Notes on Earth Fissures 

in Southern Arizona 

Notes on Earth Fissures 

in Southern Arizona 

By G. M. Robinson and D. E. Peterson 

GEOLOGICAL SURVEY CIRCULAll 4 66 

Walhingfon J 962 
United States Department of the Interior 

STEWART L. UDALL, SBCRBTAi:Y 

Geological Survey 

THOMAS B. NOLAN, DIRBCTOI. 

Free on application to the U.S. Geological Survey; Washington 25, D. C. 
CONTENTS 

Page 

Abstract----------------------------- 1 

Introduction ______ ---- ___ ------------- 1 

Black Canyon------------------------ 1 

Bowie----- _____ --- ______ -----------_ 3 

Chandler Heights--------------------- 3 

Page 

Luke Air Force Base----------------- 4 

PicachO----------------------------- 4 

Sells-------------------------------- 7 

Conclusion _ -------------------- __ __ _ 7 

References cited--------------------- 7 

ILLUSTRATIONS 

Page 

Plate 1. Index and local area maps showing earth-fissure occurrence in southern 

Arizona relative to valley flood and exposed rock masses ________________ In pocket 

Figure 1. Aerial views of fissures near Black Canyon----------------------------------- 2 

2. Aerial photograph of principal fissures near Black Canyon______________________ 2 

3. Ground views of fissures near Black Canyon---------------------------------- 2 

4. Aerial views of fissures near Chandler Heights-----------·--------------------- 4 

5. Ground view of_fissure opening near Chandler Heights-------------------------- 4 

6. Profiles of land subsidence in Eloy-Picacho area-----------------------------_ 5 

7. Ground views of fissures southeast of Picacho ____ ----_---------- ___ ----------_ 6 

8. Aerial view of fissure near Sells--------------------------------------------- 6 

III 

Notes on Earth Fissures in Southern Arizona 

By G. M. Robinson and D. E. Peterson 

ABSTRACT 

This report describes earth ~issures at six sites in southern Arizona. These notes are preliminary to a more extensive study and detailed analysis being prepared by hydrologists in the Water Resources Division. Earth fissures 

were first recorded in Arizona in 1927, and have been ne.ticed 

with increasing frequepcy since 1949. Fissures at Black 

Canyon. Bowie, Chandler Heights, Luke Air Force Base, 

Picacho, and Sells are discussed and illustrated with 

photographs. 

INTRODUCTION 

A recent short paper by Pashley (1961) 

called attention to large cracks or fissures 

that have appeared from time to time in valley 

alluvium in southern Arizona. Pashley's discussion was confined, however, to a brief 

review of several earlier accounts of earth 

fissures in the Picacho area, to his own observations during 1958-60 on fissures near Casa 

Grande, and to his hypothesis for their origin. 

No comprehensive paper has yet appeared that 

discusses the occurrence and formation of 

fissures throughout the State. 

Although certain local residents are well 

aware that earth fissures have been developing for many years in several areas in the 

southern part of the State, earth scientists 

may not have been generally aware of the 

specific areas in which these phenomena have 

been, and still are, forming. Data are being 

collected by hydrologists in the Water Resources Division but the collection, interpretation, and analysis are not yet complete. 

Nevertheless it seems timely to present these 

notes on earth-fissuring activity in six distinct local areas, so that patterns and orientation may be viewed regionally as well as in 

local reference to the exposed rock masses 

and the general geologic environment. Subsequent reports will present more data and the 

conclusions that may be drawn therefrom. 

The first earth fissure recorded in Arizona 

was discovered in September 1927, about 3 

miles southeast of Picacho (pl. 1), and was 

described in some detail by Leonard (1929)~ 

Similar cracks recurred in that area in 1935 

and 1949. Since 1949 reports-of earthfissuring have been made with increasing frequency 

from widely separated areas throughout the 

southern part of the State. 

