Smithsonian

Contributions to Astrophysics

VOLUME 2, NUMBER 7

DISTRIBUTION OF METEORITIC DEBRIS

ABOUT THE

ARIZONA METEORITE CRATER

by JOHN S. RINEHART

SMITHSONIAN INSTITUTION

Washington, D. C.

1958
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For sale by the Superintendent of Documents, U. 8. Government Printing Office

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Distribution of Meteoritic Debris About the

Arizona Meteorite Crater1

By John S. Rinehart2

The meteorite crater in northern Arizona, an

outstanding topographic feature of the earth's

surface, is the earth's largest authenticated

meteorite crater. It is a large bowl-like depression lying in a sandy semiarid region of

northern Arizona which is readily accessible by

car. In outline, the crater is a rough square,

about 4,100 feet across and 600 feet deep, with

an elevated rim rising 160 feet above the surrounding plain.

The crater has been well known since 1870.

By 1909 it had been exhaustively described

(Gilbert, 1896; Barringer, 1905, 1909; Tilghman, 1905; Merrill, 1908) and most serious investigators agreed with the view that it had

been blasted out by the impact of a large meteorite. Numerous surveys have been made

since then with various objectives. The chief

surveys were those of Barringer (1914) and

Barringer, Jr. (1927), who were intent upon

locating and, if possible, recovering the large

meteorite that made the crater; and of Nininger

(1951; 1956).

In a recent book Nininger (1956) has given

an excellent description of the researches and

surveys made since the discovery of the crater,

and has critically reviewed all of the findings

to date. He also speculates on the nature of

the event that took place at the time of the

earth's encounter with the meteorite. When

did it strike? How fast was it moving? From

what direction did it come? How large was it?

Was it a single large meteorite or a swarm of

meteorites? Speculations of Barringer (1914),

1

 This work was partially supported by Contract No. AF19(604)-1901

with the Geophysics Research Directorate, Air Force Cambridge Research Center, Air Research and Development Command.

1

 Smithsonian Astrophysical Observatory and Harvard College Ob*

•ervatory, Cambridge, Mass.

Nininger (1956), and others are inconclusive in

many instances because of the great paucity of

data.

The object of the survey reported here was

to make a careful, systematic investigation of

the distribution of the minuscule bits and

pieces of meteoritic material that are scattered

through the mantle of soil surrounding the

crater, with a view to fixing more closely the

mass of the meteorite that made the crater and

its direction of flight. Our study arose from a

suggestion by Nininger (1951), whose exploratory survey of the distribution of this material

indicated that the amount might total several

thousand tons, a weight many times greater

than the 20 to 30 tons of meteorites that have

been picked up in the surrounding territory

thus far.

To carry out this survey, the Smithsonian

Astrophysical Observatory sent an expedition

into the field during the summer of 1956. This

paper describes the results obtained.

Processing the soil sample

The expedition collected and processed some

700 soil samples. Developing techniques to

extract the meteoritic material from the samples was a major problem. Nininger's method

had employed a magnet, dragged through the

soil. The adhering magnetic material was then

collected from the magnet and separated by

hand, or by the use of an inclined surface

which divided spherical particles from those of

more irregular shape. A disadvantage of this

technique is that it collects both weakly and

strongly magnetic material, although none of

the weakly magnetic material has been found

145
146 SMITHSONIAN CONTRIBUTIONS TO ASTROPHYSICS VOL.2

to be of meteoritic origin. Such material, for

example, never gives a positive test for nickel.

Since it seemed unwise to collect such material even in a preliminary extraction, and since

we were interested only in the total amount of

meteoritic material present whether its shape

was flaky, chunky, or spheroidal, we did not

use Nininger's method, but developed a special

magnetic separator which is shown schematically in figure 1.

samples sometimes varied by several hundred

grams. This volume of dirt can be put conveniently into two paper quart containers, and

was found to contain amounts of meteoritic

material entirely adequate for the determinations. In taking a sample, we first scraped

away about an inch of surface dirt, vegetable

matter, and rocks, and then with a shovel

scooped up enough soil to fill our containers.

Each sample was labeled at the site and brought

FIGURE 1.—Magnetic separator, shown schematically.

The separator consists basically of a vibrating hopper and a slanted trough down which

the soil moves under the combined action of

gravity and vibration. The trough is about

one inch wide and two feet long. Three strong

alnico magnets are suspended above the trough.

As the soil moves downward, the magnetic

material flies up and adheres to the suspended

magnets. This method readily differentiates

between weakly and strongly magnetic material, for the separation between magnet and

trough is adjusted so that only the strongly

magnetic material flies up. This technique

worked especially well in the present instance

because the unwanted constituents were, for

the most part, only weakly magnetic and the

line of demarkation between the two was very

pronounced.

Various criteria for choosing the amount of

soil to be processed were considered, and we

fixed on a volume weighing about 2,000 grams

on the average, as best, although individual

back to the laboratory where we separated it

into four groups according to size by shaking

it down in a series of U. S. Standard Sieves,

Numbers 10, 40, and 100, which yielded four

components. These sieves, which are commonly

used for soil analysis, are made from woven

wire mesh; the No. 10 sieve is woven with ten

fairly coarse wires per inch; the No. 100 with

100 fine wires per inch.

All material larger than 2 mm in diameter

was caught on the No. 10 sieve; this fraction

contained stones, clods of dirt, vegetable matter, etc., and was always discarded. Some

meteoritic material was lost in this way; its

amount is roughly estimated in a later section.

The material that passed the No. 10 sieve and

was caught on the No. 40, referred to here as

size 40 material, was between 2 mm and 0.42

mm in diameter, about the size of coarse sand.

To be caught on the No. 100 sieve the particles

(referred to henceforth as size 100) must be as

large as 0.149 mm in diameter. The residue,
METEORITIC DEBRIS AT THE ARIZONA CRATER 147

or size "pan" particles, were then all less than

0.149 mm in diameter. The No. 10 fraction

averaged 17 percent by weight of the sample.

The remainder of the material was usually divided approximately equally among the other

three fractions. During the early stages of the

program, each of these was run through the

magnetic separator individually.

The sieving accomplished two things: it insured that large particles of soil or sand did not

seriously interfere with the extraction of small

magnetic particles while being processed in the

separator; and it enabled us to study the relative abundances of nonmeteoritic magnetic materials, which, from our point of view, were

contaminants.

The magnets collected three types of strongly

magnetic material: a meteoritic particle that

consisted mostly of nickel-iron; a meteoritic

iron-oxide particle; and a black, shiny particle.

In addition, many particles were a cross between the first two types: patches or veins of

iron-oxide would contain bits of unoxidized iron.

Some dirt and a thin layer of yellow limonite

adhered to the meteoritic particles. The black,

shiny particles were probably bits of magnetite.

The three types are most easily identified by

mounting them in plastic and then grinding the

plastic so that the particles are seen in crosssection. The copper from a copper sulfate solution plates out immediately on the iron particles

so that these can easily be distinguished from

iron-oxide particles although both have a metallic lustre. The relative percentages of each

type of material varied among the size groups.

The meteoritic particles had various shapes:

flakes, angular chunks, and ball-like masses.

No very serious attempt was made to classify

them because Nininger (1956) has already done

so well in this regard. A portion of each sample

was mounted in plastic, and many of the

specimens were polished and inspected to make

sure that the contents of each sample were

principally meteoritic.

About one particle in every ten of the size 40

group was wholly nickel-iron in samples whose

concentration of meteoritic material was high.

