'A'a: Hawaiian word used to describe a lava flow whose surface is broken into rough angular fragments.
A.D.: anno Domini, used to record the number of years after the death of Christ
Andesite: a gray, fine-grained volcanic rock
Basalt: A hard, dense, dark volcanic rock composed chiefly of plagioclase, pyroxene, and olivine, and often having a glassy appearance.
B.C.: Before Christ, used to record the number of years before the birth of Christ
B.C.E.: Before Common Era; formally known as B.C.
C.E.: Common Era; formally known as A.D.
Composite
cones (stratovolcanos): steep-sided, consist of layers of both pyroclastic
material and lava. Rocks comprising composite cones range from silica-poor varieties
(basalt) through intermediate types to silica-rich types,
ex: Cascade Range of California, Oregon, Washington, and British Columbia.
Convergent: tending to come together from different directions
Debris: what's left of something destroyed
Deformation: Change of shape by pressure or stress.
Divergent: tending to move apart in different directions
Eruption: A violent throwing out of flames, lava, etc., from a volcano
Infrared: Invisible radiation wavelengths just below the color red in the electromagnetic spectrum.
Geothermal: Internal heat of the earth.
Hotspot: a spot inside the mantle that heats areas of the plate above it
Lava: magma that reached the surface
Lahar: A landslide or mudflow of volcanic remains
Magma: a mixture of finely divided solids with enough liquid to produce a pasty mass
Mantle: The layer of the earth between the crust and the core; a solid body of rock in between the molten core and thin crust at the surface.
Pahoehoe: Lava with a smooth glassy surface.
Plates:
One part of the earth's layers that moves constantly.
Pyroclastic: Composed chiefly of
rock fragments of volcanic origin
Pyroclastic
Cones (cinder cones): small, steep-sided, composed largely of pyroclasts
of various sizes with little, if any, lava., Occur in groups and are associated
either with major volcanoes in arcs or with isolated, local volcanic terranes,
ex: Wizard Island at Crater Lake; San Francisco Mountain volcanic field, Arizona
Shield
cones: low rounded profiles (2-10°), cone-shaped accumulations
of lava containing minor amounts of interlayered pyroclastic materials,
ex: Snake River Plain in western North America
Stratovolcano: A volcano made of changing layers of ash and lava.
Subduction: When two plates meet and one slides beneath the other
Tephra: Solid matter that is ejected into the air by an erupting volcano
Tsunami: A very large ocean wave caused by an underwater earthquake or volcanic eruption.
Viscosity: thickness of a liquid (i.e. molasses)
Volcanic Domes:
small, steep-sided, shaped like inverted cups or domes, Formed by the intrusion,
extrusion, or both of thick (viscous) siliceous magma, typically associated
with major volcanoes, but can also occur in independent fields of intermediate
to siliceous volcanic structures that lack a single major volcano.
ex: Long Valley Caldera (Mono Lake area, California)
Volcano: An opening in the earth's crust through which molten lava, ash, and gases are ejected.
Volcanologist: A person who studies volcanoes
Water vapor: Water in a gaseous state, especially when diffused as a vapor in the atmosphere and at a temperature below boiling point.
Definitions courtesy of Dictionary.com, science.ubc.ca