METEORITE CRATERS AS TOPOGRAPHICAL 

 FEATURES ON THE EARTH'S SURFACE^ 



By Dr. L. J. Spencer, F.R.S. 



[With 5 plates] 



The problem of meteorite craters is quite a new one. Until 1927 

 the only known example was the " Meteor Crater " in Arizona, which 

 since 1892 has been the subject of much discussion and controversy. 

 Various theories have been put forward to explain its origin. The 

 one most generally accepted at the present time is that the crater 

 was formed by the impact of a gigantic meteorite on the earth's sur- 

 face, but this view still finds some opponents. Strong support was 

 given to this theory by the discovery made in 1931 of a group of 

 craters near Henbury in Central Australia.^ But definite proof was 

 finally given by the remarkable discovery made by H. St.J. Philby 

 during his crossing of the Arabian Desert early in 1932. The search 

 for the legendary city of Wabar was graphically described by him 

 at a meeting of the Koyal Geographical Society on May 23, 1932. 

 The " walls " of the city were found to be the rims of a series of 

 craters, and the abundant " cinders " of the city " destroyed by fire 

 from heaven " proved on examination to be a nearly pure silica 

 glass. Nearby, rusted pieces of meteoric iron were also found, the 

 largest remnant weighing 25 pounds. 



The finding of the silica glass as cindery and slaggy masses and 

 as complete " bombs " was in itself a remarkable discovery, for no 

 similar material had ever been found before, and it was found in 

 great abundance. Silica glass is, in fact, of rare occurrence in na- 

 ture. It is best known in the form of fulgurites or lightning tubes, 

 which are formed when sand dunes are struck by lightning.^ Since 

 a temperature of about 1,700° C. is required to melt quartz sand, the 

 development of a large amount of heat is here indicated. Further, 



» A paper read at the afternoon meeting of the Royal Geographical Society on Jan. 16, 

 1933. Itoprintcd by permission from the Geographical .Tournnl, vol. 81, no. 3, March in;?3. 



•Alderman, A. R., The meteorite craters at Henbury, Central Australia. Minoralopical 

 Magazine, vol. 23, pp. 10-32, 2 pis., 1932. Spencer, L. J., Meteorite craters. Nature, 

 vol. 129, pp. 781-784, May 28, 1932. 



' Mr. rhilby's collection, from localities other than Wabar, includes a few small frag- 

 ments of fulgurites, which were found in hollows between the sand dunes. An interesting 

 fact Is that the Arabs regard them as indications of the presence of water. 



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