We present spatial and dynamic information on the s=1/2 distorted kagome antiferromagnet volborthite, Cu3V2O7(OD)2.2D2O, obtained by polarized and inelastic neutron scattering. The instantaneous structure factor, S(Q), is dominated by nearest neighbo
r pair correlations, with short range order at wave vectors Q1=0.65(3) {AA}^-1 and Q2=1.15(5) {AA}^-1 emerging below 5 K. The excitation spectrum, S(Q,{omega}), reveals two steep branches dispersing from Q1 and Q2, and a flat mode at {omega}=5.0(2) meV. The results allow us to identify the cross-over at T*=1 K in 51V NMR and specific heat measurements as the build-up of correlations at Q_1. We compare our data to theoretical models proposed for volborthite, and demonstrate that the excitation spectrum can be explained by spin-wave-like excitations with anisotropic exchange parameters, as also suggested by recent local density calculations.
