New Paper: Kinematics and dynamics of the East Pacific Rise linked to a stable, deep-mantle upwelling

The East Pacific Rise (EPR) is the fastest spreading part of the global ridge system, and has a couple of other unusual features. Spreading at the ridge is asymmetric, with about 55-60% of the oceanic crust produced over the past 50 million years found on the western side of the ridge (the Nazca plate). This asymmetric spreading has contributed to the other unusual feature: if you plot the position of the EPR in a mantle reference frame, the central part of the ridge has remained stuck over the same bit of the mantle for 83 million years. This is unexpected, because divergence at ridges is generally thought to be a response to forces elsewhere in the plate system, principally slab pull at subduction zones. Without a strong dynamic reason to stay put, we would expect ridges to wander around over the underlying asthenosphere. And they all do; except for the East Pacific Rise, which, as the fastest spreading ridge, is also the least likely to stay put by chance.

In a new paper in Science Advances, we argue that these unusual features of the East Pacific Rise are combined with another: based on modelling of mantle flow, the part of the mantle that the East Pacific Rise is stuck over is the location over a strong, stable upwelling of the mantle that extends all the way down to the core-mantle boundary. It appears that this is one place in Earth’s tectonic system where the mantle drives the plates, rather than vice versa.

Read the paper here (Open Access)