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OCCASIONAL PAPERS
OF THE
California Academy of Sciences
No. 44, 154 pages, 50 figures, frontispiece
November 8, 1963
GALAPAGOS ISLANDS
A Unique Area for Scientific Investigations
A Symposium
presented at the TENTH PACIFIC SCIENCE CONGRESS of the
Pacific Science Association, held at the University of Hawaii,
Honolulu, Hawaii, U.S.A., 21 August to 6 September 1961.
Sponsored by the
National Academy of Sciences,
Bernice Pauahi Bishop Museum,
and the
University of Hawaii |yjarine B;ol ;a| La
L.IBI RY
**k NO ! 5191
San Francisco
Published by the Academy
1963
W DSftOiL
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OCCASIONAL PAPERS
OF THE
California Academy of Sciences
No. 47, 43 pages, 24 figures, frontispiece.
August 28, 1964.
THE PINACATE REGION, SONORA, MEXICO
By Ronald L. Ives
Marine Biological
L_ i B & A R Y
SEP 1 41964
WOODS HOLE, MAS
SAN FRANCISCO
PUBLISHED BY THE ACADEMY 1964
Two deposits of tuff breccia on the north face of the main Pinacate Peaks, above Tinaja de Carlina. These probably represent two discrete sequences of eruptions.
Cholla cactus growing through pumice veneer on a lake bed near Batamote. Sub- soil here is bentonitic clay, resting on substantially unaltered volcanic ash, apparently coextensive with that forming the low ridge in middle distance.
OCCASIONAL PAPERS
OF THE
CALIFORNIA ACADEMY OF SCIENCES
No. 47, 43 pages, 24 figures, frontispiece. August 28, 1964
THE PINACATE REGION, SONORA, MEXICO
By Ronald L. Ives
Introduction
Since its discovery by Eusebio Francisco Kino, S.J., on October 9,1698 (Bolton, 1948, vol. 1, pp. 187, 229), the Mexican Sierra de Santa Clara, known for the last century as the Pinacate Region, has been a land of mystery, and the source of many fantastic stories dealing with natural wonders, lost mis- sions, ancient cultures, and incredible hardships. Some of these stories are true.
Historical studies, made possible by Bolton's (1919, 1936) discovery of the Kino diaries, and Burrus' (1954, 1961) augmentation of them, show incon- trovertible' that Pinacate was identified as an extinct volcano in 1701 (Bolton, 1936, p. 283), and was probably the first specifically so identified in North America (Ives, 1942). From the summit of Pinacate, also, in 1706, Father Kino showed a group of official witnesses the place in the northwest "where the sea ends" (Bolton, 1919, vol. 2, p. 206), clearly demonstrating the penin- sularity of California, previously believed, by many geographers, to be "the largest island in the world."
A similar view, from a somewhat higher vantage point, shows not only where the sea ends, but also the relation of Pinacate to major land and sea features of the southwestern United States and northwestern Mexico (fig. 1). Kino's most famous map, the "Passo porTierra a la California," locates most points in the eastern part of this view by celestial navigation (Bolton, 1936, p. 400; Ives, 1960).
CALIFORNIA ACADEMY OF SCIENCES
(Occ. Papers
1 2 3 4 5 6 7 8
I ' ' ' ' I ' ' ' ' I ' ' ' ' I ' ' ' ' I ' ' ' ' I ' ' ' i I i ' i i I i i i ' I i i i i I ' i i ' I ' ' i i I i i i i I i i i i I i i i i I
- E
i i i i I i i i i I i i
I I I T-^-I-
I M l l l I l l l l I I I I I-
I ' ' ' ' I
Figure 1. Official U.S. Navy photograph of the lands about the head of the Gulf of California, taken from a Viking II rocket at an altitude of 143-4 miles. Note curva- ture of cloud horizon. To locate a designated point on this figure, connect the numer- ical designations for the point, at left and right of the figure, with a straightedge. Do likewise with the letter designations at top and bottom. The designated point will be at the intersection of the two straightedges. Noteworthy geographic locations are positioned as follows.:
Mouth of Colorado River Colorado Delta (apices)
Gulf of California (limits)
Salton Sea (center) Gila River
3-7:B.8
6.0:B.6 5-8:C.l 4-4:B.9
1.0:B.O 3.7:B.8 1.0:B.8 7.2:C0
8.0:A.O to 6-0:B.6
Colorado River
California Mountains
Punta Peiiasco
Mouth of Sonoyta River
Adair Bay (center) Bahia de Lopez-Collada
8.0-.B.4 to 3.7:B.8
1.0:C.O to 8.0:C3
2.5:B.3
2.1:B.l
3.0:B.4
No. 47) IVES: THE PINACATE REGION 3
After Kino's death, at Magdalena, Sonora, on March 15, 1711, his volum- inous diaries, notes, and maps were filed away in the archives of Mexico, Spain, and Rome, where they remained unread and unstudied for more than two centuries.
About three quarters of a century ago, Ygnacio S. Bonillas, a mining engineer of Nogales, Sonora, made several visits to the Pinacate region, ap- parently discovering many of the great calderas for which the region has since become famous. The Bonillas notes have not been located, but he communi- cated many of his findings verbally to Jefferson Davis Milton, a frontier peace- officer. Colonel Milton, in turn, passed this information along to Godfrey Sykes, geographer of the MacDougal-Hornaday Expedition to Pinacate in 1907, and much of the information was incorporated in Sykes' maps (Hornaday, 1908, pp. 22, 110). A detailed study of labradorite from Pinacate was published by Ygnacio S. Bonillas, Jr. (1910).
Extensive field studies in northwestern Sonora, in 1909-10, by Carl Lumholtz, produced a book, New Trails in Mexico (1912), which has become the authoritative work for all parts of Sonora west of Nogales and north of the Rio de la Concepcion. For his field companion during much of this work, Lum- holtz chose Alberto Celaya, a young Mexican from Sonoyta. This was a most fortunate choice, for during the ensuing half century, Don Alberto, the trusted informant and beloved friend of many scientists, has added greatly to our knowl- edge of this arid region (Ives, 1959a).
The account of a Mexican expedition to the Pinacates in 1925 (Esquer, 1926) contains some interesting geographical information, and a compendium of regional folklore.
The Pinacate Region has also served as the locale for at least three novels: Desert Gold (Grey, 1915); Dust of the Desert (Ritchie, 1922); and The Devil's Highway (Wright and Lebar, 1932).
The burned out appearance of the Pinacate Region evokes theological contemplations in most visitors, both ancient and modern. One of the first, Juan Maria Salvatierra, S.J., likened the lava deserts to "the condition of the world in the general conflagration" (Bolton, 1936, p. 456). In our own time, Jefferson Davis Milton opined (1936), "Hell must have boiled over at Pinacate."
Location and Accessibility
The Pinacate Region occupies the central third of the "Sonoran Trian- gle, "whose apices are the communities of Sonoyta, San Luis, and Puerto Pen- asco, all in Sonora. East of the region is the valley of the Sonoyta River, an intermittent stream which only rarely flows through to the Gulf of California; west of the area are the great "Medanos de Arena," which isolate the lava re- gion from the Gulf.
4 CALIFORNIA ACADEMY OF SCIENCES (Occ. Papers
The Pinacates are difficult of access by any standard. Until quite re- cently, the only practicable access route was the deservedly ill-famed Camino del Diablo (Sykes, 1927), along which perhaps 500 travellers have died of thirst, exhaustion, or violence. This road, actually an ancient Indian trail, connected the permanent oasis of Sonoyta with the Gila-Colorado junction, permitting overland travel from the mainland of Mexico to the once-isolated province of California whenever the Yuma crossing was useable (Martin, 1954).
During World War II, a paved highway was constructed from Ajo, Ari- zone, through Sonoyta to Puerto Pehasco, a new seaport on the Gulf of Cali- fornia. Shortly thereafter, the Sonoran Railroad, connecting Mexicali in Baja California with Benjamin Hill (Sonora), was completed along the Gulf coast through Puerto Penasco, and thence inland, across the desert, to the Magda- lena Valley. In 1960, the long-planned paving of the Mexican portions of the Camino del Diablo and the Abelardo Rodriguez Military Road was completed, eliminating many of the hazards of the journey across the desert from Sonoyta to San Luis.
These road improvements make accessible any part of the Pinacate Re- tion within a long day's walk of a paved highway. In a few places, rough trails permit a closer approach by four-wheel-drive vehicles. Summary map, showing major access routes to the Pinacate Region, comprises figure 2.
