Skip to main content

Thank you for visiting You are using a browser version with limited support for CSS. To obtain the best experience, we recommend you use a more up to date browser (or turn off compatibility mode in Internet Explorer). In the meantime, to ensure continued support, we are displaying the site without styles and JavaScript.

Aeolian sand sorting and megaripple formation


Sand is blown across beaches and deserts by turbulent winds. This seemingly chaotic process creates two dominant bedforms: decametre-scale dunes and centimetre-scale ripples, but hardly anything in between. By the very same process, grains are constantly sorted. Smaller grains advance faster, while heavier grains trail behind. Here, we argue that, under erosive conditions, sand sorting and structure formation can conspire to create distinct bedforms in the ‘forbidden wavelength gap’ between aeolian ripples and dunes. These so-called megaripples are shown to co-evolve with an unusual, predominantly bimodal grain-size distribution. Combining theory and field measurements, we develop a mechanistic understanding of their formation, shape and migration, as well as their cyclic ageing, renewal and sedimentary memory, in terms of the intermittent wind statistics. Our results demonstrate that megaripples exhibit close similarities to dunes and can indeed be mechanistically characterized as a special type of (‘reptation’) dune.

Access options

Rent or Buy article

Get time limited or full article access on ReadCube.


All prices are NET prices.

Fig. 1: Sand sorting and megaripples.
Fig. 2: Model and field data for wind-driven sand sorting.
Fig. 3: Bulk sand polydispersity and coarsening rate.
Fig. 4: Dune-type versus ripple-type analysis of megaripple morphology and migration.
Fig. 5: Transient sand sorting and megaripple evolution under variable winds.


  1. 1.

    Bagnold, R. A. The Physics of Blown Sand and Desert Dunes (Methuen, London, 1941).

    Google Scholar 

  2. 2.

    Wilson, I. G. Aeolian bedforms—their development and origins. Sedimentology 19, 173–210 (1972).

    ADS  Google Scholar 

  3. 3.

    Pye, K. & Tsoar, H. Aeolian Sand and Sand Dunes (Springer, Berlin, 2009).

    MATH  Google Scholar 

  4. 4.

    Durán, O., Claudin, P. & Andreotti, B. Direct numerical simulations of aeolian sand ripples. Proc. Natl Acad. Sci. USA 111, 15665 (2014).

    ADS  Google Scholar 

  5. 5.

    Andreotti, B., Claudin, P. & Pouliquen, O. Aeolian sand ripples: Experimental study of fully developed states. Phys. Rev. Lett. 96, 028001 (2006).

    ADS  Google Scholar 

  6. 6.

    Manukyan, E. & Prigozhin, L. Formation of aeolian ripples and sand sorting. Phys. Rev. E 79, 031303 (2009).

    ADS  Google Scholar 

  7. 7.

    Kroy, K., Sauermann, G. & Herrmann, H. J. Minimal model for sand dunes. Phys. Rev. Lett. 88, 054301 (2002).

    ADS  Google Scholar 

  8. 8.

    Andreotti, B., Claudin, P. & Douady, S. Selection of dune shapes and velocities part 1: Dynamics of sand, wind and barchans. Eur. Phys. J. B 28, 321–339 (2002).

    ADS  Google Scholar 

  9. 9.

    Sauermann, G., Kroy, K. & Herrmann, H. J. Continuum saltation model for sand dunes. Phys. Rev. E 64, 031305 (2001).

    ADS  Google Scholar 

  10. 10.

    Andreotti, B., Claudin, P. & Pouliquen, O. Measurements of the aeolian sand transport saturation length. Geomorphology 123, 343–348 (2010).

    ADS  Google Scholar 

  11. 11.

    Lämmel, M. & Kroy, K. Analytical mesoscale modeling of aeolian sand transport. Phys. Rev. E 96, 052906 (2017).

    ADS  Google Scholar 

  12. 12.

    Lapotre, M. G. A. et al. Large wind ripples on Mars: A record of atmospheric evolution. Science 353, 55–58 (2016).

