Tag: ice/snow

134 words tagged " ice/snow"

Ablation is the reduction of a glacier's snow and ice through melting, evaporation, sublimation, and calving. It occurs at every surface, all at once, though at different speeds. The ablation zone is located at the spot where more ice is lost than winter snow accumulation can replace.

accumulation zone

The upper portion of a glacier where snowfall exceeds melt, and where fresh snow compresses into firn and eventually into glacial ice. The accumulation zone is where a glacier is born — it is the account into which deposits are made. Below it, in the ablation zone, the withdrawals happen.

A seal's breathing hole in the ice — a small, cone-shaped opening maintained through the winter by the seal's repeated visits. Hunters wait at the aglu for hours in silence, reading the faintest disturbance in the water.

The proportion of light that a surface reflects — its reflectivity, expressed as a number from 0 (absorbs all light) to 1 (reflects all light). Fresh snow has an albedo near 0.9; open ocean is around 0.06; a forest canopy around 0.15. Albedo determines how much solar energy a surface absorbs and is one of the key variables in climate: as Arctic ice melts, high-albedo white surfaces are replaced by low-albedo dark ocean, which absorbs more heat, which melts more ice. The feedback loop is as simple as it is relentless.

Ice that forms on the bottom of a river or stream, attached to rocks, gravel, and other submerged objects — growing upward from the bed rather than downward from the surface. Anchor ice forms on clear, cold nights when the streambed radiates heat faster than the water above it, and it can lift rocks from the bottom as it builds and detaches. It is one of the stranger phenomena in river hydrology — ice that grows from below.

Snow used to make water. Snow selected specifically for melting and drinking — not any snow, but snow judged clean and suitable.

Untouched winter snow without tracks. Every skier's dream — a surface no one has reached yet.

Snow on the ground. Snow that has arrived and settled — no longer falling, not yet transformed by wind or sun or time.

Ice that is filled with holes. Porous, honeycombed ice in the late stages of decay — still present but no longer trustworthy.

A mass of snow, ice, and debris sliding rapidly down a mountainside. The word is clinical but the thing itself is not — an avalanche can move at 200 miles per hour and bury everything in its path in minutes.

A deep crevasse that forms where a glacier pulls away from the headwall of a mountain. Often the last major obstacle before a summit push, and sometimes impassable.

Small fragments of glacial ice floating in the sea — too large to be called brash ice, too small to qualify as icebergs. Each piece is compressed snow hundreds or thousands of years old, released into the ocean by a calving glacier.

The crackling, sizzling, popping sound made by a melting iceberg as ancient air bubbles trapped under enormous pressure during the glacier's formation are released into the water. The sound is audible from surprising distances and has been compared to soda fizzing or Rice Krispies in milk. It is the sound of air that was sealed into ice centuries or millennia ago finally escaping.

The broad, dry land bridge that connected Asia and North America during the Pleistocene, when sea levels dropped hundreds of feet during glacial periods. Not the narrow isthmus most people imagine — Beringia was a thousand miles wide, a grassland steppe roamed by mammoths, horses, and the first Americans walking east.

Drifting, blinding snow — a blizzard so thick you cannot see your own footsteps behind you. The world dissolves into white, and direction becomes a matter of faith.

Extremely hard, smooth, windblown or refrozen snow that has the density and forgiveness of sheet metal. Edges skitter across it; falls on it hurt.

The moment in spring when river ice fractures, shifts, and begins to move downstream — a violent, dramatic event in northern latitudes where rivers freeze solid for months. The ice groans, cracks, and eventually releases in a grinding, building surge of broken plates and slabs that can flood riverbanks and reshape channels. In Alaska and northern Canada, the date of breakup is one of the most anticipated events of the year.

A blizzard-force wind that blows across the steppes of Russia and Central Asia, driving snow horizontally and reducing visibility to near zero. In summer, the same wind carries dust instead of snow. On the tundra, it is called purga.

