The east and west views differ in details which, although important in connection with the origin of the crater itself, are not sufficiently conspicuous in the photographs to warrant reproduction. Gilbert's paper is described as 10 feet in height and as lying about half a mile outside the rim of the crater.
INTERIOR WALL OF CRATER, LOOKING NORTHWARD
LOOKING ACROSS CRATER FROM NORTH, SHOWING FAULTING (BENEATH ARROW) IN
MERRILL] METEOR CRATER C-E CANYON DIABLO, ARIZONA 467
This too sinks at a higher but smaller angle than the limestone, which undoubtedly faces it. MERRILL] METEOR CRATER OF CANYON DIABLO, ARIZONA 469 somewhat indistinct at the point immediately below the arrow.
MERRILL] METEOR CRATER OF CANYON DIABLO, ARIZONA 469 somewhat indistinctly at the point directly beneath the arrow in
470 SMITHSONIAN MISCELLANEOUS COLLECTIONS [VOL- 50
The Crater Floor
- DRY WASH, SOUTH SIDE OF OUTER RIM 2. WHALE ROCK ON WEST RIM
- BOULDER ON RIM OF CRATER, WEST SIDE
- MORAINE-LIKE HILLS ON NORTHERN RIM OF CRATER
- INTERIOR WALLS OF CRATER, WITH TALUS AND ALLUVIAL FANS FROM CLIFFS
MERRILL] METEOR CRATER OF CANYON DIABEO, ARIZONA 471 The yellow to red sandstone, which seems everywhere to form the
472 SMITHSONIAN MISCELLANEOUS COLLECTIONS [VOL. 5°
This, mixed with more or less solid material, occupies a large part of the crater from the 85- or 90-foot level down to the underlying red bed, a distance in round figures of 500 feet. Between the thumb and the fingers this material, in spite of its fineness, has a sharp gritty feel, and under the microscope it may consist entirely of the sharp-edged pieces of quartz resulting from the splintering of the individual grains of sand (see Fig. \ 2&) . Mixed with this material at the bottom of the crater (as .. shown by shafts), and to a lesser extent around the rim and in scattered masses outside the rim, are fragments of what is. common sandstone, but of an almost snow-white color and so brittle that it can be easily crushed between the thumb and fingers Hokaltly known as ;jJiost sandstone).
No. 76,834, U.S. 474 SMITHSONIAN MISCELLANEOUS COLLECTIONS [VOL U.S.N.M.), retaining the grainy character and 76.835, U.S.N.M.), retaining the grainy character and much of the original structure of the sandstone, but easily crushing between thumb and fingers. A description of this is given when discussing the next or second phase of metamorphism.
In this second and very complete stage, the original granular structure of the sandstone has almost completely disappeared. In mass, this variety shows an uneven planar structure that extends along the original, almost obliterated, bedding lines.
MERRILL] METEOR CRATER OF CANYON DIABLO, ARIZONA 475 of molecular strain, and the cleavage lines are themselves at times
The Meteoric Irons
History of Early Finds.—The first public notice of the discovery of meteoric iron near Canyon Diablo was that made by Mr. MERRILL] METEOR CRATER OF CANYON DIABLO, ARIZONA 479 which was published in both the Society's and.
MERRILL] METEOR CRATER OF CANYON DIABLO, ARIZONA 479 which was published in both the proceedings of the Association and
480 SMITHSONIAN MISCELLANEOUS COLLECTIONS [VOL. 50 of rupture from a parent mass, nor fusion and flow structure from
MERRILL] METEOR CRATER OF CANYON DIABLO, ARIZONA 481 gest that if due to impact of a bolide, the same came from a direction
MERRILL] METEOR CRATER FROM DIABLO CANYON, ARIZONA 481gest that if the impact caused her to fall, the same came from the direction. Brezina,5 in 1893 noted the find of iron (which he incorrectly located as in New Mexico) and noted its crystallographic structure and occurrence around the crater - a fact which. In 1895° he returned to this subject, described the external appearance of the iron found and concluded that the natural etched surfaces showed that the iron consisted mainly of kamacite plates with no noticeable tasnite.
Derby published in 18957 the results of investigations into the chemical and mineralogical nature of iron and reported the occurrence of oftasnite, schreibersite (and rhabdite), cohenite, diamonds (probably) and amorphous carbon with traces of chromium and a relatively high proportion of copper. The shape of the irons (see pi. lxxiii), he suggested, could be due to their having been "small irregular me-. Moissan in 1904 published important chemical contributions giving analyzes of the iron and the accompanying troilite nodules, and announced the discovery of carbon in three forms - amorphous, like graphite and diamond.
He also announced the finding in his insoluble remains from the iron of a green mineral in the form of MERRILL] METEOR CRATER OF CANYON DIABEO, ARIZONA 483 hexagonal plates, the analysis of which proved to be a silicide of carbon.
MERRILL] METEOR CRATER OF CANYON DIABEO, ARIZONA 483 hexagonal plates which analysis showed to be a silicide of carbon
Foote described the material as "identical in appearance with a crust formation which covered the surface of some of the irons, or filled the depressions in the same." Its occurrence in such large quantities, he suggested, that an unusually large mass, probably 500 or 600 pounds (!), had been oxidized while passing through the air, and so weakened that it burst into pieces not long before it reached the earth . Needless to say, Foote's estimate of the size of the meteoric mass was at least conservative. Barringer and Tilghman, the first named, having noted the distribution of the material in the same extent as the iron, stated his belief that it was produced by the heat generated from friction as the meteor passed through the earth's atmosphere.
