There are millions of years beneath our feet, which is probably true of everywhere we walk.
In Grayson Highlands, though, the relentless interplay of volcanic upheaval and erosion is frozen in time. The boulder fields vibrate with the history of deep geologic forces pushing ancient rock to the surface.
The landscape unfolds with geologic narratives from one of the world’s most ancient mountain chains, shaped over hundreds of millions of years by orogeny, erosion, glaciation, and shifting climates.
Over time, these mountains were worn down to their current heights—6,000 feet or less—making them far more accessible today than when they first towered as rivals to the Himalayas.
Geologist Douglas Rankin dedicated years to unraveling the region’s tectonic history, making sense of the immense forces that sculpted these peaks. In this way, a hike through Grayson Highlands is also a journey into Earth’s deep past—a story of monumental collisions, upheavals, and long periods of quiet transformation.
Quartzite and the Deep Roots of the Blue Ridge
Quartzite outcroppings punctuate the grassy balds, standing frozen in a journey that began over a billion years ago. What was once sand, deposited in a shallow sea, hardened into quartz-rich rock during the Grenville Orogeny—one of the first great mountain-building events in eastern North America.
Unlike softer sedimentary rocks, quartzite resists erosion, which is why these jagged outcrops remain while the surrounding landscape has worn away. Many formations show signs of frost wedging, a slow but powerful process where water seeps into cracks, freezes, expands, and eventually fractures the rock.
Tectonic Forces and the Appalachian Uplift
As you ascend through the highlands, you’re walking across the remnants of multiple continental collisions. The Appalachians first rose during the Taconic Orogeny (~470 million years ago), when the Iapetus Ocean closed and landmasses collided. Later, the Acadian Orogeny (~375 million years ago) and the Alleghanian Orogeny (~320–250 million years ago) further folded and compressed the ancient crust.
At their peak, the Appalachians stood as tall as the Rockies. But over hundreds of millions of years, wind, water, and ice wore them down, leaving behind the ancient roots of a once-mighty range.
Glacial Remnants on Mount Rogers
A shift in the landscape occurs as the trail enters the dense forests near the summit of Mount Rogers. Here, quartzite gives way to metamorphosed volcanic deposits—evidence of eruptions tied to the same tectonic forces that shaped the region. The Mount Rogers Formation contains rhyolite, a fine-grained volcanic rock that hints at a time when this landmass was part of an equatorial supercontinent.
The forest itself tells a story of deep climatic change. Mount Rogers is home to a high-elevation spruce-fir forest, a remnant of the Pleistocene Epoch (~2.6 million to 11,700 years ago). While the Appalachian Mountains were never fully glaciated, colder Ice Age climates allowed boreal forests to extend much farther south than they do today. As temperatures warmed, these forests retreated to higher elevations, surviving only in isolated “sky islands” like Mount Rogers.
Today, the cool, wet microclimate at the summit supports a dense canopy of Red Spruce (Picea rubens) and Fraser Fir (Abies fraseri), offering a glimpse into the past.
Erosion, Streams, and the Future of the Highlands
Descending from the summit, the ongoing forces of erosion become clear. Small streams carve through the valleys, carrying away sediment in a slow but persistent process that will, over millions of years, continue to flatten these mountains.
Unlike the rapid erosion seen in younger mountain ranges, the Appalachians wear down at a steady rate of 5-20 millimeters per 1,000 years. The grassy balds of Grayson Highlands, shaped by both geologic and human influence, are another reminder of this ongoing transformation.
While some balds formed naturally over bedrock with thin, nutrient-poor soils, centuries of livestock grazing have kept them open, preventing forest succession. Without continued grazing, these meadows would eventually give way to forest once again.