630 ANNUAL EEPORT SMITHSONIAN INSTITUTION, 19 3 



like circular hole about 4,000 feet in diameter and 600 feet deep, 

 known as Meteor Crater, situated 12 miles southeast of Canyon 

 Diablo, Coconino County, Ariz. In the summer of 1907 Merrill was 

 detailed by Secretary Walcott of the Smithsonian Institution to 

 make a study of this so-called Coon Butte or Meteor Crater. Here 

 he had the guidance of Mr. D. M. Barringer, a mining engineer who 

 had been unsuccessfully exploiting the place in the hope of recover- 

 ing the main mass of the meteorite. 



Meteor Crater has a raised rim, which stands from 120 to 160 

 feet above a plain made of horizontal strata of Permian age. At 

 the surface is the buff-colored arenaceous Kaibab limestone and 

 beneath it the very porous, gray, highly siliceous Coconino sand- 

 stone, with a thickness greater than 400 feet. Ever since the great 

 hole was found, geologists have been asking : Was it made by a blow- 

 out from within, or is it due to an external impact of a stellar 

 body? 



The rim of the crater, according to Merrill (1908a), is composed 

 of loose unconsolidated rock fragments of all sizes, from microscopic 

 dust to blocks weighing thousands of tons. Tlie crater walls " are 

 composed of the crushed, broken, and bent strata of the limestone 

 and sandstone forming the floor of the surrounding plain, and which 

 dip away from it in all directions." The dips vary between 10° 

 and 80°. " Perhaps the most significant feature of the ejectamenta 

 is the occurrence of enormous masses of the sandstone which have 

 undergone a partial metamorphism through crushing and heat. . . . 

 This material must have come from a depth of at least 300 feet below 

 the original surface." There is also a vast amount of a chalky 

 white siliceous rock-flour, the shattered grains of the gray sand- 

 stone. Outside of the rim " are many low, rounded, moraine-like 

 deposits composed of the same material as the rim, but for the 

 most part in a comparatively fine state of disaggregation." 



The deepest part of the crater is about 440 feet below the level of 

 the plain. Much loose material has been washed into the pit, hence 

 the original depth must have been considerably greater. Bore holes 

 put down to 1,100 feet reveal, below the floor of the crater, crushed 

 rock (as a rule rock-flour) down to 620 feet, and then follows undis- 

 turbed bed rock — a gray sandstone that is not metamorphosed. 



The Canyon Diablo iron meteorites found on the rim and the ad- 

 jacent plains are "the most interesting and instructive of known 

 meteorites," containing small black and white diamonds. At least 

 20 tons of these irons are known to have been gathered over several 



