Wonders Of The Natural World
Natural Phenomena
An exhaustive field guide to 91 of Earth’s most spectacular phenomena — 39 of them rare or very rare — with the science behind each one and exactly where to witness it.
Light & Sky
21 phenomena
OccasionalLight & Sky
Aurora Borealis
Shimmering curtains and arcs of green, pink, red and violet light that ripple across the night sky at high northern latitudes. They can appear as faint glows or fast-moving bands overhead.
The science
Charged particles from the Sun are guided by Earth’s magnetic field into the upper atmosphere near the poles. There they collide with oxygen and nitrogen, which emit light at characteristic colours as they return to lower-energy states.
Where to see it
Did you know?
Auroras are usually most active in a band called the auroral oval, which shifts and expands during geomagnetic storms.
OccasionalLight & Sky
Aurora Australis
The southern lights are luminous curtains, arcs and rays that flicker across dark skies in the far Southern Hemisphere. Their colours are often green, with red and purple appearing during stronger displays.
The science
Like the aurora borealis, they form when solar particles travel along Earth’s magnetic field and strike gases high in the atmosphere near the magnetic poles. Oxygen and nitrogen then glow at different wavelengths, producing the visible colours.
Where to see it
Did you know?
Because the Southern Ocean has little land at high latitudes, the aurora australis is seen by fewer people than its northern counterpart.
CommonLight & Sky
Rainbow
A rainbow is a multicoloured arc seen opposite the Sun when sunlight shines into falling rain. A bright primary bow may be joined by a fainter secondary bow outside it.
The science
Sunlight entering raindrops is refracted, internally reflected, and refracted again as it exits. Different wavelengths bend by slightly different amounts, separating white light into a spectrum.
Where to see it
Did you know?
A secondary rainbow is caused by two internal reflections inside raindrops, which reverses the colour order compared with the primary bow.
RareLight & Sky
Fogbow
A fogbow is a broad, pale white arc that appears in fog or mist, often looking like a washed-out rainbow. Its colours are very faint because the droplets are tiny.
The science
It forms when light is refracted, reflected and diffracted by extremely small water droplets in fog. The small droplet size causes the colours to overlap strongly, producing a mostly white bow.
Where to see it
Did you know?
Fogbows are sometimes called white rainbows, though they are produced by fog droplets rather than raindrops.
RareLight & Sky
Moonbow
A moonbow is a rainbow made by moonlight, usually seen as a faint whitish arc in dark skies. Under bright conditions and long-exposure photography, its colours can be clearer.
The science
The same optics that make a daytime rainbow also work with moonlight: refraction, internal reflection and dispersion in water droplets. Because moonlight is much dimmer than sunlight, the colours are often hard for human eyes to detect.
Where to see it
Did you know?
Moonbows are easiest to see around the full Moon because the Moon must be bright enough and low enough in the sky at the same time.
OccasionalLight & Sky
22° Halo
A 22° halo is a large, faint ring around the Sun or Moon, usually white with a reddish inner edge. It is commonly seen through thin high cloud.
The science
The halo is produced when light passes through millions of randomly oriented hexagonal ice crystals in cirrostratus clouds. Refraction through the crystals bends light by a minimum angle of about 22 degrees, creating the ring.
Where to see it
Did you know?
The sky inside a 22° halo often looks slightly darker than the sky just outside it because few rays are refracted at smaller angles.
OccasionalLight & Sky
Sun Dog
Sun dogs are bright coloured patches that appear on either side of the Sun, often with a reddish side nearest the Sun. They are most noticeable when the Sun is low.
The science
They form when sunlight is refracted through plate-like hexagonal ice crystals drifting horizontally in the atmosphere. The preferred crystal orientation concentrates light at about 22 degrees to the left and right of the Sun.
Where to see it
Did you know?
Sun dogs are also called parhelia, meaning ‘beside the Sun’.
RareLight & Sky
Circumzenithal Arc
A circumzenithal arc is a vivid upside-down rainbow high in the sky, often glowing with pure spectral colours. It appears near the zenith rather than near the horizon.
The science
It is created when sunlight enters the top face of flat, plate-like ice crystals and exits through a side face. This refracts and disperses the light in a way that produces a bright arc centred on the zenith when the Sun is relatively low.
Where to see it
Did you know?
The circumzenithal arc is sometimes called the ‘smile in the sky’ because of its curved, inverted shape.
RareLight & Sky
Fire Rainbow
Despite the name, a fire rainbow is not a rainbow or fire but a bright, multicoloured band in wispy high cloud. It usually appears as a horizontal patch of vivid colour.
