MERKILL] METEOR CRATER OF CANYON DIABLO, ARIZONA 495 



man, an authority on impact of projectiles from heavy ordnance, 

 has estimated that in rocks as brittle as those of this particular 

 vicinity the crater formed would be eight to ten times the diameter 

 of the projectile; that is, with a 500-foot projectile the crater might 

 be 4,000 feet in diameter, which is approximately that of the existing 

 crater. As depths below the surface increased, the upward escape of 

 material around the mass would be impeded, and that directly in 

 its path and, to a less extent, that on either side would become 

 enormously compacted. The heat generated by the sudden down- 

 ward plunge of the body would produce fusion and probably a 

 partial volatilization, and where sufficient moisture was present, other 

 conditions being favorable, would give rise to the pumiceous structure 

 found in the altered sandstone. But certain after-effects must be 

 taken into consideration. That there was moisture is evident by the 

 existence of the pumice. The effect of the impact would be to con- 

 vert almost instantly this moisture into steam with an enormous 

 explosive power. As a result, quantities — the amount being de- 

 pendent upon the amount of water — of debris, including even por- 

 tions of the meteoric fall itself would be ejected and thrown back 

 above the crater rim and scattered widely over the plain. It would 

 seemingly be safe to assume a temporary pseudovolcanic condition. 

 To this cause tne writer would ascribe the formation of the pecul- 

 iar moraine-like mounds shown in plate Lxvrn, figure 1, and indeed 

 all those heterogeneous deposits, composed of rockflour and frag- 

 ments of limestone and sandstone (a portion of the latter metamor- 

 phosed), in which the shale-ball irons are embedded. It is impossible 

 to account for the position of these last in any other way than to 

 assume that they fell at the same period of time as the material in 

 which they lie embedded. The difference in specific gravity of the 

 various materials is such that it is inconceivable that they should have 

 traveled together for any great distance. Their association may 

 be best explained on the assumption that all were poured out together 

 over the crater rim, perhaps in the condition of mud, during this 

 pseudo-volcanic stage. Only on this ground likewise is it possible to 

 explain the presence in these deposits of masses of the altered sand- 

 stone. These, seemingly, must have been formed by heat and pres- 

 sure well down toward the bottom of the crater, and have been 

 brought back to the surface through explosive action, which took 

 place some little time after the meteor came to rest. What proportion 

 of the irons scattered over the plains are the result of this secondary 

 effect one can only surmise. The fact that there is seemingly no 

 regularity in their distribution — as is almost universally the case in 



