Geography Study Material: Volcano
VOLCANOS:
A volcano is a vent or opening usually circular in form
through which heated materials consisting of gases, water, liquid lava and
fragments of rocks are ejected from the highly heated interiors to the surface
of earth.
Volcano eruptions are closely associated with several
interconnected processes such as
(ii)
orgigine of magma because of lowering of melting point caused
by reduction in pressure of overlying rocks due to fracture caused by splitting
of plates.
(iii)
Origin of gases and water-vapour due to heating of water.
(iv)
Ascent of magma due to pressure from gases and vapour.
(v)
Occurrence of volcanic eruption. These eruptions are closely
associated with plate boundaries.
Classification of volcanoes:
Volcanoes are classified under different schemes:
Classification on basis of Periodicity of Eruptions:
Active Volcano:
Volcano which erupt periodically
e.g. Mauna Loa in Hawaii, Etna in Sicily, Vesuvius in Italy, Stromboli in
Mediterranean Sea, etc.
Dormant Volccano:
Volcano which has been quiescent
for a long time but in which there is a possibility of eruption e.g. Fujiyama
in Japan, Krakatoa in Indonesia, Barren island volcano in Andamans, etc.
Classification on the basis of Mode of Eruption:
Central Eruption type or
Explosive Type:
Hawaiian Type, Strombolian Type,
Volcano Type, Vesuvius Type, etc.
Fissure Eruption or Quasi
Eruption Type:
Larger quantities of lava quietly
follow up from fissures and spread out over the surrounding areas. Successive
lava flow results in the growth of a lava plateau e.g. Deccan Plateau.
Distribution of Volcanoes:
About 15% of world’s active
volcanoes are found along the ‘constructive or divergent’ plate margins,
whereas 80% volcanoes are associated with the ‘destructive or convergent ‘
plate boundaries.
The Circum- Pacific belt or
the ‘Ring of Fair’. It extends across the Kamchatka Peninsula, Kurile
Island, the Island of Japan, Philippines, New Guinea, New Zealand and the
Solomon Island. It also passes through the Antarctica and the western coast of
America.
The Mid-Continent belt
includes volcanoes of Alpine mountain chain, the Mediterranean Sea and the
fault zone of eastern Africa e.g. Stromboli, Vesuvius, Etna, Kilimanjaro, etc.
The Mid-Atlantic belt in
which the volcanoes are fissure eruption type e.g Iceland ,canary Island, Cape
Verde Azores etc.
Do you like it? Comment about it.
Your comment is our wages.
Like us on our Facebook Page to
get regular update automatically
