Volcano, also called volcanic mountain, is a mountainside or hillslope that forms as the result of volcanism. Volcanoes are mountains, but they can also be hills, plateaus, cinder cones, and shields. A volcano is formed when hot molten rock (magma) and ash escape from an opening in the Earth’s surface. The magma and ash become solid as they cool and this makes a volcano.
Volcanoes are found where tectonic plates are pulling apart or colliding. When two plates collide, one plate may slide under the other (subduction). This process can create volcanoes at the edges of continents (such as along the Pacific “Ring of Fire”). The world’s tallest mountain is Mauna Kea on Hawaii which is actually a shield volcano that erupted very recently in geological time.
The word “volcano” comes from the name of Vulcano, a small island off the coast of Sicily in Italy where there was once an active volcano. The most famous volcano is Mount Vesuvius near Naples, Italy which famously destroyed the Roman towns of Pompeii and Herculaneum in 79 AD when it erupted. Other well-known volcanoes include Mount St. Helens in Washington state which erupted violently in 1980;Mount Etna on Sicily, Italy; Krakatoa in Indonesia;and Mount Fuji in Japan which last erupted in 1707.
Volcanoes are usually classified into four types: cinder cone volcanoes, composite volcanoes, shield volcanoes, and lava domes. Cinder cone volcanoes are made up mostly of loose pyroclastic material such as ash and scoria that has been ejected from the vent during explosive eruptions; they are usually small with steep sides. Composite volcanoes (also called stratovolcanoes) have both eruptive vents and lava flows sometimes many kilometers long; these make up some of the largest mountains on Earth like Cotopaxiin Ecuador or Fuji intheJapan . Shield volcanosare created by flowsof basaltic lava that build up slowly to form broad domeshaped edifices with gentle slopes; examplesinclude Mauna LoaandKilaueainHawaii ,as well as Olympus MonsonMars . Lava domesform when thick viscous lava oozes out onto a surface creating a bulbous feature; an exampleis Devil’s TowerinWyoming . Somevolcanic features cannot be classified easily into any one typeand instead show characteristicsof multiple types suchas Crater LakeinOregon whichwasformedbythe collapseof awildfire-scorchedcompositevolcanointo acaldera(large crater)thatlaterfilledwith waterfrom rainfalland snowmelt . Therearealso supervolcanoswhichare muchlargerthanordinary ones- so large infactthat their eruptions can cause global climate change for years afterwards due to allthe dustand aerosedsulphurthey releaseinto theatmosphere . OnefamoussupervolcanoisYellowstone National ParkinWyoming – althoughit hasn’teruptedfor 640 000 yearsit isstillconsideredactivebecausegeologistshave foundrecentlavaflowsaswellasa systemof over150 other smallercinderconesandshieldsconcentratedwithinits borders . If itwereto eruptnow howeverthe scale wouldbeunprecedented inthehistoricalrecordwith potentiallydevastatingconsequencesfor lifeonEarth… Eruptions happenwhen pressurefromgasesbeneaththe surfacebuildsupuntilanescape routefinallyopensupallowingthemto burstforth explosivelyintothe atmospherecarryingrockfragmentsashandsmokehighupinto theatmospherewhere windscoulddistributeitfarand wideacross continentscausing widespreadcoolingofthe planet(similar to whathappenedafterthe eruptionoftheTamboravolcano1815 ).Larger scaleeruptions couldblockoutthesunsothat photosynthesisceasesresultinginfamineorcouldpumpso muchashintothe atmospherethattemplaterisekeepingourplanetFrozenoverlike Snowball Earth ! Butnotall eruptionsaresochaoticortraumatic-someare beautifulexamplesof naturesrawpowerlikethe geysersfound att Yellowstoneor Iceland’s Strokkurwhichspouts steam30 m high every few minutes ! Andmanypeople livequite happilynextdoor to highlyactiveones likePiton de la Fournaisewhichhasbeenconstantly spewingsmokeandsulphurousence1932withoutany majorincidents ; whileotherslikePopocatepetlhave become partofthe dailyroutine livingclosebyina citylikeMexico City ! So whateveryourviewone thingispremieraboutthesepotentnaturalfeatures-theyneverfailtocapturethe imagination!