Strange Ice & Snow Phenomena Explained

Ice rarely freezes into a simple, motionless sheet. Rivers rotate it, waves roll it,
wind pushes it ashore and temperature changes fracture it. Water can freeze around plants,
sediment and rocks beneath a stream, while vapor can build fragile crystal gardens directly
on new sea ice.

Snow can also organize itself into remarkably ordered structures. Under a narrow combination
of temperature, wind, moisture and surface conditions, loose snow may roll into hollow
cylinders without human contact. In high mountains, sunlight sculpts snow into forests of
sharp blades known as penitentes.

These events belong to the cryosphere: the parts of Earth where water exists
in solid form. The cryosphere includes seasonal snow, lake and river ice, sea ice, glaciers,
ice sheets, frozen ground and atmospheric ice.

This guide explains the physics behind unusual ice and snow phenomena, including formations
that appear engineered, alive or even impossible.

What Creates Strange Ice and Snow Formations?

Unusual frozen formations generally develop when water changes state under highly specific
environmental conditions. The final shape depends not only on temperature but also on wind,
current speed, wave action, humidity, sunlight, dissolved material and the surface on which
freezing occurs.

Freezing

Liquid water becomes solid when enough heat is removed. Yet natural water rarely freezes
uniformly. Turbulence, salt, dissolved gases, sediment and existing crystals influence where
freezing begins and how crystals grow.

Supercooling

Water can remain liquid below its usual freezing point when suitable crystal-nucleation sites
are absent. Once nucleation begins, ice may form rapidly around suspended particles, plants,
rocks or existing crystals.

Sublimation

Sublimation occurs when ice changes directly into water vapor without first melting.
In cold, dry and sunny environments, uneven sublimation can carve dramatic blades, pits and
ridges into snow.

Deposition

The reverse process occurs when water vapor changes directly into ice. Deposition creates
frost, hoarfrost, window patterns and delicate crystal growth on cold surfaces.

Wind

Wind transports snow, rotates floating ice, pushes lake ice toward shore and helps build
ice balls or self-rolling snow cylinders.

Waves and currents

Moving water rounds ice fragments, organizes floating crystals, pumps water through shoreline
ice and drives large ice sheets onto land.

Repeated freeze-thaw cycles

Ice may partly melt during warmer periods and refreeze after temperatures fall. Repetition
strengthens some structures, weakens others and creates layered or polished surfaces.

Sunlight and radiation

Direct sunlight, reflected radiation and differences in surface color affect how quickly
particular parts of a snowfield melt or sublimate.

Ice Discs & Rotating Ice Circles

Ice discs are circular or nearly circular slabs of ice that rotate slowly within rivers,
streams or lakes. Small examples may be only a few centimeters wide, while exceptional discs
can span many meters.

Their smooth edges and steady rotation can make them appear manufactured, but they are natural
products of moving water and freezing conditions.

How river ice discs form

A floating piece of ice may become trapped in a rotating eddy. As it turns, its edges repeatedly
strike surrounding ice, slush or riverbanks.

These collisions gradually remove irregular projections, producing a rounded shape.
Water movement may also melt or erode the edge evenly.

The role of river eddies

Eddies form where the main current interacts with bends, obstacles, side channels or changes
in river width. Water circulates within the eddy instead of flowing directly downstream.

A floating ice slab caught inside that circulation can rotate for hours or days.

Why some ice discs are nearly perfect circles

Continuous rotation exposes every side of the ice to similar friction and melting.
Irregular edges are worn away until the slab approaches a circular form.

Thermal rotation in still water

Small laboratory and natural ice discs may also rotate through temperature-driven water
circulation. Cold water sinking near the melting disc can create a weak vortex.

Large river discs, however, are usually dominated by visible current or eddy circulation.

Why ice discs stop rotating

Rotation may end when:

• The disc freezes into surrounding ice.
• Water flow changes.
• The disc becomes lodged against the bank.
• It breaks apart.
• Warmer temperatures melt it.
• Changing water levels remove the eddy.

Are ice discs dangerous?

The main danger comes from unstable river ice and fast, cold water. Ice discs should be
observed from shore rather than approached on foot.

Ice Balls, Ice Eggs & Rolling Ice

Shorelines occasionally become covered with thousands of rounded ice balls resembling
snowballs, eggs or polished stones. Individual pieces may range from a few centimeters to
objects large enough to require several people to move.

