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Textbook example

A classic textbook example of such theory in action is the chain of volcanic islands that form Hawaii. The islands get progressively older as they move away from the current active volcano, and were believed to be formed by the Pacific plate moving over a stationary hotspot.

There have, however, been a number of features of Pacific island chains that have puzzled scientists. One is that there is a ‘dogleg’ turn in the Hawaiian chain of islands, which would require the massive Pacific plate to have shifted at a nearly a right-angle within just a million years or so.

Another anomaly is that when scientists have studied other chains of Pacific islands, they have found that the pattern of island ages in the chain does not fit the theory as neatly.

Tarduno noted that the active volcano of modern day Hawaii is at a latitude of 19° North. If the plume from deep below was stationary, then it would be expected to have always been at this latitude.

However when Tarduno and colleagues used ‘paleomagnetism’ to measure what latitudes extinct volcanoes on other islands erupted, they found that 40 to 60 million years ago, the volcanoes erupted much further north. This suggested that the magma plume was moving - not stationary.

“The only way to account for these findings is if the Pacific plate was almost stationary for a long time, while the magma plume was moving south,” said Dr Rory Cottrell, coauthor of the paper. “At some point about 45 million years ago, it seems the plume stopped moving, and the plate began.”