    ADS  Google Scholar 

  13. 13.

    Sharp, R. P. Wind ripples. J. Geol. 71, 617–636 (1963).

    ADS  Google Scholar 

  14. 14.

    Yizhaq, H., Isenberg, O., Wenkart, R., Tsoar, H. & Karnieli, A. Morphology and dynamics of aeolian mega-ripples in Nahal Kasuy, southern Israel. Isr. J. Earth Sci. 57, 149–165 (2009).

    Google Scholar 

  15. 15.

    Ellwood, J. M., Evans, P. D. & Wilson, I. G. Small scale aeolian bedforms. J. Sediment. Res. 45, 554–561 (1975).

    Google Scholar 

  16. 16.

    Tsoar, H. Grain-size characteristics of wind ripples on a desert seif dune. Geogr. Res. Forum 10, 37–50 (1990).

    ADS  Google Scholar 

  17. 17.

    Sørensen, M. in The Fascination of Probability, Statistics and their Applications: In Honour of Ole E. Barndorff-Nielsen (eds Podolskij, M. et al.) 1–13 (Springer International, Cham, 2016).

  18. 18.

    Sakamoto-Arnold, C. M. Eolian features produced by the December 1977 windstorm, southern San Joaquin Valley, California. J. Geol. 89, 129–137 (1981).

    ADS  Google Scholar 

  19. 19.

    Ackert, R. The origin of isolated gravel ripples in the western Asgard Range, Antarctica. Antarct. J. 24, 60–62 (1989).

    Google Scholar 

  20. 20.

    Selby, M. J., Rains, R. B. & Palmer, R. W. P. Eolian deposits of the ice-free Victoria Valley, Southern Victoria Land, Antarctica. New Zeal. J. Geol. Geophys. 17, 543–562 (1974).

    Google Scholar 

  21. 21.

    Yizhaq, H., Katra, I., Kok, J. F. & Isenberg, O. Transverse instability of megaripples. Geology 40, 459–462 (2012).

    ADS  Google Scholar 

  22. 22.

    Qian, G., Dong, Z., Zhang, Z., Luo, W. & Lu, J. Granule ripples in the Kumtagh Desert, China: Morphology, grain size and influencing factors. Sedimentology 59, 1888–1901 (2012).

    ADS  Google Scholar 

  23. 23.

    Gillies, J. A., Nickling, W. G., Tilson, M. & Furtak-Cole, E. Wind-formed gravel bed forms, wright valley, Antarctica. J. Geophys. Res. Earth Surf. 117, F04017 (2012).

    ADS  Google Scholar 

  24. 24.

    Brugmans, F. Wind ripples in an active drift sand area in the Netherlands: A preliminary report. Earth Surf. Proc. Land. 8, 527–534 (1983).

    ADS  Google Scholar 

  25. 25.

    Milana, J. P. Largest wind ripples on Earth? Geology 37, 343–346 (2009).

    ADS  Google Scholar 

  26. 26.

    de Silva, S., Spagnuolo, M., Bridges, N. & Zimbelman, J. Gravel-mantled megaripples of the Argentinean Puna: A model for their origin and growth with implications for Mars. Geol. Soc. Am. Bull. 125, 1912–1929 (2013).

    Google Scholar 

  27. 27.

    Bridges, N., Spagnuolo, M., de Silva, S., Zimbelman, J. & Neely, E. Formation of gravel-mantled megaripples on Earth and Mars: Insights from the Argentinean Puna and wind tunnel experiments. Aeolian Res. 17, 49–60 (2015).

    ADS  Google Scholar 

  28. 28.

    Blom, A. & Parker, G. Vertical sorting and the morphodynamics of bed form–dominated rivers: A modeling framework. J. Geophys. Res. Earth Surf. 109, F02007 (2004).

    ADS  Google Scholar 

  29. 29.

    Jerolmack, D. J., Mohrig, D., Grotzinger, J. P., Fike, D. A. & Watters, W. A. Spatial grain size sorting in eolian ripples and estimation of wind conditions on planetary surfaces: Application to meridiani planum, Mars. J. Geophys. Res. 111, E12S02 (2006).

