the depth. Using the fitted expressions for radius and depth, as in Figs. 3.5 and 3.6, as- craters characteristic of Eniwetok. It will apply only to Eniwetok and is probably influenced strongly by the geologic structure. It can be only a rough description in view of the paucity of experimental points, and because of the mixture of tower and surface shots. Probably neither in magnitude nor shape are the results apptfcable to other conditions; it can reasonably be hoped for an uncertainty of only a factor of 2 in any general rule which might be deduced. Figure 3.5 shows an estimate of the crater radii as a function of yield for the four shots. These are fairly certain only on the Greenhouse Easy and Ivy Mike craters, which were setat 600 ft and 3600 ft, respectively. A value of for the Greenhouse Dog crater appears reasonable from the flatness of the profile near _ and the choice of for the George suming the conical shape for theoretical rea- sons in Sec, 1.1 and with whatever empirical justification occurs in Figs. 3.1 to 3.4, the volume for an Eniwetok crater becomes Vv. tainty quoted. The volume for the Easy crater has been estimated by the author as 1.13 x 10° cu ft, in comparison with 1.14 x 10° from Eq. 3.3. At the same time, A. L. Embry has estimated the volumeof the Ivy Mike crater to be 1.15 x 10° cu ft, in comparison with 1.52 x 10° cu ft from Eq. 3.3, which is considered reasonable agreement. The volumes for Dog and George appear , if any- thing, but are subject to too great experimental uncertainties to justify a comparison. 3.3 (3.1) and sand deposition lead to uncertainties con- siderably larger than this for the case of Greenhouse Dog and George craters. Figure 3.6 has a similar plot in which the depths are obtained from Figs. 3.1 to 3.4. On 200 to 1 in 30, increasing in steepness with larger yields, at least at Eniwetok. Report LA-1529 was principally concerned with the possibility of triggering a major geo- this plot, the depth for Greenhouse Easy crater is fairly certain; the Greenhouse Dog crater is presently morelikely too shallow than too deep because of the debris within the crater. Similar remarks apply to the George crater becauseof the deposition of sand. The Ivy Mike crater has been plotted with an effective depth of 120 ft and logic failure at the Atoll which could, in turn, generate a tsunami of oceanwide proportions.' raters of depths like 100 ft do not involve sufficient volumes to result in such a catas.tréphe. On the other hand, one would feel considerable concern over a predicted depth of regarding the deep hole as a fluctuation intro- W% D= 4 ft (3.2) Owing to variations in the soil, the volume is likely to be a better average than the radius or FURTHER RESULTS Some results of these curves are of interestz Without recourse to a definite comparison,it is clear that the craters from nuclear explosions are much shallower than craters from TNT explosions. For nuclear explosions, the slopes in the craters are in the order of 1 in where W is in kilotons. The uncertainties are also shown and seem to be of the order ofat least 25 per cent, although the questionsoffill by (3,3) which seem justified within the limits of uncer- high-tide line has been shifted inward to distances like this on the southeast side of the island. A line of slope 1/3 has been passed through these points in such a waythat the mean crater radius is expressed in the form duced by geologic structure. The uncertainty in depth is a factor of 2 as indicated on the figure. A line has been passed through the points in such a way that the maximum depth is expressed 3 The validity of the various assumptions and ‘the fitting process for radius and depth are best judged by an examination of Figs. 3.1 to 3.6, crater is supported only by the fact that the R= 160 W"ft 4 olume = 6700 Wit N 1000 ft for the crater and, according to Fig. 3.6, this would occur for a surface burst in the order of 250 Mt, However, from Fig. 3.5, the crater radius for such a burst is approximately 2 miles, and the danger could probably be averted for such a large explosion by firing it on a barge in the lagoon 2 miles or more from the reef, Another item of interest is the high probability of breaching the reef during shot of the Castle series in the spring of 1954. This shot, expected to be in the order of 6 Mt, will Page (Gn ROMCobia,