Volcanoes火山

Volcanoesareoneofnature'sgreatwonders.Foryearstheycanstanddormant,butonceactivetheycaneruptintremendousexplosionsofpower.Someeruptionsaresobig,theychangetheearth'sclimate.Luckily,geologistscannowapproximatewhenaneruptionwilloccur.Whatarethecausesofaneruptionandwhatarethewarningsigns?Readandfindout!