    ADS  Google Scholar 

  30. 30.

    McKenna Neuman, C. & Bédard, O. A wind tunnel investigation of particle segregation, ripple formation and armouring within sand beds of systematically varied texture. Earth Surf. Proc. Land. 42, 749–762 (2017).

    ADS  Google Scholar 

  31. 31.

    Anderson, R. S. & Bunas, K. L. Grain size segregation and stratigraphy in aeolian ripples modelled with a cellular automaton. Nature 365, 740–743 (1993).

    ADS  Google Scholar 

  32. 32.

    Makse, H. A. Grain segregation mechanism in aeolian sand ripples. Eur. Phys. J. E 1, 127–135 (2000).

    Google Scholar 

  33. 33.

    Shiryayev, A. N. in Selected Works of A. N. Kolmogorov: Volume II Probability Theory and Mathematical Statistics (ed. Shiryayev, A. N.) 281–284 (Springer Netherlands, Dordrecht, 1992).

  34. 34.

    Yizhaq, H., Katra, I., Isenberg, O. & Tsoar, H. Evolution of megaripples from a flat bed. Aeolian Res. 6, 1–12 (2012).

    ADS  Google Scholar 

  35. 35.

    Katra, I., Yizhaq, H. & Kok, J. F. Mechanisms limiting the growth of aeolian megaripples. Geophys. Res. Lett. 41, 858–865 (2014).

    ADS  Google Scholar 

  36. 36.

    Seppälä, M. & Lindé, K. Wind tunnel studies of ripple formation. Geogr. Ann. A 60, 29–42 (1978).

    Google Scholar 

  37. 37.

    Fischer, S., Cates, M. E. & Kroy, K. Dynamic scaling of desert dunes. Phys. Rev. E 77, 031302 (2008).

    ADS  Google Scholar 

  38. 38.

    Goossens, D. Aeolian dust ripples: Their occurrence, morphometrical characteristics, dynamics and origin. CATENA 18, 379–407 (1991).

    Google Scholar 

  39. 39.

    Lorenz, R. D. & Valdez, A. Variable wind ripple migration at Great Sand Dunes National Park and Preserve, observed by timelapse imaging. Geomorphology 133, 1–10 (2011).

    ADS  Google Scholar 

  40. 40.

    Yizhaq, H. & Katra, I. Longevity of aeolian megaripples. Earth. Planet. Sci. Lett. 422, 28–32 (2015).

    ADS  Google Scholar 

  41. 41.

    Kroy, K., Sauermann, G. & Herrmann, H. J. Minimal model for aeolian sand dunes. Phys. Rev. E 66, 031302 (2002).

    ADS  Google Scholar 

  42. 42.

    Musa, R. A., Takarrouht, S., Louge, M. Y., Xu, J. & Berberich, M. E. Pore pressure in a wind-swept rippled bed below the suspension threshold. J. Geophys. Res. Earth Surf. 119, 2574–2590 (2014).

    ADS  Google Scholar 

  43. 43.

    Isenberg, O. et al. Megaripple flattening due to strong winds. Geomorphology 131, 69–84 (2011).

    ADS  Google Scholar 

  44. 44.

    Williams, S. H., Zimbelman, J. R. & Ward, A. Large ripples on Earth and Mars. In Proc. 33rd Annual Lunar and Planetary Science Conference 1508 (NASA, 2002).

  45. 45.

    Zimbelman, J. R., Williams, S. H. & Johnston, A. K. Crosssectional profiles of sand ripples, megaripples, and dunes: a method for discriminating between formational mechanisms. Earth Surf. Proc. Land 37, 1120–1125 (2012).

    ADS  Google Scholar 

  46. 46.

    Zimbelman, J. R. Transverse aeolian ridges on Mars: First results from hirise images. Geomorphology 121, 22–29 (2010).

    ADS  Google Scholar 

  47. 47.

