the seismic swarm in 1973 appears to have been a major submarine eruption. the last eruption, between 2001 and 2004, went unobserved and formed the nafanua volcanic cone; for the most part, the shape of the volcano has not changed over time. repeated eruptions like the one that formed nafanua could cause vailulu'u to emerge from the sea. the summit of vailulu'u is shallow enough that explosive eruptions may occur which can affect coastal communities and ships. it appears that isostatic effects from the growth of the seamount may have altered shorelines on tutuila.