Nearest stateside supply point to the Pinacates is Ajo, Arizona, a rail- head and mining community, about 43 miles south of Gila Bend, which is com- plete with all facilities including photographic processing services. Best Mexican supply point is Sonoyta, Sonora, a clean and orderly oasis community, two miles below the border. Facilities here include numerous stores and res- taurants, a church, a school, a telegraph office, a doctor, and a dentist. Just east of Sonoyta are the ruins of Kino's westernmost mission, San Marcelo So- noitac, in which are buried the remains of the martyr, Enrique Ruhen, S.J., murdered during the Pima revolt of 1751 (Ives, 1957).
Despite recent road improvements, travel to and in the Pinacate Region is hazardous for all but experienced desert travellers. None of the water holes, with the possible exception of Papago Tanks, are permanent; some of the springs in the sand dunes to the west are poisonous. Visibility is poor most of the time because of haze, shimmer, and mirages; compass readings are un- dependable because of local attractions in the lava flows; footing is tricky in many parts of the area.
Although the people of Sonoyta have long been noted for their compas- sionate care of people who have encountered misfortune in the desert, even the most willing help may arrive too late in an area where 24 hours without water may be fatal. Extreme caution is urged in all parts of the region.
No. 47)
IVES: THE PINACATE REGION
115* * TO SAN FELIPE
TO BENJAMIN HILL 113°
Figure 2- Summary map of the western Arizona-Sonora borderlands, showing the relative position of the Pinacate Region and major access routes.
Climate, Flora, and Fauna
The Pinacate Region is climatically, as well as geographically, a part of the Sonoran Desert. Average climatic conditions within the Pinacate Re- gion are determinable from interpolations between the nearest climatic sta- tions. Charts for these with a similarly constructed chart for Phoenix, Ari- zona, included for comparison, comprise figure 3. Climatic charts for other ad- jacent stations, and a detailed study of climatic conditions in the Sonoran Desert, have been published elsewhere (Contreras-Arias, 1942; Ives, 1949).
Within the Pinacate Region, maximum and minimum temperatures, and diurnal temperature ranges, are slightly more extreme than at the peripheral inhabited places. Maximum temperatures seldom, if ever, exceed 130° F. in the open at nose level. Soil surface temperatures, measured with an ordinary thermometer, may reach 160° F. when air temperature is 110° F. Soil surface temperature measured with a fine-wire thermocouple, under the same condi- tions, may reach 180° F. Minimum temperatures seldom fall below 20° F. in any part of the area.
CALIFORNIA ACADEMY OF SCIENCES
(Occ. Papers
SAN LUIS
SONORA SONOYTA
SONORA
PRECIPITATION IN INCHES
OFFICIAL AVERAGE
TEMPERATURES IN DEGREES F 100
PRECIPITATION IN INCHES
5
COMPOSITE RECORD
TEMPERATURES IN DEGREES F 100
60 3
40 2
20 I
10 0 5
JAN FEB MAR APR MAY JUN JUL AUG SEP OCT NOV DEC
PUERTO PENASCO
PRECIPITATION IN INCHES
5
COMPOSITE RECORD
SONORA PHOENIX
TEMPERATURES PRECIPITATION
IN DEGREES F IN INCHES 100 5
JAN FEB MAR APR MAY JUN JUL AUG SEP OCT NOV DEC
ARIZONA
45 YEAR AVERAGE
TEMPERATURES IN DEGREES F 100
MAY JUN JUL AUG SEP OCT NOV DEC
No. 47) IVES: THE PINACATE REGION 7
In the basalt arroyos leading down from the main Pinacate Peaks, strong desiccating updrafts are usual from midmorning to sunset; and bitter-cold down- drafts (katabats) are the rule on clear nights. These occasionally produce hoar-frost on exposed rock surfaces near water holes at times when daily maximum temperatures reach 100° F. More rarely, where rock configuration is favorable, small ephemeral condensation puddles may develop (Ives, 1962a). Strong, hot, desiccating nocturnal winds, resembling the "Furnace Winds" of Death Valley, have been encountered on flat areas some distance from the main peaks during the summer season only. Frequency and areal extent of these winds are at present unknown.
Sudden cold waves, accompanied by gusty, raw winds, occur several times each winter. These, locally called "nortes," cover a wide area in Ari- zone and Sonora, and are somewhat predictable by application of standard forecasting techniques (Ives, 1962b).
Relative humidity in the area ranges from "too low to measure" (per- haps five per cent) to supersaturation. During land-breeze conditions, it is commonly in the neighborhood of 20 per cent; but rises to about 60 per cent when a sea breeze sets in. This makes the afternoon summer heat extremely oppressive. Rarely, usually in winter, "salt fogs" drift into the area from the Gulf of California.
Regional rainfall is scanty, sporadic, and only slightly predictable. Dur- ing the summer "Monsoon Season," usually in August, some part or parts of the area are subjected to violent cloudbursts, which may bring as much as 5 inches of precipitation in 2l/i hours (there is no assurance that this is a max- imum figure). At the same time, areas only a few miles away may receive no rainfall at all. This spotty rainfall distribution leads to the common desert complaint that "it rained everywhere but here" (McDonald, 1959).
Winter rainfalls are gentler, more evenly distributed, and of longer dura- tion. Most of these are little more than dense mists, and are sometimes called "lloranas."
In addition to the cloudbursts, and usually during the "monsoon" sea- son, the higher peaks are subjected to extremely violent cumulus activity, ap- pearing from a distance like a thunderstorm, but producing no precipitation. These "dry thunderstorms," complete with intense lightning discharges and deafening thunder, seem to be characteristic of the area. Similar "tormentos secos" are reported from northern Baja California, particularly in the Sierra San Pedro Martir.
In clear weather, both night and day, mirages are quite common, and are somewhat predictable, particularly along the shores of the Gulf of California. Recent studies of microwave propagation across this area indicate that the
Figure 3. Climatic charts for stations adjacent to the Pinacate Region.
8 CALIFORNIA ACADEMY OF SCIENCES (Occ. Papers
atmospheric stratifications postulated by Humphreys (1942) a generation ago to explain such mirages are real, and not just "mathematical fictions."
Commonly accompanying daytime inferior mirages ("wateronthe road," etc.) are dust devils of considerable magnitude (Ives, 1947). These remove the "fines" from surficial desert deposits, and, in conjunction with the pre- vailing winds from the west and northwest, carry them far inland, where they are redeposited as a crude form of loess.
Quite commonly, at night, weak lights can be seen on high points in this area. These, despite local surmises about the "bomba atomica," "platos volantes," and "spirit candles," are electrical discharges of entirely natural origin, usually named "St. Elmo's Fire," and common not only to the Pinacate Region, but also along the sierras of peninsular Baja California.
Continuing studies of weather and climate in this general area are being conducted by Mexican agencies at San Luis, Sonoyta, and Puerto Penasco; and by U. S. agencies at Yuma, Ajo, and Organ Pipe Cactus National Monument.
Vegetation of this area is in very general terms much like that of the Phoenix-Tucson area, being characterized by low brush, giant cactus, and oc- casional specialized trees. The commonly applied term "arboreal desert" is most apt. Although this region is a desert by any rational standard, it is by no means an "abode of emptiness" like the Rub Al Khali. With the exception of a few small areas of recent lava, and of a few very active dune surfaces, a square yard without vegetation is hard to find here.
Clear and adequately illustrated descriptions of this arboreal desert have been published by Hornaday and MacDougal (Hornaday, 1908), Lumholtz (1912), and Shreve (1951). An additional study by Wiggins (1964), augmenting and continuing Shreve's thoroughgoing work, has recently appeared.
Typical arboreal desert vegetation is shown in figure 4, a view taken in the southern part of the Ajo Valley, north of Lukeville. During the course of field work in and about the Pinacate Region, numerous changes in the vegeta- tive patterns were noted between 1936 and 1946. These, in brief , consist of a marked increase in the numbers of annual plants, accompanied by a slight de- crease in those of perennials, the net result being that the desert looks much greener now (1962) than it did in 1931.
This vegetative change has been attributed to minor variations in local rainfall distribution, to lowering of local water tables, and to initiation of a new valley erosion cycle (which actually began before 1880). Total effect of all of these factors on usable biotic water seems inadequate to account for the observed vegetative changes (Ives, 1955).
Animals of the area were, until about 1936, numerous and typical of the southwestern deserts. Mountain sheep, deer, javelina, coyotes, and similar animals were common, as were the more recently introduced wild burros and wild horses. Bobcat ("gato montes") and mountain lion were plentiful in an-
No. 47)
IVES: THE PINACATE REGION
Figure 4. Vegetation in the arboreal desert. In this view, taken at the foot of La Mona, a prominent landmark on the west side of the Ajo Mountains, in Organ Pipe Cactus National Monument, creosote bush (Larrea tridentata) occupies the foreground. Toward center are three sahuaros (Carnegiea gigantea). Farther back are "jumping" chollas (Opuntia bigelovii). Trees in middle distance are Palo Verde (Cercidium mi- cropbyllum).
cient times, but became rare prior to 1890. Small rodents were numerous through- out the area.