This ratio varied a great deal however from

sample to sample. Only a few particles were

of the black, shiny type; the amount of this

contaminant was much greater in the smaller

sizes, with the No. 100 component containing

about 15 percent. The "pan" material was

found to be so highly contaminated that we

could not determine the exact amount of meteoritic material present, but examination under

a microscope showed that meteoritic fragments

formed an exceedingly small percentage of the

total magnetic component.

The correlation between the percentage of

meteoritic debris in the finer material (size

100) and that in the coarser material (size 40)

was found to be quite good; values for a number

of representative samples are plotted in figure 2.

O.l 0.2

SIZE 40 (PERCENT)

0.3

FIGURE 2.—Correlation between percents of size 100 and size

40 materials. Each point represents an individual sample.

Ordinate is the percentage of size 100 material in the sample;

abscissa is the percentage of size 40 material.

The abscissa is the percent by weight of meteoritic material in the size 40 component of soil;

and the ordinate, the percentage in the size 100

component of the same sample. On the average, the concentration in the size 40 fraction

is seen to be roughly two and one-half times

that in the size 100 fraction. A similar plot

of size "pan" versus size 40 showed only a very

slight correlation between the two, indicating

that a high percentage of the pan magnetic

material was nonmeteoritic. Usually, although

not always, the nickel test was negative with

the pan material.

Sampling procedure

The objective of the expedition was to sample

the entire area surrounding the crater and thus

determine as accurately as feasible the distribution of meteoritic debris. Many factors

influenced the manner of sampling and the
148 SMITHSONIAN CONTRIBUTIONS TO ASTROPHYSICS TOL.I

number of samples made. Because of 'united

time and funds, we decided to sample sparsely

over a wide area rather than intensively over

a small region, and to take mainly surface

samples, relying on a few representative holes

for an indication of the vertical distribution of

material. We were anxious that our sampling

area be large enough so that at its periphery

the concentration of meteoritic material would

be negligible. Our procedure was to begin in

areas where we knew the concentration to be

high and work out from these as far as we

needed to.

Approximately 700 samples were taken from

the locations shown in figure 3. The pattern is

roughly a grid of 80 square miles with the crater

near its center. The locations were separated by

a distance of one-half mile. In the early phases

of our work we occasionally took several samples

at a single location, to check reproducibility

of results or for other purposes; in general,

however, we took two samples, about 30 feet

apart. Each of these two samples was processed

individually in order to obtain a rough indication of the local variation or irregularity in

concentration. The two values were averaged

for most purposes.

With the first 60 or 70 samples, we processed

all fractions, except the size 10. It soon became clear, however, that processing the "pan"

gave no reliable information because it was

highly contaminated with nonmeteoritic material so this was abandoned. For most samples,

II Ml.-

8 Ml.

o o o o o o o

o o o o o o o

o o o o o o o

o • o

o • o

o • o

o o o o o

o o o o o

o o o o o

FIGURE 3.—Location* of sampling points. The crater is indicated at center. Open circles indicate surface points; solid

circles, hole* dug.

• 201

• 202

• 165

• 164

• 166

• 197

• 196

• 198

200 199 171 172 170 169 173 174 175 176 203 204 205 206 207

• 168

• 167 f_ ^ .

I MILE

FIGURE 4.—Locations and sample numbers of holes due.

therefore, meteoritic material was recovered

only from the size 40 and size 100 fractions.

The first step in processing was the careful

weighing of each soil fraction. The magnetic

component extracted from each fraction was

weighed on an analytical balance and the percentage of meteoritic material computed. These

percentages are listed in table 1 for all size 40

and size 100 samples; figure 9 shows their

locations.

To study the vertical distribution of material,

we dug to bedrock at 25 locations, shown in

figure 4, and sampled the soil every few inches

along the wall of the hole. Great care was

taken not to contaminate a sample with dirt

from some other part of the hole. The two

lines of holes were chosen so as to traverse areas

that could be considered representative of the

whole region over which surface samples were

taken. Bedrock was usually only one to three

feet below the surface. In most holes the

amount of meteoritic material decreased rapidly with depth in an approximately exponential

fashion. In a few holes the concentration remained about constant from top to bottom.

The distribution within each hole is shown in

figure 5. Detailed data are listed in table 2.

Estimate of total mass of meteoritic material

The data obtained provide the basis for estimating the total quantity of meteoritic^material around the crater. Such an estimate

suggests a minimum value for the mass of the

meteorite that produced the crater. The percentages of size 40 magnetic material are the
METEORITIC DEBRIS AT THE ARIZONA CRATER 149

196 198 175 166

0

0

10

to

so

-1

- 5

1

DEI

ZOO

i

199

k

\

171

f

I

4 -0.40%—

172

^ \

170

, •

1

If

f *

1

1

1

 <

169

j

|

t

173

?

BEDF

174

/

i

175

1

1

1

I

;

/

/

176

1

w

2 0 3

f

I

1

\ '•

1

\

j

--0.40%—

2 0 4

J

/

1

1

/

205

7 'v

•4

206

/

4

207

FIGURE 5.—Vertical distribution of meteoritic debris in each hole; sample numbers are given at the top.

most reliable, and we have therefore used them

throughout as primary data.

To estimate the total weight, W, we evaluate

the integral

W= ^ PmdV (1)

by soil of mass S is given by

(2)

where pm is the density (gm/cc or lb/ft3) of

meteoritic material. This density of course

varies from point to point. The volume over

which the integration is carried out is the

mantle of soil around the crater.

Certain assumptions and a number of approximations, some very good and others quite

rough, must be made in order to carry out the

integration.

First, we establish a standard soil sample.

By weight this sample consists of 17 percent

size 10 fraction, 25 percent size 40 fraction, 30

percent size 100, and 28 percent size "pan."

These percentages were obtained by averaging

values from the 700 samples taken.

Second, we assume that in situ the soil has a

void ratio of 1/3 so that the volume, V, occupied

where p is the average density of the soil

particles themselves. Since the soil is mostly

quartz sand we take p equal to 2.65 gm/cc or

2.65X62.4 lb/ft.3

Third, since the size 10 magnetic component

was not measured and the size 100 and size

"pan" were unduly contaminated with nonmeteoritic material, we must infer the amounts

of size 10, size 100, and size "pan," from determination of the amount of size 40 meteoritic

material. The amount of size "pan" was taken

as zero since there was so little correlation between size 40 and size "pan." The amount of

size 100 component, as indicated in figure 2,

averaged about 0.4 that of size 40. The size

10 fraction of soil usually consisted of small

clods of dirt which broke up into sizes 40, 100,

and "pan" when crushed. Hence we assumed

that the amount of meteoritic material could

best be approximated by taking it as equal to
150

SMITHSONIAN CONTRIBUTIONS TO ASTROPHYSICS TOI.I

the average of the other three components.

Summarizing, we have

mp=0

=O. 4 TO40

where mp is the mass of size "pan" meteoritic

material in the sample of total mass S; mm, the

mass of size 40; m100, the mass of size 100; and

r»io, the mass of size 10. Our final estimate for

the total mass, m, of meteoritic material in a

soil sample of mass S is the sum of the masses

of the individual fractions or

7Jl=1.9 WI40

Now, as mentioned above

#40=0.25 S

where S40 is the mass of the size 40 fraction of

the soil so that

m=0 5 m*° 9 (Xi

040

Combining equations (1), (2), and (3) we have

which can be integrated if we know only the

ratio, wi«//Sr«o, for each point.

