(UTC)

 I agree with User:Man with two legs that the graph is extremely misleading.  See this quote about (or maybe from?) Edward Tufte:
 Before the development of spreadsheet graphing, the most common graphical mistake was the use of artist-drawn 3-D images with the height of 3-D objects representing the magnitude of the data points.  In these charts, both the height and the width of the drawn object increase proportionate to the magnitude of the data points.  The effect is to exaggerate the differences in magnitude as the viewer tends to perceive the area of the figures rather than just the height as representing the magnitude. (Source)
 The image suggests that the Tsar Bomba, which was three or four times more powerful than Castle Bravo, is actually 40 times larger in volume (or ~10x larger in area).  If explosion volume went up by about the cube of the yield (not really accurate, but much closer than this chart) the Tsar Bomba mushroom cloud would be 1.5x taller than Castle Bravo and 15x taller than Hiroshima.  Instead, the diagram shows the CB and TB over a thousand times taller.  

 On this scale, one could conclude that since the Hiroshima bombing's mushroom cloud was about four miles high, the Tsar Bomba explosion (3,000x taller) must be larger than the Earth itself.  98.218.195.90  12:41, 6 July 2010