 25-32 degree Celsius per km.
- Origin of magma due to lowering of melting point caused by reduction in the pressure of overlying super incumbent load.
- Origin of gases and vapour due to heating of water which reaches underground through percolation.
- Ascent of magma forced by enormous volume of gases and vapour.
- Occurrence of volcanic eruptions.
Why Indonesian region experience so many volcanos? The region is located on one of the most volatile regions of the world experiencing intense tectonic convergence and subduction. As the world's largest archipelago — spread across 17,500 islands — Indonesia sits between the world's most active seismic region — the notorious Pacific Ring of Fire — and the world's second most active region — the Alpide belt. Being sandwiched between such seismicity has meant the islands experience some of the strongest earthquakes and most powerful volcanic eruptions. |