Page 1 : oe 5], elt, , , , , , A volcano is a vent or opening on the, earth surface through which magma,, ash, gases and water vapours are, ejected. The term vuleanicity covers, all the activities from the rising of, magma and gases to getting it cooled, in various forms, either on the, surface of the earth or below it. The, ejection of magma is either in the, form of central explosion or cracked, ejection. The explosion in the, volcanoes can be seen in high amount, of silicate presence in the magma., , At present, the magma or lava is classified, according to chemical and minerals present in, it. The minerals are further classified into Dark, and Light colours. The light coloured minerals, are called Felsic and dark group, silicate rich, quartz and Feldspar minerals are present, while, in Mafic group, magnesium and rich minerals, pyroxene, amphibole and olivine are present., The properties of minerals bOetween the Mafic, and Felsic are called Ultramafic. This mineral is, Tich in silicate and aluminium. According to Felsic,, Ultramafic and Mafic, Granite, Diorite and Gabbro, are intrusive and Basalt is an example of extrusive, magma respectively., , The Batholith is dome shaped lava deposition, beneath the ground surface. Since it slowly gets, Solidified, its molecules size is normally big;, Example Granite. This can be seen in the deep, Places. At the lower portion duc to different, Conditions of solidification of magmatic bodies in, an inner sedimentary rock, various shapes are, , , , Volcano, Parasitic cone, , Lava plateau built up by, successive flows, , , , Batholith, formed. Laccoliths are uplifted slope acquiring, the form of a dome, Lopoliths is solidified lava, of the basin region in saucer shape and Phacoliths, are solid arched parts of anticline and synclinal in, wavy shape. In the same way, Sills are bed-like, intrasive bodies formed by magma horizontal by, and Dykes or Dikes are perpendicular by. The, thin layer of sills is called Sheet while small, portion of dykes is called Stock., , Due to explosion and ejection of volcanoes,, different types of external ground surfaces are, formed. The crater is a depression at the mouth of, the volcanic vent which is usually funnel shaped., According to decreasing intensity of lava, can, volcano be classified into Plinian, Vuleanian,, Strombolian and Hawaiian. In this, Plinian is more, destructive in nature, due to the high amount of, silicate in magma and high level of its viscosity;, for example-hilly mountains of Martinique Island,, Karkatao near Sumatra and Java, Taal mountain,, Philippines. In Vuleanian volcano, silicate and, different type of magma are ejected. Due to the, , , , , , , , 32 | Geography: A Comprehensive Study, , , , Scanned with CamScanner

Page 2 : of gases, the gascous, , feyechon . aa, unt af eet as of these, , esky, The lav, and sticky that these are, 1 hardened. In the, , oes, duc to low amount, , lange am, , clouds spreae, , noes are 80 VISCOUs, noes 4, , J across th, , vole, quickly sohdified ane, cht, , i : lean, atian wpe OLE! : ., — ' coloumns are formed ., , Mf gases, magn ‘ m, s eyection oF magma Is, , of flow ¢, , i SANE:, In the Hawaiian vole f agen, os degree of mobility and, , and gets, , , , , t due to high, , , , magma spread out to a large a, , Sed This type of volcanoes are Tess in height, ~ . *, , dif, sod pies, ceread over large area. Due to different, alien >, , j, , and ? ree, , explouive ejection in the volcanoes, various shapes, p, , can be identified., , 1. Cinder or Ash Cone, , This type of cone is generally of lesser height, and «t forms mainly by the volcanic ash and, broken panicles. Generally, liquid particles are, not present in it. This type of cone has sharp, slope and bowl shaped wide breadth crater., Its example are Paracutine and Joruloo, mountains of Mexico ,Izalco mountain of SanSalvadore, Camiguin mountain of Philipines,, Volcan-de-Fuego of Guatemala,, , n, , Lava cone, , These type of cone formation takes place by, the action of any acidic or basic liquid magma,, Lava cone can be further classified into among, Acidic and Basic lava cones., , (i) Acidic Lave cone: This type of cone, , opening formed while voleano lava has, more quantity of silicate in it which causes, Mt to be stickier and Comes out on ground, surface with high explosion, This type of, cone * of more height and Covers less, area, Pini and Strombolian, , best cxamples,, (Il) Baste laye cone ;, , Silicate in it, then, thin, Spreads over, down because of i, , an, Vulcanian, volcano are the, , When the lava has less, it becomes lighter and, large area and coolstS because of its firm, , , , , , , , , Parasite, Cone, , \ POE io, , , , , , ¢, , 2], iio ESS Sx, , on, , , , Basic Lava Cone, , Gent, , , , , , , , , , , , Basic Lava Cone, , , , less height and large area volcanic cone, formation. Hawaiian volcano come und?", this category, such as Mauna Loa volcan, also known as sheild cone., , Geography: A Comprehensive Stud, Scanned wit CamScanner

