Vein
A mineral-filled fault or fracture.

Venom
In some insects, a secretion of glands opening through pores near the tip of each cheliceral fang, serving to immobilize prey.

Vent
The conduit and orifice through which volcanic materials (lava, gas, and water vapor) reach the Earth's surface.

Ventral
Pertaining to the underside or lower surface of the body.

Vesicle
A small cavity in a volcanic rock.

Vitreous
Glasslike in appearance or texture.

Volcanic Neck
The solidified material filling a vent or pipe of an inactive volcano. This hard igneous rock may resist erosion better than the mountain mass originally encompassing it and eventually stand alone as a column, tower, or crag.

Volcanic Plug
Necks consisting of a monolithic mass of solidified volcanic rock.

Volcanic Rock
Igneous rocks derived from magma or magmatic materials that are poured out or ejected (extruded) at or very near the Earth's surface.

Volcanism
The movement of molten rock, by way of volcanoes, fissures, vents, etc., to the Earth's surface, where it cools into extrusive (volcanic) igneous rocks.

Volcano
A vent from which magma, gas, and ash are erupted; also, the usually conical structure built by such eruptions.