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September 29, 2013

Volcanoes of the World - Continent Wise - General Knowledge for UPSC, IAS, APPSC, IBPS & Bank PO Exams

(World Geography for objective general knowledge, current general knowledge, online general knowledge quiz questions, Indian general knowledge)

VOLCANOES
Volcano is an opening or vent through which magma, molten rock, ash, and volatile erupt on to the Earth's surface. It is conduit or pipe which rises from below the crust and vents to surface of the Earth. Volcanoes tend to be conical in shape but can have a variety of forms, depending on the nature of the erupted material (particularly its viscosity), the character of recent eruptive activity, and the extent of post-erupted modification by erosion. Most of the volcanoes are concentrated at convergent and divergent plate boundaries but others, located in the interior of plates, are associated with hot spots.

TYPES OF VOLCANIC ERUPTION
1. Icelandic: Fissure eruption; releasing free flowing (fluidal) basaltic magma; quiet, gas-poor, great volumes of lava issued; flowing as sheets over large areas to build up plateaux (Columbia-USA, the Lava Plateau of India, etc).
2. Hawaiian: Fissure, caldera, and pit crater eruption; mobile lavas with some gas; quiet to moderately active eruptions; occasional rapid emission of gas charged lava; produces fire fountains; only minor amount of ash; builds up lava domes.
3. Stambolian: Strato cone (summit craters); moderate; rhythmic to nearly continuous explosions; resulting from spasmodic gas escape; clots of lava ejected; producing bombs and scoria; periodic more intense activity with outpourings of lava; light-coloured clouds (mostly steam); each upward only to moderate height.
4. Vulcanian: Stratocone (central vent); associated lavas more viscous; lavas crust over in vent between eruptions; allowing gas build-up below surface; eruption increase in violence over longer periods of quiet until lava crust is broken up; clearing vent; ejecting bombs, pumice, and ash; lava flows from top of the flank after main explosive eruption; dark ash-laden clouds, convulated, cauliflower-shaped, rises to moderate heights more or less vertically, depositing tephra along flanks of volcano.
5. Vesuvian: More paroxysmal than strambolian or vulcanian types; extremely violent explosive of gas-charged magma from stratocone vent; eruption occurs after long interval of quiescence or mild activity; vent tends to be emptied to considerable depth; lava ejects in explosive spray (glow above vent), with repeated clouds (cauliflower) that each great heights and deposits tephra.
6. Pilian: More violent form of vesuvian eruption; last major phase is uprush of gas that carries clouds rapidly upward in vertical column for miles; narrow at base but expands outward at upper elevations; clouds generally low in taphra.
7. Pelean: Results from high-viscosity lavas, delayed explosiveness; conduit to strato volcano usually blocked by dome or plug; gas (some lava) escapes from lateral (flank) openings or by destruction or uplift of plug; gas, ash, and blocks move downslope in one or more blasts as nuee-ardentes of glowing avalanches, producing directed deposits.
8. Katmaian: Variant of pelean eruption characterised by massive outpourings of fluidised ash flows; accompanied by widespread explosive tephra; ignimbrites are common end products; also hot springs and fumaroles.

CLASSIFICATION OF VOLCANOES: Volcanoes may be classified on the basis of material erupted and the periodicity.
Material Erupted
 (i)          Basalt Cone: Basalt cones are rare. They are likely to be low rather than high cones because of the fluidity of basaltic lava. The Rangitoto (New Zealand) and Skjaldbreit (Iceland) are the most suitable examples of basalt cone volcanoes.
(ii)          Basalt Dome: The Hawaiian volcanoes are an excellent example of basalt dome volcanoes. Mt. Etna and several volcanoes of Iceland are included in this category.
(iii)         Ash and Cinder Cones: Ash and cinder cones are built where eruptions are explosive type with a predominance of pyroclastic material. Growth of an ash or cinder cone begins around a crater. They may be a few hunder metres in height.
(iv)         Composite or Strato Cone: The strato volcanoes are characterised by alternating sheets of lava and pyroclastic material. Its structure attests to alternating periods of explosive and quiet eruptions. Lava intruded into fissures, solidifies to form dykes if injected between layers of fragmental ejecta it forms sills. Most of the largest volcanoes of the world fall in this category. The Fujiyama of Japan, Vesuvius of Italy, Popocateptl of Mexico, Cotopaxi and Chimbrazo of Equador, and Mayon of Philippines are some of the good examples of composite or strato volcanoes.
Periodicity:
 (i)          Active Volcanoes: Volcanoes which constantly eject lava, gases, ashes, cinder, pumice, etc. are known as active volcanoes (Figure 1.24). There are about 600 active volcanoes in the world, most of them being in the Pacific Ocean around the "ring of fire". Mt. St. Helens (USA), Stamboli and Mt. Etna (Mediterranean Sea), and Pinatubo (Philippines) are some of the examples of active volcanoes. The Stramboli volcano emits so much fire that it has been termed as the Lighthouse of the Mediterranean Sea.
(ii)          Dormant Volcanoes: A volcano which, though not extinct, has not been known to erupt within the historic period. The Kilimanjaro volcano is one of the best examples of a dormant volcano.
(iii)         Extinct Volcano: A volcano that functioned in the distant geological past and the remains of which occur in an area where there is no longer any active vulcanicity is known as an extinct volcano.

