Figure 14. Surface Phenomena for the Case of a Non-Venting Bubble. Charge: 2.75 lbs TNT and 1 

 grame KClOi/Al 50/50. Depth: 0.9 maximum bubble radii. 



The Plumes 



Placing the charge still deeper, the so-called plumes occur, Fig. 15. The first 

 frame shows the spray dome which is caused by the shockwave. Somewhat later 

 (second frame), a jet suddenly appears above the spray dome and bursts upward with 

 great violence. Such a jet is commonly called a "plume". If a distance-time plot is 

 made of this plume and if it is extrapolated back to zero distance from the water sur- 

 face, it is found that the plume started to move at the moment of the bubble pulse. 

 Thus, it appears that this plume is formed by the impact of the bubble pulse. Later 

 (fourth frame) more plumes spring up when the gas bubble breaks through the water 

 surface. Very little is known about the mechanism which leads to the formation of 

 the plumes. It seems, that a strongly accelerated water surface breaks up either into a 

 spray if the surface was originally smooth, or into plumes if the surface was already 

 grossly disturbed, for instance by the prior impact of the shockwave. Small charges 

 (below say ten pounds) do not produce such conspicuous plumes as are shown in 

 Fig. 15. 



Fig. 16 shows the water column of the nuclear underwater explosion at Bikini. 

 Here, also, plumes are formed, but in an entirely different situation from that shown 

 in Fig. 15. They emerge horizontally from the water column and later fall downward. 



Deep Explosion 



In Fig. 17, we see an explosion of a small charge in great depth. The spray 

 dome is minute and disappears quickly. After a while the gaseous reaction products 

 appear in form of a compact ball on the water surface. In the second frame, the 



340 



