368 GEOLOGY. 



Fluvio-Glacial Deposits. 



The phenomena of existing glaciers afford warrant for the view 

 that the waters arising from the melting of the ice-sheets organized 

 themselves, to a greater or less extent, into streams l before they left 

 the ice (Vol. I, p. 280). This was doubtless true to a larger extent 

 near the edge of the ice than farther back. Ultimately, the subglacial 

 and englacial waters escaped from the ice. When this took place, 

 the conditions of flow were more or less rapidly changed, for instead 

 of being confined to tunnels, under hydrostatic pressure, as hereto- 

 fore, the streams now followed the laws governing normal river-flow. 

 When the streams entered standing water, as was sometimes the case, 

 the standing water modified the results which the running water would 

 otherwise have produced (Vol. I, pp. 305-307). The water issuing 

 from the ice thus made deposits in several classes of situations. 



(1) At the edge of the ice. — Where subglacial streams flowed under 

 " head/' the pressure was relieved when they escaped from the ice, 

 and diminution of velocity and deposition of load were the common 

 results. Since these changes took place at the edge of the ice, aqueous 

 deposits were sometimes made in this position, in immediate con- 

 tact with the ice itself. The edge of the ice was probably more or 

 less ragged, and the deposits made by the issuing waters were some- 

 times left in the reentrant angles and marginal crevasses. When 

 the ice against which the river-deposited debris was banked, melted, 

 the gravel, sand, etc., assumed the form of mounds, hillocks, and short 

 ridges. Such knobs, hills, and ridges are kames (Fig. 499). Karnes 

 may be developed in other ways, but they are primarily phenomena 

 of the margin of the ice, developed by running water (the active agent) 

 in association with ice (the passive partner). 



In position, kames have some relation to terminal moraines, and 

 there is perhaps no situation in which they are so numerous as in asso- 



Minn. Geol. Surv., Vol. I (1884); Lewis and Wright, Second Geol. Surv. Pennsyl- 

 vania, Rept. Z, 1882; Tyrrell, Amer. Geol., Vol. VIII, pp. 19-28 (1891); Bell, Bull. G. S. 

 A., Vol. I., pp. 303, 306; Salisbury, Glacial Geology of New Jersey, pp. 93-100 and 

 231-260; Leverett, Monogrs. XXXVIII and XLI., U. S. Geol. Surv.; Todd, Bulls. 

 144 and 158, TJ. S. Geol. Surv., 1896 and 1899, and Am. Jour. Sci., 4th ser., Vol. VI, 

 pp. 489-477, 1898. See also State Geological Reports of States affected by the ice- 

 sheets. 



1 The general topic of ice drainage is discussed in Glacial Geology of New Jersey, 

 p. 113 et seq., and Jour, of Geol., Vol. IV, p. 950 et seq. 



