Vulcanicity is the explosiveness, stength and power of all the processes associated with the transfer of magma and volatiles from the interior of the Earth to its surface. Current volcanicity is confined to regions of the Earth where lithospheric plates converge, diverge, or pass over possible mantle hot-spots.
The Distribution of Volcanic Activity
Volcanic activity is associated with the following;
- Ocean Ridges - where plates are moving apart
- Rift Valleys - where parts of plates are moving apart (only parts not full like Ocean Ridges)
- Subduction Zones - where one plate is destroyed at depth causing magma to rise to the surface - this is also known as the Benioff zone
- Hot Spots - where plates move over rising plumes of magma
When magma is forced to the surface, only a small amount reaches it. Most solidifies in the crust, producing a range of features that are exposed by later erosion.
- Batholith - large mass, often dome-shaped and consisting of granite, e.g. Dartmoor. The rock around is altered by heat and pressure…