Eastern Mojave Vegetation Singing and Booming Sand Dunes of California and Nevada  

Dennis T. Trexler and Wilton N. Melhorn  

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Topics in this Article:
Historical Background
Location and Site Characteristics of Booming Dunes
Non-Booming Dunes
Literature Cited
 Originally published in California Geology. Republished on the World Wide Web by permission of the authors and the publisher.

Other articles:
• FAQ:  Singing Sands;  V020050306010;

Locations: Sand Mountain.
Full Size ImageSand Mountain, Nevada  

Singing and Booming Sand Dunes of California and Nevada



  • Division of Earth Sciences Environmental Research Center University of Nevada, Las Vegas Reno, Nevada



  • Department of Geosciences Purdue University West Lafayette, Indiana

    California Geology

  • 39(7), pp. 147-152, July 1986



    Literature Cited:
    - Curzon of Kedleston, Marquess, 1923.
    - Humphries, D. W., 1966.
    - Stein, M. A., 1912.

    Locations: Kelso Dunes.  

    Historical Background

    Full Size Image
    Kelso Dunes
    A characteristic of some desert dune sands is an ability to emit acoustical energy when disturbed. This phenomenon has been reported from the Middle East for more than 1500 years and in Chinese literature from as early as the ninth century (Stein, 1912). Many people are familiar with the squeaking sounds typically produced when one walks across wetted beach sands. However, sounds produced by desert sand dunes have been variously described as roaring, booming, squeaking, singing, and musical. For the latter description, the results have been compared to such musical instruments as a kettle drum, zither, tambourine, bass violin, and a trumpet (Curzon, 1923). Other more recent observations liken the sounds to a foghorn or low-flying, propellor-driven aircraft (Humphries, 1966).

    Literature Cited:
    - Lindsay, J. F., D. R. Criswell, T. L. Criswell, and B. S. Criswell, 1976.

    Locations: Kelso Dunes. Sand Mountain.  

    The production of sound in desert dunes is not as common as the squeaking of beach sands. In 1976 it was reported that only 27 areas in the world were known to exhibit the booming sound phenomenon and only three sites in the United States were known to produce booming or barking sounds: (1) Kelso Dunes, California; (2) Sand Mountain, Nevada; and (3) Barking Sands at Maria, Kauai, Hawaiian Islands (Lindsay and others, 1976).

    Literature Cited:
    - Haff, D. K., 1979.
    - Melhorn, W. N. and D. T. Trexler, 1977.

    Locations: Big Dune. Crescent Dunes. Eureka Sand Dunes. Panamint Dunes.  

    Full Size Image
    Figure 1. Location map of sand dunes described in this report.
    Subsequently, four additional sites in California and Nevada that exhibit the booming sounds in the field have been identified (Melhorn and Trexler, 1977 and Haff, 1979). These sites are Eureka Dunes and Panamint Dunes in California and Crescent Dunes and Big Dune in Nevada (Figure 1).



    Literature Cited:
    - Fairbridge, R. W., 1968.
    Full Size ImageFigure 2. Grain size vs. standard deviation of grain size.  

    Factors Necessary for Sound Production

    All sound-producing desert dune sands are medium grained, and very well sorted to well sorted, but so are many non-musical desert sands (Figure 2). The sand must be dry, because as little as 0.1% moisture makes a marked difference in sound producing capability, and 1% moisture permits only feeble sound production (Fairbridge, 1968).

    Literature Cited:
    - Lindsay, J. F., D. R. Criswell, T. L. Criswell, and B. S. Criswell, 1976.  

    Another factor which affects the ability of sands of the proper size to produce audible acoustic energy is contamination by fine-grained material such as dust or chalk powder. Probably one of the most significant controls discovered (Lindsay, 1976) is that sound producing sand grains are highly spherical, moderately well-rounded, and have highly polished (frosted) surfaces. The smoothness of a grain surface can, however, be discerned by electron microscopy, and thus infers that variability of surface roughness is important at the micron scale.
      The relative rarity of booming desert sands throughout the world indicates that they form or exist under special and limited conditions. Probably the foremost requirement for the production of sound by desert sands is an ability for the wind, through reworking of sand grains over long reaches of transport (multiple generations of sand movement), to produce well-rounded, extremely smooth, frosted sand grains.



