The White Mountains of New Hampshire may not be the tallest in North America, but they hold a unique place in the story of Earth’s geological evolution. While often thought of as ancient, the mountains themselves are relatively young—especially when compared to truly ancient ranges like South Africa’s Barberton Greenstone Belt (3.6 billion years old) or Canada’s Canadian Shield (over 4 billion years old).
So, where do the White Mountains fit in?
The bedrock of the White Mountains—mostly granite and schist—is old, dating back over 400 million years. However, the mountains themselves were shaped much more recently. They were formed during the Mesozoic Era, somewhere between 124 and 100 million years ago, making them significantly younger than the broader Appalachian range, which dates back as old as 480 million years ago.
During the Mesozoic, intense volcanic activity and the shifting of Earth's tectonic plates helped form the range, pushing molten rock toward the surface. Over time, the granite cooled and solidified, and erosion shaped the mountains into what we see today.
A Range Shaped by Ice
What really gave the White Mountains their current rugged, rounded peaks and deep valleys was the last Ice Age, which ended around 12,000 years ago. Massive glaciers carved out dramatic features like:
Tuckerman Ravine – A deep, U-shaped glacial cirque now famous for its backcountry skiing.
Franconia Notch – A striking mountain pass carved by retreating ice sheets.
The Flume Gorge – A stunning glacially-carved chasm with steep granite walls.
Tuckerman Ravine in Winter
Unlike the Rocky Mountains or Himalayas, which are still rising due to active tectonic forces, the White Mountains are shrinking due to ongoing erosion. In fact, some scientists estimate they may have once been as tall as today’s Alps before time and weather took their toll.
The Youngest of the Old?
While the Appalachians as a whole are often called one of the oldest mountain ranges in North America, the White Mountains themselves are a younger offshoot—but still far older than the Rockies (~70 million years) or the Himalayas (~50 million years).
Their relative youth means they still feature sharp ridges, steep cliffs, and exposed rock faces, but their deep valleys and rounded summits hint at their long history of erosion.
Why It Matters
The White Mountains offer a fascinating glimpse into how mountains evolve over time. They may not be the oldest mountains on Earth, but their geological history spans hundreds of millions of years, shaped by volcanic activity, tectonic uplift, and the relentless power of ice. Today, they stand as one of the most iconic natural landscapes in the Northeastern United States, drawing hikers, geologists, and adventurers eager to experience their dramatic terrain and extreme weather.