The process by which chunks of ice break off the front of a glacier or ice shelf and fall into the water as icebergs. Calving is sudden and violent — a thunderous crack, a slab of ice the size of a building tilting forward, the splash, the wave. It is the most dramatic way a glacier loses mass, and in a warming world, the most consequential.

Ice in its final stage of decay — long, vertical crystals that have separated from one another and tinkle like a glass chandelier as they collapse. Candle ice forms in spring when meltwater penetrates the crystal boundaries of lake or river ice.

A thin, hard layer of snow compacted by wind — so dense that a ski pole cannot penetrate it. The wind has blown away the loose surface and compressed what remains into something closer to stone than snow.

Snow hardened by strong wind to the point that reindeer cannot forage through it for food. A word that names a crisis — when the snow becomes impenetrable, the animals cannot eat.

The winter ice-path formed by a frozen river in Zanskar, Indian Himalayas — the only route in or out of the valley during the winter months. Parties undertaking the chadar are led by experienced ice-pilots who can tell where the dangers lie. In its deeper pools, the ice is blue and lucid.

champagne powder

Extremely light, low-density powder snow with a water content around 6–7%, compared to the usual 15%. So dry and airy it feels like skiing through nothing. Trademarked by Steamboat Springs Resort in Colorado, but used generically across ski culture.

A warm, dry wind that descends the eastern slopes of the Rocky Mountains, most commonly in winter and early spring. Its arrival is sudden and dramatic — temperatures can rise 30 or 40 degrees Fahrenheit in hours, and snow that took weeks to accumulate can vanish in a day. Called "the snow eater."

A bowl-shaped mountain basin carved by glacial erosion, steep-walled on three sides and open on the fourth, often holding a lake at its floor. An amphitheater made by ice over millennia.

Ultra-light, dry powder snow so fine that skiing through it produces a billowing cloud that rises like smoke and hangs in the air. A step beyond champagne powder — the lightest snow that falls.

Small, soft, rounded pellets of snow that form during spring freeze-thaw cycles — warm days soften the surface, cold nights refreeze it, and repeated cycles granulate the snow into corn-kernel-sized beads. When the timing is right, corn snow is some of the most enjoyable skiing of the year.

An overhanging mass of wind-deposited snow at the edge of a ridge or peak. Cornices build outward from the windward side, creating a false edge — what looks like solid ground may be an unsupported shelf of snow over empty air.

A deep, bowl-shaped hollow carved by glaciers into a mountainside — an amphitheater of rock, often holding a dark lochan at its floor. Corries are where snow lingered longest, where ice gnawed the mountain from the inside. The plural form in Scotland names some of the wildest places: the Corries of the Cairngorms.

A steep mountain gully, often filled with snow or ice, that channels everything falling from above — rockfall, avalanche debris, spindrift. A natural chute, beautiful and dangerous in equal measure.

An open crack in the surface of a glacier, formed when the ice moves over uneven terrain or flows at different speeds in different places, and the brittle upper layer fractures under the stress. Crevasses can be 150 feet deep, 60 feet wide, and hidden beneath a thin snow bridge that looks solid until you step on it. They are the constant, invisible danger of glacier travel.

Snow that has been skied through enough to lose its powder consistency but hasn't been groomed — lumpy, chunky, irregular, and unpleasant to turn in. The aftermath of a powder day, once the crowd has passed through.

The portion of Earth's surface where water exists in solid form — glaciers, ice sheets, sea ice, permafrost, snow cover, and frozen ground. The cryosphere is not a place; it is a condition, and it is shrinking. Every component of the cryosphere is in decline. The word names the frozen world as a system, and that system is coming apart.

The Welsh word for a cirque — a bowl-shaped, glacially carved mountain basin with steep headwalls. Cwm is used internationally in mountaineering: the Western Cwm of Everest, the valley between the Lhotse face and the West Ridge, is the most famous application. The word is one of the few in English with no standard vowel.

