318 



ANNUAL KEPORT SMITHSONIAN INSTITUTION, 19 3 3 



One view is that these depressions are formed by the freezing of 

 water in cavities between the permanently frozen ground and that 

 frozen only in winter, causing expansion and afterwards bursts. They 

 are said to be of normal occurrence at the southern limit of perma- 

 nently frozen ground. This view is opposed by Dr. Kulik. Another 

 view is that they were formed by the solution of limestone, salt, or 



B IPO'i. 



I ioS° A 



FiGDKE 1. — Place of fall of the Siberian meteorite of June 30, 1908. 



gypsum ^^ ; but this is at once ruled out by the bedrock being only 

 basalt. Dr. Kulik believes them to be really meteorite craters, though 

 he himself suggests some alternative explanations. They may have 

 been formed by the folding of the surface layers by the blast of hot 

 air, or by flooding following the melting of the frozen ground, or by 



" Tschirwinsky, P., Ueber die Pseudometeorkrater in Arizona und auf der Insel Osel. 

 M6m. Soc. Russe Min., ser. 2, vol. 60, pp. 135-44, 4 figs. [Russian with German 

 summary], 1931. 