Fourth, while this ratio is well established

at the surface of the soil mantle, we need to

make some assumptions regarding the variation

with depth. The vertical distribution of meteoritic material within the holes shows that the

density decays roughly exponentially with

depth and is reasonably well represented by the

equation

P«=P»O1-

44' (5)

where /»«o is the density of meteoritic material

at the surface and y is distance in feet below

the surface. The constant in the exponent was

chosen so that pm would be equal to %pm for y=

}i ft. The choice is in good accord with the

observations made in the 25 holes.

Fifth, we assume that the average depth of

the mantle is two feet. The exact depth is not

critical because the density of meteoritic material falls off so rapidly with depth; at two feet

it is only 0.06 the surface density. The average

density, pm<| , in a mantle of this depth is

If

m

<"=2j0

With these assumptions we can now perform

the integration. We have according to equation (4)

where (-~^ ) is the average value of the ratio

\04o/<

for the volume element Vt of the mantle. Now

Vi can be replaced by 2 At where Ai is a surface

element of the mantle expressed in square feel

and (-sr9) can be replaced by ^55 ( TET5 )

\O40 / i *-OO \O40 /st

where the subscript s denotes the surface value

of the ratio. Substituting these values into

equation (7) we have the weight in pounds,

The value of the summation is most easily

computed from the chart in figure 6 which gives

average values of the ratio for segments of area.

We find that

^

o > ) yl,=6.46X105

ft2.

Substituting, we have

W= 38.2 X 6.46 X10s

=24.7X106lb,

or

= 12,000 tons.

Thus the total amount of finely divided meteoritic material present in the soil is about 12,000

tons. However, this figure is subject to a still

further uncertainty. We noted that about 90
METEORITIC DEBRIS AT THE ARIZONA CRATER 151

percent of the meteoritic material that we

collected is iron-oxide, FeaO4, and contained

27.6 percent oxygen by weight. Thus, about

one-quarter of the above estimated mass is

very likely terrestrial oxygen that combined

with the meteoric iron after its encounter with

the earth.

Further, there seems to be no way to allow

precisely for the amount of contaminating material present. Increasing the area of the soil

mantle over which the integration was taken

enlarges the error caused by contamination

since in the outlying regions the ratio between

contaminant and meteoritic material becomes

ever larger. We have tried to choose an area

that minimizes the effects of contaminants but

at the same time includes almost all of the

meteoritic material. It will be noted, however, that even for the area chosen, the density

of magnetic material falls off less rapidly than

1/r2 (r equals distance from center of crater) and

the integral does not converge. At distances

of over about two miles from the crater the

percentages given on the chart are little if any

higher than the background contamination

which on the average ranged from 0.002 to

0.005 percent. To obtain a true measure of

the meteoritic material, the percentage in each

segment should be reduced by this amount.

When this is done our computed mass of 12,000

tons is reduced by about 10 to 20 percent.

Distribution of meteoritic debris

The distribution pattern of the meteoritic

debris around the crater is shown in figure 7,

based on the data for the size 40 material

MILES

FIGURE 6.—Average percentages of size 40 meteoritic material in the soil around the crater.
152 SMITHSONIAN CONTRIBUTIONS TO ASTROPHYSICS VOL.2

(given in table 1). The contour lines show

areas having equal densities of debris; the solid

lines represent 0.1 percent changes. The

broken lines indicate the 0.05 percent level.

The chart indicates several things. First,

the debris itself lies in a perfectly definite

pattern. Second, the crater itself does not lie

at the center of the pattern. Third, the debris

is symmetrically distributed about a line that

runs somewhat north of east. Its exact position is hard to fix more specifically from our data, but the outside limits are due east and 45°

north of east. Fourth, the distribution, while

symmetrical, is not smooth, but contains several

local areas in which the density of meteoritic

material is high. And, fifth, there is a concentration of material to the east of the crater.

Although the definite pattern of debris was

not surprising, it was encouraging, for it represents evidence that our data were not seriously

distorted by sample contamination with terrestrial magnetic material. The symmetry of

the pattern, its relationship to the crater, and

the localization of material are our most significant results, and will be discussed later.

It is interesting to speculate on how the meteoritic debris reached the points where it is

found today. The two chief hypotheses are:

the material fell to its present location shortly

before, just at, or shortly after, the instant of

the meteor's impact; or the material was deposited, after the impact, by the action of wind

and water or other carriers. The very close

similarity between the distribution of ponderable chunks of meteoritic material, as shown in

Barringer's (1909) chart, and the distribution of

minute pieces as determined by our survey, constitutes strong evidence pointing to the first

as the most probable hypothesis.

Nininger (1956) has suggested that a strong

wind was blowing at the time of the meteor's

impact, and that the meteoritic debris represents condensation products from a vast metallic

cloud rising vertically from the crater and distributed asymmetrically about the crater by the

wind. OUT survey does not support this theory,

FIGURE 7.—Distribution pattern of meteoritic debris around the crater. Contour lines indicate areas of equal density, given in

percents; solid lines represent 0.1 percent changes; broken lines indicate the 0.05 percent level.
METEORITIC DEBRIS AT THE ARIZONA CRATER 153

however; it is not easy to imagine a wind strong

enough to propel large chunks and minute

pieces of the same material in exactly the same

direction and for the same distance. The

present juxtaposition of the two classes of material while not irrefutable evidence, certainly

strongly suggests that both were deposited at

the same time, and that any subsequent shifting

by the wind has been negligible. Many of the

bits are probably remnants of ponderable

chunks.

Shifting of the material by the wind over the

centuries is a reasonable thing to postulate, and,

in fact, the direction of the observed asymmetry

is that of the prevailing wind. Another possibility which must be considered is that the

vaporized metal condensed in droplets which

fell with radial symmetry about thecraterand

were subsequently blown northeasterly by the

wind. The asymmetrical distribution of the

large chunks, however, cannot be explained on

this basis. If wind were a factor we might

expect that the bits would be sorted by weight;

no evidence of such a sorting was found.

A highly reasonable hypothesis is that the

meteorite approached the earth from a southwesterly direction and, when it struck, pitched

forward large quantities of meteoritic material

to the position where it now rests. (Such a

shoveling action occurs frequently with obliquely impacting high speed missiles.) Orbital

arguments do not favor any particular direction

of encounter except possibly east-west (or westeast) slightly over north-south (or south-north).

When the meteorite struck it must have been

almost completely shattered, into pieces that

weighed from a thousand pounds or so downward. No piece larger than 2000 pounds has

ever been found (Barringer, 1914) while thousands of smaller pieces weighing a few ounces

or less have been recovered. Much melting and

considerable vaporization would have accompanied this shattering. It seems unlikely, however, that much of the vaporized material would

have condensed into metallic droplets. More

probably, it would have oxidized and drifted

off as a fine powder. On the other hand, the

sprays of molten material would probably have

moved along with the solid fragments so that

deposition of molten (which of course would

quickly solidify) and of solid fragments would

have occurred at the same time.3

Eventually, of course, both forms of material

would gradually have disintegrated, by a

process of oxidation and subsequent exfoliation.

The taenite, being more resistant to oxidation

than the kamacite, would be the last to go. It

is significant that Nininger finds that the metallic bits contain about 17 percent nickel, a

composition compatible with that of taenite.

Thus, one would expect to find in the soil

minute pieces of both oxide and metallic

matter, and even to find them intimately

mixed. The observed variety in particle shape

is likewise consistent with the view that these

bits are, in the main, remnants of larger chunks

of meteoritic material. The exact nature of

the bits is still being intensively studied and

they will be described in a later report.

