​Loess is characterized by an open structure of fine volcanic sand and silt particles with connecting clay bridges and buttresses at contacts. At low moisture content, the formation presents high stiffness and shear strength. When the moisture content increases, the soil structure undergoes a sudden volume collapse. This experimental study of Argentinean loess includes laboratory tests (index properties, shear wave velocity, permittivity and conductivity) and field tests (CPT, SPT and down-hole seismic). Micro-level analytical models of electrical forces, suction and cementation are developed to gain insight into the observed behavior. It is shown that geophysical methods present significant advantages that are complementary to standard field measurements for the characterization of loess deposits.