    Groh, C., Wierschem, A., Aksel, N., Rehberg, I. & Kruelle, C. A. Barchan dunes in two dimensions: Experimental tests for minimal models. Phys. Rev. E 78, 021304 (2008).

    ADS  Google Scholar 

  48. 48.

    Kroy, K. & Guo, X. Comment on “relevant length scale of barchan dunes”. Phys. Rev. Lett. 93, 039401 (2004).

    ADS  Google Scholar 

  49. 49.

    Franklin, E. M. & Charru, F. Subaqueous barchan dunes in turbulent shear flow. Part 1. Dune motion. J. Fluid. Mech. 675, 199–222 (2011).

    ADS  MATH  Google Scholar 

  50. 50.

    Beck, C. Statistics of three-dimensional lagrangian turbulence. Phys. Rev. Lett. 98, 064502 (2007).

    ADS  Google Scholar 

  51. 51.

    Finkel, H. J. The barchans of southern Peru. J. Geol. 67, 614–647 (1959).

    ADS  Google Scholar 

  52. 52.

    Sauermann, G. The shape of the barchan dunes of Southern Morocco. Geomorphology 36, 47–62 (2000).

    ADS  Google Scholar 

  53. 53.

    Fryberger, S., Hesp, P. & Hastings, K. Aeolian granule ripple deposits, Namibia. Sedimentology 39, 319–331 (1992).

    ADS  Google Scholar 

  54. 54.

    Hesp, P. A. & Hastings, K. Width, height and slope relationships and aerodynamic maintenance of barchans. Geomorphology 22, 193–204 (1998).

    ADS  Google Scholar 

  55. 55.

    Hersen, P., Douady, S. & Andreotti, B. Relevant length scale of barchan dunes. Phys. Rev. Lett. 89, 264301 (2002).

    ADS  Google Scholar 

  56. 56.

    Andreotti, B., Fourrière, A., Ould-Kaddour, F., Murray, B. & Claudin, P. Giant aeolian dune size determined by the average depth of the atmospheric boundary layer. Nature 457, 1120–1123 (2009).

    ADS  Google Scholar 

  57. 57.

    Rasmussen, K. R., Valance, A. & Merrison, J. Laboratory studies of aeolian sediment transport processes on planetary surfaces. Geomorphology 244, 74–94 (2015).

    ADS  Google Scholar 

  58. 58.

    Ping, L., Narteau, C., Dong, Z., Zhang, Z. & Courrech du Pont, S. Emergence of oblique dunes in a landscape-scale experiment. Nat. Geosci. 7, 99–103 (2014).

    ADS  Google Scholar 

  59. 59.

    Hersen, P., Andersen, K. H., Elbelrhiti, H., Andreotti, B., Claudin, P. & Douady, S. Corridors of barchan dunes: Stability and size selection. Phys. Rev. E 69, 011304 (2004).

    ADS  Google Scholar 

  60. 60.

    Hugenholtz, C. H., Barchyn, T. E. & Favaro, E. A. Formation of periodic bedrock ridges on Earth. Aeolian Res. 18, 135–144 (2015).

    Google Scholar 

  61. 61.

    Anderson, R. S. A theoretical model for aeolian impact ripples. Sedimentology 34, 943–956 (1987).

    ADS  Google Scholar 

  62. 62.

    Larsen, S. E., Jørgensen, H. E., Landberg, L. & Tillman, J. E. Aspects of the atmospheric surface layers on Mars and Earth. Boundary Layer Meteorol. 105, 451–470 (2002).

    ADS  Google Scholar 

  63. 63.

    Sullivan, R. et al. Aeolian processes at the Mars Exploration Rover Meridiani Planum landing site. Nature 436, 58–61 (2005).

    ADS  Google Scholar 

  64. 64.

    Claudin, P. & Andreotti, B. A scaling law for aeolian dunes on Mars, Venus, Earth, and for subaqueous ripples. Earth. Planet. Sci. Lett. 252, 30–44 (2006).