Small frozen chunks of ice and compacted snow scattered across a slope, usually the debris from grooming machines, snowmaking, or avalanche activity. They catch edges, jar knees, and appear without warning.

Branching like a tree — the pattern of river systems seen from above, ice crystals forming on a window, lightning splitting the sky, or the capillaries in a leaf. The shape that nature defaults to when distributing flow.

Ice crystals suspended in clear, calm air near the ground on extremely cold days, glittering in sunlight like falling dust. Not a cloud, not precipitation — the air itself has frozen and is slowly settling. Diamond dust produces halos, sun dogs, and light pillars.

A general term for all sediment deposited by glacial action — including both till (dropped directly by ice) and outwash (sorted and redeposited by meltwater). Everything a glacier leaves behind is drift. The word predates the understanding of how glaciers work; early geologists called these deposits "drift" because they assumed the material had drifted into place during Noah's flood.

An elongated, teardrop-shaped hill of glacial till, sculpted by the movement of ice over it. The steep end faces upstream (toward the advancing glacier); the tapered end trails downstream. Drumlins rarely occur alone — they appear in fields of dozens or hundreds, aligned like a fleet of half-buried ships all pointing the same direction. Their topography is sometimes called "basket of eggs."

A thin layer of new snow sitting on top of a frozen, hard base. One of the most disappointing conditions in skiing — it looks like a powder day but is not. The fresh snow provides no cushion; the crust beneath does all the talking.

Of or relating to the underside of sea ice — the cold, dark ceiling where algae grow, invertebrates graze, and an entire ecosystem hangs upside down beneath the frozen surface.

A boulder transported by a glacier and deposited far from its place of origin, often sitting conspicuously on terrain that doesn't match it — granite on limestone, basalt on sandstone. A geological stranger, sometimes the size of a house.

A long, narrow, sinuous ridge of sand and gravel deposited by a meltwater stream flowing in a tunnel beneath or within a glacier. When the ice melts away, the stream's sediment load is left behind as a winding raised track across the landscape — a fossil riverbed, elevated and inverted. Eskers can run for miles, often through otherwise flat terrain, and have been used as natural roadways for centuries.

A long, narrow, deep lake occupying a valley carved by glacial action — the glacier excavated a trough and the meltwater filled it. The Finger Lakes of central New York are the type example: eleven parallel lakes, some over 600 feet deep, aligned like the fingers of a hand laid on the landscape. The shape is the glacier's signature — long, straight, and deep.

The interlocking pattern formed when two thin sheets of new ice collide and ride over each other in alternating layers — like shuffled cards or interlaced fingers. A delicate early stage of ice formation visible only when the sea is just beginning to freeze.

Compacted granular snow that has survived at least one summer's melt cycle without becoming ice. The intermediate stage between fresh snow and glacial ice — dense, rounded crystals bonded together, older than a season but younger than a glacier.

A long, narrow, deep inlet of the sea between steep cliffs, carved by a glacier that once flowed to the coast and scoured a valley well below sea level. When the glacier retreated and the sea flooded in, the valley became a fjord. Fjords are among the most dramatic coastal landforms on earth — sheer walls rising thousands of feet from dark water hundreds of fathoms deep. Norway's Sognefjord is over 4,000 feet deep and 125 miles long.

A predictable corridor of open water separating shorefast ice from the moving pack — a seam in the ice that follows the coastline and stays open through pressure and current. For hunters and polar bears, the flaw lead is where life concentrates.

A sheet of floating ice — ranging from a few feet across to miles wide. Pack ice is composed of floes pressed together; a floe field is an expanse of them. The word implies drift — floes are not anchored, they move with wind and current, rotating, colliding, splitting, and rafting on top of each other.

The initial oily film of crystals on the sea surface — the first visible sign that the ocean is freezing. Frazil looks like grease floating on soup. It is the beginning of everything that follows: nilas, pancake ice, pack ice, polar cap.

