Volcanic Eruptions

Volatiles- gaseous components of magma, mainly water
- the amount of volatiles contained in magma affects its mobility

-one of simplest mechanisms for triggereing volcanic eruptions is arrival of a new batch of melt into a near suface magma reservoir
-causes the pressure of magma in the other chamber to rise until cracks develop in the rock above

-All magmas contain small percentage of water and other volatiles
-as magma in the uppermost portion of the magma chamber is forcefully ejected by the escaping gases, pressure on the molten rock directly below drops


Lava Flows

aa flows- type of lava flow
-have sufaces of rough jagged blocks with dangerously sharp edges and spiny projections

pahoehoe flows- type of lava flow
-exhibit smooth sufaces that often resemble the twisted braids of ropes
-means "on which one can walk"

Lava tubes-Still molten lava within the conduits continues flowing forward motion leaving behind cave-like voids

Block Lavas-consists largely of detached blocks with slightly curved sufaces cover unbroken lava in the interior
-generated by andesitic and rhyolitic magmas

Pillow Lavas-useful in the reconstruction of the earth history
-stacked on top of each other like pillows
-indicate lava flow formed in an underwater environment