Siltstones vary in chemical composition. Siltstones vary in their degree of hardness and may act as aquifers. Rock produced from ash and rock fragments that have been ejected by violent volcanic eruptions. Some particles may partially re-melt by the residual volcanic heat, thus forming a welded tuff. Fracturing of rock resulting in parallel displacement relative to each side along the fault zone.
Faults easily act as conduits for groundwater.
Interbedding is also known as interstratification. A series of regular breaks in a rock formation. Jointing may be caused by stress or the release of pressure or chemical and temperature changes. Joints provide an easy pathway for groundwater movement. A structure formed inside rock that has been dissolved by groundwater.