Fig. 3 Rise of a 1D porosity wave with variable bulk viscosity (eq. 27). The background porosity is 2%, the initial amplitude of the cosine shaped anomaly was 10%. Rm = 1000, Rtn = 1, no melting and freezing is assumed. All quantities are non-dimensional according to the scaling laws given in equ. (19). a) Porosity at initial time and t´= 0.06, b) Divergence of the matrix at t´ = 0.06, c) Segregation velocity and its contributions due to buoyancy and compaction-dilatation of the matrix at t´ =  0.06.