Distribution of Volcanoes in the World
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.
1.The Circum-Pacific belt or the ‘Ring of Fire’. It extends across the Kamchatka Peninsula, Kurile Islands, the Islands of Japan, Philippines, New Guinea, New Zealand and the Soloman Islands. It also passes through the Antarctica and the western coast of America.
2.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.
3.The Mid-Atlantic belt in which the volcanoes are fissure eruption type. E.g. Iceland, Canary Islands, Cape Verde, Azores, etc.
Ring of Fire & Volcanoes:
The large series of volcanoes (some active) encircling the Pacific Ocean are referred to as being part of the Ring of Fire, and notorious for frequent earthquakes and volcanic eruptions.
The Ring of Fire, coinciding with the edges of one of the world's main tectonic plates, (the Pacific Plate) contains over 450 volcanoes and is home to approximately 75% of the world's active volcanoes.
Nearly 90% of the world's earthquakes occur along the Ring of Fire; most recently, the devasting quakes in Chile, Japan and New Zealand.

Volcanoes and Earthquakes of note:
  1. Christchurch Earthquake, New Zealand
  2. Mount Saint Helens, Washington, USA
  3. Mount Pinatubo, Philippines
  4. Mt. Fuji, Japan
  5. Paricutin Volcano, Mexico
  6. Santiago Earthquake, Chile
  7. Sendai Earthquake, Japan
Volcanoes in India: Barren Island, one of the most easterly of the Andaman Islands, is the only confirmed active volcano in India. The island along with the rest of the Andaman's is the Andaman & Nicobar Islands, and lies some 135 kms northeast of the territory's capital, Port Blair. The first recorded eruptions of the volcano dates back to 1787. Since then, the volcano has erupted more than six times.

Name
Elevation(mtrs)
Last eruption
Type
Barren Island
354
2013
Stratovolcano
Baratang
28
2005
Mud volcano
Narcondam
710
holocene
Stratovolcano
Deccan Traps
65 Mil. years

