1. Height above which Russia classifies tests as airburst tests (above this height, the fireball is far enough from the ground that local fallout is minimal).
2. Height below which Russia classifies tests as surface bursts (between curves 1 and 2 is an intermediate range).
3. Minimum depth which the United States considered sufficient for containment of underground bursts before 1971.
4. Minimum depth which the United States considered sufficient for containment of underground bursts after 1971.

Regarding above-ground bursts, the graph shows:

• only the United States conducted surface bursts of megaton yield or greater (such tests were conducted at Bikini and Eniwetok Atolls in the Pacific Ocean, now in the Marshall Islands);
• Soviet tests, particularly high-yield tests, were conducted at altitudes intended to minimize local fallout (such height has little effect on global fallout, however);
• the largest Soviet test, the 57 mt test conducted 30 October 1961, is shown as intermediate, although for the height and yield officially claimed by Russia it would be classified as an airburst;
• the largest French tests were in the intermediate range between airbursts and surface bursts.

• many U.S. tests smaller than 20 kt are not shown (this incompleteness is worst for tests below 1 kt);
• depths for most Soviet underground tests have not been released; most Soviet bursts shown here are for industrial applications and related research. This accounts for the wider variety of depths than those for U.S. tests.

© 2005 by Wm. Robert Johnston.
Last modified 19 June 2005.
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