Local reptiles included rattlesnakes in great profusion, numerous liz- ards of many species, a few Gila monsters, and many tortoises, such as Go- pherus berlandieri, some of which were found in the most "unlikely" places. Local amphibians include toads, frogs, and axolotl, all of which frequent the numerous temporary water holes.
After 1936, and before 1946, most of the large mammals disappeared from the Pinacate Region, and the numbers of small rodents declined markedly. No observable changes occurred in the numbers or distribution of reptiles and amphibians, and no statement can be made about bird life because of inade- ' quate data.
CALIFORNIA ACADEMY OF SCIENCES (Occ. Papers
These faunal changes are locally attributed to too much hunting. This explanation plausibly (but not necessarily correctly) accounts for the disap- pearance of the larger game animals from the region, but is not entirely satis- factory in regard to the decimation of the small rodents, and fails completely with respect to such animals as the desert skunk ("zorillo"), which is not hunted by humans, and is assiduously avoided by animal predators. Addition- ally, a decline in the numbers of predators, such as coyotes and foxes, is normally accompanied by a plague of small rodents. This has not taken place at Pinacate.
As a result of these changes, the zoological descriptions by Hornaday (1908) and Lumholtz (1912), which were found to be correct even to minor fea- tures prior to 1936, are now of historical value only, and do not apply to pre- sent (1962) conditions.
The Volcanic Features
The volcanic terrain which occupies the major part of the Pinacate Re- gion has an areal extent exceeding 1500 square miles, of which perhaps one third is surfaced by obviously recent lava flows. An additional volcanic area, of unknown extent, is buried beneath the sand dunes that fringe the shores of the Gulf of California.
Major features ofthe Pinacate Region are shown in figure 5, a summary map which is an augmentation ofthe excellent Lumholtz-Celaya-Briesemeister map of 1912.
For purposes of description, the Pinacate Region can be divided into three geographic parts: the main peaks, the peripheral lava flows, and the great calderas.
Although field studies by the present writer in the Pinacate Region have extended over more than 30 years, and have included a great many miles of travel afoot over the lava, so that all major features of the earlier reports have been identified, and many new facts uncovered, it is highly probably that many more features of this complex area, not all of them minor, remain to be discovered and studied.
The Main Peaks
The main Pinacate Peaks consist of three summits, rising close toge- ther and from a lava highland about seven miles wide and fifteen miles long. The highest summit, Pinacate Peak, rises to 4235 feet (above mean sea level); the second highest, Carnegie Peak, rises only to 3180 feet. The level of the surrounding terrain is about 900 feet.
From a distance, the Pinacate Peaks appear deceptively rounded and smooth; and, in recent years, their green color suggests a heavy vegetative cover.
No. 47)
IVES: THE PINACATE REGION
11
On closer approach, the peaks appear as "a sort of rubbish heap of tezontle stone," according to the correctly graphic description written by Fray
TO TULE WELLS AND YUMA 113 3Q
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Figure 5. Summary map of the Pinacate Region.
12
CALIFORNIA ACADEMY OF SCIENCES
(Occ. Papers
L# V.J
Figure 6. Upper part of the lava cascade northeast of Carnegie Peak, photo- graphed from a point on the main tongue, with the camera axis elevated approximately 30 degrees. Lava source is in the V-notch on the left skyline: highest point is Car- negie Peak.
Manuel de la Oyela y Velarte in 1706 (Bolton, 1919, I, p. 211; Ives, 1956). The surface is composed of all types of volcanic debris, and most of the sur- ficial lithologic features present have been split, warped, and partly buried by subsequent action. In consequence, only the most recent cones, vents, and flows are present in their entirety, and these rest, not on a relatively smooth basement, but on the piled-up and eroded wreckage of older similar lithologic structures.
Veneering the rough surface of this volcanic conglomeration, like spills from a solder-pot, are flows of relatively recent, extremely vesicular basalt. Most extensive of these is the lava cascade which issued from a crater at the 3800-foot level on Carnegie Peak, and flowed northeastward down the slopes of the main lava mass for more than seven miles. The general appearance of the upper part of this flow is shown in figure 6, which includes the source area and Carnegie Peak.
Where not covered with a veneer of lava, the underlying volcanic com- plex is exposed, and from studies of this it is concluded that the fifteen or so cubic miles now comprising the main peaks are the result of not less than several hundred discrete volcanic episodes. It is also clear, from structural
No. 47)
IVES: THE PINACATE REGION
13
features, that the present peaks are the eroded remnants of a formerly higher volcano, for which the name Santa Clara Volcano (Kino's original name for the peaks) is proposed.
On the flanks of the main volcanic mass, at lower levels, and where deeply-eroded channels provide clear exposures, another sequence of alter- nating coarse and fine tuff beds, containing occasional thin and discontinuous lava flows, is found. The exact physical relation of these to the core of the main peaks is concealed by later lava flows, ash falls, and other tuff deposits, further complicated by faulting and slumping. Structural irregularities in these deposits indicate that they had various sources, and that intervals of erosion alternated with periods of deposition. Many of these beds have a somewhat regular alternation of fine and coarse grained tuff, giving them the general ap- pearance of varved clays or tree-rings. One of the tuff-ash alternating series is shown in figure 7. Total thickness of these deposits, in any one location, never exceeds 400 feet. Individual elements are usually not more than 10 feet thick. These deposits, where the base is exposed, rest on a sequence of flows of rather compact basalt porphyry.
4T-, i.Jgg^^^
.. â– â– "
M3 -ip7^.
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Figure 7. Stratified volcanic materials, consisting of alternating coarse and fine tuff beds, capped by lava, on the north side of the Pinacate massif, between Tin- aja de Emilia and Tinaja de Carlina. Height of this exposure is about 300 feet.
14
CALIFORNIA ACADEMY OF SCIENCES
(Occ. Papers
Despite the "new" appearance of many components of the main peaks, and the areal aridity, all hard rocks (basalts and tuffs) support extensive li- chen growth, which causes extensive spalling on sheltered surfaces, indicat- ing plainly that the apparent newness of the lavas is geological, and not his- torical.
Peripheral Lava Flows
Surrounding the main Pinacate volcanic mass on all sides are lava beds, which extend outward for many miles, forming an erosion-resistant apron about the peaks, and making access to them difficult. Oldest and outermost of these flows is the thick sequence of compact, even-grained basalt, which is found at Puerto Penasco, where it forms the promontory above the seaport (the Punta Pehasco of the navigation charts); and at Batamote.
This lava, which everywhere exceeds 300 feet in thickness, is composed of two discrete series of flows, separated by an erosional unconformity. At Puerto Pehasco, the separation is further marked by the inclusions of lenses
Figure 8. The Batamote Hills from the southwest. Height of the basalt uplands here exceeds 300 feet. Foreground surface material is volcanic ash, with alluvium and scoria. Foreground vegetation is largely creosote bush (Larrea tridentata), with a few ocatillos (Fouquieria splendens).
No. 47)
IVES: THE PINACATE REGION
15
Figure 9. Escarpment of recent vesicular basalt at margin of younger flow se- quence between Batamote and Tinaja de Emilia, north of the main Pinacate massif.
of somewhat altered volcanic ash and tuffaceous material.
Greatest remainingexposure ofthis oldest basalt is at Batamote, where more than ten square miles of desert are dominated by columnar cliffs, as in figure 8. The structure here, resembling parts of the Palisades of the Hudson, or the Devil's Postpile, is typical of thick basalt flows, wherever they may occur.
Probable extension of these lavas to westward, under the many younger flows of the Pinacate lava beds, and perhaps under at least parts of the main peaks, is indicated by the inclusion, in the later flows, of unassimilated and largely unaltered chunks of this basalt. These occur as far west as the lavas bordering on the great sand dunes, and are accompanied, in some locations, by pieces of Sierra Blanca granite.
These older basalts have been somewhat eroded and extensively faulted. Vertical dislocations near Batamote, as determined from the logs of (mostly unsuccessful) water wells, may exceed 750 feet. At Puerto Penasco, the ba- salts have been submerged at least once since their extrusion so that the prom- ontory is topped by a boulder beach, under which is a thin stratum of marine shells, of no great geologic antiquity (Ives, 1951, 1959b).
Scattered throughout the Batamote Hills are small spatter cones, much younger than the main lavas, which have supplied much of the scoriaceous veneer over the various ash beds and outwash plains in the immediate vicinity.
16
CALIFORNIA ACADEMY OF SCIENCES
(Occ. Papers
Figure 10. Lava-dune contact west of Sierra Blanca, which appears on the sky- line; and south of Moon Crater. Sand, which here is largely composed of shell frag- ments, forms a thin layer over the basalt flows.