    Literature Cited:
    - Bagnold, R. A., 1954.
    - Bagnold, R. A., 1966.
    - Lindsay, J. F., D. R. Criswell, T. L. Criswell, and B. S. Criswell, 1976.  

    Sound Production

    Until recently the mechanism which produces the audible sounds was only conjecture. An early hypothesis (Bagnold, 1954) suggested that the sound is produced by a piezo-electric effect-the production of electrical currents by quartz grains under mechanical stress. More recently it has been shown that a booming sound is produced by the internal shearing of sand grains during avalanche down a dune slope (Bagnold, 1966). The overriding of superjacent layers of sand grains provides the energy of sound production. Bagnold's theory was discounted in part by Lindsay and others (1976) who state, "that two independent mechanisms must be at work ...squeaking sand suggests a simple mechanical explanation of sound production ...in both wet and dry sand. Sound production of booming sand appears to be related to mechanical coupling between grains". Whatever internal mechanisms exist, if sand of an appropriate grain-size and smoothness is naturally or artificially put into motion, sound will emanate and will in some instances provide an observer with vibrations which can be felt through the body.



    Literature Cited:
    - Lindsay, J. F., D. R. Criswell, T. L. Criswell, and B. S. Criswell, 1976.

    Locations: Sand Mountain.  

    Characteristics of the Acoustic and Seismic Signals

    The sound produced by desert dunes initially has only a single frequency, but after two or three seconds a much lower beat frequency is established. The vibration within the sand is enhanced at the aural sensation level as the low frequency wave components intensify by reinforcement. Lindsay, (1976) measured the acoustic and seismic energy emitted from Sand Mountain, Nevada, and determined that booming sand produces seismic signals composed of one or more narrow frequency peaks limited to the 50 to 80 Hz (cycles per second) range, as well as appreciable broad-band output below 20 Hz.
      Acoustic emissions overlay, but are broader than, the seismic peaks in the 50 to 80 Hz range. First-order harmonic peaks also occur between 100 and 180 Hz.

    Literature Cited:
    - Haff, D. K., 1979.

    Locations: Kelso Dunes.  

    A recording of the sound produced from Kelso Dunes in California (Figure 3) was analyzed into Fourier coefficients (Haff, 1979). The peak energy output is at 92.8 Hz, and has a full width at half maximum of approximately 4 Hz.

    Locations: Crescent Dunes.  

    Acoustic emissions from Crescent Dunes (Nevada) in July 1976 were so loud and realistic that the authors' field assistant was searching the skies for a turboprop aircraft. A recording was made recently at Sand Mountain which, after the first several seconds of sound emission, can best be characterized as resembling the flight sound of a B-29 aircraft.






    Locations: Baker. Kelso. Kelso Dunes.  

    Location and Site Characteristics of Booming Dunes

    Kelso Dunes, California

    Kelso Dunes are located in the Devil's Playground area, 28 miles (45 km) south of Baker, California (Flynn and Kerens 15-minute quadrangles, Lat. 3448'N, Long. 11543'W) near Kelso along the Union Pacific Railroad tracks. The dunes are accessible by a well-graded gravel road (Kelbaker Road) which connects Interstate 15 with Interstate 40 on the south.

    Literature Cited:
    - Haff, D. K., 1979.
    Full Size ImageFigure 3. Fourier components of induced booming event at Kelso Dunes near Baker, California (from Haff, 1979).  

    The highest part of the dune area is 656 feet (200 m) above the surrounding terrain. Acoustical events were generated on the highest dune. Haff (1979) reports that "the most spectacular and enduring vibrations were produced by the movement of large quantities of sand. This could be initiated by vigorous kicking at the sharp dune crest in order to dislodge a metastable surface layer on the lee slopes". The frequency spectra of such an event are presented in Figure 3.

    Literature Cited:
    - Sharp, R. P., 1966.

    Locations: Afton Canyon. Mojave River. Soda Lake.  

    Sharp (1966) has shown that sand which has traveled farthest in any dune field should provide the best sand for sound production. Sand at the Kelso Dunes traveled 35 miles (56 km) from the delta area of the Mojave River where it emptied into the Pleistocene lake basin now occupied by Soda Dry Lake east of Afton Canyon, the terminus of the Mojave River.

    Literature Cited:
    - Haff, D. K., 1979.  

    The sample collected by Haff (1979) from the Kelso Dunes was a medium-grained sand (1.6phi 0.33 mm) and was very well-sorted.



