Dear all, If you have an interest in the time-dependent mechanical properties of Earth's interior, please consider submitting an abstract to *Session DI015*. The official session title and description are provided below. We are also excited to advertise our two invited presenters: Joshua Russell, Syracuse University Thomas Breithaupt, University of Cambridge Looking forward to seeing you in New Orleans, Lars Hansen (on behalf of all conveners) Max Bezada Colleen Dalton Hatsuki Yamauchi *Title:* Time-Dependency of Earth's Mechanical Behaviour: a Synthesis of Observational, Laboratory, and Theoretical Approaches *Abstract:* Description: To fit a multitude of geophysical observations, from seismic attenuation to post-glacial relaxation, Earth's mantle must respond to stress in a more complex fashion than a simple Maxwell (elastic + viscous) model. Understanding the time-dependent, "transient" response of rocks between these endmember regimes is essential for an accurate description of Earth's mechanical behaviour. Moreover, the precise nature of the transient behaviour encodes information about Earth's present thermodynamic state, microphysics, and even (via crystallographic fabrics and grain size) stress and strain history. We invite contributions from the seismology, geodesy, rock-physics, and geodynamics communities to evaluate and assimilate recent progress on understanding Earth’s transient mechanics. Particular topics of interest include (but are not limited to): new lab observations of, or theoretical descriptions for, grain-scale deformation; attenuation/viscosity anisotropy; the role of partial melt; multifrequency approaches that span orders of magnitude in frequency and space; and novel geophysical measurements that address Earth's transient mechanics.