The autumn process by which a river, lake, or sea gradually freezes over — beginning with shore ice, building through slush and pancake ice, and finally locking into a solid surface. In the Arctic and subarctic, freeze-up marks the transition from one mode of travel (boats) to another (sleds, snowmobiles, walking). The period between open water and solid ice — when the surface is neither navigable nor walkable — is one of the most dangerous and isolating times of the year.

Small mounds of soil pushed up by frost action — the earth heaving as water freezes and expands beneath the surface. In spring, frost boils soften into mud. In winter, they are the tundra's knuckles.

The maximum depth to which the ground freezes in winter — the boundary below which soil temperature stays above 32°F. The frost line determines how deep foundations must be poured, how deep water pipes must be buried, and how deep roots must reach to survive winter. It varies from near-surface in the Deep South to several feet in the northern states to effectively infinite in permafrost regions.

Steam rising from leads and polynyas in winter where relatively warm seawater meets air cold enough to freeze it on contact. The smoke is not smoke but vapor — the sea breathing into the cold.

The Sámi season when the snow begins to melt — warm days and cold nights, the skiing conditions always good. The reindeer herders move toward the mountains. Spring, but defined not by a calendar date but by what the snow and the animals are doing.

A smooth, reflective surface on bedrock produced by the grinding of a glacier sliding over it — millions of rock fragments embedded in the base of the ice acting as an enormous sheet of sandpaper. Glacially polished rock shines in sunlight and is striated with parallel scratches (striations) that record the direction the ice traveled. It is the mountain's memory of being pressed.

A thin powdering, as of sifted snow — the lightest possible dusting on rock or heather. Not a snowfall but a suggestion of one. The mountain wearing powder.

Soft, small pellets of ice formed when supercooled water droplets freeze onto falling snowflakes, creating opaque, crumbly balls. Not quite hail, not quite snow — a liminal precipitation that bounces when it lands.

Thickened frazil — the next stage of sea ice formation, when the initial crystals coalesce into a grey, soupy slush. The surface takes on an oily sheen and the sea loses its chop. Waves are dampened. The ocean goes quiet.

ground blizzard

High winds swirling dry snow already on the ground — a blizzard without snowfall, in which the existing snowpack becomes airborne. Visibility drops to zero. The sky is clear above; the world is white below.

A cloud of snow that blows up from the ground during hard frost with little wind. Not a blizzard, not drifting snow — a cold exhalation from the surface itself.

The largest falcon — an Arctic resident, circumpolar, capable of taking ptarmigan on the wing in conditions that ground other raptors. White, grey, or dark morph. Medieval kings prized it above all other hawks.

A state of deep torpor entered by certain animals during winter, characterized by drastically reduced body temperature, heart rate, and metabolism. True hibernation — as practiced by ground squirrels, marmots, and some bats — is not sleep. It is a near-shutdown of the body, a metabolic last resort for surviving months without food. Bears, despite their reputation, are not true hibernators but enter a lighter state called torpor.

Ice crystals deposited directly from water vapor onto cold surfaces under clear, calm skies — the frozen counterpart of dew. Maps the ground in white, skipping warm objects: stones, paths, anything conducting heat from below. The word hoar means white-haired, ancient.

A small, rounded mound or hillock — in tundra and permafrost terrain, a frost-heaved dome of soil covered with grass or moss, one of hundreds or thousands in a field of identical bumps called hummock tundra. In swamps, a hummock is a raised island of vegetation above the waterline. In ice, a hummock is a mound of broken, refrozen sea ice pushed up by pressure. Three landscapes, one shape: a bump in a flat world.

The mythic Greek land beyond the north wind — a place of perpetual sunshine, temperate climate, and blessed inhabitants, located somewhere past the reach of Boreas. The paradise that exists only in the direction you haven't traveled yet.

