1.They helped cool off the earth removing heat from its interior.
2.Volcanic emissions have produced the atmosphere and the water of the oceans.
3.Volcanoes make islands and add to the continents.
4.Volcanic deposits are also used as building materials.
5.The lava and ash from the eruption breaks down to provide valuable nutrients for the soil.
Negative effects
1.Volcanoes are dangerous. They can kill people and damage property.
2.Economic activity can suffer as it is hard for businesses to operate after an eruption.
3.Habitats and landscapes are damaged by lava flows.
4.Human and natural landscapes can be destroyed and changed forever.
5.When ash and mud from the eruption is mixed with rain water or melting snow, rapid mudflows are produced. This can also trigger flash floods, and rock fall.