Of special interest is the fact that until 

February 1962 all reports concerned fissuring in valley alluvium. On February 1, 1962, 

however, 1ocal residents in the Black Canyon 

area north of Phoenix (pl. 1) reported new 

earth cracks or fissures; these occurred in 

a basalt and semiconsolidated sedimentary 

rock section exposed on a relatively steep 

dissected slope. Local investigation revealed 

that similar fissuring and slumping of the 

earth materials in this area had obviously 

taken place on previously unrecorded occasions. 

Presented in the following paragraphs are a 

few details on earth fissuring in the selected 

areas, arranged in alphabetical order. Fissure locations, patterns, and orientation may 

be observed on plate 1 and in the photographs 

and subsidence profile included in figures 1 

through 8. 

BLACK CANYON 

Earth fissures have formed in !"\ volcanic 

rock area about 45 miles north of Phoenix 

on the east side of Arizona Highway 69, approximately 2 miles northeast of the junction 

of Squaw Cr~ek with the Aqua Fria River. 

The fissures traverse a section of volcanic 

and semiconsolidated sedimentary rocks near 

the north edge of a small valley. Virtuallyno 

ground water is developed in the valley. 

1 
2 NOTES ON FARTH FISSURES IN SOUTIIERN ARIZONA 

A 

B 

Figure 1. -Aerial views looking north at fissures near ffiack Canyon; A, distant view; B, closer view. Light-colored areas indicate the recent exposures. Photographed on February 1, 1962, 

by H. T. Chapman and A. E. Robinson. 

Figure 2. -Aerial photograph from altitude of 4, 000 feet showing 

principal fissures near Black Canyon. Photographed on March 

26, 1962, by R T. Chapman. 

The ·sequence, in time, of the fissure development is not known. Aerial photographs of 

the general area, taken from an altituqe of 

about 11,000 feet in 1936, clearly show the 

east-West traces of earlier fissures developed in conjunction with faulting. On February 

1, 1962, however, Phoenix newspapers reported the discovery by local residents of new 

earth movement in the fissure area. The exact 

time of occurrence seems to have gone unnoticed but air and ground inspection .confirmed that the movement was indeed new and 

that it had been substantial. A photograph 

(fig. 1A) taken on February 1, 1962, from a 

A 

B 

Figure 3. -Ground views of uppermost and lowermost principal 

fissures: near Black Canyon. .A. View looking north at vertical 

displacement near east end of slippage fault produced by upper 

fissure. B, View looking west at size of opening near western 

end of lower fissure. Photographs taken on February 3, 1962, 

by H. T. Chapman. · 
CHANDLER HEIGHTS 3 

low-flying light plane, shows (white trace between arrows) freshly exposed areas on the 

face of the uppermost fissure or fault in relation to the local relief. The vertical interval 

from the valley floor (approximate elevation 

2,100 feet, mean sea level) to the small coneshaped hill that rises to the distant skyline 

(right of center) is between 600 and 700 feet. 

A similar photograph (fig. 1B) on the same 

date gives a closer aerial view of this and 

adjoining major fissures. The cone-shaped 

hill is again a convenient reference marker. 

A vertical aerial photograph (fig. 2) taken 

from an altitude of about 4,000 feet (mean 

sea level) identifies the major fissure pattern. The fresher and lighter appearing areas, 

along the northernmost fissure in the photograph, identify the new exposures associated 

with the most recent earth movement. The 

duller and darker areas denote exposures 

dating back to earlier movements. These details, as well as the vertical movement (about 

10 to 15 feet) at this particular fissure, show 

to advantage in figure 3A, as photographed on 

February 3", 1962. The black band (fig. 2) along 

the lower or southernmost principal fissure 

is the shadow that the sharply defined southern 

rim casts into the opening. The opening size 

can be judged from figure 3B, photographed on 

February 3, 19 62, from a ground vantage point 

on the fissure rim at about the western quarter 

point with respect to its length as indicated in 

figure 2. 