A steep, heavily crevassed section of a glacier where the ice flows over a cliff or sharp increase in gradient and fractures into a chaotic maze of seracs, crevasses, and unstable ice towers. An icefall is a waterfall made of ice, still moving but shattered by the terrain beneath it. The Khumbu Icefall on Everest is the most famous and most feared.

The equilibrium between the earth's crust and the denser mantle beneath it — the principle that the crust floats on the mantle the way an iceberg floats in water, and that adding or removing weight from the surface causes the crust to sink or rise in response. Load a continent with an ice sheet and the crust depresses beneath the weight; remove the ice and the crust slowly rebounds. Isostasy explains why Scandinavia and northern Canada are still rising — they are recovering from the weight of glaciers that melted thousands of years ago, and they are not done yet.

A snowpack condition in which the entire depth of snow is at the same temperature — 32°F / 0°C — meaning the whole pack is on the verge of melting. An isothermic snowpack is saturated, heavy, and structurally unstable. It is the condition that precedes wet avalanches and the final collapse of winter into spring.

A sudden surge of sea ice inland, without warning — the ice driven onto shore by wind or current, crushing everything in its path. An ivu can push ice hundreds of yards inland in minutes. There is no defense. There is only knowing when to run.

The skiing conditions created when spring arrives — warm days and cold nights produce a snow surface that is reliable, fast, and forgiving. The Sámi word for good spring skiing.

A sudden, catastrophic flood caused by the release of water from beneath or within a glacier — often triggered by volcanic activity beneath an ice cap, or by the failure of an ice dam holding back a glacial lake. Jökulhlaups can discharge millions of cubic feet of water per second, reshaping valleys in hours. Iceland, with its volcanoes under ice caps, is the type locality.

A wind that flows downhill under the influence of gravity, formed when air in contact with a cold surface — a glacier, a snow-covered plateau, a mountain slope at night — becomes denser than the air around it and drains downslope. Katabatic winds range from gentle nocturnal breezes to the 200-mph piteraqs of Greenland.

A depression in glacial outwash formed when a block of ice left behind by a retreating glacier is buried in sediment and eventually melts, leaving a hole. Kettles often fill with water to become kettle lakes or kettle ponds — small, round, self-contained bodies of water with no inlet or outlet, sitting in the middle of otherwise dry ground. Walden Pond is a kettle.

A passage through sea ice navigable by a surface vessel — a crack in the pack wide enough to sail through. Leads open and close with wind and current. They are the highways of Arctic travel and the hunting grounds of polar bears.

A vertical column of light extending above or below the sun, moon, or streetlight, caused by reflection off the flat faces of ice crystals drifting horizontally in calm, cold air. The pillar is not a beam — it's an illusion made by millions of tiny mirrors, each reflecting the light source at a slightly different altitude.

Fine-grained, wind-deposited silt — soil carried aloft from glacial outwash plains, riverbeds, or desert surfaces and laid down in thick, uniform blankets hundreds of miles from its source. Loess is among the most fertile soils on earth. The agricultural wealth of the American Midwest, the Central European plains, and the Yellow River valley of China is built on loess deposited during the Ice Ages. It erodes vertically — loess bluffs stand in sheer faces rather than slumping — and it holds its structure when dry but collapses catastrophically when saturated.

Wet snow that can be used to ice a sleigh's runners. Snow defined not by what it looks like but by what it can do.

A ridge or mound of rock, gravel, and debris deposited by a glacier — the rubble it carried, pushed, and left behind. Terminal moraines mark the farthest advance of the ice. Lateral moraines line the valley walls. Medial moraines form where two glaciers merge, their lateral moraines combining into a dark stripe running down the center of the combined flow. Moraines are the glacier's autobiography, written in stone.

A vertical shaft or tube in a glacier through which meltwater pours from the surface to the base. Moulins form when surface streams find a crevasse and begin to bore downward, the falling water enlarging the hole through thermal and mechanical erosion. The sound of water falling into a moulin is audible from a distance — a deep, roaring pour.