Page 3 : 3., , Mixed Volcano cone, , These are the highest volcano cones. These, are also called strato velcones composed of, layers of lava, ash and rock debris, These cones, are formed by the deposition of alternate layers, of lava and fragmented materials (Pyroclastic), wherein lava acts as a cementing material,, Fujiyama of Japan, Mayon of Philippines,, Rainier . Mt Hood, USA ete arethe important, examples., , , , Parasitic or Dependent cone, , When the volcano spread over large area,, , , , sometimes, several branches of the vents also, get form along with main vent due to explosion., This causes another volcanic cone formation, on the slope of main volcanic cone. Mount, Shastina of U.S.A. is located on Shasta, , Mountain., , , , Lava Dome and Diatreme, , , , , , , , These type of surface structures are formed when, magma of the volcano has extra silicate in it. In, , that condition, a strong strip of solid magma is, deposited at different depth of vent funnel and, crater (Volcano opening point). When the volcano, vent funnel is completely closed by the solidification, of magma, then it is called Volcano Plug or, Magma Dot. The magma solid in the vent funnel, is called Extrusive neck magma. Volcano plug/, Magma dot and Neck magma are together called, Diatreme. Shiprock diatreme of New Mexico of, USA is its example and Black Hills Devil Tower, of the same range are example of neck magma., All these are formed during cooling of volcanic, magma,, , The opening of exploded volcano is of different, , type from which some example are as follow, (a) Crater : This is a funnel or cup-shaped, , Opening at the top of the volcanic cone. It gets, filled up with rain water then it forms a crater, , The volcano Is built up of alternate layers of LAVA and ASH |, They con explode with great violence, , , , , , , , a, 5 Ama, , (b) Caldera :, , lake. Like Lonar Lake in Buldhana district of, , arashtra, Sometimes many small craters, are formed ina single crater, When the eruption, ts of less intensity than that of pre-existing, crater, the, , , , , t, , , , are known as Nested crater; egthe three small crater of Taal Mountain,, Philippines ts its example., , Composite Cone, , Crater, , , , This is widened form of crater, formed due to subsidence of the crater or, expansion of volcanic mouth or vent due to, successive eruptions. In this regard first, opinion was given by Geological Survey, Department of U.S.A. According to it, the size, of crater increases due to explosion and forms, caldera. The Aso of Japan, is the example of, caldera., , According to John Daly, a volcano trench is, , formed due to the subduction of the crater. When, the crater explodes due to closing of vent, it causes, greater explosion and exploded particles spread to, a great distance, If the size of the crater increases, then it is known as Caldera. Karakatau and, Vesuvius, Italy and Katmai mountain region of, Alaska can be found with this, The second opinion, has more support where big Caldera is called Super, Caldera, Lake Towa in the north-west of Sumatra, Island of Indonesia is its example., , Lava field and Lava traps are formed by the, , eruption from the crakes, Volcanic clouds & Geyser, , , , , , , , , , , , Geography: A Comprehensive Study, , Scanned with CamScanner

Page 5 : orld Distribution of Volcanoes, , , , , , , , , , , , explanation of voleanic regions of the world,, ed on the Plate tectonic theory is the most, epted one, According to this theory, destructive, te boundaries account for about 80"% of the, canic regions, constructive plate margins for about, % of the volcanic regions and remaining are in the, rior parts of the plates not yet explained by the, te tectonic theory. Major volcanic belts are, Circum-Pacific Belt, , In this belt, volcanoes are found along the, destructive plate margins. Here, volcanic, eruptions are primarily caused due to collision, of Pacific plate with American and Asiatic, plates. Two-third of the world’s volcanoes are, found in the coastal regions of the Pacific, ocean, archipelagoes and oceanic islands., Hence, the name given to this belt is the Fire, Girdle of the Pacific or the Fire Ring of the, Pacific., , This belt begins from Erebus Mountain, of Antarctica and runs northward through, Andes and Rockies mountains of South and, North Americas, respectively. At Alaska this, belt turns towards eastern Asiatic coast to, include the volcanoes of island arcs and, festoons. The belt ultimately merges with the, Mid-continental belt in the East Indies., , Mid-continental belt, , Most of the volcanoes of this belt are found, along the destructive plate margins, due to, collision of Eurasian plate with African and, Indian plates. One branch of this belt runs along, the fault zone of east Africa and the other turns, southward to meet the Circumpacific belt after, running through Spain, Italy, Caucasus and, Himalayas. This belt also include the volcanoes, of the Alpine chains and the Mediterranean Sea., Stromboli, Vesuvius and Etna are the important, , volcanoes of the Mediterranean region., Dama-vand and Koh-i-sultan volcanoes (Iran), and Ararat volcano (Armenia) are also included, in this belt. In this belt, the volcanoes of Europe, are found along the Median Mass and the, volcanoes of Africa are found along the fault, valley. The important volcanoes of the fault, , , , Major Volcanoes of the World, , , , , , , , , , , , Volcano Country, Ojos del Salado Argentina-Chile, Cotopaxi Equador, Chimborazo Equador, Popocatepetl Mexico, , , , Mauna Loa Hawaii Island, , , , Mt. Cameroon Cameroon (Africa), , , , Mt. Erebus Ross (Antarctica), , , , , , , , , , , , , , , , , , , , , , , , , , , , , , Mt. Etna Sicily (Italy), , Mt. Pelee Martinique Island, Hekla Iceland, , Laki Iceland, , Vesuvius Gulf of Naples (Italy), Stromboli Lipari Island (Italy), Krakatao Indonesia, , Katmai Alaska (USA), , Mt. Rainier USA, , Mt. Shasta USA, , Fujiyama Japan, , Mt. Taal Philippines, , Mt. Pinatubo Philippines, , Mt. Mayon Phillippines, , , , Dama-vand Iran, , , , , , , , , , , , , , Koh-i-Sultan Pakistan, Mt. Popa Myanmar, Elbrus Georgia, Kilimanjaro Tanzania, Mt. Kenya Kenya, , , , , , , , , , 36 | Geography: AComprehensive Study, , , , , , , , , , Scanned with CamScanner