How ice balls form

Small fragments of slush or ice act as starting cores. Waves repeatedly roll them through
near-freezing water, adding thin layers of ice and snow.

Continued tumbling rounds the pieces and prevents them from freezing immediately into one
continuous sheet.

Conditions needed for natural ice balls

• Air temperatures near or below freezing
• Water cold enough to add new ice
• Open water or broken shoreline ice
• Moderate waves
• Slush, snow or small ice fragments
• A gently sloping shore
• Enough movement to roll the ice without destroying it

Why they appear suddenly

Ice balls may form offshore or along a hidden section of coast before wind and waves deposit
them together on a beach.

A change in wind direction can reveal a large accumulation within hours.

Ice eggs

The term “ice eggs” is commonly used when the pieces are oval rather than spherical.
Their shape depends on wave motion, collisions and how quickly new ice accumulates.

Giant ice boulders

Larger rounded ice masses may grow when waves add layers around an existing chunk over a
longer period. Some are less perfectly shaped and may contain snow, sand and layered ice.

Ice balls versus hailstones

Shoreline ice balls grow through rolling and freezing near the water surface. Hailstones grow
inside thunderstorm clouds through repeated collisions with supercooled droplets.

Ice Flowers & Frost Flowers

Frost flowers are delicate clusters of ice crystals that grow on new sea ice, lake ice,
plant stems or exposed soil. Their petals, feathers and branching forms can resemble miniature
flowers.

Frost flowers on sea ice

When thin new sea ice forms beneath extremely cold air, the ice surface can remain warmer than
the atmosphere. Moisture moves upward and deposits as crystals.

The result is a field of fragile crystalline structures rising above the ice.

Why sea-ice frost flowers are salty

Brine is expelled as seawater freezes. Frost flowers growing near the surface can incorporate
concentrated salts and other marine material.

Their chemical composition makes them important in research on polar atmospheric chemistry
and sea-salt aerosol production.

Frost flowers on plants

A different phenomenon occurs when liquid water inside a plant stem freezes and expands.
Water is pushed through tiny cracks and freezes into thin ribbons or curls.

These formations are also called ice flowers, frost flowers or ice ribbons.

Needle ice

Needle ice forms when groundwater rises through soil by capillary action and freezes into
slender columns. It may lift small stones, soil particles and plants.

Why frost flowers disappear quickly

Their crystals are extremely thin and sensitive to sunlight, warming, wind and physical contact.
A slight temperature increase can destroy them.

Ice Volcanoes

Ice volcanoes are cone-shaped mounds that form along frozen shorelines when waves force water
through openings in an ice shelf. Each burst sprays water and slush from the summit, resembling
a miniature volcanic eruption.

Despite the name, ice volcanoes have no connection to magma or geological volcanism.

How an ice volcano forms

1. Shore-fast ice develops along a lake or sea coast.
2. Waves continue moving beneath or beyond the ice shelf.
3. Pressure forces water through a crack or opening.
4. Spray freezes around the opening.
5. Repeated eruptions build a hollow cone.

Why waves are essential

Calm water cannot repeatedly pump water through the vent. Active ice volcanoes require
sufficient wave energy beneath or against the shoreline ice.

How large can ice volcanoes become?

Small cones may be less than a meter high, while sustained wave action can create structures
several meters tall.

What comes out of an ice volcano?

The eruptions consist of water, slush, spray and small ice fragments. In very cold weather,
much of the ejected water freezes onto the cone.

Why ice volcanoes are dangerous

The cones are often hollow and stand above moving water. Their crust may collapse without
warning, dropping a person into freezing waves beneath the ice.

Snow Rollers

Snow rollers are hollow cylindrical formations created when wind pushes loose snow across the
ground. As the snow moves, it gathers additional layers, much like a naturally rolled carpet.

They are sometimes called snow donuts, snow bales or wind snowballs.

Conditions required for snow rollers

• A thin surface layer of wet, sticky snow
• A weaker or smoother layer beneath it
• Temperatures near freezing
• Wind strong enough to move the snow
• Wind not strong enough to break the roll apart
• An open field, slope or frozen lake

How the roll begins

A small clump of cohesive surface snow is lifted or pushed by wind. It begins rolling and
collects more snow with every rotation.

