20. Indian-World Geography [Geomorphology] [Volcanism] [Part-20] [08-11-2024]

-Contents :
Volcanoes :
-Vulcan-In Roman and Greek mythology, Vulcan is the god of fire, metalworking, and the forge
-Phenomenon of eruption of molten rock, pyroclastics [volcanic materials, including rocks, flows, and deposits, that are produced by explosive volcanic eruptions] and volcanic gases [SO2, CO2, H2S, etc.] to the surface through a vent
Note :
-Pyroclasts : Include :
-Pyroclastic Rock: A hardened, compressed, or solidified version of a pyroclastic deposit.
-Tephra: A term that was originally used as a synonym for pyroclastic materials, but is now used more specifically to describe pyroclastic materials that fall through the air.
-Tuff: A deposit made up of ash-sized fragments.
-Nuée Ardente Deposits: Deposits that are mainly found in valleys.
-Ignimbrites: Deposits that form plateau-like structures that bury the previous topography.
-Causes of Volcanism :
-Radioactivity : Differential Heating (Temperature) leads to Differential Pressure and rise of the magma
-Convection Current leads to rise in the magma and escape through the Convergent and Divergent Boundaries
-Types of Lava :
1. Andesitic or Acidic or Composite or Stratovolcanic Lava :
-Nature : Highly Viscous
-Composition : Silica
-Colour : Light
-Density : Low
-Speed : Slow
-Explosion : Violent
-Landform : Formation of steep-sided Strato Volcanoes
-Examples : Mount Vesuvius (79 ce), Mount Tambora (1815), Krakatoa (1883), Novarupta (1912), and Mount Pinatubo (1991)
2. Basic or Basaltic or Shield Lava :
-Nature : Highly Fluid
-Composition : Iron and Magnesium [Poor in Silica]
-Colour : Dark
-Density : High
-Speed : High [10-30 mph]
-Explosion : Less Violent
-Landform : Formation of gentle sided-Shield Volcanoes
-Examples : Mauna Kea and Mauna Loa
-Distribution of Earthquakes and Volcanoes throughout the world :
1. 70 % : Circum-Pacific Belt [Includes-New Zealand-Tonga Belt, Melanasia and Aleutian-Kurile Islands
2. 20 % : Mediterranean-Himalayan Belt [Includes-Asia Minor, Himalayas and the North-West China]
3. Rest : 10 % : Rest of the World
Note :
-10-20% of all volcanoes occur over the sea level, i.e. in land and rest 80% volcanoes are formed below sea level.
-The volcanoes formed at the submarine ridges are larger than their terrestrial counterparts
Important Location : Volcanism
1. Pacific Ring of Fire : The Aleutian Islands [Alaska] into Kamchatka [Russia], Japan, the Philippines, and Indonesia (Java and Sumatra in particular), Pacific Islands of Solomon, New Hebrides, Tonga and North Island, New Zealand, Andes to Central America (particularly Guatemala, Costa Rica and Nicaragua), Mexico and right up to Alaska.
2. Atlantic Coast : St. Helena, Cape Verde Islands and the Canary Islands
3. Great Rift Region : East African Rift Valley, E.g. Mt. Kilimanjaro and Mt. Kenya.
4. Lesser Antilles [West Indian Islands]
5. Mediterranean Region : Vesuvius, Stromboli (Light House of the Mediterranean) and Aegean Islands.
6. Volcanos in India :
-No volcanoes in India Peninsular
-Active Volcano : India-Barren Island
-Extinct Volcano : Narcondam Island
-Note :
The Greater Antilles are larger than the Lesser Antilles, with the four largest islands in the Caribbean making up the Greater Antilles.
Location :
The Greater Antilles are located in the north of the Caribbean Sea, while the Lesser Antilles are located to the east and south.
Composition :
The Greater Antilles are made up of continental rock, while the Lesser Antilles are made up of volcanic rock or coral islands.
Greater Antilles :
-Cuba
-Jamaica
-Hispaniola (Haiti and Dominican Republic)
-Puerto Rico
-The Cayman Islands
-Navassa Island
Lesser Antilles :
-The Virgin Islands
-The Leeward Islands
-The Windward Islands
-The Leeward Antilles
-Barbados
-Saint Lucia
-Trinidad and Tobago
Types of Volcanoes : Based on Frequency of Eruption
1. Active Volcano : Eruption-Fairly Frequent. Eg-Barren Island [India] and Anak Krakatoa [Indonesia]
2. Dormant Volcano : Eruption-Not present in near recorded history. Eg-Mount Kiliminjaro [Tanzania]
3. Extinct Volcano : Eruption-Present in recorded history. Eg-Mount Kenya, Narcondam Island [India]
-Volcanic Landforms :
-Intrusive Volcanic Landforms : Plutonic Rocks, Batholiths, Horizontal Magma Deposits-Sills and Laccoliths, Vertical Magma Deposits-Dykes and Diatremes, etc.
-Extrusive Volcanic Landforms : Lava Plateau (Deccan Plateau), Cinder Cone, Ash Cone, Cladera, Composite (Strato)/ Basaltic (Shield) Volcanoes etc.
-Hotspot Volcanism