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Geological Terms Beginning With "V"



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Vadose Water:

Water that exists in the pore spaces of a rock or soil, between the ground surface and the water table.

Valence Electrons:

Electrons in the outermost shell of an atom. The electrons that are typically involved in making chemical bonds.

Valley Glacier:

A glacier that occurs in a mountainous region and occupies a valley. Also known as an Alpine Glacier.

Van der Waals Bond:

A weak chemical bond in which atoms are held together by weak electrostatic attraction.

Varve:

A thin layer of fine-grained sediment deposited in the still waters of a lake. Varves are frequently associated with glaciation and represent a yearly sedimentation cycle - a silty, light-colored layer deposited in summer and a darker, organic-rich clay layer deposited during winter.

Vein:

A fracture that has been filled with mineral material.

Ventifact:

A rock that has been shaped or polished by the sandblasting effect of wind-blown sand.

Vertical Exaggeration:

In making sketches of landscapes and cross-sections, the vertical dimension is frequently exaggerated to show detail. Vertical exaggeration is a number that represents the magnitude of this exaggeration. It is a proportion between the vertical scale and the horizontal scale. For example, a cross section with a vertical exaggeration of 4 has a vertical scale that is four times the horizontal scale (in this example the vertical scale could be 1:25 while the horizontal scale is 1:100).

Vesicle:

Spherical or elongated cavities in an igneous rock that are created when a melt crystallizes with bubbles of gas trapped inside.

Viscosity:

The resistance of a fluid to flow. Fluids with a high viscosity resist flow. Fluids with a low viscosity flow freely.

Volcanic Ash:

Sand-sized particles of igneous rock that form when a spray of liquid magma is blown from a volcanic vent by escaping gas. More Information

Volcanic Ash Fall:

An accumulation of volcanic ash produced by an eruption. These can be very thick near the vent and decrease to a light dusting in a downwind direction.

Volcanic Bomb:

A projectile of hot magma or rock that is blown from the vent during a volcanic eruption. These solidify in flight and frequently form an elongated rock of streamlined shape.

Volcanic Breccia:

A rock made up of pyroclastic fragments that are at least 64 millimeters in diameter.

Volcanic Cone:

A cone-shaped hill or mountain composed of pyroclastic debris and/or lava which builds up around a volcanic vent during eruptions.

Volcanic Dome:

A steep-sided extrusion of very viscous lava that is squeezed from a volcanic vent without major eruption. These are frequently rhyolitic in composition and produce a rounded mound above the vent.

Volcanic Neck:

A vertical intrusion with the geometry of a volcanic pipe. An erosional remant of a volcanic pipe.

Volcanic Pipe:

A vertical or nearly vertical tunnel which connects a magma reservoir to the surface. Magma and gas travel up this tube to produce the eruption. After the eruption the tube can be filled with a cooling magma which preserves its shape as an intrusive body.

Volcano:

A vent in Earth's surface through which molten rock and gases escape. The term also refers to deposits of ash and lava which accumulate around this vent.

V-shaped valley:

A valley with a narrow bottom and a cross section shaped like the letter "V". Valleys of this shape are almost always cut by stream erosion.

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