Sinkhole swarms from initiation to stabilisation based on in situ high-resolution 3-D observations

Abstract

We study in this paper the evolution of sinkhole fields along the Dead Sea coastal plains, from initiation to stabilisation. The prevailing hypothesis attributes their formation to the dissolution of a buried halite layer by groundwater but fails to explain their evolution in some places and their stability in others. Based on thirteen years of high-resolution laser scanning and field surveys, we trace a complete evolutionary cycle of sinkholes and show that the prevailing theory explains only the first out of a four-stage cycle. We show that following the formation stage an acceleration phase begins when the sinkholes interact with the drainage system. A deepening and spatial localisation phase ensues. Then, some parts of the field cease to expand, leading to a fourth stage of stabilisation. We further show that during their embryonic stage, sinkhole development is limited due to a lack of connectivity between the surface and subsurface hydrological processes, but as this connectivity evolves, the development rate increases up to three orders of magnitude. Moreover, observations show a high correlation with hydrological seasonality. The most active field demonstrated a development rate of 13,540m3/month during the wet season, in contrast to a rate of 1010m3/month during the dry season. These measurements and observations allow us to propose a new theoretical model for sinkhole swarm development, from initiation to stabilisation, with linkage to seasonality and hydrology.