Figure 2 is one of a series of six overlapping aerial photographs which when viewed 

stereoscopically give dramatic evidence of 

the substantial earth movement. At each 

opening the earth or rock material appears 

to have failed in tension or to have been 

literally pulled apart. The photographs show 

no significant differential horizontal movement along the fissures. Elongate islands or 

blocks of material, created when fissures 

intersected one another, in some instances 

settled or slumped as grabens. Examples 

are found by carefully studying stereoscopically various pairs of fissures~ 

BOWIE 

Approximately 6 miles east of Bowie on 

State Highway 86 an earth fissure crosses 

both the highway and the Southern Pacific 

Railroad. The fissure is in the center of a 

broad alluvial valley, north of the Dos Cabezas Mountains, and extends about 1 mile 

northward and about 1 mile south-southeastward from the highway (pl. 1). The use of 

ground water for irrigation has lowered water levels in the Bowie area more than 100 

feet since 1950 (U.S.GeologicalSurvey,1940-

61). The fissure site is near the common 

perimeter between two centers of heavy 

pumping, namely, the Bowie and San Simon 

areas. Compaction of the sediments in these 

two areas. accompanying the water-table 

decline, could gradually have built up tensile 

stresses in the peripheral area comrrion to the 

two centers of pumping, leading to ultimate 

rupture of the earth material in the form of 

the observed fissure. 

CHANDLER HEIGHTS 

Close to the northernmost flank of Santan 

Mountain, approximately 30 miles southeast 

of Phoenix and 12 miles southeast of Chandler, local residents report that earth fissures 

have occurred on several occasions. The fissures are oriented roughly parallel to the 

nearest exposed segment of the mountain 

mass (pl. 1). The trace of a spectacular 

opening that formed in 1961 is marked on 

photographs (figs. 4A and B), which were 

taken from the air on February 10, 1962, 

to show the fissure site and part of the surrounding area. The lower left part of figure 

4A is viewed closer up in figure 4B to show 

more clearly some details of the fissure 

trace. The circled saguaro cactus, about 30 

feet tall, is also partly circled in the lower 

left corner of figure 4A. Irrigated land is 

visible to the north (fig. 4A) of the fissure 

site but the principal irrigated acreage and 

area of ground-water withdrawal lies to the 

northwest. The white scar bracketed by arrows A and B marks the interval in which 

the fissure terminated. The area was reworked by earth-moving equipment to fill the 

fissure. The magnitude of the fissure opening 

is graphically revealed in figure 5, as photographed on September 16, 19 61 , from a ground 

site near arrow A (fig. 4A). These photographs 

suggest that again the earth material has 

simply pulled apart. No differential horizontal movement can be seen along the fissure and no differential vertical movement 

is apparent. Where islands or blocks of 

matenal have been ieft standing in the larger 

openings some crumbling and slumping have 

occurred. 
4 NOTES ON EARTH FISSURES IN SOUTHERN ARIZONA 

A 

B 

Figure 4. -Aerial views looking north at fissure near Chandler 

H_eights. A, General view of the area with arrows denoting 

fissure trace. B, Closer view of fissure trace with same saguaro 

cactus circled. Photographs taken on February 10, 1962, by H. 

T. Chapman and A. E. Robinson. 

LUKE AIR FORCE BASE 

Earth fissures were first observed in the 

fall of 1959 in a 300-acre well-field area 

1·~ miles east of Luke Air Force Base which 

js about 15 miles northwest of Phoenix (pl. i}. 

The well field has yielded substantialquantities of water for irrigation since 1936, with 

annual pumpage ranging between 4,000 and 

8,000 acre-feet. The well-field area itself, 

in which the fissures occur, has never been 

in cultivation. To shallow depths, at least,the 

soil consists of caliche. Surrounding the well 

field are cultivated fields and additional wells 

for irrigation. The longest fissure extends for 

a distance of about 1 mile in a northwestsoutheast direction. 

Figure 5. -Magnitude of fissure opening near Chandler Heights, 

viewedJroii1 site II1arked by arrow.A,.in figure4A,. Photographed 

on SepteJl1ber 16, J96J , ,by,D. E. Peterson. 1'· .·· ,... . . . • 

PfCACHO 

Heretofore 'the limited notes and observaticms oh earth . f1ssur~s in Arizona, published 

in technical journals, have .focused· attention 

princi~~lly OJT the Pi each~ portion of the general PlCacho-Eloy-Casa 'Grande area (pl. 1). 

