Ash: fine particles of rock from a volcanic vent
Ash Cloud: A collection of hot ash, gas and steam that is emited from a volcanic vent
Branch Pipe: a conduit below a volcano through which magma has passed and has become filled with solidified magma and fragments of older rock
Caldera: a steep-walled depression, commonly found at the summit of a volcano, formed when a large volume of magma is removed quickly from an underlying magma reservoir and the overlying rocks slide down along faults to fill the vacated space
Conduit: a channel through which magma flows from the magma chamber to the surface
Cone: a conical hill produced by volcanic eruption of ash, cinders or lava piling up around the volcanic vent
Crater: a large pit or hollow that forms the mouth of a volcano
Dike: a fracture filled with volcanic material cutting through earlier emplaced host rocks
Eruption: a sudden violent discharge of steam and volcanid materials
Fissure: a fracture in rock, more particularly an elongaged surface vent from which magma erupts
Flank: the sides of a volcanic ediface
Lava: molten or partially molten rock that has been extruded to the surface
Lava Flow: an individual deposit of a discrete phase of an effusive eruption
Magma: molten or partially molten rock beneath the surface of the earth
Magma Chamber or Reservoir: a long-lived body of magma beneath the surface that forms when new magma from the mantle is added faster than the existing magma body can cool or be extruded
Pyroclastic Flow: a mixture of gas and suspended or entrained solids released in a sustained explosive eruption forming a dense fluid that moves along the ground at high speed
Sill: a sheet-like body of magma, often approximately horizontal, intruded at some depth below the surface along an interface between two pre-existing rock layers
Throat: area where the width of the conduit increases to allow greater molten lava ejection
Vent: location from which lava flows and pyroclastic material is erupted