ClASSIFICATION OF SPRINGS 561 



4. Fracture Artesian Springs. All the conditions above, except 

 that lower end of porous bed does not crop out but an 

 opening allows water to escape. Opening due to fracturing 

 with or without faulting. 



D. Springs in Impervious Rock: 



1. Tubular Springs. Due to more or less rounded channels 

 in impervious rocks. 



a) Solution Tubular or Cavern Springs. Due to solu- 

 tion channels in limestones, calcareous sandstones, 

 gypsum, salt. 



b) Lava Tubular Springs. Due to caverns and tunnels 

 in lava flows. 



c) JVIinor Tubular Springs. Due to channels made 

 by movement of water, decay of tree roots, sand 

 streaks, or shrinkage cracks, usually in unconsol- 

 idated sediments. 



2. Fracture Springs. Due to fractures consisting of joints, 

 bedding planes, columnar joints, openings due to cleavage, 

 fissiUty, schistosity, cross-bedding planes, and faults in 

 impervious sedimentary, igneous, and metamorphic rocks. 



a) Quadrille Fracture Springs. Due to more or less 

 rectangular system of fractures, one of which is 

 parallel to the horizon. 



b) Crosshatch Fracture Springs. Due to more or less 

 rectangular system of fractures, inclined toward 

 the horizon, 



c) Inclined Fracture Springs. Due to inclined frac- 

 tures, not necessarily systematic. 