Sea ice that has survived at least two summer melt seasons — thicker, harder, and less salty than first-year ice. Multiyear ice was once the dominant ice type in the Arctic Ocean. It is disappearing.

Snow. The base word in Lule Sámi for the substance itself — the starting point from which over 200 terms for snow conditions, snow quality, and snow behavior radiate outward.

Polar bear. In Inuktitut the word carries more than species identification — nanuq is a being of intelligence and spiritual power, a creature that commands respect because it can kill you and chooses, most of the time, not to.

The unicorn of the sea — a medium-sized Arctic whale whose males grow a single spiraling tusk up to ten feet long. The tusk is actually a canine tooth, threaded with nerve endings, possibly a sensory organ for reading the water. Medieval Europeans believed the tusks were unicorn horns.

Sharp spikes of ice forming at the bottom of melt pools or in wet soil — individual crystals growing upward, lifting soil or pebbles on their tips. Also called pipkrake. The ground itself pushed upward by the force of freezing water.

The accumulation zone of a glacier where snowfall exceeds melt, and where firn is actively compacting into ice. Also used loosely as a synonym for firn itself.

A thin, elastic layer of ice crystals that bends with the waves like watered silk — the stage between grease ice and solid cover. Nilas is ice you can see through, ice that moves with the sea rather than against it.

The largest polynya in the North American Arctic, located in northern Baffin Bay between Greenland and Ellesmere Island. Open water persisting through winter, sustained by currents and wind — a biological oasis in the frozen sea where whales, seals, and seabirds gather.

A rocky peak or ridge that protrudes through the surface of a glacier or ice sheet — an island of rock in a sea of ice. Nunataks are refugia: during glaciations, plants and animals survived on these ice-free summits while the world around them was buried. Some of the genetic diversity of modern alpine species can be traced to populations that held on, isolated, on nunataks.

Sediment — sand, gravel, silt — carried away from the front of a melting glacier by meltwater streams and deposited in broad, flat plains. Outwash is drift that has been sorted by water: the heaviest material drops first, near the ice; the finest is carried farthest. Outwash plains are the aprons of debris spread before a retreating glacier, often remarkably flat and fertile.

Ice-loving — organisms whose lives are oriented around ice, who depend on it for habitat, hunting, breeding, or rest. Polar bears, ringed seals, ice algae, Arctic cod. As the ice retreats, the pagophilic world shrinks.

paleocrystic ice

Very old, formidable polar pack ice — ice that has survived many years of melt and refreeze, compressed and hardened into formations up to fifty feet thick. The word sounds ancient because the ice is ancient.

Round plates of ice with upturned edges, formed when frazil and grease ice consolidate and are shaped by wave action — each plate bumping against its neighbors and curling up at the rim. A field of pancake ice looks like a sea of lily pads made of white stone.

patterned ground

The distinctive geometry of frost cracks in the tundra — circles, polygons, and stripes formed by repeated freezing and thawing that sorts stones by size. The ground organizes itself into patterns visible from the air. Nobody arranged them. The cold did.

Tall, thin blades of hardened snow or ice that form in clusters at high altitude, pointing toward the midday sun. They can range from a few centimeters to several meters tall and make travel across snowfields extremely difficult.

Ground that remains frozen continuously for two or more years — soil, rock, and sediment held together by ice. Permafrost underlies roughly a quarter of the Northern Hemisphere's land surface and can extend to depths of over a thousand feet. It is not permanent despite its name. As the Arctic warms, permafrost is thawing — releasing stored carbon, destabilizing infrastructure, and reshaping landscapes into the pitted, slumping terrain called thermokarst.