    ADS  Google Scholar 

  65. 65.

    Kok, J. F. An improved parameterization of wind-blown sand flux on mars that includes the effect of hysteresis. Geophys. Res. Lett. 37, L12202 (2010).

    ADS  Google Scholar 

  66. 66.

    Lämmel, M., Dzikowski, K., Kroy, K., Oger, L. & Valance, A. Grain-scale modeling and splash parametrization for aeolian sand transport. Phys. Rev. E 95, 022902 (2017).

    ADS  Google Scholar 

  67. 67.

    Andreotti, B., Claudin, P. & Douady, S. Selection of dune shapes and velocities part 2: A two-dimensional modelling. Eur. Phys. J. B 28, 341–352 (2002).

    ADS  Google Scholar 

  68. 68.

    Kroy, K., Fischer, S. & Obermayer, B. The shape of barchan dunes. J. Phys. Condens. Matter 17, S1229–S1235 (2005).

    ADS  Google Scholar 

  69. 69.

    Parteli, E. J. R., Durán, O. & Herrmann, H. J. Minimal size of a barchan dune. Phys. Rev. E 75, 011301 (2007).

    ADS  Google Scholar 

  70. 70.

    Ho, T. D., Valance, A., Dupont, P. & Ould El Moctar, A. Scaling laws in aeolian sand transport. Phys. Rev. Lett. 106, 094501 (2011).

    ADS  Google Scholar 

  71. 71.

    Jenkins, J. T. & Valance, A. Periodic trajectories in aeolian sand transport. Phys. Fluids 26, 073301 (2014).

    ADS  Google Scholar 

  72. 72.

    Castaing, B., Gagne, Y. & Hopfinger, E. Velocity probability density functions of high Reynolds number turbulence. Phys. D 46, 177–200 (1990).

    MATH  Google Scholar 

  73. 73.

    Bohr, T., Jensen, M. H., Paladin, G. & Vulpiani, A. Dynamical Systems Approach to Turbulence (Cambridge Univ. Press, Cambridge, 2005).

  74. 74.

    Sullivan, R. et al. Wind-driven particle mobility on mars: Insights from Mars Exploration Rover observations at “El Dorado” and surroundings at Gusev Crater. J. Geophys. Res. Planets 113, E06S07 (2008).

    Google Scholar 

Download references


We thank E. Schmerler for his kind help with the sand sample preparation and analysis. This research was supported by a grant from the GIF, the German-Israeli Foundation for Scientific Research and Development (no. 1143-60.8/2011). We also acknowledge the hospitality of the KITP in Santa Barbara and the MPI-PKS in Dresden, where this work was started, and financial support by the National Science Foundation under grant no. NSF PHY-1125915, the MPI-PKS Visitors Program, and the German Academic Exchange Service (DAAD) through a Kurzstipendium (for M.L.).

Author information




M.L. and K.K. developed the theory; M.L., A.M., H.Y., H.T. and I.K. designed and conducted the experiments and field surveys; M.L., A.M., I.K. and H.Y. analysed the data; M.L. and K.K. wrote the paper. All authors discussed the results and implications and commented on the manuscript at all stages.

Corresponding author

Correspondence to Klaus Kroy.

Ethics declarations

Competing interests

The authors declare no competing interests.

Additional information

Publisher’s note: Springer Nature remains neutral with regard to jurisdictional claims in published maps and institutional affiliations.

Supplementary information

Supplementary Information

Supplementary Figures 1–4, Supplementary Tables 1 and 2, Supplementary References 1–7

Rights and permissions

Reprints and Permissions

About this article

Verify currency and authenticity via CrossMark

Cite this article

Lämmel, M., Meiwald, A., Yizhaq, H. et al. Aeolian sand sorting and megaripple formation. Nature Phys 14, 759–765 (2018).

Download citation

Further reading


Quick links

Nature Briefing

Sign up for the Nature Briefing newsletter — what matters in science, free to your inbox daily.

Get the most important science stories of the day, free in your inbox. Sign up for Nature Briefing