Salt dissolution and sinkhole formation along the Dead Sea shore

Abstract

[1] The formation of sinkholes at the Dead Sea area reflects subsurface cavities formed by salt dissolution. This dissolution is related to the recession of the Dead Sea; the groundwater level and the fresh/saline water interface along the shore decline at a similar rate to the rate of the Dead Sea recession, and brines that used to occupy layers below this interface are flushed out by freshwater. Our finite element modeling shows that dissolution of this salt layer is a plausible mechanism to explain the rapid creation of subsurface holes that collapse and form sinkholes. The positive feedback between the rate of flow, the rate of chemical reaction, and the change in permeability accelerates the dissolution processes and might result in ''reactive infiltration instability'' which is manifested in ''fingers'' of cavities, into which fluid is channeled, and salt is dissolved. The spacing between the sinkholes and the rate of their creation is controlled by several factors including properties of lineaments/faults, incoming groundwater flux, the salinity of the incoming groundwater, the rate of dissolution, the effective specific surface area, the permeability of the salt and clay layers, the permeability-porosity relation, the dispersivity, and the thickness of the layers. We show that the creation of sinkholes occurs only under specific conditions. These conditions must cause an unstable dissolution front which then causes formation of cavities and eventually sinkholes. The simulations, which utilized the best estimated parameters of the studied area, yield results that are similar to those exhibited in the field.

Overview of the geophysical studies in the Dead Sea coastal area related to evaporite karst and recent sinkhole development

“…The drop in the DS level has to lead to the migration of unsaturated (in relation to Cl − ) groundwater into the coastal area, accelerating the dissolution process at the zone in which groundwater comes in contact with the salt layer (Yechieli et al, 2006;Frumkin et al, 2011).…”

“…The salt edge to the west of the DS is often in contact with the sandy-gravel sediments (Yechieli et al, 2004). Thus, salt and clayey sediments divide sand and gravel formations into several subaquifers (Yechieli et al, 2006).…”

“…The first hypothesis ("structural" one) is based on a visual correspondence between sinkhole lineaments and western and eastern fault escarpments (Abelson et al, 2003(Abelson et al, , 2006Closson, 2005;Closson & Karaki, 2009). Based on this similarity, a structural control was assumed and a corresponding numerical model of fault-induced sinkholes was developed (Shalev et al, 2006). Abelson et al (2003) suggested that sinkholes tend to develop along faults, which serve as preferential hydraulic pathways, bringing confined aggressive water upwards to come in contact with salt.…”

“…Gutiérrez et al (2008) propose a phased approach for the identification, investigation, prediction, and mitigation of sinkholes in evaporite terrains. The protective measures were proposed by Taqieddin et al (2000) and Yechieli et al (2006). Probabilistic sinkhole modeling for hazard assessment and sinkhole susceptibility mapping were attempted for evaporite karst (Galve et al, 2009a, b).…”

Salt-dissolution-induced subsidence in the Dead Sea area detected by applying interferometric techniques to ALOS Palsar Synthetic Aperture Radar images

“…In 2006, Shalev et al [28] published the results of a sinkholes inventory constructed for the western side of the Dead Sea. They recorded sinkholes from inventory maps produced in 1980, 1990, 1997, 2001, 2003, and 2004.…”