Deep beneath Alaska’s frozen landscape, a hidden world of ice formations is taking shape. While you might think of permafrost as simply frozen ground, the reality is far more complex and fascinating. Permafrost continuously remains below 0 °C for two years or more, with the deepest extending greater than 1,500 meters. Within this frozen realm, enormous crystalline structures are developing in patterns that would amaze any scientist or explorer.
These aren’t your typical ice formations. We’re talking about massive hexagonal ice structures that can dominate entire underground landscapes. The phenomenon occurs when permafrost cracks during cold winter days, and snowmelt and runoff water seep into empty spaces, eventually freezing to create wedge-shaped spears of ice that extend vertically down into the permafrost. Think of it as nature’s own underground architecture, built one freeze-thaw cycle at a time.
The Science Behind Underground Ice Formation
The structure of ice is primarily characterized by its hexagonal crystal formation, formed from water (H-O-H) molecules linked through hydrogen bonds. This isn’t just academic knowledge – it’s the foundation for understanding how these massive structures develop beneath your feet. By vapor process, ice crystals grow into hexagonal form, creating the distinctive six-sided patterns that characterize these underground formations.
The process begins when temperatures drop and permafrost undergoes thermal contraction. Soil contraction creates cracks that collect water above the permafrost layer, which then freezes and expands, forming ice wedges that force the cracks to widen. Over time, these simple cracks transform into elaborate crystalline caverns that can extend for meters in every direction.
Massive Ice Bodies in Alaska’s Permafrost
You might be surprised to learn just how substantial these ice formations can become. It has been estimated that 10 percent by volume of the upper 3 metres of permafrost on the northern Coastal Plain of Alaska is composed of foliated ground ice (ice wedges). That’s an enormous volume of crystalline ice hiding beneath what appears to be ordinary tundra.
When the ice content of permafrost exceeds 250 percent (ice to dry soil by mass) it is classified as massive ice, with bodies ranging in composition from icy mud to pure ice. Massive icy beds have a minimum thickness of at least 2 meters and a short diameter of at least 10 meters. These aren’t small formations – they’re underground ice chambers that could easily accommodate a person walking upright.
The Discovery of Underground Ice Tunnels
Scientists have made remarkable discoveries about these subterranean ice worlds through careful study of permafrost exposures. Studies at the CRREL permafrost tunnel near Fairbanks, Alaska revealed multi-directional reticulate ice veins and massive ice bodies formed by inward closed-system freezing of pools of water and saturated sediments trapped in underground tunnels. These findings suggest that Alaska’s underground ice formations are far more complex than previously understood.
The tunnels were filled with massive ice and/or organic-poor, stratified silts, sands and gravels sediments, creating intricate networks of frozen chambers. The observed tunnels were slightly inclined and could often be traced for several meters, indicating extensive underground ice systems beneath Alaska’s surface.
Ice Wedge Polygons: Nature’s Geometric Patterns
Ice wedges actively reshape the tundra by freezing, growing and expanding outward, pushing against bordering permafrost and active layer, with permafrost and soil pushing upwards to form ridges on the surface. The result is a spectacular geometric display that you can observe from space. The ridges interlock and form distinct shapes called ice-wedge polygons, with ridged borders forming directly above expanding ice wedges below the surface.
These polygonal patterns aren’t random – they follow precise mathematical principles. These polygons are visible all the way from space, allowing scientists like researchers to monitor ice-wedge polygons remotely using satellite imagery. When you look at aerial photographs of Alaska’s tundra, those honeycomb-like patterns you see are actually the surface expression of massive underground ice structures.
The Formation Process of Giant Ice Crystals
Understanding how these enormous crystals form requires looking at the freeze-thaw cycle in detail. During cold winter, polygonal thermal contraction cracks form in frozen ground, then in early spring, water from melting snow runs down these cracks and freezes, creating vertical veins of ice that penetrate into permafrost. Each annual cycle adds another layer to these growing ice formations.
Some large ice wedges may have taken 1000 years to form, demonstrating the incredible patience required by nature to create these underground monuments. The process is slow but relentless, with each winter adding incremental growth to structures that can eventually reach extraordinary proportions. Most foliated ice masses occur as wedge-shaped, vertical sheets 2.5 cm to 3 metres wide and 0.3 to 9 metres high when viewed in cross section.