Eastern and northern edges of the younger flow sequence are commonly low escarpments of contorted vesicular basalt, having a "just cooled" ap- pearance shown in figure 9. Several hundred miles of such escarpments form a multiple sequence of interrupted walls about the main Pinacate Peaks, mak- ing point-to-point travel within the flow area must difficult.
On the western margin of the later lavas, however, there is no bold es- carpment because the great sand dunes are banked up against the lavas, and in_some places cover an unknown number of square miles of recent flows. Such conditions are shown in figure 10. The length of this dune-lava contact ex- ceeds thirty miles.
Within the area of the younger flow sequence, it is not at all uncommon to find half a dozen discrete flows, superposed in a square mile or so. All sorts of flow types, evidencing various degrees of fluidity, are present; and a few of the flows have an exploded appearance, characteristic of extrusion into water.
Roughest and most spectacular of these younger flow sequences is the lava chaos, between the main peaks and Crater Elegante (fig. 5). This lava chaos is a "textbook example" of flow breccia, a type of lava terrain pro- duced when a flow hardens on top, but continues molten and mobile below the
No. 47)
IVES: THE PINACATE REGION
17
surface, so that surface blocks are tilted and moved in all directions, much like the ice blocks in arctic pressure ridges. Although this flow is certainly many hundreds of years old it is still unstable, so that many lava blocks, as much as 30 feet across, rock when walked on. Portions of this flow have col- lapsed long after cooling because the volcanic ash basement, upon which the lava poured out, has been partly removed by flood waters.
Figure 11. Interior of the lava chaos. The road-like structure in the center of this view is not the original alignment of the Camino del Diablo, but an entirely na- tural flow phenomenon.
Detail of the interior of the lava chaos is shown in figure 11. The lava chaos is commonly reputed to be completely impassible. This is not the case. It can be crossed by a man afoot in any direction, sustained walking rate be- ing approximately one-half mile per hour. Approximately 30 feet of vertical travel are needed for each 100 feet of horizontal course. Ten miles of walking on this lava damages a pair of field boots beyond repair ("totalmente ruinada").
Scattered with apparent random distribution throughout the area of the peripheral lava flows are numerous cinder and lava cones, of all sizes from "not much bigger than a birdbath" to structures almost 1,000 feet high. These are in all stages from apparently "formed last week" to collapsed and partly assimilated by surrounding lava. The present condition of a cone structure is not necessarily an indication of its age.
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i^X,
" so> ;-..i-v. -■•'■*"
Figure 12. Rim structure on the west side of Salvatierra Cone. Vegetation here is tree cholla, Opuntia bigelovii.
About half of the flows in the peripheral lava area originate from vents at the bases of cinder cones, and are of approximately the same age as the cones with which they are associated. In some instances, lava outpouring from the vent has undermined one side of the cone, leading to rim collapse and pro- duction of a breached structure. Typical rim structure of a cinder cone is shown in figure 12, a view of the west rim of Salvatierra Cone, northwest of Crater Elegante.
Although many flows originate at the bases of cinder cones, no example has been found of a cone which filled up and overflowed. Most cones are com- posed of much more vesicular material than the flows issuing from their bases. Only at the lower levels does the cone material begin to compare with the as- sociated flows in compactness, even though the cone and flow may have sub- stantially identical chemical composition.
Despite the extremely youthful appearance of many of the perfect cones, most of the unbreached structures contain a central playa, with a floor of al- luvium, and some to much vegetation. Studies of soil profiles in a number of such central playas lead to age estimates considerably in excess of 1,000 years; and suggest a dry-wet-dry climate sequence since cone formation. De- tailed chemical studies, augmented by radiocarbon datings, should be most productive here.
No. 47)
IVES: THE PINACATE REGION
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The plant community within the cone of Iitoi's Castle (fig. 5) is shown in figure 13. Note the white caliche deposit among the plants. So far as can be determined from visits to the interiors of several such botanical enclaves, this plant population is typical.
■fee, . ~- — .^*-v; ^^m^^^ :*. .- -.
-rf*«.* ^*"*
IMS
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'-.r^f^-^lttfc
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Figure 13. Vegetation in the playa within the cone of Iitoi's Castle. Evident here are sahuaro (Camegiea gigantea), ocatillo (Fourquieria splendens), tree cholla (Opuntia bigelovii), creosote bush (Larrea tridentata), burro weed ( Franseria dumosa)t and organ pipe cactus (Cereus tburberi).
A number of the peripheral lava flows are quite definitely not associated with cinder cones, and no fissure sources for the lavas were found by either ground studies or aerial reconnaissance. Near the centers of some of these flows, however, some interesting circular pressure-ridge patterns were found. Further study of the flow patterns indicated that they were the surface mani- festations of lava upwells. A plan view and schematic section of such an up- well are shown in figure 14.
Another family of circular lava structures, somewhat resembling up- wells, and initially so classified, were first found in aerial photographs tak- en by another worker. These are eddy structures, initially formed by a process somewhat analogous to slagging in an iron-furnace. When fluid lava ponds, the less-dense fractions, which may include not only partly assimilated base- ment materials, but -also vesicular components of the lava itself, are buoyant and rise to the surface as a slag or scum. As the ponded lava deepens by in-
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PLAN
ESCARPMENT
SMOOTH CENTERS
M\Ar~
LAVA MOTION
-ESCARPMENT
BOLDER LAVAS
SECTION
,PRESSURE RIDGES
â– AAflr-
LAVA MOTION
ESCARPMENT-
FROM
LAVA
SOURCE
t _t _+_ I_ -L -i .
? ?
NOT TO SCALE
Figure 14. Plan view and schematic section of lava upwell structure.
No. 47) IVES: THE PINACATE REGION 21
flow (and gains in surface area), the hardened surface material becomes a "floating island" of hard lava on the still-molten basement. This usually ac- quires a rotational motion from natural forces, including, at times the "Cori- olis Force" owing to the earth's axial rotation. Although it is difficult to de- termine, long afterwards, the exact cause of rotation, a non-rotating floating island, be it of cooled lava, woody material, ice, or seaweed ("sargasso"), is a rarity.
Several osculating eddy structures have been spotted from the air; for example, between Manje Cone and Kino Crater. They are most difficult to find on the ground.
Eddy structures differ from upwells in that the peripheral pressure ridges in an eddy tend to be spiral sectors, like the blades of an air impeller; where- as those in an upwell tend to be concentric like the rings of an equatorial section of an onion.
Despite considerable searching, no large lava tubes or caves were found at or near Pinacate; but subdrainage of the peripheral lavas, usually through collapse sinks, indicates the presence, at unknown depth, of voids of fairly large dimensions. Maximum sink depth probably does not exceed 200 feet, this figure being an "educated guess" fortified by timing stones dropped into several lava sinks. Some of these buried drainages may be ancient channels of the Sonoyta River, which was dammed and diverted several times by volcan- ic activity at Pinacate.
Hydrostatically closed depressions within and peripheral to the lava flows, when not subdrained, characteristically contain ephemeral playa lakes, usually floored with volcanic ash and caliche, and in many instances covered by a veneer of evenly-distributed pumice, almost certainly water-laid. Some of these playas are serious obstacles to vehicular travel, as they retain their "liquid goo" characteristics for weeks or months after all surface water has disappeared. Chemical tests show that these playa deposits contain an ap- preciable percentage of bentonite.
The Great Calderas
Erratically distributed- through the peripheral lavas are the great cal- deras for which the Pinacate Region is famous. From the air, the crater zone looks as if the region had been worked over with a giant pin-punch. Locations of the major known calderas are indicated in figure 5. Because of haze and other natural concealments, it is entirely possible that other calderas remain to be discovered.
The first English-language descriptions of some of these craters were published by Hornaday (1908), who, with other members of his party, is com- monly credited with their discovery.
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Search of literature in the Spanish language indicates quite plainly that Engineer Y. S. Bonillas, of Nogales, Sonora, visited some of the craters con- siderably prior to 1900. Folkloric studies show that tales of craters that "went cleardown to Hell," in the Pinacate Region, were current shortly after 1850. These strongly suggest that some wanderer visited the Pinacate Region more than a century ago (l^.
Recent findings and study of a number of Spanish documents show in- controvertibly that at least one caldera at Pinacate was seen and described more than two and a half centuries ago by the exploration team of Kino, Manje, and Salvatierra (Bolton, 1919, 1936; Karns, 1954) <2), all of whom wrote diar- ies of their expeditions. During a journey near Papago Tanks, Father Kino climbed a mountain to the northwest, "to perceive the sea." From this summit, the party saw a bighole of such depth thatit caused them "terror y espanto." The diary date is March 20, 1701. From the itinerary given, complete with
distances and latitudes, the mountain climbed can be identified as the Sierra Hornaday, and the bighole as MacDougal Crater. An aerial view of these com- prises figure 15.
