  We investigate the dynamical properties of the classical antiferromagnetic
Heisenberg model on the kagome lattice using a combination of Monte Carlo and
molecular dynamics simulations. We find that frustration induces a distribution
of timescales in the cooperative paramagnetic regime (i.e. far above the onset
of coplanarity), as recently reported experimentally in deuterium jarosite. At
lower temperature, when the coplanar correlations are well established, we show
that the weath- ervane loop fluctuations control the system relaxation : the
time distribution observed at higher temperatures splits into two distinct
timescales associated with fluctuations in the plane and out of the plane of
coplanarity. The temperature and wave vector dependences of these two
components are qualitatively consistent with loops diffusing in the
entropically dominated free energy landscape. Numerical results are discussed
and compared with the $O(N)$ model and recent experiments for both classical
and quantum realizations of the kagome magnets.
