Volcanoes
How and Where Volcanoes Form
volcano hot spot is Volcanic activity takes place primarily at subduction boundaries,
1. Water in the subducted rock is released into the asthenosphere.
2. The water lowers the melting temperatures of materials in the asthenosphere, leading to magma formation.
3. The magma is less dense than its surroundings, so it rises.
4. Some of the magma reaches Earth’s surface, and volcanoes form on the overriding continental plate.
Major Volcanoes Around the World
Magma and Erupted Materials
Gases escape easily from basaltic magma, generating relatively quiet eruptions. Hardened basaltic lava flows on land are characterized as pahoehoe or aa; if the lava cools underwater, it is characterized as pillow lava.
A.Parameters of volcanism:
1.Viscosity
2.Chemistry of Magma
3.Gases within the magma
4.Water content of magma
