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ters in the Earth's surface. The formation of such craters mdicates the destruction of the entire perma- 

 frost layer under the explosion site and the formation of a so-called chimney over the explosion cavity. 

 Leakage of a significant amount of radionuclides through such structures is inevitable, and some por- 

 tion (possibly a substantial one) of the released radioactivity could have entered the sea. In principle, 

 the entry of radioactivity from underground explosions mio the sea through soil and ground water can- 

 not be ruled out. As yet, e\en an approximate estimate of the amount of radioactive contamination that 

 could have entered the ecosystems of the Barents and Kara Seas has not been made. — A. Yablokov. 