The valley o'r '-basin floor · is characterized by 

R northwesterly· sloping·plane that ranges in 

elevation :froin '1~ 750 'feet (mean sea-level 

datum) near Picachb Peak 'and ·the Picacho 

Mountains to 1,400 feet near the CasaGrande 

Mountains. These mountains rise abruptly 

from the basin flooi\ ·effectively bounding it 

on the east and west. Agricultural development ·in the ba'sin has been extensive. · 

Gr·ound-water production· for irrigation began near El6y;in l9·3Bbecause of the favorable 

market for ·cottorL A; sle.aay'increase in irrigated acreage continued until after the war' 

at which time a sharp rise was noted. The 
following data on ground-water pumpage furnish a partial index to the agricultural development: 

Year Pumpage Data source 

{acre.;.feet) 

1937--- 64,000 Smith, 1940, p. 26. 

1940--- 172,000 u.s. Geol. Survey, 

1940-61. 

1948--- 360,000 Do. 

1952--- 300,000 Do. 

1960--- 330,000 Do. 

The ground-water production has been accompanied by a steady water-table decline 

throughout the area. Present water levels 

range from 100 to nearly 200 feet below an 

assumed static level for 1930. Until the late 

1940's the center of the cone of depression 

in the water table remained slightly west of 

Eloy. Subsequently the cone center has migrated steadily eastward in consort with the 

development of new irrigated acreage and 

the consequent production from new irrigation wells. 

First - order leveling and subsequent 

checks, by the U.S. Coast and Geodetic Survey, of bench marks along Arizona Highway 

84 yield extremely valuable subsidence data. 

The surveys span the 55-year period from 

1905 to 1960 and show (fig. 6) how markedly 

subsidence rates have increased in the valley 

alluvium, especially in the Eloy-Picacho region. Of particular interest is the fact that 

the data show some land-surface subsidence 

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PICACHO 5 

centered around Eloy over the period from 

1905 to 1934, before extensive ground-water 

development. However, the process seems to 

have been greatly accelerated, probably beginning in 1936, by the effects ofpersistently 

increasing ground-wat.er pumpage and application of the water to the steadily increased 

acreage placed under cultivation. The correlation between subsidence rate and groundwater development is strengthened by noting 

{fig. 6) how the point of maximum subsidence 

migrated southeastward with time. This 

roughly correlates with the similar shift in 

the deepest part of the cone of depression in 

the water table. Maximum subsidence along 

the profile is now approaching 4 feet. 

Also shown in figure 6 are the points at 

which several observed earth fissures intersect the profile along Arizona Highway 

84. As might be expected, the fissures are 

near the outer limits of the subsidence profiles where the earth material could have 

been subjected to tensile stresses. 

The fissure shown at the extreme right in 

figure 6, at a point on Highway 84 about 3 

miles southeast of Picacho, is the one described by Leonard (1929) as having first 

opened in September 1927. Subsequent filling 

and reopening of this and other·fissures in the 

general area are described by Heindl and 

Feth (1955). Leonard's description mentions 

. the fissure length as one-folJ.rth mile; it is 

now at least 8 miles long. Part ofthe fissure 

appears in a photograph (fig. 7 A) taken on 

August 6, 1961, looking northeast across 

LLI 

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=>N..riOID 

(/)O)(J)(J)(J) CJ)----

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Prof i I e s prepared from 

U.S.C. and G.S.data 

SE 

4~----------------------------------------------------------------------------~--~ 

Figure 6.-changes in land-surface elevation in the Eloy-Picacho area. Pinal County. Arizona. 
6 NOTES ON FARTH FISSURES IN SOUTHERN ARIZONA 

A B 

Figure 7. -Views looking northeast . at fissures crossing Arizona Highway 84 near Picacho Mountains. A, Fissure 3 miles southeast of town of 

Picacho; 2 days previous width appeared less than half an inch; torrential rain on previous day revealed this opening; note vegetal growth 

along fissure. B, Fissure 1 mile southeast of Picacho. Photographs taken on August 6, 1961, by D. E. Peterson. 