    Locations: Eureka Sand Dunes. Eureka Valley. Last Chance Range.
    Full Size ImageEureka Sand Dunes, California. Photo by R. Rust.  

    Eureka Dunes, California

    Eureka Dunes are located in Eureka Valley, north of Death Valley, along the western edge of the Last Chance Range (Last Chance 15-minute quadrangle, Lat. 376'N, Long. 11740'W). The dune is accessible via a sign-marked dirt road leading off the main Eureka Valley road.

    Literature Cited:
    - Anonymous, 1984.
    Full Size ImageEureka Sand Dunes  

    Eureka Dunes form a singularly massive dune complex, without a large present-day sand supply area. It reaches an elevation of 680 feet (207 in), is 3.3 miles (5.3 km) long, 1.5 miles (2.4 km) wide (Anonymous, 1984), and is undoubtedly the highest dune in California. In 1984, the dune area was designated a National Natural Landmark by the U.S. Department of the Interior.

    Literature Cited:
    - Haff, D. K., 1979.  

    Sand collected by Haff (1979) at this dune was medium-grained (1.6phi 0.33 mm) and very well-sorted. Haff reports that the dune "demonstrated all the booming properties observed at Kelso Dunes, although the acoustic intensity did not appear to be as great".
      [I have been able to produce sound from the Eureka Dunes. I did this by running along the crest of the steepest slip face in a way to get a lot of sand moving down slope. The sound produced is reminescent of multi-engine propeller-driven aircraft, such as a B-29, shown in movies about World War 2. The same vibration can also be felt in your feet, and the sand can be seen vibrating.

    Christopher sent me this little bit of video: http://www.schweich.com/images/MOV08493.MPG. Adjust the sound to the maximum, and listen carefully about 2/3 through the video.]



    Literature Cited:
    - Haff, D. K., 1979.

    Locations: Panamint Dunes.  

    Panamint Dunes, California

    This dune complex is located at the north end of Panamint Valley (Panamint Butte 15-minute quadrangle, Lat. 3628'N, Long. 11727'W). The dunes are accessible by an indistinct dirt road leading north from California Route 190. These dunes are considerably lower than Kelso Dunes and occupy a rather small area (Haff, 1979). Abundant vegetation covers the southern portion of the dune complex.
      The dune crests exhibit moderate acoustic activity. Sand avalanches were easily initiated on the steepest slopes. No significant booming sounds were apparent. Forced displacement initiated by walking on steep leeward slopes or by moving one's hands through the sand did elicit audible vibrations.



    Other articles:
    • Field Notes:  20020605330;
    • U. S. Highway 50:  Sand Mountain;

    Locations: Campbell Valley. Fallon. Four Mile Flat. Lake Lahontan. Sand Mountain. Walker River.
    Full Size ImageSand Mountain, as seen from US. Highway 50  

    Sand Mountain, Nevada

    Sand Mountain is a terminal, seif dune complex located at the margin of Four Mile Flat playa approximately 3 miles (5 km) east of U.S. Highway 50, 18 miles (25 km) southeast of Fallon, Nevada (Four Mile Flat 7-minute quadrangle, Lat. 3919'N, Long. 11824'W). Some of the sand forming the dune at Sand Mountain has traveled more than 36 miles (40 km) northeastward from the source area in Campbell Valley, the delta of the Walker River where it was debouched (transported by streams) into ancient Lake Lahontan more than 20,000 years ago. The dune is nearly 400 feet higher than the surrounding terrain, and is 4 miles (6 km) long and more than 1 mile (1.6 km) wide.

    Literature Cited:
    - Criswell, D. R., J. F. Lindsay, and D. L. Reasoner, 1975.
    - Lindsay, J. F., D. R. Criswell, T. L. Criswell, and B. S. Criswell, 1976.  

    Criswell and others (1975) and Lindsay and others (1976) investigated the acoustic and seismic signals of the dune in 1973. During our initial visit to the dune in 1975, we were unable to elicit the booming sounds described previously by other investigators, although local inhabitants of the area assured us that the booming sounds were very prevalent (Margaret Wheat, personal communication, 1975). The sand appeared to be dry. However, as already mentioned, less than 0.1 percent moisture can adversely affect the ability of the sand to produce sound.
      In August of 1985, booming sounds were produced at Sand Mountain by initiating an avalanche by moving down the lee slope of the dune. The sound at first was a basal beat frequency, but after several seconds the sound resembled the over flight of a squadron of propeller driven aircraft.