The several local areas of high concentration

indicate that the rain of meteoritic debris was

spotty. Each area would then represent a

region in which a large swarm of fragments fell

after being ejected from the crater. This

theory receives strong support from the data

yielded by our pairs of samples. Recall that

two samples, about 30 feet apart, were taken

from each location; and the percentage of

meteoritic material in the two often differed

by a factor of two or three, and had no relation

to local irregularities of terrain. Local wind

eddies may have affected the distribution

slightly. Such highly localized variation in the

distribution indicates a second order patchiness

of the ejecta that is entirely consistent with our

knowledge of the phenomena of high speed

impact.

• E. P. Henderson, of tbe U. S. National Museum, after reading this

paper in manuscript, made the following comment:

"Possibly the mass that made the crater had some satellite masses.

These, being smaller, were retarded during the fall through our atmosphere, so possibly they fell outside the area of the crater. Being small,

they did not make a crater. Tbe crater-forming mass retained its velocity and was ablating until tbe moment of impact. Quantities of

material were removed and carried into the turbulent wake of tbe meteorite. Since these pieces were small, their velocity was quickly lost.

They should settle to the ground at a considerable distance short of the

end point of the large crater-producing mass. It would seem that such

material should be tracked almost up to the rim of the crater. On the

opposite side and in line with the trajectory of the falling meteorite, one

should get pieces that broke from the large meteorite and rocks that

were tossed out of the crater. This point was stressed earlier in the

paper."
154 SMITHSONIAN CONTRIBUTIONS TO ASTROPHYSICS VOL.2

The direction of impact

The fact that the meteoritic debris is distributed

symmetrically about a line gives us the direction

but not necessarily the sense of the trajectory

of the meteorite. Experience with the effects

of high speed impact shows that one can unambiguously associate symmetry of the ejected

missile and impact debris with direction of

impact. The axis of symmetry and the trajectory of the missile always lie in the same

plane. The same situation must obtain here.

Thus, if we assume that the debris now lies

where it originally fell, then there is little doubt

that the meteorite approached the earth along

the axis of symmetry of our pattern: roughly,

north of east or south of west.

Whether the approach was from the east or

from the west is debatable. If the meteorite

approached its point of impact at a steep angle

from the east, shedding material as it neared

the ground, deposited a substantial amount of

debris to the east of the crater and then buried

itself beneath the floor of the crater, it could

now lie under the southwest corner of the crater.

The assumption of a steep approach would be

required to account for the fact that very little

meteoritic material is found to the west of the

crater although a large field of ejected boulders

lies on this side. On the other hand, the

meteorite could well have approached from the

west and thrown debris forward, to the east,

where we find an even greater accumulation of

large fragmented limestone boulders and other

ejecta than on the west. The boulders east of

the crater have been thrown farther than on the

west, in some cases two or three miles (Barringer, 1909, 1914). A western approach

would not require us to assume so steep an

angle of impact since we are now permitted to

assume also that meteoritic material was

thrown forward by the force of the impact.

The evidence for a western approach is therefore the stronger.

Impactite and rock flour are other forms of

ejecta (Merrill, 1908; Nininger, 1954). Impactite is sandstone metamorphosed by the intense

heat of the impact, and impregnated with fine

bits of meteoritic material and, occasionally,

bits of limestone. Two large patches have

been found, southeast and northwest of the

crater. The sandstone from which this material

was made lies deep in the crater. Rock flour is

similar sandstone that was ground to fine

powder at the time of impact. Large quantities lie within and piled more or less uniformly

around the rim of the crater (Barringer, 1909).

Large masses of meteoritic oxide and meteorites

are occasionally found embedded in it. It is

not at all obvious how the impactite and rock

flour got to their present position. They probably were thrown out immediately after the

limestone boulders and meteoritic debris were

ejected, although it is difficult to demonstrate

this conclusively.

The structures of recovered meteorites also

suggest an approach from the southwest or

west. Meteorites found to the east and northeast of the crater have been severely altered by

heat and deformation. Those found far out on

the plain to the southwest and west, however,

are in their virgin state (Nininger, 1956), and

may well be pieces that broke from the meteorite

as it approached from the west. Usually these

specimens are fairly large and are sparsely

distributed.

Heretofore, it has been postulated that the

meteorite approached from a north-northwesterly direction (Barringer, 1909, 1914; Nininger,

1956). This conclusion was based, at first,

on a reconnaissance examination of the tilting

of the rock strata; later, on extensive drillings

made in the crater and on its south rim; and

finally, on magnetic, electrical, and gravimetric

surveys. These data are difficult to evaluate.

Many investigators have attempted to do so

and much of what has been written is naturally

conjectural. The magnetic, electrical, and

gravimetric surveys seem, in spite of some

contradictory evidence, to favor a southwest

to northeast direction. The observed anomalies, shown in figure 8 (from Nininger, 1956),

are not pronounced but they all seem to lie

either in or beyond the southwest part of the

crater.

Barringer made extensive drillings over a

long period of years, and thus established the

fact that large masses of fragmented rock lie

buried beneath the floor and south rim of the

crater. Since drillings have not been made at

other locations we have no way of knowing how

much fragmented rock lies beneath the east,

north, and west rims, and we know very little
METEORITIC DEBRIS AT THE ARIZONA CRATER 155

*-•»«.„*/

FIGURE 8.—Results of various geophysical surveys of crater.

about the shape of the subsurface region that

was shattered by the impact. Further data

on this point could be of very great help in

establishing the direction of impact.

As well as we can determine, the only study

of the tilting of strata was a reconnaissance

surface examination made by Barringer (1909)

whose findings have been summarized by

Watson (1936):

The least amount of tilt is found in the northern

wall. The slope increases along both the eastern and

western walls, until in the southeast and southwest

the strata are practically vertical. In contrast to the

strata so tilted, and separated from them by an abrupt

discontinuity, there occurs, along the rim slightly east

of south, a broad arch, 2,700 feet long, the almost flat

strata of which have been raised vertically about 100

feet. The arch appears to be a localized uplift possibly

due to steam explosion subsequent to the complete

deceleration of the penetrating body. The peculiarity

of the tilting combined with the rock structure beneath

the crater, suggests that the impact was not vertical,

as previously supposed, but at a considerable slant

from the north.

Location of meteoritic mass as concluded by Barringer

surveys and drillings up to 1928.

Location of electrical and magnetic anomaly recorded by

Jakosky, 1939 (described as definite but weak).

Location of magnetic anomalies determined by Lundberg in

1937 (depth about 1200 to 1500 feet).

Locations of two high-density areas as indicated by gravimetric survey conducted by Roswell Miller, HI, and

financed by the Barringer Company in 1951.

Three magnetometer traverses (470 stations at 30-foot

intervals) run by A. Whelan for American Meteorite

Museum in 1947. (Only highly localized anomalies due

to near-surface materials were encountered.)

To test this theory of the direction of impact, a

churn-drill was put down through the center of the

arch in the south rim of the crater wall. Below a

depth of 1,200 feet the drill passed through a region

increasingly rich in loose meteoritic material and finally

stuck at 1,340 feet, a region very rich in nickel-iron and

exceedingly resistant to boring. The drill was slowly

forced through 30 feet of this material but it stuck and

remains completely immovable at 1,376 feet. The

behavior of the drill shows that the meteoritic penetration continued to a depth of over 1,300 feet and also

that very probably a portion of the original mass lies

buried beneath the southern rim of the crater. From

the position of this mass, the various depths of the

undisturbed strata under the crater, and the symmetrical

tilting of the crater walls around the north-south axis,

it was concluded by the Barringers and their associates

that the body struck from the north and at an angle of

approximately 45°.

