Sand dunes are a distinctive feature of many desert regions on Earth. They also occur on other planetary bodies, notably Mars and Titan. This book provides an in-depth assessment of current knowledge of their morphology and sediments as well as key processes and dynamics. It blends legacy knowledge and concepts with the latest developments in the field.
Recent and ongoing research shows that desert sand dunes form part of self-organized complex systems of aeolian bedforms that are part of local to regional-scale sand transport systems in which sand is moved by the wind from source zones to depositional sinks via transport pathways. The state of these systems can be evaluated in terms of sediment supply, availability, and mobility. This approach enables assessment of the response of dune systems to changes in hydroclimate and other boundary conditions on a range of spatial and temporal scales. These include annual to decadal changes in precipitation, including drought cycles and mega-droughts; through long term climate changes (e.g. glacial-interglacial cycles) throughout the Quaternary.
Dune systems provide excellent examples of self-organized systems, which develop over time and in space as the non-linear response of sand surfaces to the wind regime (especially its directional variability) and the supply of sand. As the spatial scale increases, the number of variables decreases and smaller-scale processes (e.g. the saltation of sand grains) are subordinated to and decoupled from emergent, larger-scale behavior, such as interactions between dunes. This reduction of variables with increasing scale facilitates understanding of key aspects of dune-field patterns, such as dune spacing and dune reorientation with changes in wind regime as well as the assessment of responses to external changes on differing spatial and temporal scales. It also provides a framework in which to transfer knowledge of dune systems on Earth to other planetary bodies, such as Mars and Saturn’s moon Titan.
Sand seas and many dune fields contain large volumes of sand, implying that their accumulation has taken place over many thousands or tens of thousands of years, during which Quaternary climatic and sea level changes have had a significant impact on sediment supply, availability, and mobility. Analysis of patterns of dune morphology and morphometry, as well as stratigraphic and dating studies of dune sediments in many areas indicates the importance of the legacy of Quaternary periods of dune construction, stability, and reworking.
The original version of the “Geomorphology of Desert Dunes” was published in 1995 and preceded many important developments in the field including: the luminescence dating revolution, enabling a chronology of periods of aeolian accumulation and dune formation in many areas, as well as assessment of rates of dune accumulation and movement; the advent of ground penetrating radar, facilitating imaging of the sedimentary structures of dunes; advances in technology, facilitating more detailed measurements of winds and sand transport on dunes, and their relationships to the formation and dynamics of desert dunes; studies of the mineralogy and provenance of dune sand using geochemical, isotopic, and remote sensing approaches, and numerical modeling of dune processes and dynamics. The insights gained by these new approaches have enabled greater understanding of the dynamics of desert dune systems on different timescales, but also have posed many new questions to be addressed by field studies and numerical modeling. In many cases, modeling of processes and forms has resulted in new insights, but also greatly exceeded the ability to test the models in the field. This new edition of the Geomorphology of Desert Dunes has been extensively revised to reflect the advances in the understanding of desert dune processes, dynamics, and history that have taken place over the past three decades, building on the work discussed in the original edition. As before, the content and approach of this book reflects the author’s experience in studies of dunes in different desert regions.
Author: Nicholas Lancaster