Volcanic Eruption

active volcano

has erupted in the last 10,000 years

dormant volcano

eruption in the past few million years

extinct volcano

eruption in the past few million years, but unlikely to erupt again due to moving mantle plume

igneous

formed by solidification of magma

magma

molten/liquid rock material, cools as volcanic rock on surface, solidifies as plutonic rock at depth

lava

magma that flows on earth's surface until it cools to form a volcanic rock

ash/tephra

fine pyroclastic material, blows into air from volcanoes

pyroclastic

pertaining to magma and volcanic rock blasted into air

cinder cone

steep volcanic hill made of loose pyroclastic debris

scoria cone

a small cone of pyroclastic debris from Hawaiian/Strombolian eruptions

caldera

a large, basin-shaped volcanic depression, roughly circular, formed by a piston-like collapse of a cylinder of overlying rock into an underlying, partially evacuated magma chamber

types of lava: pahoehoe

folds in surface of lava, viscous, looks like ropes

types of lava: aa

broken up, rough, grainy, cools faster

types of volcanoes: cinder

numerous locations, low viscosity, basalt

types of volcanoes: shield

mostly ocean islands and above mantle plumes, basalt

types of volcanoes: stratovolcano (composite)

volcanic arcs above subduction zones, andesite

types of volcanoes: caldera (super)

involve continental crust, high viscosity, very explosive, rhyolite

elements in rocks (basalt/dacite)

Mg, Ca, Fe

elements in rocks (andesite/rhyolite)

Na, K, Al

most explosive elements in rocks

Na, K, and Si (more Si = more explosive)

Igneous rocks form by

the crystallization of molten magma or lava (intergrown crystals)

plutonic rocks form...

underground, crystals grow large because magma cools slowly

volcanic rocks form...

at Earth's surface, small crystals

atoms bind together to form

molecular crystals

bond energies

Si-O: 798 kJ/mol

Al-O: 512 kJ/mol

Fe-O: 409 kJ/mol

which bond is hardest to break?

Si-O

volcanic eruption types

basaltic flood, hawaiian, strombolian, vulcanian, sub-plinian, plinian (in order of increasing viscosity, gas, and silica content)

++ phreatic and phreatomagmatic, water or glacier interaction