It is hard to appreciate, however, what these

tilt measurements do in fact signify. They

show us only the condition at the surface and

leave us completely in the dark as to how much

tilting and faulting has occurred below the

surface. Our best evidence on this point is the
156 SMITHSONIAN CONTRIBUTIONS TO ASTROPHYSICS

overall shape of the rim of the crater. The

rim rises above the surrounding plain to a

height, about 160 feet, which is almost the same

at all points. The rock strata are completely

exposed along the crest of the rim. The strata

and the general area of the crater lie more or

less horizontally although they dip slightly to

the north. The uniformly high rim must mean

that gross tilting and faulting are about the

same all around the rim.

This situation is not surprising. At the

meteorite's impact, one would expect the strata

to fragment rather than to tilt, and tilting

would be in the form of faulting, not bending,

which can be accomplished only under slow

application of load. Fragmentation or faulting

would radiate out from the point of impact and

would cease only when the stress of impact had

decayed to a value less than the fracture

strength of the rock. Oblique impact into

a perfectly brittle, homogeneous, isotropic

medium would produce no rim at all. In

a plastic medium, such as steel, a flow of

material would occur and a rim would be built

up very asymmetrical in height which would

be greatest on the side away from that of the

missile's approach. The rim would possess a

bilateral symmetry about a line parallel to the

trajectory of the impacting missile.

In the case of the Arizona Meteorite Crater,

the mechanical properties of the strata in situ

must play an important role in influencing the

configuration that the strata assume after impact (see Hager, 1953, for a detailed discussion

of the strata). The general drift of the strata

is in a northerly direction. It is reasonable to

suppose that the mechanical properties of the

strata in situ possess an anisotropy which is

directly related to this northerly dip, and could

easily cause a failure pattern of the rock to

assume an east-west symmetry. The pattern

1

313

3M

MS

302

3OI

3 0 0

2 99

303

3 0 4

312

305

— •

306

307

301

309

3D

311

1

1

265

284

283

262

281

2 8 0

279

2 8 9

2 9 0

291

292

•

293

2 9 4

270

236

2*7

298

1

1

286 287

288

255

254

253

252

251

. 278

277

276

275

•

274

292

273

270

221

268

1

1

319

320

69

7 0

71

72

73

7 4

77

9 9

98

97

9 6

243 242

267 266

1

318

6 8

177

8 4

•85

a

83

8 8

179

91

181

9 5

241

269

1

317

321

67

7 8

83

85

8 0

86

76

87

8 9

92

9 3

2 4 0

265

1

316

4 0

186

8 2

182

7 9

82

75

178

9 0

180

9 4

239

2 6 4

2 5 0

249

39

41

4 2

4 3

4 4

4 5

46 \

47

4 8

4 9

5 0

237

2 6 3

1

248

38

187

5 8

188

57

7RATER

195

63

194

53

238

262

1

245

244

54

56

13

15

.

6 0

5 9

62

6 4

6 6

51

2 3 6

261

1

2 4 6

55

190

II

129

3

191

61

192

65

193

52

235

2 6 0

1

247

324

17

n

9

7

5

19

2 0

21

22

23

2 4

234

2 59

1

25

2 0 8

100

2 0 0

101

210

102

211

103

212

37

233

258

1

2 6

27

28

2 9

30

31

32

33

3 4

35

36

232

257

1

153

213

151

214

120

215

125

216

129

217

134

231

256

1

152

147

148

150

122

123

124

127

128

131

132

163

160

161

159

1

146

2 2 4

149

223

121

222

126

221

130

220

133

218

162

219

158

1

NORTH

145

144

143

142

140

141

139

138

137

136

135 322

154

155 323

156

157 230

1

1

225

226

227

228

231

1

FIGURE 9.—Locations of.all sampling points. • Distance between grid lines: rmile.
NO. 7 METEORITIC DEBRIS AT THE ARIZONA CRATER 157

might therefore bear little relationship to the

direction of the impact.

Our argument here leaves much to be desired

in the way of completeness. It is indeed

unfortunate that we have so little experimental

data on these matters.

Evidence for large buried mass

The data presented here give no direct indication as to whether a large mass of meteoritic

material lies buried in the crater. If one accepts the low estimates, 10,000 to 15,000 tons

(Rinehart, 1950; Wylie, 1943) of the mass

needed to form the crater then no large mass

could possibly remain. If, on the other hand,

one accepts the 5,000,000 ton estimate of Opik

(1936) and of Rostoker (1953) as more realistic,

then the amount of meteoritic debris so far

recovered is insignificant and a large mass could

well lie buried. According to F. L. Whipple

(personal communication), a most reasonable

mass is that given recently by Hill and Gilvarry

(1956), between 80,000 and 400,000 tons.

TABLE 1.—Horizontal surface distribution of meteoritic

material

TABLE 1.—Horizontal surface distribution of meteoritic

material—Continued

Location of

sample (see

fig. 9)

1

3

5

7

9

11

13

15

17

18

19

20

21

22

23

24

25

26

27

28

29

30

31

32

33

34

35

36

37

38

39

40

41

42

43

44

46

46

47

Percent b y weight of magnetic material

SUe 40

In samples

.078

.206

.328

.303

.004

.012

.022

.230

.0119

.0331

.0532

.0580

.1090

.0129

.2960

.1565

.0047

.0023

.0055

.0075

.0332

.1876

.2820

.0412

.1105

.0502

.0011

.0800

.0400

.0013

.0008

.0030

.0022

.0066

.0002

.0561

.0741

.1295

.0059

.076

.211

.218

.838

.004

.032

.009

.112

.0166

.0199

.2840

.0633

.0478

.0063

.0796

.3660

.0029

.0020

.0024

.0054

.0753

.6300

.1456

.0169

.0833

.0447

.0033

.0914

.0488

.0015

.0006

.0026

0021

.0031

.0020

.1568

.0707

.0053

.0236

Average

.077

.208

.273

.570

.004

.022

.016

.171

.0142

.0265

.1686

.0606

.0779

.0096

.1878

.2612

.0038

.0022

.0040

.0064

.0542

.4088

.2138

.0290

.0969

.0474

.0022

.0857

.0444

.0014

.0007

.0028

.0022

.0048

.0011

.1064

.0724

.0674

.0148

Size 100

In samples

.025

.077

.136

.089

.018

.011

.019

.097

.0198

.0334

.0779

.0332

.0865

.0268

.0575

.0456

.0111

.0098

.0244

.0209

.0522

.2050

.1298

.0162

.0651

.0463

.0175

.0570

.0723

.0097

.0018

.0292

.0088

.0113

.0008

.0125

.0124

.0184

.0061

.026

.096

.104

.112

.014

.019

.011

.057

.0262

.0245

.1434

.0351

.0606

.0119

.0566

.0591

.0107

.0126

.0150

.0135

.0637

.5490

.1020

.0093

.0541

.0569

.0269

.0604

.0606

.0069

.0067

.0063

.0072

.0261

.0019

.0107

.0417

.0084

.0212

Average

.026

.086

.120

.100

.016

.015

.015

.077

.0230

.0290

.1106

.0342

.0736

.0194

.0570

.0524

.0109

.0112

.0197

.0172

.0580

.3770

.1159

.0128

.0596

.0516

.0222

.0587

.0664

.0078

.0042

.0178

.0080

.0187

.0014

.0116

.0270

.0134

.0138

Location of

sample (see

fig. 9)

