[ Volcanic Islands : ]

Volcanic Islands
During the voyage, it was quite interesting to see the lands’ art of volcanoes. A volcano can be any space on the earth’s surface which primarily forms like a conical peak and that too with a beautiful snow-capped like structure. But it is a huge hole or cracks inside the ground that is filled with molten rock and other gases.

Place of occurrence

Accordance to studies, the volcanoes occur either

  • Along the Plate Margins: This could be along the spreading margins like mid-ocean ridges or the drifting continental structures or on the converging margins that include the island arcs or continental margin types.
  • On the Plate Interiors: This includes the oceanic or continental plates.

The official statement based on historical observations records that most of the volcanic eruptions are linked with the subduction zones.

Some interesting facts

Although a great number of volcanoes occur, some are categorised into three main types

  • The Active ones: This includes the volcanoes that have erupted during the historical phase
  • The Dormant ones: These are the types that already have erupted in the historical times, but more chances exist that it might erupt again
  • Finally, the Extinct ones: These have also erupted in the historical period but will not erupt again.

In addition to this information, there are nearly 650 volcanoes that are in the active stage and among them, 6 to 10 are erupting per month that accounts for over 60 volcanoes per year.

A Brief Description on Volcanic Rocks

A building volcanic structure contains the following constituents

  • The MAGMA: This includes the molten stage rocks and other highly pressurised and dissolved gases. The major constituent includes the rock crust or mantle part that melts to form the magma.
  • The Gases: These are a combination of water, sulphur and fluorine constituents that can be further classified as
  1. High gas content ones or the explosive eruptions: Basically, this includes the highly gaseous or explosive eruptions or the Pyroclastic that can further be subdivided into Ash clouds, Lapilli and Volcanic bombs.
  2. The quiet eruptions or the low gas ones: This contains the lava fluid.

Commonly, all the volcanoes are subjected to be classified based on the

  • Nature of vents: This consists of central vent type and the fissure type
  • The eruption style: Examples to this include the Hawaiian, Plinian and much more

The actual blasting occurs when the pressure inside the volcanoes reduce to dissolve the gases inside the magma that further leads to its expansion and finally, the explosion of magma fragments. The ash contents fall back to ground blanketing the whole area with thick ash deposits.

 

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