Near-Surface Geophysics in Geomorphology

Near-surface geophysical methods can provide information on subsurface structure and stratigraphy that is critical to understanding surficial processes. Gravity, magnetics, resistivity, electromagnetics, ground-penetrating radar, and various seismic methods are applied across a range of process domains, including faulting, volcanism, topography and weathering, hillslope processes, coastal and sea-level change, aeolian and fluvial processes, and glacial and periglacial processes. Gravity and magnetic methods have long been used to image faults and other tectonic and volcanic features, and they have also been used to document weathering patterns. With the development of multi-electrode resistivity systems, resistivity profiling has become a staple tool to map the structure and water content of slope deposits and volcanic features. Ground-penetrating radar studies have been crucial to understanding of geologic features as varied as the internal structure of aeolian dunes, coastal and fluvial deposits, the structure and volume of glaciers, the spatial distribution of sinkholes, and the geometry of tephra and lahar deposits. Key to successful studies are calibrations against direct observations and/or uses of multiple complementary methods. Increased efficiencies in geophysical data acquisition and positioning in recent years have made possible very-high-resolution three-dimensional (3-D) or quasi-3-D imaging of subsurface structures. However, there is still a mismatch in the typical spatial scales of large remote-sensing-based studies and smaller geophysical surveys. Bridging this disconnect with new geophysical acquisition techniques and new instrumentation such as terrestrial laser scanning should improve our understanding of the role that subsurface structure plays in the evolution of topography