48

49

50

51

52

53

54

55

56

57

58

59

60

61

62

63

64

65

66

67

68

69

70

71

72

73

74

75

76

77

78

79

80

81

82

83

84

85

86

87

88

89

90

91

92

93

94

95

96

97

98

99

100

101

102

103

104

105

106

107

108

109

110

111

112

113

114

115

116

117

118

119

120

121

122

123

124

125

126

127

128

129

130

131

132

133

134

135

Percent b y weight of magnetic material

Size 40

In samples

.0277

.0115

.0022

.0611

.0056

.0236

.0700

.0069

.0054

.0949

.0023

.0254

.1124

.6280

.1348

.1655

.0607

.0456

.0072

.0004

.0020

.0014

.0206

.0160

.0064

.0147

.0332

.0276

.0089

.0046

.0874

.0100

.0136

.0012

.0062

.0076

.0128

.0124

.0561

.0765

.0169

.0453

.0124

.0053

.0005

.0144

.0203

.0108

.0030

.0191

.0411

.3850

.0263

.0433

.0005

.0008

.0013

.0008

.0001

.0010

.0005

.0004

.0001

.0007

.0590

.0009

.0000

.0009

.0014

.0253

.0062

.0001

.0085

.0025

.0012

.0048

.0000

.0044

.0103

.0000

.0070

.0007

.0011

.0004

.0159

.0366

.0195

.0008

.0123

.0032

.0218

.1007

.0035

.0065

.0789

.0055

.0333

.0850

.4150

.1922

.1438

.1290

.0361

.0073

.0002

.0013

.0015

.0154

.0175

.0062

.0146

.0138

.0311

.0005

.0027

.0120

.0063

.0110

.0014

.0004

.0007

.0178

.0131

.0897

.0698

.0849

.0143

.0103

.0050

.0003

.0241

.0122

.0077

.0094

.0128

.0846

.0611

.0177

.0322

.0000

.0004

.0026

.0002

.0004

.0029

.0084

.0004

.0008

.0006

.0003

.0005

.0005

.0003

.0005

.0313

.0051

.0019

.0095

.0098

.0012

.0019

.0035

.0008

.0281

.0002

.0023

.0003

.0005

.0007

.0047

Average

.0322

.0155

.0015

.0367

.0044

.0227

.0854

.0052

.0060

.0869

.0039

.0294

.0987

.5215

.1635

.1546

.0948

.0408

.0072

.0003

.0016

.0014

.0180

.0168

.0063

.0146

.0235

.0294

.0047

.0037

.0497

.0082

.0123

.0013

.0078

.0042

.0153

.0128

.0729

.0682

.0509

.0298

.0114

.0052

.0004

.0192

.0162

.0092

.0062

.0160

.0628

.2230

.0220

.0378

.0002

.0006

.0020

.0005

.0002

.0020

.0044

—

.0006

.0004

.0005

.0007

.0002

.0006

.0010

.0283

.0056

.0010

.0090

.0062

.0012

.0034

.0018

.0026

.0192

.0001

.0046

.0005

.0008

.0006

.0103

Sice 100

In samples

.0251

.0181

.0027

.1190

.0264

.0845

.0267

.0145

.0058

.0624

.0032

.0214

.0204

.0217

.0197

—

.0542

.0230

—

.0047

.0017

.0264

.0483

.0146

.0112

.0203

.0155

.0507

.0124

.0148

.0418

.0126

.0118

.0085

.0459

.0107

.0234

.0132

.0226

.0462

.0143

.0464

.0138

.0090

.0033

.0239

.0289

.0158

.0111

.0621

.0434

.0299

.0274

.0214

.0002

.0004

.0000

—

.0005

.0011

.0005

.0005

—

.0008

.0004

.0009

.0012

.0001

.0005

.0106

.0096

.0018

.0024

.0209

.0028

.0023

.0038

.0011

.0029

.0391

.0013

.0054

.0016

.0046

.0039

.0154

.0128

.0246

.0059

.0062

.0039

.0502

.0588

.0130

.0130

.0054

.0023

.0064

.0042

.1395

.0530

—

.1200

.0309

.0106

.0010

.0017

.0153

.0157

.0389

.0214

.0228

.0347

.0257

.0037

.0202

.0140

.0264

.0208

.0078

.0332

.0107

.0314

.0262

.0627

.0402

.0097

.0206

.0303

.0130

.0007

.0404

.0082

.0248

.0086

.0126

.0995

.0443

.0128

.0138

—

.0020

.0066

.0004

.0003

.0002

—

.0001

.0030

.0014

.0005

.0009

.0008

.0014

.0017

.0014

.0433

.0019

.0022

.0191

.0126

.0067

.0093

.0127

.0018

.0118

.0017

.0072

.0019

.0053

.0139

.0037

Average

.0190

.0214

.0043

.0626

.0152

.0674

.0428

.0138

.0094

.0314

.0028

.0139

.0123

.0806

.0364

—

.0871

.0270

—

.0028

.0017

.0208

.0320

.0268

.0163

.0216

.0251

.0382

.0080

.0175

.0279

.0195

.0163

.0082

.0396

.0107

.0274

.0197

.0426

.0432

.0120

.0335

.0220

.0110

.0020

.0322

.0180

.0203

.0098

.0374

.0714

.0871

.0201

.0178

—

.0012

.0033

—

.0004

.0006

—

.0003

—

.0011

.0004

.0009

.0005

.0007

.0011

.0060

.0264

.0018

.0023

.0200

.0077

.0045

.0066

.0069

.0024

.0254

.0015

.0063

.0018

.0050

.0089

.0098
158

TABLE 1.-

SMITHSONIAN CONTRIBUTIONS TO ASTROPHYSICS

-Horizontal surface distribution of meleoritic

material—Continued

TABLE 1.- -Horizontal surface distribution of meteoritic

material—Continued

Location of

sample (see

fig. 9)

