Marginal and extra-marginal features are extended in the direction of the margin or, in other words, perpendicular to the local ice movement; while the intra-marginal deposits are as noteworthy for being perpendicular to the margin, or in correspondence with the direction of local ice movement. Each of these features possesses characteristic marks in its form, its size, proportions, surface molding and orientation, as well as in its constituent materials. It should perhaps be pointed out that the existing continental glaciers, being in high latitudes, work upon rock materials which have been subjected to different weathering processes from those characteristic of temperate latitudes. Moreover, the melting of the Pleistocene glaciers having taken place in relatively low latitudes, larger quantities of rock débris were probably released from the ice during the time of definite climatic changes, and hence heavier drift accumulations have for both of these reasons resulted. =Marginal or “kettle” moraines.=—Wherever for a protracted period the margin of the glacier was halted, considerable deposits of drift were built up at the ice margin. These accumulations form, however, not only about the margin, but upon the ice surface as well; in part due to materials collected from melting down of the surface, and in part by the upturning of ice layers near the margin (see _ante_, p. 277). [Illustration: FIG. 336.—Sketch map of portions of Michigan, Ohio, and Indiana, showing the festooned outlines of the moraines about the former ice lobes, and the directions of ice movement as determined by the striæ upon the rock pavement (after Leverett).]