    Locations: Big Smoky Valley. Crescent Dunes. Tonopah.  

    Crescent Dunes, Nevada

    This dune complex is in western Nye County on the east side of Big Smoky Valley, approximately 10 miles (16 km) northeast of Tonopah (Lone Mountain, Nevada, 15-minute quadrangle). The area of active dunes is easily accessible by car over well-maintained roads. From Tonopah, one proceeds west on U.S. Highway 50 and 95 approximately 2.1 miles (3.3 km) to a paved county road to Anaconda's Molybdenum mine; turn right (north) and go 10 miles (16 km). The dune is visible on the right and a sign denotes the turn off.

    Locations: Lake Tonopah. San Antonio Mountains.  

    The dunes rise only 230 feet (70 m) above the surrounding terrain. The sand which currently comprises these dunes at the western toe slope of the San Antonio Mountains has been derived by deflation from the now dry bed of prehistoric Lake Tonopah, which occupied the lowest portions of southern Big Smoky Valley during the late Pleistocene. The sand at the dune crest has a mean grain-size of 1.63 phi (0.32 mm) and is very well-sorted. A sample analyzed under a microscope contained 80 percent quartz, 15 percent accessory minerals, and 5 percent rock fragments. Approximately one-half of the sample is comprised of grains with a wellrounded appearance, and one-quarter of these grains are frosted. The remaining 50 percent of the grains are subrounded to subangular.
      The highest dune in the Crescent Dunes complex provided the best acoustic characteristics of all dunes visited by the authors. The sounds produced by this dune may not be as sonorous as one might expect, but were easily produced on two occasions during the summer months of 1975 and 1977. The sounds that have been produced resemble that of a low-flying turboprop aircraft.



    Other articles:
    • Field Notes:  6-Jun-06 near Big Dune;
    • U. S. Highway 95:   near Big Dune;

    Locations: Amargosa Desert. Beatty. Big Dune.
    Full Size ImageBig Dune from US Highway 95  

    Big Dune, Nevada

    Big Dune is located in the Amargosa Desert, 10 miles (16 km) south of the town of Beatty in southeastern Nevada, 5.5 miles (9 km) northeast of the California-Nevada state line (Big Dune 15minute quadrangle, Lat. 3630'N, Long. 11635'W). The dune area is easily accessible by paved and dirt roads. Turn off U.S. Highway 95 at the Amargosa Farm area sign approximately 10 miles (16 km) south of Beatty, and proceed approximately 2.5 miles (4 km) to the turn-off (dirt road) into the dune area.
      Big Dune has been misnamed. The elevation of the dune crest above surrounding terrain is approximately 300 feet, which is considerably lower than Sand Mountain, Nevada, and Eureka and Kelso dunes in California.

    Literature Cited:
    - Haff, D. K., 1979.  

    Material collected during a 1977 visit, from a location two-thirds up the dune, has a mean grain-size of 1.4 phi (0.38 mm) and an inclusive graphic standard deviation of 0.43phi (well-sorted). At the time of our visit, the dune did not emit acoustical energy upon initiation of avalanches. Haff (1979) reported that acoustical energy was released during man-made avalanches. Dr. Richard Rust (personal communication, 1984) also was able to elicit sound from the dune while performing research on the Guiliani's Dune Scarab Beetle for the U.S. Fish and Wildlife Service.



    Literature Cited:
    - Rice, Kevin P., 2007.

    Locations: Dumont Dunes.  

    Dumont Dunes

    [I have received one report of sound production from the Dumont Dunes. Sound can be produced by riding down-slope on a motorcycle with the engine turned off (Rice, personal communication, 2007).] Mr Rice writes: "Possibly, because dirt-bikes are heavier, they cause more slip action when bull-nosing down a dune? I've noticed it happens when there is quite a bit of slipping when sand has built up to the angle of repose. I have the impression that slightly damp sand helps, also. The sand seems to shear at the line between the dry sand and the damp sand underneath. Maybe the damp sand is locked in place by moisture and the sound is produced by the sloughing of sand grains over the locked in grains? Basically, two slabs of sand grinding over each other?"




    Literature Cited:
    - Haff, D. K., 1979.  