196

137

138

139

140

141

143

143

144

145

146

147

148

149

MO

151

153

163

154

155

156

157

1S8

159

160

161

163

163

177

178

179

180

181

183

183

In

1865

187

188

189

190

191

193

193

194

195

208

209

210

211

212

213

214

215

216

217

218

219

220

231

232

223

224

225

226

237

328

229

230

231

232

233

234

235

236

237

238

239

240

341

242

243

Percent b y weight of magnetic material

Size 40

In samples

.0015

.0003

.0002

.0065

.0010

.0016

.0003

.0000

.0017

.0013

.0049

.0010

.0012

.0045

.1760

.0244

.0018

.0067

.0933

.0061

.0001

.0023

.0000

.0039

.0013

.0068

.0003

.0003

.0009

.0125

.0113

.0118

.0157

.0191

.0004

.0032

.0056

.0017

.0043

.0231

.0017

.4830

.2160

.0158

.0042

.0376

.0083

.1595

.0087

.0523

.0307

.0057

.0035

.0045

.0189

.0009

.0008

.0017

.0002

.0180

.0065

.0024

.0006

.0000

.0008

.0125

.0042

.0010

.0030

.0009

.0005

.0288

.0001

.0154

.0003

.0203

.0117

.0090

.0032

.0099

.0023

.0068

.0114

.0004

.0018

.0070

.0027

.0067

.0007

.0002

.0074

.0007

.0016

.0067

.0045

.0003

.0048

.0230

.0004

.0031

.0512

.0007

.0007

.0020

.0006

.0012

.0018

.0202

.0000

.0002

.0036

.0157

.0159

.0035

.0080

.0138

.0004

.0035

.0034

.0032

.0108

.0766

.0110

.2490

.1169

.0557

.0167

.0265

.0103

.0659

.0083

.0620

.0568

.0034

.0063

.0054

.0062

.0020

.0007

.0029

.0007

.0147

.0013

.0003

.0017

.0000

.0005

.0002

.0005

.0039

.0025

.0002

.0003

.0269

.0017

.0172

.0000

.0129

.0056

.0110

.0023

.0073

.0040

.0066

Average

.0064

.0004

.0010

.0068

.0018

.0042

.0004

.0001

.0046

.0010

.0032

.0038

.0028

.0024

.0904

.0237

.0011

.0044

.0722

.0034

.0004

.0022

.0002

.0026

.0016

.0145

.0002

.0002

.0022

.0141

.0136

.0076

.0118

.0164

.0004

.0034

.0045

.0024

.0076

.0498

.0064

.3660

.1664

.0358

.0104

.0320

.0093

.1127

.0085

.0572

.0438

.0046

.0049

.0050

.0126

.0014

.0008

.0023

.0004

.0164

.0039

.0014

.0011

.0000

.0006

.0064

.0024

.0025

.0022

.0006

.0004

.0278

.0009

.0163

.0002

.0166

.0086

.0100

.0028

.0086

.0032

.0067

Size 100

In samples

.0221

.0025

.0089

.0318

.0004

.0158

.0037

.0009

.0037

.0022

.0003

.0173

.0006

.0028

.0269

.0292

.0005

.0047

.0121

.0049

.0059

.0088

.0012

.0159

.0007

.0096

.0022

.0013

.0030

.0068

.0038

.0072

.0235

.0030

.0024

.0011

.0097

.0015

.0048

.0127

.0020

.0314.

.0285

.0072

.0083

.0028

.0171

.0241

.0023

.0213

.0071

.0311

.0052

.0050

.0048

.0038

.0006

.0053

.0011

.0187

.0053

.0050

.0016

.0003

.0005

.0001

.0054

.0061

.0036

.0011

.0012

.0053

.0003

.0084

.0007

.0348

.0107

.0022

.0023

.0065

.0061

.0096

.0249

.0050

.0100

.0014

.0038

.0026

—

.0002

.0079

.0006

.0005

.0047

.0021

.0028

—

.0300

.0002

.0041

.0125

.0001

.0033

.0026

.0077

.0030

.0073

.0064

.0004

.0028

.0037

.0094

.0010

.0102

.0064

.0126

.0022

.0015

.0086

.0061

.0128

.0168

.0105

.0120

.0423

.0176

.0025

.0046

.0151

.0256

.0047

.0274

.0115

.0073

.0090

.0125

.0564

.0018

.0005

.0052

.0040

.0032

.0100

.0014

.0009

.0014

.0015

.0007

.0042

.0035

.0044

.0007

.0016

.0185

.0005

.0115

.0009

.0040

.0048

.0178

.0034

.0060

.0042

.0069

Average

.0235

.0038

.0094

.0166

.0021

.0092

—

.0006

.0058

.0014

.0004

.0110

.0014

.0028

—

.0296

.0004

.0044

.0123

.0025

.0046

.0057

.0044

.0094

.0040

.0080

.0013

.0020

.0033

.0081

.0024

.0087

.0150

.0078

.0023

.0013

.0092

.0038

.0088

.0148

.0062

.0217

.0354

.0124

.0054

.0037

.0161

.0248

.0035

.0244

.0093

.0192

.0071

.0088

.0305

.0028

.0006

.0052

.0026

.0110

.0076

.0032

.0012

.0008

.0010

.0004

.0048

.0048

.0040

.0009

.0014

.0119

.0004

.0100

.0008

.0144

.0078

.0100

.0028

.0062

.0052

.0082

Location of

sample (see

fig. 9)

