Sinkholes (dolines) are a huge threat for infrastructures, inhabitants, agriculture and tourism at the Dead Sea. In the last decades a continuous increase of sinkholes particularly along the coastline, both at the western and eastern side of the lake has been observed. The rapid fall of the water level (1-1.5 m per year) is supposed to explain this process - left is a vast area of salt-rich ground of the fallen dry Dead Sea. Sinkholes are caused by the dissolution of soluble minerals (like gypsum, calcite, salt). This enormeous water recession generatesadditionallyhighergroundwater influx,which is driving the subsurface dissolution process.

Atthe DeadSea, thisphenomenonmanifestsitselfin anincreasing formationofdolinesof differentdimensions. They can be either narrow but deep (up to 20 m) or wide (up to 80 m) but shallow. The dimensions as well as the time scale (minutes to days) in which sinkholes occur are depending very much on the mechanical properties of the underground.

Thepicturesshowboththeextentandthedestructive forcesofsinkholes,butalsotheaestheticbeautyof thosestructures

Due to the formation process of void structures and subsequent sinkholes physical parameters are changing and can be detected and monitored by geophysical and remote sensing techniques. To track the changes of those parameters and to characterize the sinkhole affected areas, their vulnerability and possible early warning scenarios, geophysical field surveys (e.g. S-wave reflection seismics, Georadar) are performed regularly in the framework of the Helmholtz Virtual Institute DESERVE.

In addition to the geophysical investigations aerial photography is carried out frequently by using a Helium filled balloon.

On the one hand the pictures help to quantitatively estimate the hazard potential and development of the sinkholes. On the other hand they offer valuable hints on possible processes that lead to the formation of huge depression zones, e.g. the groundwater inflow and the existence of vegetation and water sources.

Moereover it gives useful insights into e.g. the morphology and, by performing repeated surveys, subsidence rates of the sinkholes, which can help to limit hazardous areas and warn the inhabitants in the near future.

*Virtual Institute DESERVE:
DESERVE deals
withthreemajorchallenges:environmental risks,water availabilityandclimate change.TheHelmholtz Virtual InstituteDESERVEis basedontheHelmholtz-expertiseinthedisciplines of "AtmosphereandClimate","Solid Earth"and"Water" fromtheKarlsruheInstituteofTechnology (KIT),theGermanResearch Centre for Geosciences (GFZ)andthe HelmholtzCentrefor Environmental Research (UFZ).

Thereareothercontributionstoatmospheric research (KIT),decreasing water level (UFZ)andseismic risk (GFZ).