According to measurements carefully made by Godfrey Sykes, halfacent- uary ago, MacDougal Crater is about 3600 feet in diameter at the bottom, 400 feet deep, and has its present flat floor about 50 feet above sea level. The rim, composed of stratified volcanic ash, is only about 50 feet high. Adjacent Molina Crater, which has a roughly clover-leaf shape, is only about 250 feet deep, and about 1500 feet in average diameter at the bottom. It, like MacDoug- al Crater, has a very low rim of volcanic ash.
Somewhat of a maverick among the Pinacate craters, although formed of similar materials to the others, at about the same time, and in approximately the same manner, is Sykes Crater, also known as Crater Grande. This volcan- ic landmark, 750 feet deep from rim crest to bottom, 1400 feet in diameter at the bottom, and with present floor about 150 feet above mean sea level, is characterized by a sharp steep rim of volcanic ash, so that it resembles "a mountain with a hole in the top." Sykes Crater, which is approximately three and one-half miles northeast of Papago Tanks, is closely flanked by cinder cones and lava flows of considerable roughness. The appearance of this crater and its relation to the surrounding terrain are shown in figure 16.
These tales almost certainly were first told by Peter H. Brady, or some member of bis party, after a journey to Adair Bay, via Pinacate, in 1854. The trip is summar- ized in Brady's (1898) autobiography. Alphonse Pinart, a French traveller, also visit- the region during the 1850's, leaving a quasi-legible diary which is now in the Ban- croft Library, Berkeley, California.
2) The Salvatierra diaries and documents are currently bei ng prep ared for publication by the (lev. Dr. Ernest J. Burrus, S-J-. of the Institutum Historicum S. J • , in Rome.
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IVES: THE PINACATE REGION
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^J|LiU^'k^^~4l. ' JJ'-m -*£!?*! "-.--. !_"'-''■-i'.'--.-
r -. - «*•
Figure 15. Aerial view of the northwestern edge of the Pinacate Region, show- ing the Sierra Hornaday (right middle distance), and MacDougal Crater (left of center). Background range is the Sierra de Tuseral, here "fuzzed" by atmospheric turbulence. The sharp peak in upper left is Pyramid Peak; the small crater at left center is Molina Crater. Note the recent lava flow in foreground, and several cinder cones.
Largest, most spectacular, best known, and most controversial of the great calderas at Pinacate is Crater Elegante, located approximately six miles northeast of Pinacate Peak, and sometimes accessible by four-wheel-drive vehicles from Mexican Route 8, by way of Batamote.
Crater Elegante is about 4800 feet in diameter, nearly circular in shape, and almost 800 feet deep, from rim crest to floor, which is approximately 200 feet above mean sea level. The rim, which rises as a very gentle slope, is about 120 feet high, and is composed entirely of thinly stratified volcanic ash, which has been slightly dissected by erosion.
The crater walls, below the ash zone, are stratified basalts, evidence of at least two sequences of effusive eruptions, each subdivided into an unknown number of discrete eruptive episodes. The base of this lava is concealed by talus which rests on a bench of deltaic beds, some feet above the crater floor.
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Figure 16. Aerial view of Sykes Crater, east northeast of Papago Tanks. Rim of crater is clearly shown here, as is recent lava flow (lower right). Note cinder cone (lower left) with central playa, and dendritic drainage patterns on both flanks. (Tucson Daily Citizen photograph, courtesy of Jane Ivancovich.)
These beds show that the crater at one time contained a lake, which lasted long enough to permit the development of a gastropod fauna. Below the delta beds is a small central playa, which under present conditions of sub-surface drainage, results in the crater seldom containing water, even after local tor- rential rains.
An aerial view of Crater Elegante, from the northeast, comprises figure 17. Note the superposition of recent lavas associated with the Lava Chaos (fig. 5) on the rim of this crater.
The excellently developed rim beds at Crater Elegante, as well as those less well developed at the other craters, are composed of thinly bedded vol- canic ash, buff-colored, and but slightly dissected, evidence of the geologic youth of the craters. This material superficially resembles the "paper shales" of the Colorado high plains. Ash from Crater Elegante is banked up against the twin cones of Dos Mujeres, three miles distant, forming a steeply sloping
No. 47)
IVES: THE PINACATE REGION
25
ramp on the west side. Both the rim beds and the Dos Mujeres ramp show aeolian cross-bedding, indicating deposition on dry land. Ash beds some dis- tance from Crater Elegante, particularly to the northeast, in contrast, do not have this aeolian cross-bedding, and were either deposited in water (very probably a playa lake), or were repeatedly flooded shortly after deposition. The general appearance of the rim beds, in a shallow wash on the southeast side of the crater, is shown in figure 18-
Badilla, Kino, and Celaya craters are all of similar formation, although smaller than Crater Elegante. Celaya Crater, the northern-most of the group, and the least accessible, is slowly being filled with surface wash, and ap- parently also acts as a sump for some of the under-lava drainage channels in the vicinity. Although these craters receive only minor mention here, each is a spectacular landform, and each has geologic features meriting intensive study.
Southwest of the Pinacate Peaks is Moon Crater, discovered and ex- plored by Glenton G. Sykes, of Tucson, during the winter of 1956-57. This
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X
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Figure 17. Aerial view of Crater Elegante from the northeast. The bench below talus and above crater floor is composed of delta-like beds. Lava Chaos occupies the middle distance; and the Pinacate Peaks showing the lava cascade and other recent lava flows, are on the horizon. (Aerial photograph by Tad Nichols, Tucson, Arizona.)
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Figure 18. Rim beds of Crater Elegante. This thinly-bedded volcanic ash is nearly 100 feet thick here. Note the fragments of basalt which have weathered out of the ash deposit.
crater, somewhat smaller and less spectacular than Crater Elegante, is the only known caldera southwest of the main peaks. It is possible that Moon Crater is somewhat younger than the others of comparable size in this area. So well concealed is the Moon Crater, by "natural camouflage," that the writer has twice walked within a few hundred feet of its rim without detecting its presence.
Some crater southwest of Pinacate, probably Moon Crater, emitted enor- mous quantities of volcanic ash, still evidenced by a pair of ash ramps, sev- eral hundred feet high, piled against the east face of Pelican Point, 28 miles to the south, on the seaward side of Bahia La Cholla (fig. 2). Another enor- mous ash deposit, of undetermined origin, occupies the triangular embayment between the Sierra Blanca and the lava flows to the west. This ash bed, rough- ly one mile wide and five miles long, has a thickness exceeding eighty feet, as shown by the log of a well dug there by Armando Valle, of Puerto Penasco. Study of this well discloses that it penetrated dry, gritty, uniform, unstrati- fied volcanic ash, which contains no fragments of basalt or other country rock (unlike most other ash deposits), but includes numerous pea-sized nodules of sulfur. Although the bottom of this well is at present sea level, and had been below sea level one or more times during the last 10,000 years or so, the well is completely dry, and the ash from the bottom is not salty (by "taste test").
No. 47)
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Several dozen other ash beds, not surely associated with craters now extant, are found in the Pinacate Region. Representatives of these is the thick bed on the northeast side of the main peaks, between Tinaja Suvuk and Tinaja de Emilia. Exposure here is ten feet high, and several miles long, with the upper surface capped in some places by coarse alluvium, and in others by lava. At many places in this bed, aeolian cross-bedding, evidencing deposi- tion during windy conditions, is apparent, as in figure 20. From observations during the eruption of Katmai, which formed the "Valley of Ten Thousand Smokes" in Alaska, in 1912 (Griggs, 1918), it is apparent that an ash deposit of this magnitude can be laid down in something less than two weeks. In con- sequence, the cross-bedded section probably represents only a single "blow," such as a present-day "Norte."
Numerous erosional unconformities, some of them discontinuous, are found in these ash exposures. With most geological materials, such unconform- ities would be indicators of a relatively long time lapse between depositions. Here, where ash deposition was geologically "instantaneous," they may rep- resent only a single desert thunderstorm, lasting perhaps two hours.
Genetically related to the great calderas, although resembling them only in some features, is Cerro Colorado, a pinkish ash cone which forms a prom- inent landmark on the east side of the Pinacate Region, just outside of the lava margin. Cerro Colorado is about 350 feet high, and about a mile in diam- eter at its base. Surrounding it is an apron of outwash, perhaps a mile wide,
Figure 19. Cero Colorado, an eastern outlier of the Pinacate Volcanic area. The white patch in extreme upper right is a playa, which has contained water several times since 1931, was completely grass-covered in the spring of 1961, and contained more than a foot of water in late October, 1963- The dark patch beyond the playa is a flow associated with the most recent ropy lava sequence. (Pacific Air Industries Pho- tograph, courtesy Richard H. Jahns.)