And again (p. We have assumed that these small particles (*. i.e. of shale in the form of fragments and globules) once formed part of the great luminous tail of the meteoric body.' Tilghman puts the matter a little more clearly. stating that it is 'fused and massive and at the same time layered and laminated and generally has a different appearance from any known terrestrial magnetite, and closely resembles what would a priori be thought to be the appearance of such a product of molten iron. and burned up on the surface of a large meteorite during its passage through the air.' This has led to the supposition that they are composed, at least in part, of iron in the form of magnetite.
Nichol's analyses, given by Farrington,1 showed that the material consists mainly of iron in the form of FeO and Fe2 3 with minor amounts of other constituents characteristic of unaltered material. From these analyzes Farrington calculated the constitution of the clay as follows.
486 SMITHSONIAN MISCELLANEOUS COLLECTIONS [VOL- 50
MERRILL] METEOR CRATER OF CANYON DIABLO, ARIZONA 487 mospheric fractional heat would ignite and burn away the sulphide portions
Origin of the Crater
488 SMITHSONIAN MISCELLANEOUS COLLECTIONS [VOL. 50 and several petrographic and chemical analyses made, all of which
MERRILL] METEOR CRATER OF CANYON DIABLO, ARIZONA 489 cussed the physical aspects of the crater with reference to its similar-
Summary
MERRILL] METEOR CRATER OF CANYON DIABLO, ARIZONA 489 expressed the physical aspects of the crater with reference to its similar.... The association of the fused pumice masses with the fractured material, together with the transition from one form to another, is such that a suggestion is created. The slightly disturbed and unchanged condition of the deeper sandstone seems to prove the superficial character of the phenomena.
These last, however, are the initial velocities, the velocities which the meteors possess when they enter our atmosphere and while still at considerable altitudes—in some cases 50 or 60 miles—and which are very materially reduced by atmospheric friction long before they reach the earth . Indeed, from the calculations of Schiaparelli and others, it is generally accepted that a meteorite reaches the surface at the speed of an ordinary falling body. Herschell, as quoted by Flight,1 calculated the velocity of the Yorkshire (England) meteorite when it reached the ground to be only 412 feet per second.
Newton4 calculated the speed of the fireballs that passed over the Ohio and Mississippi valleys in August 1860 to be 30 to 35 miles per second, and stated5 that the Stannern, Moravia, stone entered our atmosphere with a velocity of 45 miles per second. MERRILL] METEOR CRATER OE CANYON DIABLO, ARIZONA 49Doubtless those of bodies pursuing a retrograde course over the.
MERRILL] METEOR CRATER OE CANYON DIABLO, ARIZONA 49I doubtless those of bodies pursuing a retrograde course about the
The Williamette iron, weighing 15.6 tons, apparently lay as it originally fell, and in a region of no considerable erosion—rather one of organic deposition, for it was found in a jungle; yet the mass was scarcely buried, a small protuberance leading to its discovery. The Bacubirito iron, with a rough estimate of 20 tons, lay in a soft soil, its surface but little below the general surface of the field around it. MERRILL] METEOR CRATER OE CANYON DIABLO, ARIZONA 493These illustrations are sufficient to show the contradictory nature.
MERRILL] METEOR CRATER OE CANYON DIABLO, ARIZONA 493 These illustrations are sufficient to show the contradictory nature
SO miles per second, if all the equivalent energy were converted into heat and stored in the mass of the falling body, would be sufficient to raise its temperature, supposing it to be composed of ordinary volcanic rock, by 3500 degrees Fahrenheit, or within 400 degrees of temperature , necessary for smelting quartz. To what extent these results are applicable to the present case is problematic, since as Huxley remarked, "what one will get out of a mathematical mill depends on what is put into it," and in this particular case the size and velocity of the body, and to some extent its composition, must be assumed.
It is, however, almost impossible that a force so great and applied, as it appears, within an instant of time, would not have been productive of a quantity of heat so enormously greater than 3,900° as to render its expression utterly meaningless. would not be and incomprehensible, and in the author's. The formation of the crater rim and the presence of the enormous blocks of stone in it can, as mentioned above, be explained on the basis of either the blow-out-impact hypothesis. The presence in this rim of blocks of the altered sandstone, both pumiceous and of the white or "ghost".
Hypothetical Considerations and Conclusion.—Let one imagine a spheroidal mass of meteoric iron, perhaps 500 feet in diameter, falling on the earth at a speed of 5 miles per second. The surface rocks are crushed and thrown back onto the plain in an amount more than equal to the bulk of the meteorite.
MERKILL] METEOR CRATER OF CANYON DIABLO, ARIZONA 495 man, an authority on impact of projectiles from heavy ordnance,
In this connection it must be observed that the most liberal estimate of the material carried away by the collectors, or still remaining as slate on the plain, would scarcely amount to a thousandth of the mass sufficient to form a crater. The failure so far to find a large intact mass inside the crater could be further explained on the basis that a considerable part of it was vaporized by the intense heat generated at the moment of impact with the surface, and the relatively small remnant has largely succumbed to oxidation. Even if the dimensions of the hole allowed it, their high specific gravity would cause them to be left behind, bringing only the lighter sand grains and finer particles to the surface.
This study, detailed above, has been made possible only through the generous and hearty co-operation of Messrs. Barringer and Tilghman, to whom reference has been made so repeatedly that further allusion seems almost superfluous. The author Gilbert is also indebted for notes, maps and other material collected at the time of his studies.
Tassin, of the Division of Mineralogy, allowed the use of his unpublished chemical notes. A set of specimens of the meteoric irons, altered sandstones, and allied products were obtained by Messrs.
EXPLANATION OF PLATES