    Non-Booming Dunes

    Dunes and sand fields which did not emit the booming sounds characteristic of other well-developed terminal dunes have been visited by the authors and by Haff (1979).



    Locations: Death Valley Dunes. Stovepipe Wells.
    Full Size ImageSand dunes at Stovepipe Wells in the late afternoon.  

    Death Valley Dunes, California

    Death Valley Dunes are several miles southeast of Stovepipe Wells (Stovepipe Wells 15-minute quadrangle, Lat. 3637'N, Long. 11707'W). These dunes are easily accessible by foot from California Route 190.

    Literature Cited:
    - Haff, D. K., 1979.  

    Haff (1979) reported that this was the only site of dunes of great height for which no acoustical activity could be generated in the field. He also stated that the dunes are extensively vegetated, which possibly may indicate high moisture content and preclude the ability of the sand to generate acoustical energy.



    Locations: Olancha. Olancha Sand Drift. Owens Valley.  

    Olancha Sand Drift, California

    Located at the southern end of the Owens Lake Valley near the town of Olancha, these dunes are accessible from California Route 190 near the turn off to Dirty Socks Hot Mineral Springs (Keeler 15-minute quadrangle).

    Literature Cited:
    - Haff, D. K., 1979.  

    Haff (1979) apparently did not investigate the well-developed dunes located several miles farther south, instead collecting a sample from a small (1 m) high eastwest trending sheet sand drift near Highway 190. He reported that no sounds could be produced from this site. This is not surprising due to the fact that free movement of the sand over some distance on a steep slope under optimum moisture conditions would be necessary to provide optimum sound producing conditions. Since the sand sample collected by Haff (1979) falls within the realm of sound producing sands (Figure 2, no. 12), the potential for the highest dunes in the field to produce booming sounds would not be surprising.



    Literature Cited:
    - Trexler, Dennis T., and Wilton N. Melhorn, 1986.

    Other articles:
    • FAQ:  CW124001;
    • U. S. Highway 95:  Winnemucca Dunes;

    Locations: Winnemucca. Winnemucca Dunes.  

    Winnemucca Dunes, Nevada

    Full Size Image
    Winnemucca Dunes along US Highway 95
    Full Size Image
    Winnemucca Dunes, Nevada
    This is the largest dune field in Nevada and is located approximately 10 miles (16 km) north and northeast of Winnemucca, Nevada. The eastern extent of the 40 mile (60 km) long dune field is located in the Bliss 15-minute quadrangle (approximately Lat. 4107'N, Long. 11745'W). The dunes do not reach heights of more than 100 feet (30 m), and mostly are stabilized by vegetation near the periphery of the dune field. Active migration, however, is occurring where the dunes cross U.S. Highway 95. The Nevada Department of Transportation removes sand drifts from the highway several times a year.
      The sand from the distal end of the field is very fine-grained (2.6 phi 0.17 mm) and well-sorted. During visits to the area in 1979, booming sounds could not be elicited from several of the highest dunes in the eastern part of the dune field.



    Locations: Clayton Valley. Clayton Valley Dunes. Silver Peak.  

    Clayton Valley Dunes, Nevada

    This complex dune field is located in the southern part of Clayton Valley, 7 miles (11 km) south of Silver Peak, Nevada (Lida Wash 15-minute quadrangle, Lat. 3740'N, Long. 11737'W), and is easily accessible via gravel road. The highest dune rises 280 feet above the valley floor.

    Full Size ImageClayton Valley Dunes from Coyote Summit.  
    The dune sand is of local origin, derived from local deflation of a playa-alluvial fan covered valley only 120 mi² (310 km²) in area. A sample collected from the north end of the dune complex consisted of fine grained sand (2.4phi 0.19 mm) and was well-sorted. Abundant vegetation is present in the interdune areas and on the slopes of the tallest dune. The current trend toward stabilization of the dune was confirmed by the abundance of numerous animal burrows and tracks, even on dune crests.
      This dune did not emit acoustical energy during our 1977 visit and would not be expected to do so because of the fine-grained size of the sand.



    Other articles:
    • Long Valley Road:  Long Valley;

    Locations: Long Valley. Long Valley Dunes.  

