Natural Disasters-Volcanic Eruption

Natural Disasters-Volcanic Eruption

Natural Disasters – Volcanic Eruption

  • Volcanic Eruption happens when the molten rock from inside the Earth flows into the surface.
  • Volcanic Eruption is caused by the Earth’s internal heat, and is associated with tectonic processes and is a part of the rock cycle.


  • A volcano is a vent through which molten magma and gases are discharged to the surface.
  • Volcanos can be formed when the rock near the surface becomes hot enough to melt.
  • This often happens in in locations which are also plate boundaries.
  • In a divergent boundary, such as at mid-ocean volcanic ridges, material from Earth’s interior slowly rises up, melts when it reaches lower pressures, and fills in the gap.
  • Chambers of magma may form in places where one plate is being subducted under another.
  • These magma bodies feed the volcanic islands which help mark the locations of subduction zones.

Significance of Volcanoes:

  • The presence of volcanos on Earth tells us that Earth’s interior is circulating and is hot enough to melt rocks.
  • Earth is constantly cooling and volcanos are one way to lose heat.
  • The pattern of distribution of volcanos on Earth gives us a clue into the is divided into plates on Earth’s outer surface.
  • The chains of volcanos associated with mid-ocean ridges and subduction zones mark the edges of tectonic plates.

Types of Volcanoes

Shield Volcanoes
  • These are not very steep but are far and wider and extend to great height as well as distance.
  • Lava erupts commonly from vents along fractures aka rift zones, that develop along the flanks of the cone.
  • These volcanoes are made up of basaltic rocks which are less viscous and is very fluid during eruption.
  • They are generally not very explosive, but may turn explosive if water gets into the vent somehow.
Cinder Cone Volcanoes
  • These are small volcanoes formed by loose, grainy cinders which are extrusive igneous rocks and almost no lava.
  • Cinder cones are the simplest type of volcano and have very steep sides and usually have a small crater on top.
Composite Volcanoes
  • They are cone shaped with moderately steep sides and having small craters in their summits.
  • They are characterized by the eruption of a cooler and more viscous lava than basaltic volcanoes.
  • The deterministic feature of a composite volcano is the presence of a conduit system through which magma from a reservoir deep in the Earth’s crust rises to the surface.
  • The material accumulates in the vicinity of the vent openings which leads to the formation of layers, and this gives them their alternate name as stratovolcanoes.
  • They are the most explosive type of volcanoes on Earth.
  • Their eruptions result in them collapsing on themselves rather than building any tall structure.
  • They gained their name from these collapsed depressions which are also called as calderas.