Boiling (motion, not temperature) sand springs fed by ground water moving upward along distinct conduits occur along the Dismal River in the Nebraska Sand Hills. The cylindrical conduits are developed in alluvium and are as large as 10 m in diameter and 44 m deep. Sides of the spring conduits are firm. Boiling sand is overlain in several places by a clear layer of water in the spring. Time-varying wave patterns and boils can be observed along the interface between these layers. Sediment within the conduits is generally well sorted, although some debris is present. Because of their large size, firm sides, and persistence in time, the conduits have the potential for preservation as vertical cylindrical structures comparable to those reported in sedimentary rocks of several ages. The discovery of preserved structures is evidence of paleo-ground-water discharge, and therefore the structures are a useful mapping tool for determining position in landscape evolution.
- Geological Society of America