Trimble Knob

Trimble Knob is an isolated conical hill in Highland County, Virginia, southwest of Monterey, rising from a flat farming valley and standing out as the most conspicuous igneous feature in the area. It is the eroded remnant of an ancient volcano or diatreme, with a basalt core cutting through older Devonian shale and calcareous mudstone. Its form makes its volcanic origin especially clear in the landscape. The site is important because its volcanic activity dates to the Eocene, with basalt dated to about 35.0 ± 0.5 million years ago, making it one of the youngest volcanoes on North America’s east coast and part of a subtle central Appalachian volcanic province.

Monterey, Virginia · United States