Arizona Highway 84 at the distant Picacho 

Mountains. A second photograph (fig. 7B) 

shows a similar fissure about 1 mile southeast 

of Picacho. Again the view is northeastward 

across Highway 84 with the Picacho Mountains in the distance. Note the absence (figs. 

7 A and B) of differential vertical or horizontal 

movement along the two fissures. The openings are characterized by clean breaks and 

near-vertical walls. 

Numerous other earth fissures have been 

observed from time to time in the general 

area of Picacho. Those examined as recently 

as 1961 are shown in the large circled area 

on plate 1. Some fissures intersect Picacho 

Reservoir (pl. 1) and in 1961 a retaining 

embankment overlying a fissure failed. Although the reservoir is only occasionally 

used to collect surplus water, the Bureau of 

Indian Affairs, responsible for its operation, 

is debating whether or not to discontinue its 

maintenance. 

Figure 8. -Aerial view looking northeast at east-west trending 

fissure near, Sells. Fissure intersects, nearly at right angles, a 

wash that is tributary to Chukut 'Kuk Wash. Photographed on 

February 8, 1962, by H. T. Chapman and A. E. Robinson. 
REFERENCES CITFD 7 

During the summer of 1961 the junior author 

surveyed the general area of Picacho by gravity meter and certain Bouguer gravity anomaly highs were observed. These are apparent 

highs but they can be related to the amount of 

rock mass present between the meter station 

and the mean sea level datum. Significantly, 

the location and trends of the earth fissures 

in the Picacho-Eloy basin are in general 

linear conformity with the gravity anomaly 

highs. This would appear to support the hypothesis advanced by Heindl and Feth (1955) 

that some fissures are tensional breaks that 

may result from differential settlement along 

the edge of a concealed (buried) pediment. 

SELLS 

An earth fissure 1/2 to 3/4 mile~ long was 

first observed in the early 1950's bypersonnel of the Bureau of Indian Affairs. The fissure is about 12 miles southwest of Sells 

near (east of) the Indian settlement of Chukut Kuk (pl. 1), in an area where irrigation 

farming, using ground water, has not been 

extensively practiced. A photograph (fig. 8) 

taken on February 8, 1962, from a lowflying light plane shows the straight eastwest fissure trace intersecting at right angles 

with a wash tributary to Chukut Kuk Wash. 

CONCLUSION 

Observing the development, with respect to 

time, of earth fissures like those described in 

these brief notes affords an excellent opportunity to document the rates of certain geomorphic processes. In the Black Canyon area, 

for example, periodic detailed mappingofthe 

local fissure area, using photogrammetric 

techniques, will reveal the rates and manner 

in which the landform changes and talus or 

debris accumulates. In valley-floor areas the 

occurrence of fissures in alluvial materials 

may present another useful key in the continuing search for improved understanding of the 

natural and man-induced mechanisms of sediment compaction and earth subsidence. Corollary thereto are changes in the landform, the 

surface drainage pattern, and the movement of 

sediment to streams-. 

REFERENCES CITED 

Heindl, L. A., and Feth, J. H., 1955, Symposium on landerosion--"Piping"--adiscussion: Am Geophys. Union Trans., v. 

36, no. 2, p. 342-345. 

Leonard, R. J ., 1929, f-n earth fissure in 

southern Arizona: Jour. Geology, v. 37, 

no. 8, p. 765-774. 

Pashley, E. F., Jr., 1961, Subsidence cracks 

in alluvium near Casa Grande, Arizona: 

Arizona Geol. Soc. Digest, v. 4, p. 95-101. 

Smith, G. E. P., 1940, The ground-water supply of the Eloy Distri'ct in Pinal County. 

Arizona: Arizona Univ. Agr. Expt. Sta. 

Tech. Bull. 87. 

U.S. Geological Survey, 1940-En. Annual report on ground water in Arizona: U.S. 

Geol. Survey open-file reports, issued 

annually. 

INT. DUP. , 0, C, 62-lS 268