Ground-Penetrating Radar Investigation of a Rapidly Developed Small Island in a Lake in Southern Georgia, USA

Abstract

Collapse sinkholes commonly form in karstic limestones of the Floridan aquifer of southern Georgia, USA. The limestones are capped by impermeable strata that can obscure developing sub-surface voids and catastrophically collapse when too much of their underlying support has been removed. We investigated the overnight appearance of an island in a Georgian lake and its possible relationship to the underlying Floridan aquifer using ground-penetrating radar and global-positioning-satellite spot elevations. The island is adjacent to a submerged sinkhole with an arcuate depression and whose development included convergent downward slumping. Compression created by the convergence probably squeezed lake-bottom sediments upward to form the unusual island. Our methodology can be applied to other lakes in karst regions and may prove useful for diagnosing existing or future subsidence risks.