Dynamics of the Earth’s mantle play an important role in processes that occur farther up toward the surface. For instance, although the eastern coast of the United States is considered a passive margin, convection in the upper mantle can result in activity in the crust. To get a better look at the mantle underneath the North American plate, Schmandt and Lin analyzed data collected by the EarthScope project, which installed a vast network of seismometers across the United States.
By cataloguing the different types of waves that propagate through the mantle underneath the continental United States, the authors built a model of what this mantle looks like and how it interacts with the overlain crust. Major findings from the research include two low-velocity anomalies detected in the central and northern Appalachians that coincide with a known episode of basaltic magmatism that occurred 56–33.9 million years ago and volcanism from a hot spot, respectively.
The authors also found high-velocity anomalies beneath the central and eastern United States, which they suggest could be remnants of a subducted slab that has not yet sunk into the lower mantle. Although their findings provide a new, more in-depth look at the Earth’s mantle, the authors note that more investigations are needed to understand how some mantle processes affect the geologic evolution of various parts of the United States. (Geophysical Research Letters, doi:10.1002/2014GL061231, 2014)
—JoAnna Wendel, Staff Writer
Citation: Wendel, J. (2014), Mantle below North American plate newly modeled, Eos Trans. AGU, 95(50), 484, doi:10.1002/2014EO500013.