Brains
Glaciers today are usually associated with melting and retreat. Yet inside the shattered crater of Mount St. Helens, Washington, something unexpected is happening. Against the backdrop of a warming world, this young and restless volcano is slowly rebuilding itself, and within its crater walls sits a rare anomaly: a glacier that is actually growing.
Its name is Crater Glacier, the world’s youngest glacier, sitting at an approximate elevation of 6,526 feet. It is also officially known as Tulutson Glacier, its original Indigenous designation, though the U.S. Board on Geographic Names formally approved the name “Crater Glacier” in 2006.
Before we get into the core of this story, let’s zoom out for a quick glacier 101. A glacier is a large body of densely compacted snow and ice that forms over years to decades when snowfall consistently exceeds melting. Over time, the snow compresses into ice, and under its own weight, the glacier slowly flows downslope, reshaping the landscape beneath it.
What makes this glacier unique, especially in a warming climate, comes down to a near-perfect combination of three key factors:
1) A protective blanket: Rockfall and volcanic debris constantly cascade onto the glacier, forming a natural insulating layer. This debris acts like a shield, reducing direct solar heating and slowing the melt rate.
2) A north-facing, shaded crater: Crater Glacier sits tucked against the north side of Mount St. Helens’ inner crater. The steep crater walls block much of the sun’s direct radiation, keeping temperatures lower than the surrounding terrain.
3) A relentless supply of snow and avalanches: Snow doesn’t just fall here; it pours in. Frequent avalanches from the crater walls continuously feed and build the glacier, creating one of the most efficient accumulation zones in the entire Cascade Range.
But perhaps the most striking part is just how quickly the glacier formed.
From virtually no ice after the 1980 eruption, Crater Glacier has thickened to approximately 600 feet (about 200 meters) near the central dome complex. A 2023 peer-reviewed paper published in the Bulletin of Volcanology found that from 2009 to 2019, the glacier grew by approximately 13.8 million cubic meters, while the glacier toe advanced several hundred meters.
Unlike most glaciers, which primarily flow downslope, Crater Glacier is also being shaped from within. As lava domes continue to grow inside the crater, they physically deform the ice, thickening, splitting, and driving it outward. The United States Geological Survey estimates the glacier’s advance rate at roughly 4 inches per day.
Despite an active eruptive period from 2004 to 2008, the glacier continued to grow and, by mid-2008, had completely encircled the lava domes — ice surrounding active lava.
As the climate continues to warm, the future of Crater Glacier remains uncertain. Its evolution will depend on the balance between volcanic reshaping, snowfall, and rising temperatures. Time will tell whether it continues to grow or eventually retreats as it moves beyond the crater’s protection.
