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Volcanism ''is a phenomenon in which materials are erupted from Earth's interior onto the surface through volcanoes. Volcanoes are mostly found along subduction zones. Subduction zone is an area where the magma rises up due to friction. Friction heats rocks as one plate moves downward. The additional heat contributes to the melting of rocks turning into molten rocks (or magma). Magmas that are generated in the subduction zone is more viscous and the trapped gas cannot escape easily. Because of this, the eruption is explosive and produces ash.''

MAGMA PRODUCTION AT SUBDUCTION ZONES

Magma production at the subduction zone occurs because of the following:

1. Increased temperature due to friction. As I've said earlier, due to friction and additional heat, rocks melt and forms into magma.

2. Addition of water in the asthenosphere. ''A subducting plate is covered by oceanic crust which is soaked in seawater. The addition of hot water (steam) in the subducting plate, it melts portions of asthenosphere, forming large quantities of magma.''

3. Pressure-relief melting. Melting due to pressure relief happens when rocks in the asthenosphere flow upward as a subconducting plate descends.

MATERIALS EJECTED DURING VOLCANIC ERUPTION

EFFECTS OF VOLCANIC ERUPTIONS

REFERENCES: 1. You and the Natural World Earth and Life Science book by Lilia G. Vengco and Teresita F. Religioso 2. http://www.bbc.co.uk/schools/gcsebitesize/geography/natural_hazards/volcanoes_rev5.shtml 3. https://rocogeog.files.wordpress.com/2013/11/the-positive-and-negative-effects-of-volcanic-activity-by-sam-mccormack.pdf