Brent Finnegan -- November 22nd, 2010
Mole Hill, that lonely mound of earth just west of Harrisonburg is a lot younger than the rest of the mountains that define the Shenandoah Valley. And the rocks that make up the formation are significantly different than those commonly found in nearby George Washington National Forest. (Previously mentioned on hburgnews.com)
Very little is known about Rockingham County’s lone volcano, but that’s beginning to change. JMU geology professor Elizabeth Johnson got permission from the landowner to study the area, and takes students to explore the volcanic formation. (Disclosure: I’m currently employed by the JMU Office of Public Affairs. My tenure in that office ends this week)
Jenny Marder reports for PBS News Hour:
Several times a semester, Liz Johnson, a geochemist and a James Madison University professor, packs her geology students into a van and heads west on Route 33 from Harrisonburg, beyond the local youth center and the Miracle Car Wash, and through the Mennonite part of town. As the van rounds a turn, the mountain looms suddenly into view.
Most of the rocks in Virginia’s Valley and Ridge Region are sedimentary, and date back roughly 300 to 540 million years to the early Paleozoic Era. But Mole Hill, which rises 1,895 feet above sea level, is geologically much younger. Radiometric dating shows that it was formed about 48 million years ago, in the Eocene Era, a time in which the region was otherwise tectonically quiet. “It may not seem obvious if you don’t know a lot about rocks,” says Callan Bentley, a local geologist and professor at Northern Virginia Community College. “But if you’ve got a whole bunch of sedimentary rocks that make up a province, then what the hell is a volcano doing there?” (read more)