V - Valley glacier to Vulcanism - Geography Dictionary

Valley glacier -a glacier which extends from a larger body of ice, often in a corrie, and moves downslope, initially following existing river channels but increasingly cutting its own bigger, straighter trough.

Varve -a two-layered deposit in a lake near to a glacial area. During spring and summer meltwater discharge is high and so larger load is carried. If the river enters a lake then this larger, sandy load will be deposited. In autumn and winter, meltwater discharge falls and smaller silts are carried and deposited. The sand/silt combination is called a varve.

Vector -the unaffected carrier of a disease.

Vent -a pipe-like gap in the ground which allows volcanic material to pass through to the surface.

Vertical integration -when companies at different stages of the same industry merge or buy one another. E.g. oil companies now own the vast majority of petrol stations.

Vertical transfer -the transfer or transmission of energy from the surface to the atmosphere, and up through the atmosphere.

Village -a clustered human settlement or community, larger than a hamlet, but smaller than a town or city.

Vicious circle -a downward spiral of negative feedback where a trigger event starts a sequence of effects which continue to make the situation worse.

Viscosity -lit. how resistant a substance is to a change in form. In geography, mostly applied to lavas. Highly viscous lavas do not change form easily and therefore flow very slowly.

Visibility -the distance from which an object can be seen. Visibility is typically reduced by fog, smog or smoke.  The maximum distance that can be seen depending on the particulate content of the atmosphere.

Visible trade -import and export of physical goods. Forms the balance of trade and thus part of the balance of payments.

Volcanic cone -see volcano.

Volcanic plume -the cloud of gases and solids ejected into the atmosphere from a volcano and then carried by the wind.

Volcano -a mountain created by the eruption and deposition of lavas and ashes from a vent in the ground in a volcanic area.

von Thunen model -a model to explain differences in agriculture with distance from the market. For an in-depth explanation see:

http://people.hofstra.edu/geotrans/eng/ch6en/conc6en/vonthunen.html

V-shaped valley -the V-shape of the cross profile of a river valley in its upper course. As the river has little energy, most erosion is confined to periodic spurts when rainstorm events allow an increase in energy and thus traction and abrasion of the channel bed. The channel thus cuts vertically into the surface and the slopes are then weathered back into a V-shape.

Vulcanism -the study of volcanic activity.