A mound of earth-covered ice that forms in permafrost regions when water is forced upward through the frozen ground and freezes, pushing the surface into a dome. Pingos can be 200 feet tall and 2,000 feet in diameter. They are among the most striking landforms of the Arctic — solitary, symmetrical hills rising from an otherwise flat tundra. When a pingo collapses, it leaves a circular depression that may fill with water.

A katabatic wind that pours off the Greenland ice sheet and down the coastal mountains, reaching speeds of up to 200 miles per hour. One of the most powerful winds on Earth. It occurs when cold, dense air pooled on the ice cap spills over the edge and accelerates downslope.

A relatively large area of persistent open water surrounded by sea ice — kept open all winter by upwelling currents, tidal action, or wind. Polynyas are oases in the frozen ocean, concentrating marine life the way springs concentrate life in a desert.

Freshly fallen, uncompacted snow — light, dry, and deep enough to ski or ride through rather than on top of. The substance around which an entire culture of obsession has formed. Powder varies enormously: cold and dry ("blower," "champagne") or warm and dense ("Sierra cement").

Huge walls of rubble ice, twenty to forty feet high, formed when opposing ice floes collide and crumple — the tectonic plates of the frozen sea. Crossing a pressure ridge on foot is like climbing through a junkyard made of ice boulders.

Crystalline, granular powder snow on the ground that looks like salt. The dry, sugary layer that forms near the base of a snowpack through temperature-gradient metamorphism.

Snow falling. Not snow on the ground, not snow remembered — snow in the act of coming down.

A geographic area where a population of organisms survived a period of unfavorable conditions — glaciation, drought, fire — that eliminated the species from the surrounding landscape. When conditions improved, the surviving population expanded outward from the refugium and recolonized. Nunataks served as refugia during ice ages; desert springs served as refugia during droughts. A refugium is the place that kept the thread of continuity unbroken.

A feathery, opaque coating of ice that forms when supercooled water droplets in fog or cloud freeze on contact with a surface. On mountain summits, rime grows into elaborate, wind-facing sculptures on rocks, signs, and structures.

Extremely fine-grained sediment produced by the grinding of bedrock beneath a glacier — particles of silt and clay so small they stay suspended in water, giving glacial meltwater streams their distinctive milky, turquoise, or gray-green color. Rock flour is the powder that results from stone being crushed between two moving surfaces — the glacier and the earth.

Sharp, irregular ridges of snow formed on a flat surface by wind erosion and deposit. Beautiful to look at — the snow carved into frozen waves, fins, and furrows — and miserable to walk or ski across.

Granulated snow that forms at the bottom of the snowpack when the winter has been cold. Good snow for reindeer — easy for them to dig through to reach the pasture plants beneath. Also the type of snow that melts rapidly and represents clean water supply.

A tower or pinnacle of ice, formed where a glacier fractures into chaotic blocks as it flows over a steep drop — an icefall. Seracs are unstable, beautiful, and lethal. They can be the size of houses, standing at improbable angles, and they collapse without warning. Climbing through a serac field is a calculated gamble with time.

Terrain accessible from a ski resort's lifts or boundaries but outside the patrolled, controlled area. Neither fully backcountry nor resort skiing — a liminal zone where the infrastructure ends but the mountains continue.

Heavy, wet, high-moisture snow characteristic of California's Sierra Nevada. Dense enough to build excellent base layers but exhausting to ski through. The opposite of champagne powder.

A patchwork layer of crystals that forms as the sea begins to freeze. The first architecture of ice on open water — not yet solid, not yet safe, a threshold between liquid and locked.

The slow compression of snow into ice — grain by grain, layer by layer, as trapped air is squeezed out over years or centuries. Sintering is how snowfall becomes glacier. The process is invisible and relentless.

Fine snow or ice particles blown from a ridge or summit by the wind, streaming off the peaks like smoke. Also used for sea spray carried by gale-force winds.

In snow science, a stellar dendrite — the classic six-armed, branching snowflake shape formed in clouds between -12°C and -16°C with high humidity. The platonic ideal of a snowflake. Stellar crystals interlock when they land, creating the light, cohesive powder that skiers dream about.

