We present new laboratory experiments on the development of thermal plumes out of a localized heat source in Carbopol, a yield-stress and shear-thinning fluid. Depending on the yield number Y-0, which compares the thermally-induced stress to the yield stress, three different regimes obtain. For low Y-0 (<120), no convection develops; while for intermediate values, a small-scale convection cell appears and remains confined around the heater. For high Y-0 (>260), thermal plumes develop. Their morphology differs from the mushroom-shape typically encountered in Newtonian fluids. Combined temperature and velocity field measurements show that a plug flow develops within the plume thermal anomaly, therefore producing a rising finger-shape. Moreover, light scattering highlights the development of a damaged zone prior to the plume onset, and the peculiar structure of the gel around the plume as it rises. This brings new insights into the solid-liquid transition of soft gels. (C) 2012 Elsevier B.V. All rights reserved.