Curved shape of Hawaiian island chain may be due to hot-spot plumes in the deep mantle

Ars Technica : A kink in the Hawaiian seamount chain has prompted researchers to look more closely at plate tectonics and associated mantle plumes of hot rock. Rakib Hassan and Dietmar Müller of the University of Sydney and their coworkers have used computer modeling to study that sharp bend, once thought to be caused by a change in direction of the tectonic plate. The researchers focused on the underlying plumes to simulate what happens deep in Earth’s mantle. At that depth, the rock is unusually dense and hot and becomes putty-like. As the oceanic crust sinks, that dense bottom layer of the mantle appears to get squeezed like toothpaste from a tube and bulges up beneath the Pacific Plate as a series of hot-spot plumes. Moreover, the plumes can migrate. Based on paleomagnetic and radiometric age data, the Hawaiian plume experienced a rapid southward motion between 100 million and 50 million years ago. Because the top of the plume can move at a different pace than the bottom, the plume can tilt and straighten over time, like smoke from a chimney. Not only does that movement correlate well with the sharp bend in the Hawaiian chain, it also explains the more subtle bend in another seamount structure, the Louisville chain, located in the South Pacific.