CLASSIFICATION OF SPRINGS 559 



fractures and give rise to springs near Mount Carmel, Connecticut, 

 as shown in Figure 23.' Far more abundant, however, are irregular 

 systems of joints, all of which are inclined toward the horizon, 

 and springs due to such systems may be called inclined fracture 

 springs (Fig. 22 c). 



KEY TO THE CLASSIFICATION OF SPRINGS 



I. Springs due to deep-seated waters, juvenile and connate, admixed with 

 deeper meteoric water; do not flow under hydrostatic head and are usually 

 not subject to seasonal fluctuation. 



A. Volcanic Springs. Associated with volcanism or volcanic rocks; 

 water commonly hot, highly mineralized and containing gases. 

 Grade from gas vents into springs of normal temperature indis- 

 tinguishable from those due to other causes. 



B . Fissure Springs. Due to fractures extending into deeper parts of the 

 crust ; water usually highly mineralized and commonly warm or hot. 



1. Fault Springs. Associated with recent faults of great 

 magnitude. 



2. Fissure Springs. No direct structural evidence as to origin, 

 but because of temperature and steady flow believed to 

 have deep origin. 



II. Springs due to meteoric and occasionally other waters moving as ground 

 water under hydrostatic head; many fluctuate in flow with the rainfall. 



A. Depression Springs. Due to land surface cutting water table in 

 porous rocks. 



1. Dimple Springs. Due to depressions in hillsides. 



2. Valley Springs. Due to abrupt change in slope at edge of 

 flood plain. 



3. Channel Springs. Due to depressions in flood plains or 

 alluvial plains caused by channel cutting of stream. 



4. Border Springs. Due to change in slope at border between 

 alluvial plains and playas, lake beds, or river bottoms; 

 relative imperviousness of central clay deposits assists flow. 



B. Contact Springs. Due to porous rock overlying impervious rock. 



I. Impervious rock has a horizontal and regular surface. 



a) Underlying bed is of large extent; common in 

 consolidated sedimentary rock. 



(i) Gravity Springs. Overlying material is soft. 



(2) Mesa Springs. The overlying material is 



hard, usually sandstone or lava flow ; water 



contained in pores and joints of the rock. 



' H. E. Gregory and E. E. Ellis, "Underground Water Resources of Connecticut,"' 

 U.S. Geol. Survey, Waier-Supply Paper 2;^2 (1909), p. 136. 



