is easy to overlook the fact that the depth is quite small when compared to the diameter. To make this point clear the upper part of Fig. 3.1 has been drawn to show typical profiles of Shots 1, 3, and 4, ala to the same scale and with the same scale for vertical depths and horizontal depths. These same profiles are repeated in the lower part of Fig. 3.1 where vertical distances are enlarged by a factor of 10. ‘This expansion of depths has been made in all of the following figures. :': It will be noted from Fig. 3.1 that the depth on Shot 3, rela- tive!to diameter, is very much greater than on Shot 1. In scaled terms the-‘thickness of sand below the shot point and above the water was much greater on} Shot 3 than on Shot 1. It 1s probable, however, that the greater relative depth of Shot 3 is primarily a function of the yield, since it/séems to be well established that small explosion craters have greater relative depth than large ones. 3.2 SHOP.) Figure 3. 2 is a preshot photograph of the Shot 1 area on which the CASTLE grid is ‘shown. On Fig. 3.3, which is the postshot photograph of the same area, in addition to the CASTLE grid, three lines (A-B, C-D, and E-F) have been drawn. These lines represent the tracks that the survey ship followed while the profiles presented in Fig. 3.4 were obtained. On, theseand all other profiles zero elevation has been taken as the datum planeon’‘which the tide tables are based: 0.5 ft below mean low-water springs. = ~ The survey with the sonic.fathometer showed a uniform flat bot- tom at a depth of 170 ft. Thisflat bottom undoubtedly represents the upper surface of mid and suspended-Band which was settling in the cra- ter. In mooring the barge for Shot,-2at the same ground zero, H&N ob- tained lead line soundings of 240 aeand it is believed that this figure ots represents the depth of the crater-of ser 1. 3.3 sHor2 \ Pee Leena Since Shot 2 was fired on a barge in thecenter of the Shot 1 crater, no military significance attaches to the crater formed by it and no fathometer measurements of it were made;on aerial survey, however, was made and a photograph is shown as Fig. Ht Figures 3.6 and 3.7 are pre- and post-Shot 3 “photégtaphs. It should be noted that these photographs are to a different-scale than Figs. 3.3 and 3.4 so that the size of the craters cannot|ibe compared from the photographs. Figures 3.8 and 3.9 are contour maps showing the situation’ for Shot 3 before and after the shot, respectively. In the upper part of Fig. 3.10 these two contour maps have been combined to show the’gontours of the difference in elevation produced by the shot. On this same chart, the location of the traverses run by the LCU are also shown. In the lower part of this figure and in Fig. 3.11, crater profiles are shown 25