496 H. L. FAIRCHILD OKIGIN OF METEOR CRATER, ARIZONA 



trains of boulders were swept far out on the floor of the crater, while 

 the shaft-house, tool-house, and other buildings in the middle of the pit 

 had their floors buried in mud. 



It would appear that the original diameter of the crater must have 

 been appreciably less than now, the walls steeper, and depth of the 

 pit greater. The nearly circular floor of the crater is about 1,800 feet 

 across, with a nearly flat, or gently rolling, surface. The floor consists 

 of aqueous sediments, with intercalating inwashed beds of the talus about 

 the margin. -These sediments have been found to average depth of 70 

 feet, and contain vegetal or peaty layers, beds of diatomaceous material, 

 pond snails, and a stratum of volcanic dust and lapilli from one-fourth of 

 an inch to three inches in thiclaiess ;■ also scattered boulders, which were 

 probably rolled in on the lake ice or rafted in on floating ice cakes. The 

 volcanic debris suggests that the crater antedates the latest volcanic erup- 

 tions of the region. At present no water stands in the crater, but it 

 is encountered 200 feet beneath the floor, or over 600 feet below the sur- 

 face of the plain, which suggests possible climatic change. Mr Holsinger 

 states that cedars growing on the crater rim are over 700 years old. 



The bottom of the pit when formed must have been at least 540 feet 

 below the level of the plain and about 750 feet below the rim, the latter 

 now being, after centuries of storm-wash, 130 to 160 feet high above the 

 surrounding plain. This crater rim consists of the uplifted rocks capped 

 by an enormous mass of rocks debris, giving the appearance from a dis- 

 tance of a range of low hills with rough surface (see plate 54). 



Volcanic Theory untenable 



Beneath the central area of the crater the red standstone (number 4) is 

 found in place beneath the white sandstone (number 3), which shows the 

 absence of any chimney or volcanic pipe of considerable size and posi- 

 tively rules out any explosion from beneath. The conception of a vapor 

 explosion in the thick white sandstone is ruled out by the existing phe- 

 nomena. Mr Barringer and Mr Tilghman have given the' facts bearing on 

 this theory, and in impublished writing Mr Tilghman has clearly dis- 

 cussed the mechanics and the subsequent effects of a steam explosion. 

 The white sandstone, nearly 1,000 feet thick and imderlying all the 

 country, is very porous and would contain a large volume of water. The 

 pressure of any heated water or vapor sufficient to throw the mass of 

 rock out of the pit must have existed through an immense horizontal 

 extent of the strata, and a long time would have been required for entire 

 relief of the pressure through the vent, anS with decided hot spring or 



