Vadose Zone – Region in the ground between the surface and the water table in which pores are not filled with water.

Valence Electron – Electron of the outermost shell of an atom and is one of those most active in bonding.

Valley Glacier – Glacier that is smaller than a continental glacier or an icecap and which flows mainly along well-defined valleys, many with tributaries.

Van der Waals Bond – Bond much weaker than the ionic or covalent, which bonds atoms by small electrostatic attraction.

Variabledensity Log (VDL) – VDLs are also known as 3-dimensional logs and are logs of the acoustic wave train that is recorded photographically so that variations in darkness are related to the relative amplitude of the waves.

Varve – Thin layer of sediment grading upward from fine to coarse and light to dark that are found in a lake bed and represent roughly one year’s deposition of glacial outwash.

Vein – Tabular deposit of minerals occupying a fracture, in which particles may grow away from the walls towards the middle, or alternatively, foreign minerals that have intruded within a rock fracture fissure or crack.

Veinlet – Small vein.

Velocity Panels – Set of stacked test sections with a progression of assumed normal-moveout velocities applied, which some consider a powerful method for determining velocities if distinct reflection events are present, as the reflections will be coherent where the velocities are correct and be degraded in appearance at higher or lower NMO velocities.

Ventifact – Rocks that have been abraded, pitted, etched, grooved, or polished by wind-driven sand or ice crystals.

Vertical Exaggeration – Ratio of the horizontal scale to the vertical scale, such as 1000:1 or 50:1, used in the scale of an illustration.

Vesicle – Small round hole formed in volcanic rock by a gas bubble trapped when the rock solidified.

Viscosity – Measure of resistance to flow in a liquid.

Volcanic – Action or process of magma and gases rising to the earth’s crust and being extruded onto the surface and into the atmosphere such as the igneous rocks originating from volcanic activity that cool on the earth’s surface.

Volcanic Arc – Curved chain of islands that rise from the sea floor, usually near a continent. The convex side usually faces the open ocean, while the concave side usually faces the continent.

Volcanic Ash – Volcanic sediment of rock fragments.

Volcanic Ash Fall – Deposit of volcanic ash dropped by eruptions and winds.

Volcanic Ash Flow – Mixture of volcanic ash and gases that moves downhill as a density current in the atmosphere.

Volcanic Block – Pyroclastic rock fragment ranging from about fist- to car-sized.

Volcanic Bomb – Pyroclastic rock fragment that shows the effects of cooling in flight in its streamlined or bread-crus like surface.

Volcanic Breccia – Pyroclastic rock in which all fragments are more than two millimeters in diameter.

Volcanic Cone – Deposit of lava and pyroclastic materials that has settled close to the volcano’s central vent.

Volcanic Dome – Rounded accumulation around a volcanic vent of congealed lava that is too viscous to flow away quickly, resulting in rhyolite lava.

Volcanic Ejecta Blanket – Collective term for all the pyroclastic rocks deposited around a volcano.

Volcanic Emanations – Gases, especially steam, emitted from a vent or released from lava.

Volcanic Pipe – Vertical chamber along which magma and gas ascend to the earth’s surface or alternatively an igneous rock mass that cooled in a pipe and remains after the erosion of the volcano.

Volcanic Rock – Igneous, extrusive rock that solidified on the earth’s surface following a volcanic eruption and often cools quite quickly.

Volcaniclastic – Sedimentary rock that is formed as a result of volcanic activity.

Volcanism – Process by which magma and associated gases rise to the crust of the earth and are extruded onto the surface and into the atmosphere.

Volcano – Vent opened through the earth’s crust that has allowed magma to reach the surface.

V-Shaped Valley – Valley whose walls have a more-or-less uniform slope from top to bottom, usually formed by stream erosion.