The National Science Foundation Division of Earth Sciences awarded the University of Illinois a $127,723 Project Grant under the Geosciences federal grant program (CFDA 47.050) to conduct collaborative research on interpreting mantle deformation from September 2022 through August 2027. The University will integrate theory, experiments, and observations spanning seismic to convective timescales to better understand the Earth's mantle rheological response and the underlying microphysical processes that control viscoelasticity. Key products and services include observational work characterizing frequency dependent upper-mantle dissipation in three locations using seismic and geodetic data; experimental work investigating how dislocations affect transient creep under various conditions; and modeling work developing new constitutive laws for transient creep and incorporating more sophisticated rheologies into viscoelastic deformation codes. Broader impacts involve training 10 graduate and undergraduate students and convening a 120-person synthesis workshop to outline recent advances and shape future research topics.