Explosive and gentle eruptions

Explosive and gentle eruptions


Explosive volcanoes usually have thick viscous magma, which comes from melted crust or from the mantle. The slow-flowing magma often solidifies and blocks the vent. The pressure builds up beneath the vent because of heating and gas expansion. Eventually it blows out the solidified rock in an explosion.
Gassy lava froths out of vents and hurtles down the steep volcanic slopes as clouds of molten ash engulfing everything in its path.
Dense clouds of hot ash and gases rise up into the atmosphere. Winds spread ash over large areas, killing plant and animal life. The clouds contain steam, carbon dioxide and sulfur dioxide gases which add to atmosphere pollution.
Blobs of lava are often thrown up into the air by the explosion. They are called lava bombs and some cool into tear-drop shaped rocks.
Lahar (mudflows) occurs when ice on the slopes of a volcano melts and muddy slush is swept down the valleys.
Volcanoes that erupt gently ooze steams of runny, red-hot basalt lava. This lava spreads out across the landscape at speeds of up to 50km/hr.
Basalt magma comes from melted mantle rock deep inside earth as it is less viscous this type of magma does not tend to block volcano vents causing large explosions. Basalt lava volcanoes do have smaller volcanic explosions that may eject red hot lava bombs.