Beneath the snow — the hidden winter world of tunnels, chambers, and runways that exists between the snowpack and the frozen ground. Lemmings, voles, and shrews live entire winters in the subnivean zone, insulated from the cold above, invisible to predators.

A thin, breakable layer of refrozen snow formed when the sun melts the surface during the day and cold air freezes it at night. The crust may hold your weight for a step or two before giving way — a sustained betrayal.

Bowl-shaped depressions that form on a snow surface through uneven melting caused by solar radiation. The cups deepen as dirty or darker patches absorb more heat. A late-season snowfield covered in suncups looks like the surface of a golf ball.

The snow condition created when the sun warms a wind-packed surface into something perfectly soft — skis become one with the snow, nearly frictionless. The Sámi also use this word for reindeer meat that has been thawed perfectly, easy to cut into thin slices.

A small, deep mountain lake, especially one occupying the floor of a cirque or sitting in a glacially scoured basin above treeline. Clear, cold, and usually without a visible inlet or outlet. The kind of water that stops you in your tracks.

The irregular, pitted, hummocked terrain that forms when ice-rich permafrost thaws and the ground collapses into the voids left behind. Thermokarst landscapes are full of subsidence pits, slumping banks, tilting trees ("drunken forests"), and shallow lakes that appear, expand, drain, and disappear as the ice beneath them melts. It is the landscape of permafrost coming undone.

A thunderstorm in which snow falls instead of rain — lightning and thunder during a blizzard. Rare, disorienting, and loud. The combination of blinding snow and electrical discharge creates a sensory environment that feels like the weather has lost its mind.

The unsorted mixture of clay, silt, sand, gravel, and boulders deposited directly by a glacier — dropped in place as the ice melts, without the sorting that water would provide. Till is the glacier's residue: everything it picked up, ground down, and carried along, dumped in a jumble when the ice retreated. The soil of much of the American Midwest is glacial till.

A void around a tree trunk where snow has been kept from accumulating — a hidden pit beneath the snow surface, sometimes several feet deep. Tree wells are among the most dangerous hazards in deep snow: fall in headfirst and the loose snow collapses around you.

A visible boundary on the wall of a glacier valley marking the maximum recent thickness of the ice — a horizontal line separating weathered rock above (which was exposed to the sky) from polished or unweathered rock below (which was covered by ice). The trimline is the glacier's high-water mark, etched into the valley wall. As glaciers thin and retreat, trimlines become increasingly visible — stark evidence of how much ice has been lost.

The farthest north — the edge of the known world, the place beyond which maps give way to imagination. In classical geography, Thule was the northernmost land; ultima Thule was the point past which no one had been.

Ice that lasts year after year. Permanent ice — the ice that does not melt, that the community can rely on as a feature of the landscape across seasons.

A thin, transparent glaze of ice over rock. Extremely hazardous — crampons can't penetrate it and rock shoes can't grip it. The rock looks bare until you touch it and your hand slides.

The process by which a plant requires a prolonged period of cold before it can flower or germinate. The plant must experience winter in order to know that spring has come. Without the cold, the biological clock doesn't start. Vernalization is the body's memory of seasons — proof that winter is not just endured but needed.

A dark patch on the underside of cloud cover that indicates open water below, visible from a distance across ice. Arctic navigators read the sky as a map of the surface — water sky is dark; ice blink, its opposite, is bright. The clouds become a mirror, and the navigator reads the reflection.

The condition where snow, cloud, and blizzard dissolve the world into depthless pallor — no horizon, no shadow, no up or down. A white-out removes every visual reference point. You cannot tell ground from sky. People have walked off cliffs.

Snow scenery — the landscape transformed by snow, everything softened, simplified, and made new. The world under white. A winter kigo that names not just the snow but the seeing of it.