Oceanic Ridge		The shell within the earth, some tens of kilometers below the surface and of undefined thickness, which is a shell of weakness where plastic movments take place to permit pressure adjusments.
Seafloor Spreading		A volcano that is erupting. Also, a volcano that is not presently erupting, but that has erupted within historical time and is considered likely to do so in the future.
Dome		System of undersea mountain ranges that wind around the earth.
Volcano		The zone of convergence of two tectonic plates, one of which usually overrides the other.
Eruption		The middle layer of the atmosphere.
Ring of Fire		The midle area of the earth.
Core		The subterranean cavity containing the gas-rich liquid magma which feeds a volcano.
Seismograph		A flow of water-saturated earth material possessing a high degree of fluidity during movement.
Mesosphere		Magma which has reached the surface through a volcanic eruption.
Thermosphere		A steep-sided mass of viscios (doughy) lava extruded from a volcanic vent (often circular in plane view) and spiny, rounded, or flat on top.
Pangaea		A vent in the surface of the earth through which magma and associated gases and ash erupt.
Rift System		The earth's crust where it underlies oceans.
Atmosphere		A gentle sloping volcano in the shape of a flattened dome and built almost exclusively of lava flows.
Fissures		A volcanic cone built entirely of loose fragmented material.
Subduction Zone		Steep, narrow valley formed as lithospheric plates seperate.
Continental Crust		An outpouring of lava onto the land surface from a vent or fissure.
Oceanic Crust		The Spanish word for cauldron, a basin-shaped volcanic depression.
Vent		The angle between the slope of a volcano and some reference.
Troposhere		The innermost part of the earth.
Magnitude		The layer touching outer space.
Exosphere		Movement in a fluid caused by uneven heat.
Lava		The regions of mountain-building earthquakes and volcanoes which surround the Pacific Ocean.
Oceanic Trench		The layer of the atmosphere we live in.
Lithosphere		An inactive volcano which may erupt again.
Ocieanic Trench		Earth quake waves that move up and down as the wave itself moves.
Crater		The uppermost part of the earth.
Shear Waves		The buffer between the earth and the sun.
Asthenospehere		A submarine volcano.
Seamount		The rigid crust and upermost mantle of the earth. Stronger than the underlying asthenosphere.
Magma Chamber		A numerical expression of the amount of energy relesed by an earthquake, determined by measuring earthquake wave on standardized recording instruments (seismographs.)
Magma		Fine particles of pulverized rock blown from an explosion vent.
Dormant Volcano		The layer below the exosphere.
Rift Valley		Lateral flowage of a turbulant mixture of hot gases and unsorted pyroclastic material (volcanic fragments, crystals, ash, pumice, and glass shards) that can move at high speed.
Caldera		The opening at the earth's surface through which volcanic materials issue forth.
Active Volcano:		Elongated fractures or cracks on the slopes of a volcano.
Pyroclastic		Deep valley in the ocean floor that forms along a subduction zone.
Shield Volcano		The Point on the earth's surface directly above the point where an earthquake or other underground explosion originate.
Mantle		The zone of the earth below the crust and above the core.
Tilt		Undersea mountian range with a steep, narrow valley along its center.
Stratosphere		The ocianic ridges formed where tectonic plates are seperating and a new crust is being created.
Convection		Boundary formed by two lithospheric plates that are moving apart.
Continental Drift		A crack or fracture in the earths surface.
Midocean Ridges		The second layer of the atmosphere.
Ash		Movement of the ocean floor away from either side of a mid-ocean ridge.
Convergent Boundry		Pertaining to fragmented (clastic) rock material formed by a volcanic explosion or ejected from a volcanic vemt.
Mantle		Molten rock beneth the surface of the earth.
Cinder Cone		A steep-sided, usually circular depression formed by either explosion or collapse at a volcanic vent.
Divergent Boundry		The process by which solid liquid and gaseous materials are ejected into the earths atmosphere ans onto the earth's surface by volcanic activity.
Epicenter		The 10 major pieces of the broken lithosphere.
Fault		Single landmass thought to have been the origin of all continent.
Lava Dome		Mass of lava, created by many individual flows, that has built a dome-shaped pile of lava.
Plate Tectonics		An instrument that records seismic waves.
Crust		Topographical depressions of the sea floor.
Lahar		The theory that horizontal movement of the earth's surface causes slow, relative movements of the continents toward or away from one another.
Mud Flow		Border formed by the direct collision of two lithospheric plates.
Convection Current		The theory that the earth's crust is broken into and about 10 fragmentswhich move in relation to one another, shifting continents, forming new ocean crust, and stimulating volcanic eruptions.
Tectonic Plates		A torrential flow of water-saturated volcanic debris down the slope of a volcano in response to gravity. A type of mudflow.
Pyroclastic Flow		Transfer of heat through the movement of a fluid material.
Lava Flow		Solid outer layers of the earth, including the rocks of the continents.
Mid Atlantic Ridge		A major submarine ocean range