Prof. Yishai Weinstein of the Department of Geography and Environment is focused on the geochemistry of water, volcanology and magmatic geochemistry. Weinstein has conducted research studies in major bodies of water including the Mediterranean Sea, the Gulf of Mexico and the Pacific Ocean.
Among his major interests are the interactions between groundwater and the sea, which he has studied using radon and radium isotopes. In addition, his team is exploring the generation of magmas and their aggressive interaction with surface water (phreatomagmatism).
Weinstein’s group studies the patterns and controls on the discharge of groundwater to the sea (known as “SGD”) using a multi-methodological approach, which includes isotopic tracers, as well as direct and geophysical methods.
Their offshore research is accompanied by an onshore investigation, as well as modeling of the coastal aquifer hydrology and its sensitivity to sea level rise.
Recently, the team has become intensively involved in the biogeochemical and microbiological investigation of the submarine aquifer (‘subterranean estuary’), and the impact of SGD on coastal ecology. Another recent research project is that of the bilateral interaction between estuarine rivers and the aquifer.
Weinstein’s group also uses the short-lived radium isotopes 224Ra and 223Ra to determine the age of off-shore seawater, namely the rate of mixing of coastal and offshore seawater.
The Dead Sea is a highly saline lake, with very high concentrations of radium (1,000 times that of ocean water).
Weinstein and his students study the activities and the mass balance of the four naturally occurring radium isotopes in the Dead Sea and in the adjacent aquifer in order to define the extent of lake water circulation in the aquifer during steady states, as well as during the recent sharp lake level decline (1 m/yr).
Radium isotopes are also used to determine the residence time of water (water ‘ages’) in the aquifer and the age of ‘meromixis’ (stratification of the lake with a deep anoxic water body, which terminated with a whole-lake mixing in 1979).
Weinstein’s team studies tuff and other volcaniclastic deposits both in the field and in the lab in order to better understand the various ways by which magmas interact with surface water (‘phreatomagmatism’).
They have focused on two phreatomagmatic structures from the northern Golan – Birket Ram and Mt. Avital, where activity abruptly shifted from typical strombolian activity to a wet hydrovolcanic one.
The causes for these shifts, the time schedules involved, and the relationship between deep and surface processes are studied using various methodologies including field mapping, detailed petrography, granulometry, Ar-Ar age determination and optically stimulated luminescence (OSL) dating.