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which has bifurcated a formerly extensive play a to the northwest. The central part of the crater is occupied by a flat-floored basin, which is perhaps 200 feet above the "outside" playa floors. An aerial view of Cerro Colorado com- prises figure 19.
'. -
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Figure 20. Typical exposure ash, showing aeolian cross-bedding in central portion, and still-air deposition above and below.
No. 47) IVES: THE PINACATE REGION 29
Studies of this ash cone indicate that there were at least two ash-emit- ting vents during the most recent activity, and that there were at least two episodes of ash emission. Soundings in the extensive playas and ash flats to the south show that there were at least three ash eruptions at no great dis- tance, and that all three were deposited in water. Similar ash several miles north of Cerro Colorado shows the typical vague stratification and gritty tex- ture of ash that has settled in a dry environment, and has been undisturbed since its initial fall.
An ash eruption, probably at Cerro Colorado, is graphically described in Papago legends (Lumholtz, 1912, p. 203; Ives, 1935), and other considera- tions lead to the conclusion that Cerro Colorado is more than 250 years old, but probably notmorethan 1,000 years old (Ives, 1956). It is surely the young- est of the major volcanic structures at Pinacate.
Notable, throughout the Pinacate Region, is a complete absence of ac- tive or extinct hydrothermal phenomena, such as hot springs or mud pots, al- though such features accompany relatively recent volcanic activity in adja- cent areas, such as at Cerro Prieto, Baja California (Ives, 1951c), which is sometimes visible from the summit of Pinacate Peak. The "hot wells" north- east of Lukeville have no known relation to the Pinacate volcanism.
Most of the volcanic features at Pinacate differ from similar and well understood textbook examples of volcanic landforms only in their magnitude, plentitude, and excellent exposure. This is not the case, however, with the great calderas, which are somewhat unique in origin and structure, and prob- ably are more numerous at Pinacate than in any other similar area on earth.
The great calderas have a number of features in common, and hence are all probably of similar origin. Most of them are of similar age, although it is improbable that they were formed simultaneously.
All of the calderas penetrate stratified basalt several hundred feet thick. Dips of these basalt layers suggest that the vents from which the lava issued were within a short distance of the centers of the present calderas. Flow se- quences indicate that there were two groups of lava effusions, separated by a time interval probably some centuries in duration.
Closely associated with all of the major calderas, generally cut into by the crater walls and partly buried, in most instances, by the rim beds, are a number of cinder cones, usually three. Materials constituting these cinder cones are similar to, but more vesicular than, those comprising the upper lava sequences exposed in the calderas.
Masses of material identical to that in the rim beds are found on the crater floors with stratification, dip and strike randomly disarranged, as in a dropped layer-cake, plainly evidencing cave-in conditions, or structural col- lapse.
Adjacent to each crater, and overlying the rim beds in some places are flows of relatively recent lava, extruded in a rather viscous state, so that
30 CALIFORNIA ACADEMY OF SCIENCES (Occ. Papers
flow brecciation is well developed. The lava chaos, south of Crater Elegante, is an excellent example of this.
From this evidence, the great craters at Pinacate can be classified as typical collapse calderas, according to Williams' (1941) definition.
Steps in the formation of the Pinacate calderas are approximately the following. After a period of reasonably normal volcanic activity, with inter- mittent outpourings of lava, eruption of fragmentary ejecta, which may have continued intermittently for hundreds, or even thousands of years, the source magma beneath the vent began to emit great quantities of gases, which carried basalt foam, small ("football-sized") pieces of hardened basalt, and chunks of country rock torn away from the walls of the magma chamber.
The ejecta, after being carried high into the atmosphere, fell back to earth, forming the rim beds and a cone of unknown dimensions at the present site of the caldera. At some craters, at least, there occurred more than one episode of ash eruption.
At some time after the ash eruption, the magma, having lost its gas con- tent, shrank in its underground chamber, producing a void into which the cen- tral part of the cone and parts of the vent walls collapsed. The resultant col- lapse depression was the ancestor of the present caldera. There is some rea- son to believe that the reduction in magma pressure, at each major caldera, was brought about by a flow of lava from an adjacent vent tapping the same magma.
Although minor details remain to be worked out, and there is no assur- ance that these were exactly the same at every caldera, the situation at each is definitely one of a volcano whose cone collapsed, rather than that of one whose cone was blown away.
Cause of the change of volcanic emission from fluid lava to ash-carrying gases is most plausibly explained by assuming that the local magma chamber under the caldera site stoped its way upward until it came in contact with the local water table. When this occurred, crater eruptions became largely super- heated steam under high pressure. The local water table here today is approx- imately at present sea level, and is recharged by the Sonoyta River, whose ancient buried channels crisscross the northern lava apron of Pinacate Peak. The foregoing paragraph, it should be understood, is a working hypothesis which cannot be rigorously tested on the basis of currently available field data.
Recently, Kelly (1952) pointed out a number of similarities between Crater Elegante and a meteor crater (such as Coon Butte, near Winslow, Ari- zona), suggesting a meteoric origin for Crater Elegante. The similarities point- ed cut by Kelly are real, and demonstrate keen and accurate observation. Un- happily, however, Kelly's tabulation is actually a list ofthe features common to both impact and collapse craters.
Differentiation between a meteor crater and a caldera is most easily
No. 47) IVES: THE PINACATE REGION 31
done by study of the structure and composition of the rim beds. Those of a meteor crater, being formed by a single impact and explosion, are laid down in one continuous episode, lasting at most a few hours. Their mass will never be more than that of the "missing" crater material, and they are most unlikely to have any consistent bedding or stratification.
Rim beds of a caldera, in contrast, are laid down during one or more eruptive episodes, each lasting an appreciable time (days, weeks, or months). Volcanic rim beds, wherever seen, have a rough stratification; and commonly, as at Pinacate (also at Katmai), contain aeolian cross-bedding and cut-and- fill structures. The mass of rim-bed material and volcanic ash commonly great- ly exceeds that of the "missing" crater material, sometimes by a factor of ten or more.
Meteor crater rim beds are composed of mechanically shattered country rock, and can be substantially duplicated by crushing the same material in a mortar. Rim beds of volcanic origin, however, even though they are chemically similar to the source rocks, are of much lesser density, and of a more glassy texture. An appreciable percentage of these fragments contain locked-up stress- es, so that, when scratched with a diamond point, they disintegrate explosive- ly, like "Rupert's drops." Volcanic rim-bed components closely resemble com- mercial insulatingmaterials ("rock wool," etc.) made by blowing superheated steam through molten slag; which is just about the way they were produced in nature.
The presence of magnetic rock fragments on the desert surface near Crater Elegante, cited by Kelly, is a normal desert phenomenon. Nodules com- posed of various magnetic iron-manganese oxides, but lacking a metallic core and hence lacking the Widmanstatten lines characteristic of meteoric iron, are normal components of the "desert pavement" in most parts of western North America.
Water Holes
Because of their survival importance, the water holes of the Pinacate Region could well be regarded as the principal geographic features of the area. Known water holes which can be found in the lava region are shown in figure 5. Whether or not a given water hole will contain water at a specific time depends upon the nature of the natural reservoir, and the previous sea- son's rainfall intensity and distribution.
The largest and most dependable water hole in the area is Tinaja de Los Papagos, which consists of three rock pools, and has a very large col- lecting area. These natural tanks normally contain water for two or more years after a heavy rainfall, and have seldom been completely dry during recorded history. The water in them, however, becomes most foul ("como un pozo neg- ro") two years after a natural replenishment.
32 CALIFORNIA ACADEMY OF SCIENCES (Occ. Papers
Batamote, the easternmost of the Pinacate water holes, apparently re- ceives some of the underflow of the (usually dry) Rio de Sonoyta. Although it reportedly never goes completely dry, the water becomes almost undrinkably saline, and highly cathartic, during dry seasons.
Tinaja de Carlina, Tinaja de Emilia, and Tinaja de los Chivos usually contain water for slightly more than a year after refilling, so that, until the recent diminution in summer storms, they were classified as "permanent" water holes.
The other water holes are much more ephemeral, most of them contain- ing water for only a few weeks or months after a heavy rain in their immediate vicinity. The writer has never seen water in the unnamed tinaja on the east side of the Sierra Blanca, for example, although an excellent pool structure is present, which should hold water for several years if ever filled.
