Giant, strongly nonlogarithmic, magnetic relaxation was observed in BSCCO-2212 crystals irradiated with 5.8-GeV Pb ions due to flux pinning in columnar defects. The underlying flux-creep mechanism was identified as a vortex-loop nucleation process proposed by Nelson and Vinokur [Phys. Rev. Lett. 68, 2398 (1992)]. The crossover in the creep regime from depinning from a single rod to variable-range hopping was observed as a function of rod density. Another type of crossover, from combined pinning involving preexisting defects to purely columnar defect pinning, was observed on crossing the irreversibility line of the pristine material.