If groundwater were any less acidic, not enough material would be removed to make a cave. As it turns out, karstic conditions are just right for the formation of caves. In geologic terms, this is a very fast process. Acidic water trickles down by gravity through a network of small fissures, called joints and partings . Joints are vertical cracks in bedrock caused by flexing due to the gravitational pull of the moon, like the tides.
Partings are separations parallel to the bedding.
When the bedding becomes tilted due to mountain-forming uplifts, the angle the bedrock is to horizontal is known as the strike . This affects the shape of the passage being formed. Water is collected from many surface input points, gradually converging into a major underground stream carrying the water to lower elevations. This vertical watershed is called a dendritic pattern . In the aerated zone, passages that form tend to be vertical, with migrating, fluctuating cross-sections known as vadose canyons .