What is the lithosphere-asthenosphere boundary?



EarthScope Institute on the Lithosphere-Asthenosphere Boundary; Portland, Oregon, 19–21 September 2011 The lithosphere-asthenosphere boundary (LAB) marks a pronounced transition in the mechanical behavior of the upper mantle, separating the strong lithosphere from the weak asthenosphere beneath it. Although this boundary is fundamental to scientists' understanding of plate tectonics, identifying which factors (e.g., temperature, melt, volatiles, mineralogy) are responsible for the rheological contrast at the LAB remains a challenge. Recent geophysical and geochemical observations of the uppermost mantle have motivated a new discussion of this fundamental boundary.