Why snow rollers are hollow

The first layer at the center is often thin and fragile. It may fall out as the roller grows
or collapse after the formation stops.

Why tracks appear behind them

A moving roller compresses or removes the surface snow, leaving a visible trail.

Why hundreds can appear together

When the correct snow and wind conditions extend across an entire field, many separate clumps
begin rolling at approximately the same time.

Snow rollers versus human-made snowballs

Natural snow rollers commonly have hollow centers, irregular cylindrical shapes and long
wind-aligned tracks. They may appear across areas too large for human construction.

Colored Snow

Snow may naturally appear pink, red, orange, yellow, green, brown, gray or black.
Color can originate within the snowpack or arrive from the atmosphere as dust, pollen,
volcanic ash, wildfire particles or other material.

Watermelon snow

Pink or reddish snow is often associated with cold-adapted microscopic algae.
Pigments protect the organisms from intense sunlight while absorbing heat.

The snow may smell faintly sweet or watermelon-like when compressed, giving the phenomenon
its common name.

Why dark biological snow melts faster

Red, green or brown pigments reduce the snow’s reflectivity. More solar energy is absorbed,
which can accelerate melting around the organisms.

Desert dust on snow

Winds can carry mineral dust across continents. When deposited on snow or mixed with snowfall,
it creates orange, red, yellow or brown layers.

Volcanic ash

Eruptions can cover snow with gray or black ash. Dark ash strongly reduces reflectivity and
may speed surface melting.

Pollen

Spring pollen can create bright yellow patches on melting snow and around puddles.

Natural versus pollution-related colored snow

Not all colored snow is natural. Soot, industrial emissions, chemical releases and waste can
discolor snowfall or existing snowpacks.

Confirmed industrial or pollution-driven cases belong under

Pollution Phenomena Explained
.

Should colored snow be eaten?

No unfamiliar colored snow should be consumed. Natural coloration may involve microorganisms,
animal waste, mineral dust or volcanic material, while human contamination cannot be excluded
from appearance alone.

Ice Crystals & Frost Patterns

Ice crystals build branching ferns, needles, plates, columns, feathers and star-like forms on
windows, plants, soil and frozen surfaces.

Their geometry reflects the molecular structure of ice and the temperature and humidity under
which each crystal develops.

Why ice crystals are six-sided

Water molecules arrange into a hexagonal crystal lattice under ordinary atmospheric conditions.
This structure produces sixfold symmetry in snowflakes and many frost crystals.

Hoarfrost

Hoarfrost forms when water vapor deposits directly as ice onto surfaces below freezing.
It often creates feathery white crystals on trees, fences and exposed objects.

Rime ice

Rime forms when supercooled fog droplets strike a cold surface and freeze.
It commonly builds into white, rough deposits on mountains, aircraft, trees and towers.

Window frost

Frost patterns develop when moist indoor or outdoor air contacts cold glass.
Tiny imperfections, dust and temperature differences guide branching growth.

Fern frost

Fern-like patterns emerge through repeated branching as vapor is deposited along favorable
crystal edges.

Ice feathers

Very thin, elongated crystals may grow from moist surfaces when vapor supply, temperature and
airflow favor one direction of growth.

Why no two snow crystals are exactly alike

Each crystal follows a unique path through changing temperature and humidity.
Even tiny differences alter the final branching pattern.

Frazil Ice

Frazil ice consists of loose, needle-shaped or plate-like crystals suspended in turbulent,
supercooled water. It often resembles slush but begins as countless individual crystals
forming throughout the moving water.

How frazil ice forms

In calm water, ice usually begins at the surface. In turbulent rivers or open water,
mixing can cool the entire water column slightly below the freezing point.

Tiny ice crystals then nucleate within the water and remain suspended by turbulence.

Where frazil ice occurs

• Cold, turbulent rivers
• Rapids and waterfalls
• Open leads within sea ice
• Wind-mixed lakes
• Below dams and spillways
• Polar coastal waters

Grease ice

At the ocean surface, dense concentrations of frazil crystals can give the water a dull,
oily appearance known as grease ice.

Pancake ice

Frazil and slush may collect into rounded floating plates. Waves cause the pieces to collide,
building raised rims and producing pancake ice.

Why frazil ice matters

Frazil crystals can clog water intakes, screens and hydropower infrastructure.
They may also attach to submerged objects and contribute to anchor ice.

