Thermal Anomalies Associated with Forced and Free Groundwater Convection in the Dead Sea Rift Valley
Haim Gvirtzman Grant Garven and Gdaliahu Gvirtzman

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ABSTRACT

Thermal Anomalies Associated with Forced and Free Groundwater Convection in the Dead Sea Rift Valley The Dead Sea Rift Valley is a left-lateral transform, along which several rhomb-shaped grabens were formed. At the Sea of Galilee, which is one of these rhomb-shaped grabens, ambiguous heat fluxes were measured: 70-80 mW/m2 at the central part of the lake, 36 mW/m2 at the lake's southern coast (10 km apart), and most surprisingly, about 135 mW/m2 at the southern Golan Heights, 6-8 km east of the graben margin. A detailed geological cross-section, traversing the entire sedimentary basin, was constructed. The hydrodynamics in this cross-section was analyzed quantitatively using a two-dimensional finite element code that solves the coupled variable-density groundwater flow and conductive-convective heat transfer equations. Based on the numerical simulations, different mechanisms of basin-scale groundwater convection are suggested for the two sides of the rift that could influence the transport of heat: (1) forced convection (gravity-driven flow) of hot brines from deeper aquifers to the land surface at the western side; and (2) large-scale free convection (buoyancy-driven flow) of deep groundwater at the eastern side. The different heat fluxes within the rift valley itself are attributed to the different lithology and to the locations of specific conduits through which the hot groundwaters ascend from deeper horizons. These simulations also explain the different salinities of the hot springs on the two sides of the rift.


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