METEORITE CRATERS — SPENCER 315 



produced by the vaporization of the desert sand and part (perhaps a 

 large portion) of the meteorite. The minute pimples on the surface 

 were dewdrops from these vapors formed in the last stages. 



The group of craters in Estoii'm are on the Baltic island of Oesel 

 ( = Saare Maa) at 20 kilometers northeast of Arensburg ( = Kure- 

 saare) on the farm Sail ( = Kaali) (58^24' N., 22°43' E.). They 

 have long been known and often described, first by J. von Luce in 

 1827. They have been thought to be earthworks made by man, and 

 they have been compared with the crater lakes of the Eifel and the 

 Campi Flegrei. Other modes of origin that have been suggested 

 are that the craters were formed by (1) gas explosions, (2) oozing 

 out of a bed of clay, (3) weathering of limestone, (4) solution of 

 salt or expansion of anhydrite. In 1922 J. Kalkun compared them 

 with the Arizona meteorite crater. Kecently, in 1927 and again in 

 1929, a detailed survey with borings and trenches has been under- 

 taken by J. A. Reinvaldt, Inspector of Mines in Estonia, and he 

 comes to the conclusion that the craters were formed by the fall of 

 a shower of iron meteorites. While his work was in progress a 

 visit was made to the locality by E, Kraus and R. Meyer, of Riga, 

 and Alfred Wegener, of Graz, and he freely supplied them with full 

 details and drawings. As a result they published a long joint paper, 

 which appeared only shortly after Reinvaldt's own paper.^- Kraus 

 inclines to the view that the craters were formed by the solution, of 

 the salt in saltdomes; but Meyer and Wegener, wdiile considering 

 this mode of origin to be possible, favor the meteorite theory as the 

 more probable. 



The main crater, which is occupied b}^ a lake, is nearly circular in 

 outline wdth a diameter of 92 to 110 meters. Its rim is 6 meters above 

 the surrounding ground, while inside the depth is 15.5 meters. The 

 steep inside walls show beds of dolomite (Silurian age) dipping 

 away from the center at angles of 30° to 40°. Beneath this there is 

 a zone of pulverized rock containing rock fragments; and the rocl« 

 at the bottom of the crater are shattered. Five other smaller craters, 

 irregularly distributed over an area of three-fourths of a square 

 kilometer, are described in detail. Four of these are circular in 

 outline with diameters of 10 to 39 meters and depths of 1 to 4 

 meters. The fifth is oval, 53 by 36 meters, suggesting that two masses 

 of iron fell together. In the bottom of one of these smaller craters 

 the shattered bedrock shows an impression which is believed to rep- 



" Kninvaldt, L., with Luba, A., Hcriclit iiber Keologlsche Untcraucliungon am Kaalijiirv 

 (Krater von Sail) auf (Jsel. Tartu IJlikooli juurcs oleva Loodusmirijate Si-ltsl Aruandod 

 (Sltzungsber. Naturfors. Gpsell. Univ. Tar(u), vol. 35. pp. ."^O-TO, 8 pis., 1928. Separate 

 as I'ubl. Geol. Inst. Uuiv. Tartu, no. 11, pp. 1-42, 8 pis., 1928. 



Kraus, E., Meyer, U., and Wegener, A., Untorsuchungen iiber den Krater von Sail auf 

 Osel. Gerlands P.eitriige zur Geophysik, vol. 20, pp. 312-378, 1 pi., 10 text-flgs., 1928 ; 

 Nachtrag, pp. 428-429. 



