Mount Shasta's Glaciers Are Vanishing
What the Data Shows
Seven named glaciers crown Mount Shasta, California's second-highest peak. They've been there for millennia, shaping the mountain's hydrology, its alpine ecology, and the identity of the region. But over the last few years, something has shifted. These glaciers are no longer in slow decline—they're in rapid retreat, and scientists who have monitored them for decades now say their extinction is not a question of whether, but when.
The data is unambiguous, and it tells a story about what's happening across the Sierra-Cascade region under today's warming climate.
The Numbers: How Fast Are They Shrinking?
Whitney Glacier: California's Longest, Now Fragmenting
Whitney Glacier holds a distinction: it's the longest glacier in California. It's also the clearest example of what rapid glacial collapse looks like.
Between 2020 and 2024, Whitney Glacier lost approximately 25 to 30 percent of its total area. That's a quarter of the ice in just four years. More dramatically, the glacier is actively fragmenting—it's breaking apart into at least two separate ice masses, a sign of extreme stress and thinning. Over the past 16 years (since around 2008), the glacier has retreated roughly 800 meters and has thinned by nearly half its original volume.
To put that in perspective: an 800-meter retreat is about half a mile of ice disappearing upslope. That's the kind of change you can see in photographs taken a decade apart.
Konwakiton Glacier: When Glacial Melt Becomes a Hazard
Konwakiton Glacier, on the north-east flank, has drawn attention for a different reason: in 2021, accelerated meltwater from the glacier produced a destructive outburst flood that scoured Mud Creek canyon and threatened the water supply for the nearby town of McCloud. This wasn't a slow seepage—it was a sudden release of accumulated meltwater that demonstrated how unstable the system has become.
Outburst floods from glaciers aren't uncommon, but their frequency and intensity increase as glaciers destabilize and thin. Konwakiton's 2021 event is part of a broader pattern: the mountain's remaining ice is no longer a stable, predictable feature of the landscape.
Snowcover: The Summer Signal
One of the clearest metrics scientists use to assess glacier health is late-summer snowcover—the percentage of the glacier that still retains snow by the end of the melt season. A healthy glacier in equilibrium with its climate needs roughly 60 percent of its surface to maintain snow cover year-round. That snow acts as an insulating cap, slowing ablation and allowing the glacier to persist.
On Mount Shasta, late-summer snowcover has collapsed:
- Late summer 2021: Less than 5 percent of glacier area retained snowcover.
- Summer 2022: Only marginally better, with less than 10 percent.
- Fall 2024 (after two consecutive very-snowy winters in 2023 and 2024): Approximately 25 percent snowcover by mid-October.
Even in the best conditions—two above-average snow years in a row—the glaciers could only reach about 40 percent of the equilibrium threshold. That means volume loss continues regardless. The glaciers are losing mass faster than they can accumulate it, season after season.
Why They're Disappearing: The Climate Shift
The science here is straightforward, even if the consequences are profound. Three factors are driving the retreat:
Hotter Summers
Every summer from 2021 through 2024 has run 1 to 2 degrees Celsius above the long-term average. That might sound modest, but on a glacier it's catastrophic. Warmer air accelerates melt, but it also does something subtler: it strips away the accumulation zone—the higher-elevation area where new snow would normally be protected from melt. When summer heat penetrates far enough upslope, it melts not just the lower glacier but the replenishing snowpack at high elevation.
Repeated heat waves have become the norm in recent years. In the summers of 2021 and 2022, multiple heat waves pushed temperatures well above normal, and each one carved away at the accumulation zone before the following winter's snow could rebuild it.
Drought and Snowpack Loss
The 2020 to 2022 drought was severe across California. On Mount Shasta, that drought removed most of the protective snowpack that would normally reflect sunlight and insulate the ice below. Bare ice, once exposed, absorbs solar radiation and melts far faster than snow does. The combination of below-average snowfall (from the drought) and above-average melt (from heat) created a one-two punch that left the glaciers devastated.
Elevation Insulation Lost
What used to be perennial snow above 11,200 feet—a permanent, year-round feature—is now dry ridgeline. This loss of high-elevation insulation has fragmented the accumulation areas, leaving them isolated and vulnerable. Ice can't flow efficiently into smaller, separated zones, so the glaciers are no longer feeding their lower sections the way they historically did. The system is coming apart.
The Tipping Point: What Scientists Say
Scientists from universities and the U.S. Geological Survey have been monitoring Mount Shasta's glaciers for over 40 years. Their assessment is stark.
