The moduli space of slope-stable vector bundles on a normal projective variety over an algebraically closed field of characteristic $p\geq 0$ is stratified with respect to the decomposition type. On a smooth projective curve of genus at least 2 we obtain mostly sharp dimension estimates for these strata. As an application, we obtain a dimension estimate for the closure of the prime to p trivializable stable bundles in the moduli space of stable vector bundles.