A plate tectonics model comprised of three major subduction zones explains many major geophysical anomalies and geologic structures observed in the southern Appalachians. The Brevard zone is thought to mark the southeastern boundary of a major Caledonian subduction zone. Many thrust faults of the Blue Ridge and eastern Smoky Mountains are thought to root in this zone. A subduction zone extending along the western margin of the Blue Ridge in Virginia and Smoky Mountains in Tennessee is thought to be an en echelon extension of the Brevard zone. A minimum of 55 km crustal shortening has been calculated for the Brevard zone in western North Carolina. Minor subduction occurred along the Blue Ridge-Smoky Mountain zone during the Hercynian orogeny. The main locus of the Hercynia subduction is thought to have been the Knoxville zone, so named because the basement subcrop of the zone passes beneath Knoxville, Tennessee. Most thrust faults along the Cumberland Plateau-Valley and Ridge boundary are thought to root in this zone. The amount of subduction seems to have been less than that of the Caledonian orogeny. Each inferred subduction zone coincides with northeast-southwest linear gravity lows and parallel discontinuities in the magnetic field. Basement anticlines occur northwest of the Brevard and Knoxville zones.

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