Cryostructures: The Architecture of Frozen Ground
Structures formed by the amount and distribution of ice within sediment and rock are termed cryostructures, with layered cryostructures indicative of syngenetic permafrost while reticulate and irregular cryostructures are indicative of epigenetic permafrost. These technical terms describe the beautiful, complex patterns that develop within Alaska’s frozen ground over centuries.
Cryofacies can be defined according to patterns of sediment characterized by distinct ice lenses and layers, volumetric ice content and ice-crystal size, and can be subdivided according to cryostructure. Think of these as geological fingerprints that tell the story of how different ice formations developed under varying environmental conditions.
Thermokarst Processes and Ice Crystal Degradation
Climate change is dramatically affecting these underground ice palaces. Ice wedges are a common form of massive ground ice that typically occupy 10–30% of the volume of upper permafrost in the Arctic and are particularly vulnerable to thawing from climate warming. When warming occurs, these carefully constructed crystalline structures begin to collapse and transform.
Thermokarst is characterized by very irregular surfaces of marshy hollows and small hummocks formed when ice-rich permafrost thaws. These small but abundant water features form rapidly in depressions caused by melting of ice wedges, with pool expansion impacting subsequent thaw rates through complex positive and negative feedbacks. The loss of these underground ice formations creates a cascade of landscape changes across Alaska’s tundra.
Underground Ice Cavities and Pool Ice Formation
Some of the most fascinating discoveries involve what scientists call “pool ice” or “thermokarst-cave ice.” Closed-cavity ice is formed by the freezing of water trapped in underground cavities cut into permafrost by flowing water, also called thermokarst-cave ice. These formations create genuine underground chambers filled with crystalline ice structures.
Closed-cavity ice usually forms within and next to ice wedges, suggesting that Alaska’s permafrost contains interconnected networks of ice-filled caverns. This indicates that the process of underground thermo-erosion has occurred widely in Alaska, creating extensive subterranean ice cave systems that remain largely unexplored.
The Scale of Alaska’s Underground Ice Reserves
The sheer volume of ice beneath Alaska’s surface is staggering. The total ice content in the permafrost of the Arctic Coastal Plain of Alaska is estimated to contain substantial volumes of ground ice. To put that in perspective, that’s enough ice to cover the entire state of Connecticut in a layer more than two miles thick.
Taber ice is the most extensive type of ground ice, representing 75 percent of the ground by volume in places, with pore and Taber ice content calculated at 61 percent by volume between 0.5 and 3 metres depth. These numbers reveal that much of what appears to be solid ground in Alaska is actually a complex matrix of soil and massive ice formations.
Future Research and Implications
Scientists are increasingly recognizing the importance of understanding these underground ice systems. Detailed calculations of ground-ice volumes in permafrost deposits are necessary to understand the response of permafrost landscapes to thermal disturbance, with ice wedges and their polygonal surface expression being a widespread ground-ice component of permafrost lowlands.
The implications extend far beyond academic curiosity. Humans are also impacted when homes become dangerous to live in as ground supporting vital infrastructure collapses, and roads connecting communities to important resources are destroyed by subsiding ground. Understanding these underground ice formations is crucial for predicting and adapting to changes in Alaska’s frozen landscape.
Conclusion
Alaska’s tundra conceals one of nature’s most spectacular and least understood phenomena: vast networks of giant ice crystals and underground cavities that have been forming for millennia. These hexagonal structures, some reaching several meters in width and height, represent a hidden world of crystalline architecture that rivals anything found in nature’s most famous caves. From the intricate cryostructures that tell stories of ancient climate cycles to the massive ice wedges that reshape entire landscapes, Alaska’s permafrost contains geological treasures that continue to amaze researchers.
As our climate continues to change, these underground ice palaces face an uncertain future, making their study more urgent than ever. What secrets might these frozen formations still hold about Alaska’s past, and what role will they play in shaping the landscape of the future?
Hi, I’m Andrew, and I come from India. Experienced content specialist with a passion for writing. My forte includes health and wellness, Travel, Animals, and Nature. A nature nomad, I am obsessed with mountains and love high-altitude trekking. I have been on several Himalayan treks in India including the Everest Base Camp in Nepal, a profound experience.
