July 18, 2003
Mole Hill in Rockingham county near Harrisonburg, Virginia is all that remains of what may have been the last active volcano in Virginia. The igneous rocks that form the core of the hill have been age dated as 47 million years old, considerably younger than the other igneous rocks in the area, and are the remnants of a conduit of molten rock that fed a volcano long since eroded away in the heart of the Appalachians. Mole Hill rock contains the mineral olivine, typically formed at great depth, and fragments of sandstone torn from country rock far beneath as the hot magma rose to the surface. This modest bump rising from the Shenandoah Valley between the Allegheny Mountains and Massanutten Mountain still has a story to tell for those willing to look at the rocks.