Long-term evolution of the 1 M_⊙, Z = 10^-8 stellar model during the development of the core He-flash, the PIE, and the subsequent dredge-up event. t = t₀ corresponds to the time of maximum He-burning luminosity. As in Fig. 2, thick solid and dot-dashed lines represent the position of maximum energy release due to H-burning and He-burning, respectively. Merging of the HCZ and the stellar envelope occurs around 1100 yr after the PIE takes place.