the origin of the samoan volcanic chain has been explained with either a hotspot influenced by the tonga trench or by cracking of the pacific crust; today the preferred theory is that the samoan chain is a hotspot-generated volcanic chain while the "anomalous" younger volcanism is produced through an interaction between the islands and the tonga trench and a neighboring transform fault. this hotspot is under the influence of the mantle flows triggered by the tonga trench, which distort the rising plume and also changes its upwelling flux. this interaction has only begun recently.