Recent field studies have shown a great confusion of names and loca- tions with respect to the Pinacate water holes, and these same investigations have given clues to the reason. Various travellers have gone to the described sites of named water holes, and found water. In natural consequence, they have assumed that the water hole found was the named water hole. Later, in comparing notes and photographs with others, it was learned that the "Tinaja del Zorillo" of one worker bore little physical resemblance to the "Tinaja del Zorillo" of another worker, even though the locations were substantially identical. There is also the problem of several names attached to (supposedly) the same water hole. Tinaja de Emilia, for example, is also known as "The Old Pinacate Tank," and as Tinajas (note plurality) de Palo Verde. Recent field work has shown that this is not a single water hole, as was commonly believed, but a family of four large pools and half a dozen smaller ones in an area perhaps half a mile square. Interestingly, the Papago Indians were aware of this multiplicity many generations ago, for they named the area Moitjutupo (many pools). A similar situation seems to prevail at every other water hole in the area, with only some of the subsidiary pools as yet surely located. There is no assurance that all of the water holes or groups of water holes at Pinacate have been located by white men.
Studies of the reservoir structures at Pinacate disclose that most of them are plunge pools below knick-point waterfalls, the knick-point usually being located at the edge of a lava flow. A typical water hole, the lower pool at Tinaja de Carlina, due east of Pinacate Peak, is shown in figure 21. There are six other pools, most of them leaky and of small capacity, up canyon from this site. In a number of arroyos, former water hole structures can be found, with the reservoir structure completely eroded away, so that it will no longer store water.
Because of the geologic youth of the area, and of the great hardness of the local basalts, many observers have found great difficulty in reconciling
No. 47)
IVES: THE PINACATE REGION
33
*m
^-v
;**••
fa
Figure 21. Tinaja de Carlina, a typical plunge-pool water hole at Pinacate.
the deep erosion of the water hole structures with the known scanty rainfall of the region. Actually, the problem was completely solved by G. K. Gilbert (1917), almost half a century ago, when he observed deep channeling of ba- salt lavas, in a matter of weeks, by the debris-laden runoff waters of hydraulic mining operations. The same general erosion situation prevails at Pinacate, although the erosion proceeds intermittently there, and not continuously, as in a hydraulic mining operation.
During the "annual" rains, when all of a year's rainfall occurs in one afternoon (always in folklore, commonly in actuality), the runoff waters chan- nel into the steeper arroyos, there attaining measured speeds exceeding 1,000 feet per minute. At the same time, they carry, in suspension, up to 35 per cent, by volume, of rock fragments, which are at least as hard, on the average, as the basalt forming the walls and floors of the arroyos. Additionally, the runoff waters carry and roll along a considerable bed load of basalt and other fragments.
In consequence, the runoff waters in contact with the walls and floors of the arroyos have most of the properties of grade-B valve -grinding compound, and very rapidly corrade the confining rocks. Because of the increased vis- cosity of the runoff, by virtue of its suspended and transported debris load, and the rapidity of motion, the corrosion shapes are largely determined by lo-
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Figure 22. Sculpture of basalt by debris-laden flood waters.
cal flow pattern of the runoff, and are little influenced by the joint arrangement in the rock.
The typical rock sculpture by rapidly-flowing and debris-laden runoff waters, in an arroyo at the western extremity of the lava cascade, on the north- east slope of the main Pinacate massif, is shown in figure 22. Note that the corrasion structures here cut directly across the local joint pattern, which here is mostly cooling-cracks.
At present rainfall frequencies and intensities, it appears that a lava flow, in this environment, having suitable knick-points, will develop plunge- pool structures, and hence water holes, in about five centuries after the lava cools. An increase in the rainfall will speed up this process only if the tor- rential nature of the runoff is maintained.
Former Inhabitants
The Pinacate Region today is completely uninhabited, and goes unvis- ited for weeks and sometimes months at a time. The last regular resident of the area, the hermit Carvajales, an Arefiero Papago, disappeared from the record about 1912. For some years prior to that, he lived in a cave near Tina- ja de los Papagos, at first with his wife, and later alone. He subsisted on
No. 47) IVES: THE PINACATE REGION 35
camotes ("roots of the sand," Ammobroma sonorae), which he dug in the sand dunes west of the lavas, and corn and beans which he grew at an ancient temporale about two miles downstream (west) from Tinaja de los Papagos. About once a year, he went to Sonoyta with his burro, to purchase luxury items (flour, sugar, tobacco) and to get drunk.
During most of the nineteenth century, and for an unknown time before, there were two bands of Indians, iocally called Areneros (sand people), living at Pinacate. The eastern band were essentially Papago in their language and culture, and remained on friendly terms with the inland Papago of Arizona and Sonora. Most of these died of some sort of a plague about 1851 (Lumholtz, p. 329), the survivors went inland, and were absorbed into the Papago population. One of these, Jose Juan of Quitovaquita, lived to a great age, and was a fre- quent visitor to Sonoyta, where he was regarded as "un buen Indio— un cabal- lero."
The western band of Areneros were apparently linguistically Papago, but had close cultural relationships with the Yumas, to the northwest, from whom they obtained most of their pottery. During the mid-nineteenth century, they became known as bad actors, and were accused (probably correctly) of numerous robberies and murders along the Camino del Diablo. Finally, about 1890, a Mexican posse, sent out to avenge two murders near Sonoyta, killed or drove out the Areneros on the west side of Pinacate. These numbered about 100 at the time.
Dependable local informants, such as Alberto Celaya, of Sonoyta, state that the Areneros probably never numbered more than about 200, a figure sub- stantiated by the census contained in the Kino-Manje-Salvatierra narratives of two and a half centuries ago. This figure is also compatible with the water and game availability at Pinacate prior to about 1940.
For some centuries prior to 1910, the Areneros were regularly visited by groups of inland Papago, who journeyed to the shores of the Gulf of Cali- fornia to gather salt (Lumholtz, 1912, pp. 99, 163, 218, 269-272, 285). Addi- tionally, there were periodic visits, by inland Papago parties, to various "holy places" at Pinacate; and various tribal gatherings, apparently for games and ceremonials, at Tinaja de los Chivos.
Evidence left behind by the Areneros includes a profusion of pottery shards at all campsites, groups of shelter circles (Ezell, 1954) and bedrock mortars at major water holes, several agricultural sites ("temporales"), and a complicated network of trails from water hole to water hole. Remaining sec- tors of these trails are mapped in figure 5. The appearance of such a trail, between Tinaja de Emilia and Tinaja de Carlina, is shown in figure 23. Many other trail sectors, not shown in the map, are visible from the air.
Throughout the Pinacate Region, and in surrounding areas, there is a profusion of marine shells, mostly of types, such as Cardium, which are use-
36
CALIFORNIA ACADEMY OF SCIENCES
(Occ. Papers
ful as utensils and tools. Edge wear on many specimens shows clearly that they were so used. Some of the shells are quite young, still containing organic material, suggesting an age of less than about 100 years. Other ages are rep-
23- This dim narrow trail was worn into the lava mantle rock at by the bare or sandled feet of Arehero Papagos.
Pinacate
No. 47) IVES: THE PINACATE REGION 37
resented. The oldest shells which are classified as artifacts only by infer- ence, not only contain no organic material, but are decalcified and disintegrat- ing, suggesting ages of many hundreds of years. These shells and small frag ments show clearly that the Areneros, and perhaps their predecessors, either visited the seacoast frequently, or had close relations with people who did. Some reports (Childs, 1954) indicate that the western Areneros augmented their diets with fish and shellfish.
Extrapolation of dates from other areas (Rogers, 1958) suggests that the beginning date of the Arenero occupation of the Pinacate Region was about 700 A.D. This is a tentative date, which could well be in error by a century or more, and should be reviewed whenever radiocarbon datings of salient or- ganic cultural materials become available.
Voluminous, but not very specific, evidence in the form of very old transported marine shells and bones; lithic artifacts with weathered, oxidized, or sandblasted surfaces or with caliche induration; shell mounds on the aban- doned "25-foot" complex of shorelines; and old campsites in places that are now unsuitable; strongly suggest the presence of one or more pre- Arenero cul- tures in and about the Pinacate Region.
Recent and continuing studies by Paul Ezell (1954), of San Diego, and Julian Hayden, of Tucson, Arizona, show plainly that there were pre-Arenero cultures in the Pinacate Region. The immediate predecessors of the Aren- ero were the Amargosa people, who first came to the area about 2,000 years ago as Amargosa I, and who vanished from the record, as Amargosa II, about 700 A.D., probably by assimilation into the group now known as Arenero.
During an appreciable part of the period from about 5,000 to about 2,000 years ago, the Pinacate Region was occupied by the SanDieguito I people, who are known principally for their lithic artifacts. Details of the transition from San Dieguito I to Amargosa I are not shown by available evidence, al- though a drying climate at roughly the time of the transition is somewhat sug- gestive.
During the Altithermal interval, a time of high temperatures and great drought, filling an appreciable part of the interval from 10,000 to 5,000 years ago, there is no record of human occupation of the Pinacate Region, or of other sites for some distance to the north and west.
