262 PRINCIPLES OF STRATIGRAPHY 



solidification of water, or to the atmogenic when precipitated as snow 

 and snow ice. Ice is thus a substance intimately uniting the hydro- 

 sphere and lithosphere, just as water in the form of vapor unites 

 the hydrosphere and atmosphere. The freezing of water has been 

 dealt with to some extent under the heading of temperature influence 

 on the hydrosphere. As a rock it will be dealt with in Chapter VI 

 and its larger structural features will be taken up in Chapter VI 11. 

 Glacial deposits naturally fall under the heading of autoclastic rocks 

 and are discussed in Chapter XII, while deformation due to glacial 

 motion is considered in Chapter XX. Finally, the results of glacial 

 sculpture are treated under the head of glyptogenesis, or the land 

 forms produced by the sculpturing agents. In the present chapter a 

 brief preliminary summary of the movement of water in the solid 

 form and its geological effects will be given. 



Kinds of Movement of Solid Water. Water in the solid state 

 may become translocated either ( i ) passively by transportation, or, 

 (2) actively by movements due to its own gravitative and internal 

 readjustments. Transportation may be either by wind, as in the 

 case of snowflakes and ice crystals, or by water, as icefloes or ice- 

 bergs. Wind-transported snowflakes and ice crystals may accom- 

 plish a certain amount of geological work by corrasion, as noted 

 in Chapter II, and they may be heaped up in dunes or deposited in 

 strata, which may be temporary, or may endure for a long time, with 

 gradual metamorphosis into crystalline ice. One result of wind- 

 transported, snow is a special distribution, and consequently the 

 placing of sources of water supply in positions which might prob- 

 ably not be accessible to vhem in any other way. Water-transported 

 ice blocks often act as powerful agents in erosion and destruction, 

 and they may be responsible for groovings and markings on rock 

 surfaces not otherwise explainable. Extensive deposits of trans- 

 ported material frozen into the ice block or resting on its back 

 are also sometimes formed, as in the case of the Grand P>anks of 

 Newfoundland, where the debris brought by the icebergs from the 

 north is dropped upon their melting and so embedded in and made 

 part of contemporaneous marine sediments, boulder conglomerates 

 here accumulating beneath the zone of wave activity. The anomal- 

 ous occurrence of erratics or strayfd rock masses in marine forma^ 

 tions is also accounted for by floating icebergs. Such ice-rafted 

 erratics have been found in the Caney shale of Oklahoma (Car- 

 bonic) (Woodworth-74). 



Ice masses, moving over the surface of the land constitute the 

 glaciers, which may be either glacial streams or glacial sheets. 

 Their motion is due to a variety of causes, among which partial 