    Long Valley Dunes, Nevada

    The dunes in Long Valley are a very localized phenomenon, generated by a blow-out of playa deposits derived from the carbonate bedrock which bounds the valley on both east and west. The dune is located in the Sunshine 7 -minute quadrangle (Lat. 3937'N, Long. 11523'W) in eastern Nevada (Figure 1). A sample collected from the highest dune was a moderately well-sorted, medium-grained sand (1.94phi, 0.28 mm).
      Sound could not be produced from this location during July 1977 by any means of forced displacement.



    Literature Cited:
    - Haff, D. K., 1979.  

    Observations and Conclusions

    To hear the sounds produced by booming dunes in the desert environment is a unique and fascinating experience. Some specific observations, apparent from our casual investigations and those of Haff (1979), are:
    • Sands that have traveled the farthest in a particular dune field have the greatest potential to produce acoustical energy.
    • High dunes with steep, quasi-stable slip faces that are easily put in motion produce the best sounds.
    • Dunes that contain medium-sized sand grains which are very well-sorted to well-sorted are the best prospects for production of acoustical energy.
    • The sands must be very dry and meteorological conditions must provide low-humidity.
    • Well-rounded, frosted sand grains derived from long-distance transport, or multiple generations of sand movement resulting from variable azimuth wind direction appear best suited to the production of booming sounds.
    • Vehicular traffic on dune surfaces tends to degrade the ability of the sands to produce sounds under natural conditions.




    Locations: Crescent Dunes. Sand Mountain.  


    We thank George Ghusn, Jr., who assisted us during the 1977 field session and performed the size analyses on samples collected during that time. Also, Thomas Flynn, of the University of Nevada, Las Vegas, persevered in 1985 at Sand Mountain, Nevada, and produced the booming sounds after unsuccessful attempts at Crescent Dunes. The support provided by the Nevada Bureau of Mines and Geology during the early phases of the study also is appreciated.




    Literature Cited

      A list of all literature cited by this web site can be found in the Bibliography.
      Anonymous. 1984. Eureka sand dunes landmark. California Geology. 37(3):42.
      Bagnold, R. A. 1954. The physics of wind blown sand and desert dunes. Chapman and Hall: London. 265 p.
      Bagnold, R. A. 1966. The shearing and dilation of dry sand and the "singing" mechanism. Royal Society of London, Proceedings Series A. 295: 219-232.
      Criswell, D. R., J. F. Lindsay, and D. L. Reasoner. 1975. Seismic and acoustic emissions of a booming dune. Journal of Geophysical Research. 80(35):4963-4974. Washington DC: American Geophysical Union, December 10, 1975. {TAS}
      Curzon of Kedleston, Marquess. 1923. Tales of Travel. London: Hodder and Stroughton. 344 p.
      Fairbridge, R. W. 1968. Encyclopedia of geomorphology. New York: Reinhold Book Corporation.
      Haff, D. K. 1979. Booming sands of the Mojave Desert and the Basin and Range Province, California. Caltech Internal Report NSF PHY7683685. 26 p.
      Humphries, D. W. 1966. The booming sand of Korizo, Sahara, and the squeaking sand of Gower, South Wales -- A comparison of the fundamental characteristics of two musical sands. Sedimentology. 6: 135-152.
      Lindsay, J. F., D. R. Criswell, T. L. Criswell, and B. S. Criswell. 1976. Sound-producing dune and beach sands. Geological Society of America Bulletin. 87(3):463-473. Boulder, CO: Geological Society of America (GSA), March 1976.
      Melhorn, W. N. and D. T. Trexler. 1977. The Maria effect -- Equilibrium and activation of aeolian processes in the Great Basin of Nevada (abstract). 8th Annual Geomorphology Symposium. Binghampton, New York.
      Rice, Kevin P. 2007. Personal Communication.
      Sharp, R. P. 1966. Kelso Dunes, Mojave Desert, California. Geological Society of America Bulletin. 77: 1045-1074.
      Stein, M. A. 1912. Ruins of Desert Cathay. 2. New York: Macmillan, Inc. 492 p.
      Trexler, Dennis T., and Wilton N. Melhorn. 1986. Singing and booming land dunes of California and Nevada. California Geology. 39(7):147-152. San Francisco, CA: California Division of Mines and Geology, July 1986. {TAS}
    If you have a question or a comment you may write to me at: tomas@schweich.com I sometimes post interesting questions in my FAQ, but I never disclose your full name or address.  

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    Date and time this article was prepared: 7/13/2024 8:13:12 AM