Welcome to the world “beyond the ice”, a realm of bizarre patterns, icy hills, and shivering soils that reveals the profound artistry of cold.

What Exactly is a Periglacial Environment?

The term “periglacial” literally means “around the ice.” These are environments that are cold enough to be dominated by intense freezing processes but are not permanently covered by glaciers or ice sheets. The key ingredient is permafrost—ground that remains frozen for at least two consecutive years. Today, these regions cover roughly 20% of the Earth’s land surface, primarily in high-latitude areas like Siberia, northern Canada, and Alaska, but also in high-altitude mountain ranges like the Tibetan Plateau and the Andes.

A periglacial landscape has two critical layers:

• Permafrost: The deep, permanently frozen layer of soil, sediment, and rock.
• The Active Layer: The top layer of ground that thaws during the brief summer and refreezes in the winter. This is where almost all the geomorphic action happens.

The constant freezing and thawing within this active layer is the engine that drives the creation of some of the strangest landforms on the planet.

The Engine of Change: Freeze-Thaw Cycles

To understand periglacial landscapes, you need to appreciate the incredible power of freezing water. When water turns to ice, it expands by about 9%. This expansion exerts immense pressure on its surroundings. In periglacial environments, this happens over and over, year after year, century after century.

Two key processes are at work:

1. Frost Shattering (or Frost Wedging): Water seeps into cracks in rocks. When it freezes, it expands, widening the crack. The ice melts, more water gets in, and the process repeats. Over time, this can shatter massive rocks into angular fragments without any force other than frozen water.
2. Frost Heave: As the ground freezes, water within the soil turns into ice crystals and lenses. These lenses grow by drawing in more water from the surrounding soil, heaving the ground surface—along with any stones or objects—upwards.

This constant churning, sorting, and shifting of the ground gives rise to a suite of truly unique features.

Weird and Wonderful Landforms of the Periglacial Realm

Forget rolling hills and gentle streams. The periglacial world is one of geometric precision and bizarre formations.

Patterned Ground: Nature’s Geometry

Imagine flying over a vast, treeless tundra and seeing the ground covered in perfectly formed stone circles, polygons, or stripes, as if laid out by an obsessive landscape artist. This is patterned ground.

It’s a direct result of frost heave. As the active layer freezes, the upward pressure of ice lenses pushes larger stones up and outwards, while finer sediments remain in the center. On flat terrain, this sorting process creates stone circles and polygons, which can range from a few centimeters to several meters in diameter. On gentle slopes, gravity pulls the sorted material downhill, stretching the circles into elongated stone stripes. You can find spectacular examples across Svalbard, the Canadian Arctic, and on high mountain plateaus worldwide.

Pingos: Ice-Cored Hills

Perhaps the most dramatic periglacial landform is the pingo. These are large, conical, ice-cored hills that erupt from the flat tundra, some reaching heights of over 50 meters. They look like small, dormant volcanoes, but their core is made of solid ice, not magma.

Pingos form in two main ways:

• Closed-system pingos typically form in the beds of drained lakes. The ground beneath a lake remains unfrozen (a talik). When the lake drains, the permafrost begins to close in from all sides, pressurizing the trapped, water-saturated soil. This water is squeezed upwards and freezes into a massive ice lens, pushing the overlying earth into a dome. The Mackenzie River Delta in Canada is famous for its dense concentration of these pingos.
• Open-system pingos form on slopes where groundwater is forced up under artesian pressure. This water freezes when it reaches the permafrost layer, gradually building an ice core that domes the surface. These are common in parts of Alaska and the Yukon.

When a pingo’s ice core eventually melts, the hill collapses, leaving behind a crater-like depression often filled with water, known as a pingo remnant.

Blockfields: Seas of Rock

Also known as a felsenmeer (German for “sea of rock”), a blockfield is a vast, chaotic expanse of angular boulders and rocks covering a summit or gentle slope. From a distance, it looks like a frozen, rocky sea.

These features are the ultimate expression of frost shattering. They form in situ, meaning the rock was shattered in place by countless freeze-thaw cycles and has not been transported by a glacier. The bedrock is broken down into a jumble of blocks that slowly settle over the landscape. Blockfields are characteristic of alpine periglacial zones, such as the summits of the Cairngorm Mountains in Scotland and across the Appalachian Mountains in North America, often representing landscapes that were high enough to escape glaciation but cold enough for intense frost action.

Solifluction and Thermokarst: The Landscape in Motion

Not all periglacial features are static. Solifluction (meaning “soil flow”) is the slow, downslope movement of the waterlogged active layer over the impermeable permafrost below. In summer, the thawed soil becomes saturated and weak, and it oozes downhill like thick, cold porridge, creating lobes and terraces on hillsides.

More dramatically, there is thermokarst. This is not a landform but a process of landscape collapse. When ground ice within the permafrost thaws due to warming temperatures or human disturbance, the ground loses its structural integrity and subsides. This creates an uneven, hummocky terrain of pits, hollows, and thaw lakes. Thermokarst is a growing concern across the Arctic, as it can damage infrastructure like roads, pipelines, and buildings, and it signals a profound shift in the stability of these frozen environments.

A Fragile World on the Edge

Periglacial landscapes are more than just geographical curiosities; they are sensitive barometers of climate change. The permafrost that underpins them stores vast amounts of carbon. As it thaws, it releases greenhouse gases like carbon dioxide and methane, creating a dangerous feedback loop that accelerates global warming.

From the challenges of building cities like Yakutsk, Russia—the world’s largest city built on continuous permafrost—to the slow creep of solifluction reshaping mountain slopes, these landscapes remind us that the Earth is a dynamic system. They are a testament to the subtle but immense power of the freeze-thaw cycle, a force that continues to shape a significant, though often overlooked, portion of our planet.