METEORITE CRATERS — SPENCER 311 



away. There are still supporters of this theory; but it does not 

 explain the intimate intermingling of shattered terrestrial rocks with 

 meteoritic material, nor the presence of silica glass. It would be a 

 strange coincidence for such a volcanic outbreak to take place just at 

 the spot where masses of meteoric iron had previously fallen, and 

 they certainly could not have fallen afterward. 



Further, the temperature of a steam explosion would not be high 

 enough for the production of silica glass. The same, and more, 

 objections would appl}^ to the theory that the crater has been formed 

 by the solution of limestone, being of the nature of a sink hole.^ 

 The crater extends downwards into sandstone, far beneath the base 

 of the bed of sandy limestone. 



The Arizona crater, like the craters of Henbury and Wabar, shows 

 an intimate association of meteoric iron and silica glass with frac- 

 tured terrestrial rocks, and it was undoubtedly formed by the fall 

 of a large meteorite. But whether the main mass of this meteorite 

 still lies buried in the crater is extremely doubtful.^ More probably 

 such portions as were not vaporized by the intense heat developed 

 by the impact were shot out by the gaseous explosion and scattered 

 around the crater. 



The Texas crater ° is situated about 9 miles southwest of Odessa in 

 Ector County. It is a shallow depression roughly circular in outline 

 with an average diameter of 530 feet. The rim is about 18 feet above 

 the bottom of the hole, but only 2 or 3 feet above the surrounding 

 desert plain where horizontally bedded limestone is exposed. The 

 steep inner slopes show the limestone dipping at 20° to 30° away 

 from the center. A much-rusted fragment (1,120 grams) of meteoric 

 iron was found here in 1922, and the crater was first mentioned in 

 1927. Amongst the fragments of limestone and sandstone forming 

 the rim of the crater a fcAV more small pieces of iron have been 

 found together Avith numerous pieces of iron shale. The various 

 suggestions made to account for the origin of this crater are discussed 

 by E. H. Sellards, namely: (1) volcanic explosion; (2) salt dome; 

 (3) expansion by hydration of anhydrite; (4) explosion of gas; 

 (5) fall of a meteorite. The last is considered to be the most prob- 

 able, and this view is supported by D. M. Barringer. 



The Ilenhury craters (pi. 2) in Central Australia, known locally 

 as the Double Punchbowl, are situated 7 miles west-southwest of 

 Henbury cattle station on the Finke River, about 50 miles south of 



^ Dollcnbaugh, F. S., Meteor Butte. Science, vol. 73, pp. 38-39, 1931. 



* The only known case of a meteoric iron found luslde a crater is mentioned below under 

 Henbury. 



" Sellards, B. 11., Unusual structural feature In the Plains region of Texas. Bull. Geol. 

 Soc. Amer., vol. 38, p. 149, 1927. 



Barringer, D. M., Jr., A new meteor crater. I'roc. Acad. \at. Sci. Philadelpliia, vol. 80 

 (for 1928), pp. 307-311, 1929. No pictures are available of tills crater. 



