The Sand at the Far End of a Chevron Tells You Exactly How Far the Wave's Energy Reached

Chevron deposits are not random accumulations of material. They are a precise record of the energy dynamics of the wave that created them, and Randall Carlson explains exactly how to read them.

The process is bimodal - the incoming wave carries a mixture of sediment of different sizes, and as it moves inland it progressively loses energy. Water in motion has what geologists call competency - the capacity to transport particles of a given size. As that competency decreases, the water begins to drop its load in a predictable sequence. The largest, heaviest material is deposited first, closest to the source. As the wave continues inland and slows further, progressively finer material falls out of suspension. By the time the wave reaches its furthest inland extent, only the finest sand remains in transport - which is why the distal end of a chevron deposit is characteristically sandy while the proximal end contains coarser material. The grain size gradient across the deposit is a direct record of how the wave's energy dissipated as it moved across the landscape.