Frazil ice hazards

Dense frazil can alter river flow, create ice jams and make water surfaces appear more stable
than they really are.

Anchor Ice

Anchor ice is submerged ice attached to the bottom of rivers, lakes or shallow coastal water.
It may coat rocks, plants, sediment and human structures beneath flowing water.

How can ice form underwater?

Turbulent water can become slightly supercooled. Frazil crystals carried by the current then
attach to submerged surfaces and continue growing.

Why the riverbed provides nucleation sites

Rocks, vegetation and sediment offer surfaces where suspended crystals can lodge and freeze.

Anchor ice growth

Continued crystal accumulation produces white, porous masses that may surround stones and
aquatic plants.

How anchor ice rises

Ice is less dense than liquid water. As a mass grows, its buoyancy may overcome its attachment
to the riverbed.

The ice can then break free, carrying sediment, stones or plants toward the surface.

Ecological effects

Anchor ice can disturb habitat, move gravel and temporarily cover organisms.
It may also influence oxygen exchange and winter river structure.

Infrastructure effects

Growth on screens, intakes, bridge structures and equipment can obstruct water flow or damage
installations.

Frazil ice versus anchor ice

Frazil ice consists of suspended crystals moving through the water. Anchor ice forms when
those crystals attach and grow on submerged surfaces.

Methane Bubbles in Frozen Lakes

Frozen lakes sometimes contain stacks of white bubbles trapped beneath clear ice.
These formations can create striking patterns that look like suspended pearls or miniature
clouds.

Where the methane comes from

Microorganisms living in oxygen-poor lake sediment decompose organic matter and release methane.
The gas rises through the water in bubbles.

How bubbles become trapped

When the lake surface freezes, rising gas collects beneath the ice. Additional water freezes
around the bubble, preserving it.

Repeated releases and freezing episodes can create vertical stacks.

Are all frozen bubbles methane?

No. Bubbles may contain methane, carbon dioxide, ordinary air or mixtures of gases.
Visual appearance alone cannot determine composition.

Why some lakes produce more methane

Methane production is favored by:

• Abundant organic sediment
• Wetlands and peat
• Shallow lake bottoms
• Low-oxygen conditions
• Microbial activity
• Thawing organic-rich ground

Can the bubbles burn?

Methane-rich bubbles can ignite after being deliberately released and exposed to a flame.
This is sometimes demonstrated in controlled scientific or educational settings.

Why visitors should not ignite lake gas

Fire can spread unpredictably, damage equipment, cause burns and distract from unstable ice.
Gas composition is also unknown without testing.

Climate significance

Lake methane is part of the natural carbon cycle, but changes in temperature, organic input
and permafrost thaw can alter emissions from some northern lakes.

Penitentes

Penitentes are narrow blades or spikes of hardened snow and ice that point generally toward
the Sun. Fields of these formations occur at high elevations in dry mountain regions,
especially in the Andes.

Their name refers to the resemblance between rows of bowed figures and religious penitents.

How penitentes form

In cold, dry, sunny conditions, snow may lose mass mainly through sublimation rather than
melting. Small surface depressions absorb and reflect sunlight differently from exposed ridges.

The hollows deepen as reflected radiation becomes concentrated within them, while the ridges
remain standing.

Why the blades point toward the Sun

Solar angle controls which surfaces receive and reflect the most energy.
Continued differential sublimation gradually aligns the formations.

Where penitentes occur

They are best known from high, dry mountain environments with:

• Strong solar radiation
• Low humidity
• Cold temperatures
• Limited melting
• Persistent snow or firn

How tall can penitentes grow?

Small examples may be only a few centimeters high. Mature fields can contain blades taller
than a person.

Why penitentes matter to travelers

Dense fields are difficult to cross and can damage equipment. Their presence influences
mountaineering routes, snow stability and surface-energy balance.

Penitentes on other worlds

Similar blade-like structures have been proposed or observed on icy planetary surfaces,
where sublimation may sculpt frozen material under thin or dry atmospheres.

Ice Tsunamis, Ice Shoves & Ice Heaves

Ice tsunamis occur when strong winds or currents push large sheets and piles of broken lake
or sea ice onto shore. The advancing mass may move slowly but with enough force to damage
buildings, docks, roads and trees.

