On the Atlantic Seaboard, south of the terminal moraine, the Pleistocene formations are composed of gravel, sand, silt, and clay, ranging in thickness from a few feet to a score or more. They lie unconformably on the unconsolidated sediments of the Coastal Plain. At many places, these deposits form terraces, with what is considered to be a low wave-cut bluff, or beach ridge, at the landward margin. So characteristic is the terrace aspect that the formations are frequently spoken of as terraces. A series of these terrace remnants ranges from 25 to 270 feet above sea level, and possibly higher. The higher ones are largely discontinuous and patchy; the lower ones are fairly continuous broad stretches of flat country, 30 to 50 miles wide. These terraces become increasingly more conspicuous, as one goes southward from New Jersey. The higher ones are considerably eroded by streams, but . . .