The glaciers are now in what's technically called "disequilibrium with the current climate." In plain language, that means the ice can no longer sustain itself under present conditions. Every year, the glaciers lose more mass than they gain. That deficit compounds. The ice thins. The crevasses become wider and more unstable. The system unravels.
Researchers who have spent decades watching this mountain now describe the glaciers' extinction as "a matter of when, not if." That's not hyperbole or worst-case modeling. It's the consensus of people who hold the data.
The one scenario that could reverse this trajectory would require a decade or more of sustained above-average snowfall—the kind of climate pattern that would need to persist year after year to allow the glaciers to rebuild and reestablish equilibrium. Given the direction of climate projections for the region, scientists consider that scenario improbable.
What's left is a timeline. Depending on how quickly temperatures rise and how consistently snowfall falls short of replenishment, the glaciers could be functionally gone—no longer flowing, no longer feeding downstream systems—within decades. Some may persist in small remnants longer than others, but the named glaciers as recognizable features of the landscape are expected to vanish within the lifetimes of people alive today.
The Seven Glaciers: Naming the Loss
Mount Shasta's seven named glaciers are Whitney, Bolam, Hotlum, Wintun, Konwakiton, Watkins, and Mud Creek. Each has its own topography, its own microclimate, and its own historical record. Each is shrinking.
The names matter. They're not abstract features—they're part of the mountain's identity, part of how people navigate and understand the landscape. Their disappearance is a loss with real weight.
What Happens When the Glaciers Are Gone
The disappearance of Mount Shasta's glaciers isn't just a tragedy for climbers or photographers. It has cascading impacts on the region's water and ecosystems.
Water Supply
Late-summer glacial melt currently acts as a natural reservoir, buffering streamflow during the dry season. When snow has stopped falling and late-summer heat is at its peak, glacier melt sustains creek flows that would otherwise dwindle to nothing. Communities that depend on reliable water supplies in July, August, and September benefit from this glacial discharge.
Once the glaciers are gone, that buffer disappears. Streams will run lower and hotter during late summer, putting pressure on regional water availability and on the cold-water habitat that some species depend on.
Aquatic Ecosystems
Glacial melt is cold. That cold water sustains salmonid—salmon and trout—habitat. Glaciers act as a cooling system for streams that would otherwise warm to lethal temperatures in mid-summer. Remove the glaciers, and stream temperatures will rise. For species like Coho salmon that are already stressed by warmer, drier conditions, loss of glacial cool-water refugia is an additional threat.
Hazards and Infrastructure
As glaciers thin and thin, the ice becomes increasingly unstable. Debris flows triggered by avalanches, rockfall, and ice collapse can tear down the north and east flanks of the mountain. Trail and road closures have already been documented as a result of these hazards.
The infrastructure threat will likely increase as the remaining ice becomes more precarious.
Mount Shasta in a Changing Climate
What's happening on Mount Shasta isn't unique. Across the Sierra-Cascade region, glaciers are retreating. Some have already disappeared entirely. The story on Shasta is simply more visible because it has multiple named glaciers and a well-documented research history.
The data from Mount Shasta's glaciers serves as a regional signal: the climate is warming faster than it was, the drought patterns are becoming more severe, and the consequences for water and ecosystems are tangible and measurable.
For anyone paying attention to how climate change manifests in real time, Mount Shasta's glaciers offer clarity. They're not a model or a projection. They're ice, rock, and water—the actual response of a physical system to the climate it inhabits. And right now, that system is telling us that the warming is not slowing down.
Seeing the Glaciers While They Remain
If you're interested in witnessing this shift firsthand, the window to do so is real but finite. Glaciers that are in steep decline can disappear faster than anyone expects. Whitney Glacier, which has been the subject of detailed research and photography, may not look the same in five years.
Several climbing routes and hiking trails offer access to Mount Shasta's glaciers for those with appropriate skills and experience. The technical Hotlum-Bolam route gives direct glacier access to experienced mountaineers. Easier alternatives like Brewer Creek Trail offer glacier views without technical climbing. And several hot springs dot the region, offering a way to combine mountain time with geothermal recovery.
For those curious about how climate change translates into landscape, and for those who simply want to see something extraordinary before it's gone, Mount Shasta is a destination worth taking seriously.
The seven glaciers—Whitney, Bolam, Hotlum, Wintun, Konwakiton, Watkins, and Mud Creek—are shrinking quickly, have likely passed a tipping point, and are expected to vanish within decades without a dramatic, sustained reversal of regional climate trends. That reversal is not on the horizon. What we have instead is time—limited, but real—to witness and understand what we're losing.