244

245

246

247

248

249

250

251

252

253

254

255

256

257

258

259

260

261

262

263

264

265

266

267

268

269

270

271

272

273

274

276

276

277

278

279

280

281

282

283

284

285

286

287

288

289

290

291

292

293

294

295

9OA

£tfO

297

298

299

300

301

302

303

304

305

306

307

308

309

310

311

312

. 313

314

315

316

317

318

319

320

321

322

323

324

325

Percent b y weight of magnetic material

Size 40

In samples

.0013

.0019

.0065

.0006

.0001

.0001

.0005

.0066

.0109

.0188

.0142

.0039

.0006

.0013

.0225

.0065

.0002

.0005

.0112

.0068

.0114

.0370

.0023

.0018

.0014

.0032

.0035

.0008

.0055

.0182

.0099

.0098

.0080

.0171

.0264

.0042

.0180

.0024

.0114

.0214

.0049

.0171

.0064

.0098

.0066

.0133

.0057

.0074

.0050

.0082

.0009

.0092

.0623

.0117

.0032

.0060

.0058

.0049

.0066

.0031

.0036

.0196

.0037

.0140

.0048

.0152

.0344

.0005

.0100

.0075

.0021

.0013

.0026

.0016

.0012

.0129

.0029

.0045

.0005

.0040

.0015

.0016

.0081

.0006

.0002

.0007

.0023

.0066

.0086

.0056

.0083

.0063

.0007

.0036

.0390

.0008

.0011

.0027

.0080

.0042

.0106

.0329

.0027

.0042

.0025

.0014

.0022

.0014

.0106

.0203

.0093

.0116

.0044

.0113

.0162

.0093

.0118

.0172

.0043

.0165

.0187

.0042

.0174

.0100

.0154

.0115

.0043

.0109

.0050

.0085

.0024

.0069

.0197

.0340

.0094

.0060

.0272

.0085

.0080

.0049

.0017

.0095

.0121

.0241

.0038

.0190

.0146

.0009

.0037

.0100

.0072

.0000

.0104

.0081

.0022

.0034

.0052

.0002

.0002

.0006

Average

.0014

.0018

.0073

.0006

.0002

.0004

.0014

.0066

.0098

.0122

.0112

.0050

.0006

.0025

.0308

.0036

.0006

.0016

.0096

.0055

.0060

.0350

.0025

.0030

.0020

.0023

.0028

.0011

.0080

.0192

.0096

.0107

.0062

.0142

.0213

.0068

.0149

.0098

.0078

.0190

.0118

.0106

.0119

.0099

.0110

.0124

.0050

.0092

.0050

.0084

.0016

.0080

.0410

.0228

.0063

.0060

.0165

.0067

.0073

.0040

.0026

.0146

.0079

.0190

.0043

.0171

.0245

.0007

.0068

.0088

.0046

.0006

.0065

.0048

.0017

.0082

.0040

.0024

.0004

.0023

Size 100

In samples

.0119

.0132

.0462

.0104

.0003

.0058

.0017

.0065

.0094

.0349

.1361

.0925

.0015

.0029

.0257

.0088

.0036

.0029

.0098

.0215

.0041

.0046

.0039

.0023

.0020

.0010

.0040

.0007

.0062

.0123

.0094

.0113

.0050

.0123

.0212

.0082

.0093

.0474

.0398

.0196

.0162

.0302

.0158

.0162

.0224

.0193

.0028

.0079

.0077

.0090

.0099

.0050

.0093

.0181

.0377

.0306

.0396

.0432

.0035

.0083

.0039

.0068

.0074

.0040

.0021

.0027

.0047

.0007

.0053

.0076

.0056

.0057

.0038

.0039

.0076

.0151

.0017

.0022

.0008

.0050

.0057

.0196

.0262

.0026

.0007

.0030

.0013

.0140

.0148

.0409

.0728

.0464

.0014

.0016

.0089

.0008

.0027

.0166

.0226

.0059

.0041

.0131

.0042

.0038

.0047

.0026

.0033

.0014

.0062

.0073

.0130

.0262

.0080

.0242

.0171

.0026

.0050

.0296

.0189

.0320

.0072

.0229

.0069

.0276

.0321

.0140

.0063

.0042

.0074

.0304

.0132

.0063

.0284

.0052

.0334

.0231

.0545

.0206

.0083

.0022

.0047

.0294

.0174

.0030

.0020

.0113

.0000

.0007

.0123

.0058

.0079

.0016

.0013

.0067

.0051

.0099

.0021

.0011

.0008

.0024

Average

.0088

.0164

.0362

.0065

.0005

.0044

.0015

.0102

.0121

.0379

.0994

.0694

.0014

.0022

.0173

.0018

.0032

.0098

.0162

.0137

.0041

.0088

.0040

.0030

.0034

.0018

.0036

.0010

.0062

.0098

.0112

.0188

.0065

.0182

.0192

.0054

.0072

.0385

.0294

.0258

.0117

.0266

.0114

.0219

.0272

.0166

.0046

.0060

.0076

.0197

.0118

.0056

.0188

.0116

.0356

.0268

.0470

.0319

.0069

.0052

.0043

.0181

.0124

.0036

.0020

.0070

.0024

.0007

.0088

.0067

.0068

.0036

.0026

.0053

.0064

.0126

.0024

.0016

.0008

.0037
METEORITIC DEBRIS AT THE ARIZONA CRATEB 159

TABLE 2.—Distribution of meteoritic material in vertical

shafts

TABLE 2.—Distribution of meteoritic material in vertical

shafts—Continued

Location of

sample

164

165

166

167

168

169

170

171

172

173

174

175

176

196

197

198

199

200

201

202

203

204

Depth

(Inches)

0

2

12

24

0

2

12

30

0

2

18

33

0

1

6

15

0

1

6

0

1

12

21

0

1

25

54

0

1

12

27

0

1

15

33

0

1

13

27

0

1

18

39

0

1

12

39

0

1

9

0

1

15

30

0

1

9

18

0

1

21

42

0

1

7

0

1

9

0

1

6

15

0

1

18

36

0

1

13

0

1

18

45

Percent by weight

Size 40

.5600

.3500

.0590

.0084

.0035

.0033

.0011

.0017

.0748

.1600

.0118

.0054

.3930

.2050

.1400

.0455

.2220

.0788

.1360

.0834

.0630

.0036

.0054

.0320

.0435

.0033

.0002

.0032

.0603

.0274

.0013

.0054

.0056

.0003

.0001

.1295

.0810

.0756

.0635

.1654

.0924

.0430

.0250

.0179

.0103

.0036

.0018

.0736

.0570

.0378

.0751

.0990

.1630

.1425

.1748

.0903

.0171

.0426

.1218

.1031

.0039

.0032

.0297

.0081

.0080

.0072

.0101

.0069

.0052

.0048

.0103

.0164

.0212

.0122

.0010

.0008

.0105

.0221

.0223

.0287

.0060

.0006

.0066

Size 100

.0302

.1080

.0408

.0057

.0160

.0021

.0188

.0057

.0589

.0771

.0054

.0163

.0207

.0274

.0288

.0043

.0128

.0459

.0150

.0337

.0224

.0036

.0048

.0431

.0139

.0168

.0042

.0234

.0286

.0066

.0008

.0036

.0050

.0014

.0009

.0411

.0241

.0180

.0137

.0695

.0458

.0088

.0054

.0141

.0143

.0016

.0008

.0132

.0144

.0104

.0250

.0134

.0195

.0174

.0668

.0104

.0384

.0023

.0307

.0150

.0013

.0043

.0060

.0049

.0117

.0017

.0027

.0036

.0124

.0075

.0144

.0536

.0117

.0099

.0007

.0030

.0307

.0053

.0033

.0209

.0141

.0005

.0021

Location of

sample

205

206

207

Depth

(inches)

0

1

9

0

1

11

0

1

5

Percent by weight

Size 40

.0064

.0012

.0030

.0007

.0000

.0000

.0012

.0001

.0000

Size 100

.0013

.0031

.0006

.0011

.0005

.0000

.0016

.0003

.0000

Acknowledgments

In conclusion I wish gratefully to acknowledge

the assistance of several persons. The results

could not have been obtained without the

whole hearted enthusiasm and hard work, often

under trying conditions, of members of the

expedition. These were Mr. Nicholas Matalas,

Mr. Kobert O'Neil, and Mr. Robert Olson.

The helpful cooperation of Mr. Ernest Chilson,

vice president of the Bar-T-Bar Ranch, Mr.

George Foster, curator of the crater Museum,

Mr. D. Moreau Barringer of the Barringer

Crater Company and Mr. Sid Griffin of Rimmy

Jim's contributed greatly to the success of the

program. Dr. F. Behn Riggs, Jr., designed the

magnetic separator and helped in many other

ways. Mr. Paul Hodge analyzed much of the

data. Dr. Agnes M. Allen was good enough

to let us use her facilities at the Northern

Arizona State College, Flagstaff, for weighing

our samples. And finally, Dr. Fred L. Whippie's constant enthusiasm for the project and

his many stimulating suggestions and criticisms

during all phases of it were invaluable.

References

BARRINGER, D. M.

1905. Proc. Acad. Nat. Sci. Philadelphia, vol. 57,

p. 861.

1909. Paper read before the National Academy of

Sciences, at Princeton University Nov.

16, 1909. Privately printed.

1914. Proc. Acad. Nat. Sci. Philadelphia, vol. 66,

p. 556.

BARRINGER, D. M., JR.

1927. Scientific American, vol. 137, p. 52.
160 SMITHSONIAN CONTRIBUTIONS TO ASTROPHYSICS V0L2

GILBERT, G. K. OPIK, E.

1896. The Geological Society of Washington; also, 1936. Publ. de L'Observatoire Astronomique de

Science, new ser., vol. 3, p. 1. L'Universite" de Tartu, vol. 28, No. 6

HAGER, D. 27 pages.

1953. Bull. Amer. Assoc. Petroleum Geologists, RINEHART, J. S.

vol. 37, p. 821. 1950. Pop. Astron., vol. 58, p. 458.

HILL, J. E. AND GILVARRT, J. J. ROSTOKER, N.

1956. Journ. Geophys. Res., vol. 61, p. 501. 1953. Meteoritics, vol. 1, p. 11.

MERRILL, G. P. TILGHMAN, B. C.

1908. Smithsonian Misc. Coll., vol. 50, p. 461. 1905. Proc. Acad. Nat. Sci. Philadelphia, vol. 57

NININGER, H. H. p. 887.

1951. Scientific Monthly, vol. 72, p. 75. WATSON, F., JR.

1954. Amer. Journ. Science, vol. 252, p. 277. 1936. Pop. Astron., vol. 44, p. 2.

1956. Arizona's Meteorite Crater, American Me- WTLIE, C. C.

teorite Museum, Sedona, Ariz. 1943. Pop. Astron., vol. 51, p. 97.