Crustal Strain and Deformation

We stand at a critical juncture in the evolution of the Pacific/North America plate boundary system. This major transform plate boundary system that began 12-14 million years ago has both grown and migrated inland, generating distributed shear across California and the Great Basin. The evolution continues to the present. Although a map of the Basin and Range suggests spatially uniform extension, geodesy reveals a recent focusing of deformation near its western and eastern edges. This, in turn, suggests dramatic differences in the material properties within the crust and mantle across the Basin and Range that are probably thermally induced.

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Deformation within the Pacific/North American plate boundary zone occurs over a wide range of spatial and temporal scales. On the largest scale, shortening that produced the North American Cordillera is giving way to shear and extension that is now pulling this region away from the stable continent. This provides us with an actively deforming natural laboratory that should greatly increase our understanding of plate-boundary processes.

Because these processes have dominated North American geology over the last several billion years, the North American continent is an excellent place to unravel the general evolution of our continent.

Scientific Focus Points