A hole in a rock. If they are interconnected, voids form paths along which water and other fluids may flow. In increasing order of size, the major types of voids are: intercrystalline boundaries; intergranular pores
or spaces between the grains of a sediment
; microfractures or local cracks, usually extending for only a few tens of centimetres and from a few micrometres to 0.1 mm wide; fractures
, small faults
, and bedding planes
, which are often extensive and may have openings up to a few millimetres wide; fissures formed by solution, weathering
, or local gravitational or tectonic
displacement, and up to about 10 cm wide; and solution channels
, which range up to several metres wide and many hundreds of metres long.
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