Subspace barrier is the term used of subspace when it acts as a barrier between two places. An anti-time eruption was located inside a subspace barrier. A convergence of three inverse tachyon pulses from three different timeperiods ruptured the barrier and paradoxically created the anomaly. A new subspace barrier was generated artificially around the anomaly, with static warp shells, to collapse it. (TNG: "All Good Things..." )