The phenomenon is also known as an ice shove, ice push or ice heave. It is not a true tsunami,
because it is not primarily a long water wave generated by sudden displacement of the lake
or seafloor.

How ice is pushed ashore

A large floating ice cover offers a broad surface for wind stress. Persistent wind transfers
force across the sheet and drives it toward the downwind shoreline.

Broken ice can pile into ridges, while intact sheets may buckle and fracture as they encounter land.

Why ice tsunamis deserve a child pillar

Ice shoves involve distinct mechanics, hazards and recurring events across large lakes,
inland seas and polar coasts. They also represent one of the most destructive strange-ice
phenomena.

Ice Tsunamis Explained: Ice Shoves, Ice Heaves and Frozen Walls Moving Ashore →

Megacryometeors

Megacryometeors are unusually large blocks of ice reported falling from clear or only weakly
stormy skies. Unlike ordinary hailstones, they are not necessarily associated with a severe
thunderstorm.

Some reported masses have damaged roofs, vehicles or ground surfaces, creating the impression
of a giant hailstone appearing from nowhere.

Why megacryometeors are controversial

Large falling ice can have several possible sources, including aircraft ice, fragments from
structures, hail and atmospheric ice growth. Establishing a purely atmospheric origin requires
careful exclusion of these alternatives.

Possible atmospheric formation

One hypothesis suggests that unusual temperature and moisture structures in the atmosphere may
allow ice to grow outside a conventional thunderstorm.

The mechanism remains less firmly established than ordinary hail formation.

Aircraft ice

Ice can form on aircraft surfaces or result from frozen water released from aviation systems.
Falling aircraft ice may be mistaken for a natural megacryometeor.

Why the topic deserves a child pillar

Megacryometeors have a distinct atmospheric origin debate, investigative method and hazard
profile. They should not be reduced to a short subsection about ordinary frost or snowfall.

Megacryometeors Explained: Giant Ice Blocks Falling From Clear Skies →

What About Booming and Singing Lake Ice?

Frozen lakes can produce booming cracks, metallic pings, laser-like pulses and whale-like
calls as temperature changes create stress within the ice.

These sounds are clearly cryospheric, but their primary search intent concerns natural acoustics.
They therefore belong in the dedicated pillar:

Strange Geological Sounds & Rock Phenomena Explained

The dedicated lake-ice child page can be linked from both pillars:

Lake Ice Sounds & Booming Frozen Lakes Explained

Safety Around Strange Ice & Snow Phenomena

Unusual frozen formations attract visitors precisely when water, ice and weather conditions
may be unstable.

Never judge ice by appearance

Clear, smooth ice may be thin. White or snow-covered ice may conceal cracks, moving water and
areas weakened by springs or currents.

Moving water weakens ice

Rivers, channels, narrows and shoreline wave zones often remain dangerous even during prolonged
cold weather.

Stay off ice volcanoes

Ice-volcano cones are hollow and commonly stand over active water.

Observe ice discs from shore

Rotating discs usually occur where current and open water are present.

Keep away from advancing ice

Ice shoves may accelerate, fracture suddenly and exert enormous pressure against structures.

Do not ignite trapped lake gases

Flames, unknown gas mixtures and unstable lake ice create unnecessary risks.

Protect fragile formations

Frost flowers, snow rollers and biological snow communities can be destroyed by a single step.

Why Study Strange Ice and Snow Phenomena?

Ice oddities reveal how sensitive frozen water is to small changes in temperature, wind,
radiation and flow.

• Ice discs reveal river circulation.
  Their rotation makes otherwise invisible eddies easy to observe.
• Frazil and anchor ice reveal supercooled water.
  They show that freezing can begin throughout turbulent water, not only at the surface.
• Frost flowers reveal vapor and brine transport.
  Their chemistry connects sea ice with the polar atmosphere.
• Penitentes reveal solar sculpting.
  Their shape records interactions among sunlight, sublimation and snow texture.
• Frozen bubbles reveal lake carbon cycling.
  Gas trapped in ice makes microbial activity beneath lakes visible.
• Ice shoves reveal mechanical force.
  Thin-looking ice sheets can transmit enough pressure to damage buildings and infrastructure.
• Colored snow reveals biological and atmospheric transport.
  Pigments, dust and ash change both appearance and melting behavior.

Related Strange Natural Phenomena