1 1150 ± 150 1450 ± 200 1:100 ± 20 30 ± 5 2 1450 ± 200 1650 ± 150 1:275 ± 25 40 ± 15 3 1650 ± 150 2150 ± 200 1:90 ± 30 30 ± 15 Lower continental rise 1 2150 ± 200 2350 ± 100 1:250 ± 50 40 ± 10 2 2350 ± 100 2350 ± 100 1:1400 ± 1000 50 ± 20 3 2350 ± 100 2725 ± 100 1:150 ± 30 60 ± 20 ---------------------------------------------------------- The upper continental rise and the lower continental rise are essentially terrace or shelflike features. Each has a relatively steep (1:50-1:200) outer face (segment 3) and a relatively gentle (1:250-1:2000) shelflike surface (segment 2). In each case a slope of intermediate gradient (1:80-1:300) (segment 1) connects the upper shelflike surface with the next higher face. In the case of the upper continental rise the next higher face is the continental slope. Other smaller-scale terracelike features may eventually be correlated along the strike when more data are available. The local relief exceeds 20 fathoms in the deeper parts of segment 3 of the lower continental rise. A range of hills extends for a few hundred miles along the base of the continental rise as indicated on the physiographic province chart (Pl. 20). These hills, known as the lower continental rise hills, are 30-100 fathoms high and each is 1 to 3 miles wide. An echogram (Pl. 3, fig. 4) shows three continental rise hills. The only other part of the continental rise where relief of more than 20 fathoms is generally encountered is in segment 1 of the upper continental rise. The irregularity in this case is probably related to the extensions of numerous continental-slope canyons onto the continental rise. Relief of 5-10 fathoms is almost universal in segments 1 and 2 of the upper continental rise. The echogram reproduced in Figure 1 of Plate 3 shows typical minor-relief features of the upper continental rise. An oblique crossing of a submarine canyon on the upper continental rise is shown in Figure 2 of Plate 3. The smooth topography typical of most of the remainder of the continental rise is well illustrated by the echogram shown in Figure 3 of Plate 3. The Hudson Submarine Canyon cuts across the continental rise in this sector. A chart contoured by Ivan Tolstoy and the authors from surveys made in 1949 is shown in Plate 2 (Ericson, Ewing, and Heezen, 1951). A series of 30 cross profiles is shown in Figure 17. [Illustration: FIGURE 16.--_Tracings of PDR records of continental and insular slopes_ (a). Insular slope of Madeira southwest of Funchal. (b). Continental slope of Europe. (c). Continental slope off northeastern United States.]