Not satisfactorily fitted into the regional archaeological record are the people who accumulated shell mounds and middens along the shores of the Gulf of California during the occupation, by the sea, of the "25-foot" shore- line sequence (Ives, 1963a). Marine occupation of this shoreline sequence oc- curred several times duringthe approximate interval 10,000 B.C. to 2,000 B.C., and some crustal warpage took place during this time, producing a multipli- city of shorelines in some places, as at Bahia laCholla. At various locations on this shoreline are shell mounds and middens, some containing shells that are unquestionably old, and some certainly of no great antiquity. None of these
38 CALIFORNIA ACADEMY OF SCIENCES (Occ. Papers
mounds are as large as the great shell mound at Punta Antigualla, between Kino Bay and Boca del Infierno, west of Hermosillo.
Present evidence does not disclose with any assurance whether there was once a shore culture west of Pinacate, somewhat like the Seri of early historic times; or whether the shell mounds were built by members of other identified cultures, who visited the shores of the Gulf repeatedly, as did the western Arenero. Quite obviously, more specific datings of the shorelines are much to be desired.
No evidence has been found, in the Pinacate Region, of any early men who hunted the mammoth and ground sloth, nor is there any present evidence or suggestion of human occupation of the lava areas prior to San Dieguito I time (about 5,000 years ago).
Tentative Chronology
Field evidence in the Pinacate Region discloses a complex sequence of physiographic and climatic changes, all taking place within a relatively short time, geologically speaking. Some of the stratigraphic sequences permit datings, but these can be only tentative. Most of the materials at Pinacate are too old for effective radiocarbon dating; and much too young for effective use of helium-lead 206, and similar methods.
Largely by extrapolation from other areas, it is concluded that the first major lava outpouring at Pinacate occurred at about the time of the Pliocene- Pleistocene transition, or perhaps one million years ago. The topography at that time was considerably rougher than at present, as the immense deposits of Quaternary alluvium had yet to be eroded from the uplands and laid down upon the bolson floors. The climate was much like that at present, with rain- fall scanty and torrential, as is shown clearly by sediments laid down by riv- ers in the Sonoyta Valley and elsewhere.
From the sequence at Punta Pehasco it is plain that the first major lava outpouring was followed by a period of erosion, then by eruptions of ash, and still later by another massive outpouring of basalt. These lavas were ex- tensively faulted and eroded, so that only the exposures at Punta Penasco and Batamote remain today. During a part of this time the lava at Punta Penasco, but not that at Batamote, became the floor of a playa, as is indicated by a deposit of gypsum atop the promontory. Shortly after this, for the gypsum is nowhere deeply eroded, the area was submerged, producing a bed of turritella shells and a boulder beach on the summit of Punta Penasco. This submerg- ence is related to the "300-foot" shoreline of other reports. As this shore- line cannot be traced northward beyond the Pinacates, or southward much be- yond the mouth of the Rio Concepcion, the submergence of the Punta Pehasco area is attributed to local crustal warpage, rather than to a widespread change of sea level.
No. 47)
IVES: THE PINACATE REGION
39
Shells connected with this shoreline are of modern types, still living in the Gulf; they lack organic matter, and are slightly decalcified, making them somewhat fragile. From this evidence, it is concluded that the "300-foot" shoreline is not much older than early Wisconsin.
If, as is usually the case, the regional water table rose in response to the rise in sea level producing the "300-foot" shoreline (and later reverted to its present stand at approximately modern sea level), the maximum level of the lake which once occupied Crater Elegante is explained, as is also the present adequate subdrainage of the crater, and a check on the dating of the crater is furnished.
A second stratigraphic sequence, partly overlapping the first, is furn- ished by the sediments and shorelines at Pelican Point, just west of Bahia la Cholla. Here, on the east face of a granite faultblock mountain, there is a large stratified deposit of "marine peat," composed of roots, muck, and shell fragments. This is correlated with the "300-foot" shoreline on the basis of type and condition of organic content. The "marine peat" has been eroded con- siderably, and is overlain by volcanic ash, present as a large ramp (fig. 23) to the north, and as a smaller ramp to the south. The base of the large ramp is clearly truncated by both members of the "25-foot" shoreline, here more than 60 feet above msl. owing to local crustal warping. This places the age of the ash ramp, attributed to Moon Crater (fig. 5), somewhere between earli- est Wisconsin, the probable age of the "300-foot" shoreline, and 10,000 to 2,000 B.C., the age of the "25-foot" shoreline. Inspection of the degree of erosion of the various deposits indicates that the ash ramps are not very much older than the "25-foot" shoreline; and that they are very much younger than the "marine peat" associated with the older (and higher) shoreline. This evidence is shown in figure 24.
Figure 24. Eastern face of Pelican Point, west of Bahia la Cholla, Sonora, showing sedimentary veneers and shorelines. M = "marine peat," A = ash beds, SS = shorelines, both being members of the "25-foot" complex. North, and Bahia la Cholla, are to the right of this view.
40 CALIFORNIA ACADEMY OF SCIENCES (Occ. Papers
Study of more complicated geological sequences suggests that the main Pinacate Peaks attained approximately their present height and shape perhaps 100,000 years ago; and that the lava cascade, many of the peripheral lavas, and most of the cinder cones date from the Wisconsin, during which most of the great calderas were formed. The most recent lavas, and some of the small- er spatter cones (as at Batamote), are probably of very late Wisconsin age.
Most recent major activity at Pinacate was almost certainly the last ash eruption at Cerro Colorado, concerning which there is apparently aPapago legend, suggesting that it took place after 700 A. D. The presence of volcanic ash in a sedimentary stratum also containing Hohokam artifacts (about 700- 1300 A.D.), at Sonoyta, lends support to this speculation.
Available evidence furnishes no clue concerning the period of dormancy of Pinacate. It is entirely possible that the source magma is now exhausted, so that the various volcanos there can be classed as extinct. It is equally possible, however, that the area is merely quiescent, and is "building up steam" for another series of eruptions. Present conditions (June, 1962), which include lack' of hydrothermal phenomena, absence of local hot areas, and ab- sence of recurrent local microseisms, give considerable assurance that Pina- cate will not go into violent eruption without some such warnings.
Work in Progress
Because of its size and complexity, the Pinacate Region is by no means scientifically "worked out" by the publication of this geographical paper. A number of other studies by the author are now under way. These include: (1) a study of drainage and drainage changes in the Pinacate Region as a result of volcanic activity; (2) a study of Pleistocene shoreline warpages along the Gulf coast; (3) and a study of flooding in the Sonoyta Valley. Other continuing studies on the Region are those of Paul Ezell (1954) of San Diego State Col- lege, on Arenero and related cultures; Julian D. Hayden of Tucson, Arizona, on the cultures at Pinacate, together with detail mapping of ancient trails in the area; and Richard H. Jahns (1955) of Pennsylvania State College, on the caldera morphology at Pinacate. A "Discovery" report on Moon Crater, and a summary of the field findings during more than two decades of work at Pina- cate, by Glenton G. Sykes of Tucson, Arizona, is much hoped for.
Acknowledgments
During the long course of this study, which was twice interrupted by military service, valuable assistance of many sorts was received from a large number of people. Unhappily, a majority of them have not lived to see the completion of the field work. These include Dr. Daniel Trembly Mac Dougal of Carmel, California; Col. Jefferson Davis Milton, of Tombstone, Arizona; Judge Isuaro Quiroz, of Sonoyta, Sonora; Mr. Pedro Bravo, of Ajo, Arizona; and Jose Juan (Orozco), of Quitovaquita, Arizona-Sonora.
No. 47) IVES: THE PINACATE REGION 41
To Alberto Celaya, of Sonoyta, Sonora (1885-1962: Ives, 1962c), the writer is indebted for hospitality on many occasions over a period of more than thirty years, for sound advice, and for a great quantity of useful and de- pendable information. Several other members of the Celaya family have also given valuable help. To Mr. Ygnacio C. Quiroz (1887-1962: Ives, 1963b), pio- neer settler at Bahia la Cholla, the writer is indebted for hospitality on many occasions, transportation to many historic sites, and helpful discussions of local historical and anthropological problems. Mr. Caesario Mota, long time Chief of Immigration at Sonoyta, assisted the writer on many occasions by un- tangling the red tape incident to border crossings, and provided helpful local information.
Mr. Julian Hayden, of Tucson, Arizona, assisted greatly in this work by supplying advance information on the archaeological phases of his investi- gations at Pinacate. The writer is greatly indebted to Rev. Dr. Bonaventure Oblasser, O.F.M., known to the Papago people for the last half-century as "Palthi Ventura," for helpful discussions of field problems.
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