The
volcanic Samoa island chain may have been formed by the activity of the
Samoa hotspot at the eastern end of the Samoa Islands. In theory, that hotspot was created by the movement of the
Pacific tectonic plate over a 'fixed' deep and narrow
mantle plume spewing up through the Earth's crust. One piece of evidence that this activity may have created the islands is that they generally lie in a straight east-to-west line, and the plate is moving from east to west. However, some characteristics of the Samoa islands are inconsistent with this theory. The classic hotspot model (based mostly on studies of the
Hawaii hotspot) predicts that, if plate movement over a hotspot is what created a volcanic island chain, then the farther away from the hotspot the islands and
seamounts in the chain are, the older they will prove to be. Some of the evidence is inconsistent with this explanation for the creation of the Samoa island chain, creating an enigma for scientists. For one thing,
Savai'i, the most western of the Samoa island chain, and
Ta'u Island, the most eastern, both erupted in the last century. For another thing, the
subaerial rock samples initially collected from Savai'i, the westernmost of the islands, are too young by several million years to fit the classic hotspot model of age progression in an island chain. These facts led some scientists to suggest that the Samoa islands were not formed by the hotspot plume. One possible explanation for the inconsistency of the data with the hotspot formation theory is the fact that the island chain lies just north of the
Tonga Trench. An alternative theory is that the islands were formed by
magma seeping through cracks in stressed
fracture zones. However, in 2005, an international team found new evidence that supports the hotspot model. They gathered additional samples from Savai'i – submarine samples from the deep flanks and
rifts of the island. Tests found that these samples are much older than the previously collected samples: They are about five million years old, an age that fits the hotspot model.
2009 Samoa earthquake and tsunami south of the Samoa Islands and north of
New Zealand. The
2009 Samoa earthquake and tsunami killed more than 170 people in the Samoa Islands and
Tonga. The M8.1
submarine earthquake took place in the region at 06:48:11 local time on September 29, 2009 (17:48:11
UTC, September 29), followed by smaller aftershocks. It was the
largest earthquake of 2009.
Vailulu'u Seamount The
Vailulu'u Seamount, an active submerged volcano, lies east of Ta'u in
American Samoa. It was discovered in 1975 and has since been studied by an international team of scientists, contributing towards understanding of the Earth's fundamental processes. Growing inside the summit crater of Vailulu'u is an active underwater
volcanic cone, named after Samoa's goddess of war,
Nafanua. ==Climate==