Important Points on Volcanoes:
  1. Tamu Massif is largest volcano on the earth lies in Pacific Ocean, is a recent discovery in 2013.
  2. South America has the most volcanoes.
  3. The most active volcanoes, however are located in Asia. This is because of the tectonic plates activity.
  4. Australia is the only continent without any active volcanoes. However, there is one active volcano on Australian territory, that being Big Ben on McDonald Island in the sub-Antarctic territory of Heard & McDonald Island.
Active Volcanoes of the World Continent Wise:
Africa
  • Kilimanjaro in Tanzania is Africa's tallest peak at 5895 m (19,340 ft). It has a series of concentric summit craters apparently less than 10,000 years old and may have last erupted less than 2000 years ago. The name Kilimanjaro means "shining mountain"
  • Ol Doinyo Lengai ("Mountain of God" in the Masai tongue), in Tanzania, is the only volcano on Earth that erupts natrocarbonatite lava.
  • Mount Cameroon The only volcano outside of Europe to have records of an eruption before the Common Era in 5 BC. It remains active today, with its most recent eruption in 2000.
Asia
Indonesia - With 167 known active volcanoes, Indonesia is the world's most volcanic country by far.
  • Mount Semuru
  • Mount Bromo in East Java is known for its unreal scenery, especially with Mount Semeru, Indonesia's third highest active volcano nearby.
  • Krakatoa in West Java famously exploded so violently in 1883 that the sound was heard 5,000 km away and global temperatures dipped by over a degree.
  • Mount Batur in Bali is a very accessible active volcano which takes just 2 hours to climb.
  • Mount Merapi is perhaps Indonesia's single most active volcano (no mean feat). It looms large over the major cities of Yogyakarta and Solo, and the very popular temples of Borobudur and Prambanan.
  • Mount Rinjani in Lombok is Indonesia's second highest volcano with a stunning crater lake. For much of 2009 the summit of the mountain was closed to the public due to eruptive activity.
  • Mount Tambora in Sumbawa is one for the truly adventurous. Only about 50 visitors a year make it to this very remote volcano. In 1814 Tambora was 4,200 metres high. It erupted with such force the following year that 1,400 metres was lost from its top.
  • Mount Aso on the island of Kyushu in Japan, is one of the largest active volcanoes in the world with the largest caldera.
  • Mount Fuji in central Japan near Tokyo, is Japan's highest and most beautiful volcano. It is also the most climbed mountain in the world because so many people climb it to view the sunrise from its summit crater.
  • Mayon Volcano, near Legazpi City in the Philippines, described as the world's most perfect volcano cone. Mayon’s last fatal eruption was in 1993.
Europe
  • El Teide in Tenerife, is the highest active volcano in the Canary Islands at 3715 m (12,188 ft). A flank vent at El Teide was observed erupting by Christopher Columbus and his crew in 1492.
  • Vesuvius near Naples in Italy is an active (but presently "dormant") volcano. It has not been smoking since it last erupted in 1944, but it is still very closely monitored because of its seriously hazardous proximity to Naples, which is southern Italy's largest city.
  • Stromboli in the Aeolian Islands of Italy and Mount Etna in Sicily, Italy are two of Italy's most active volcanoes. At 3350 m (10,991 ft), Etna is Europe's highest volcano. Stromboli has been in near continuous activity since at least the time of the Ancient Greeks and has been billed as the "Lighthouse of the Mediterranean".
  • Nisyros in the Greek Dodecanese islands is mildly active with smoking fumaroles. It is possible to walk into the crater floor for a closer look.
  • Santorini in the Aegean Sea, is probably Greece's most famous volcano because of its eruption that destroyed the Minoan civilization over 3,600 years ago. It is still active, for it last erupted in 1950 out of Nea Kameni ("New Burnt" in Greek), an island made up of lava flows in the middle of the caldera bay.
North America and Caribbean
  • Mount St. Helens, in Washington State, USA, is famous for its May 18, 1980 eruption. Since late 2004, it has been erupting once again, but not nearly as violently - this time, a new lava dome is slowly being extruded in its crater.
  • Popocatepetl, near Mexico City, often has a volcanic plume above its crater which is 5,450m high. The name means "smoking mountain" in the native Nahuatl language.
  • Soufriere Hills volcano on Montserrat, previously considered dormant, began erupting again in 1995, forcing the closure of the southern half of the island (including its capital and airport in 1997). It is still active, though mostly a nuisance seeping lava and spewing ash into the air.
South and Central America
  • Cotopaxi in Ecuador, often misquoted as being the highest volcano in the world ( despite its elevation of 5911 m (19, 393 ft), it does not even make the top ten list of highest active volcanoes - see this list here), is still one of South America's most spectacular volcanoes.
  • Arenal in Costa Rica can be viewed lighting up the night sky with its highly frequent eruptions.
  • Volcan Masaya in Nicaragua, near Managua.
  • Volcan Santa Maria and Volcan Santiaguito in Guatemala, near Quetzaltenango.
  • Volcan de Fuego and Volcan Pacaya in Guatemala, near Antigua Guatemala.
  • Volcan Atitlan, Volcan San Pedro and Volcan Toliman in Guatemala, on the southern shores of Lake Atitlán.
  • Volcan Lascar in the Atacama Region of northern Chile.
Oceania
Hawaii
  • Kilauea in the Big Island of Hawaii, has been erupting continuously out of its flank vent, known as Pu'u O'o ("Hill of the O'o bird" in the native Hawaiian language) since 1983.
  • Mauna Loa, also in Hawaii, is the state's highest historically active volcano and is topped by the Moku'aweoeo Caldera. It is also the largest volcano by volume in the world. Don't be fooled by its gentle slopes - with its highest point at 4170m/13,683 ft), the altitude can be hard on inexperienced hikers and its summit is often covered in snow during the winter.
  • Mauna Kea is the highest volcano in Hawaii at 4205 m (13,796 ft), and is pockmarked with cinder cones. Its high elevation is also a magnet for astronomers with their giant telescope facilities - and even skiers.
  • Haleakalā ("House of the sun" in Hawaiian), is the tallest volcano on the island of Maui, and is renowned for its erosional crater and the cinder cones nestled inside.

New Zealand
  • Mount Ruapehu, Mount Ngauruhoe and Mount Tongariro in New Zealand's Tongariro National Park. Ruapehu, New Zealand's highest volcano, has a crater lake that forms and fills when the volcano is not erupting.
  • White Island, also in New Zealand, is the most active volcano in that country and is a volcanic island in the Bay of Plenty southeast of Auckland. Organized tours are operated out to this volcano.

Papua New Guinea
  • Mount Tavurvur is a very active volcano right next to the city of Rabaul on the island of New Britain. 

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2 comments:

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