The science
This phenomenon is a circumhorizontal arc, formed when sunlight passes through horizontally aligned plate-shaped ice crystals in high clouds. It requires the Sun to be high in the sky so that refraction sends the colours into a nearly horizontal band.
Where to see it
Did you know?
True circumhorizontal arcs cannot be seen from places much poleward of about 55° latitude because the Sun does not climb high enough.
OccasionalLight & Sky
Light Pillar
A light pillar is a vertical shaft of light that seems to extend above or below the Sun, Moon or bright artificial lights. It can look like a glowing column standing in the air.
The science
Light pillars form when flat ice crystals reflect light from their horizontal faces as they drift through cold air. The many reflections from crystals at different heights create the impression of a vertical beam.
Where to see it
Did you know?
A light pillar is mainly a reflection effect, unlike many other halo displays that are produced by refraction.
CommonLight & Sky
Crepuscular Rays
Crepuscular rays are bright and dark beams that appear to fan out from the Sun, especially near sunrise or sunset. They are often seen streaming through gaps in clouds or over mountains.
The science
The beams are columns of sunlight separated by shadows cast by clouds, terrain or other obstacles. Perspective makes these nearly parallel rays appear to diverge from the Sun.
Where to see it
Did you know?
The visible bright rays are easiest to see when dust, haze or water droplets scatter sunlight toward the observer.
RareLight & Sky
Anticrepuscular Rays
Anticrepuscular rays are faint light and shadow bands that seem to converge at the point opposite the Sun. They can span the whole sky and are easiest to notice when the atmosphere is hazy.
The science
They are the continuation of crepuscular rays across the sky, produced by the same sunbeams and shadows. Perspective makes the nearly parallel bands appear to meet at the antisolar point.
Where to see it
Did you know?
Although they appear to converge opposite the Sun, the rays are actually almost parallel to one another.
RareLight & Sky
Green Flash
A green flash is a brief green gleam seen at the upper edge of the Sun just as it sets or, more rarely, rises. It lasts only a second or two under most conditions.
The science
Earth’s atmosphere refracts light and separates colours slightly, with shorter wavelengths bent more than longer ones. When the horizon is very clear and the air is stable, this dispersion can isolate the green rim of the Sun momentarily.
Where to see it
Did you know?
A green flash is not caused by the ocean; it is an atmospheric refraction effect that can occur over land as well.
OccasionalLight & Sky
Alpenglow
Alpenglow is the rosy or orange light that bathes mountains and sometimes clouds around sunrise or sunset. It can linger on high peaks even after the Sun has dropped below the local horizon.
The science
The colour comes from sunlight that has travelled a long path through the atmosphere, where shorter blue wavelengths are scattered out more strongly. The remaining red and orange light illuminates distant peaks and airborne particles, producing the warm glow.
Where to see it
Did you know?
The term is often used loosely, but in its stricter sense alpenglow can refer to glow on mountains when the Sun itself is already below the horizon.
CommonLight & Sky
Belt of Venus
The Belt of Venus is a pink to orange band that appears above the horizon opposite the Sun during twilight, with a darker blue-grey band below it. It is a broad, delicate colour wash rather than a sharp line.
The science
The pink band is sunlight reddened by its long path through the atmosphere and backscattered toward the observer. The darker band beneath is Earth’s shadow projected onto the lower atmosphere.
Where to see it
Did you know?
The dark band under the pink glow is literally the shadow of Earth.
OccasionalLight & Sky
Glory
A glory is a set of coloured rings surrounding the shadow of the observer’s head, often seen on cloud or mist below. The rings are usually red on the outside and bluish toward the centre.
The science
Glories are produced by backscattering of light by tiny water droplets, involving wave effects such as diffraction and surface waves. The geometry concentrates coloured light around the antisolar point, where the observer’s shadow falls.
Where to see it
Did you know?
Each person sees a glory centred on their own antisolar point, so the rings are effectively centred on their own shadow.
RareLight & Sky
Brocken Spectre
A Brocken Spectre is a magnified shadow of an observer cast onto cloud or mist below, often ringed by a glory. The figure can look huge and ghostly because of perspective and moving fog.
The science
It appears when the Sun is low behind an observer who is looking into mist or cloud below. The shadow is projected onto droplets, and a glory may form around the head due to backscattering by the droplets.
Where to see it
Did you know?
The name comes from the Brocken, the highest peak in Germany’s Harz Mountains, where the effect became famous.
CommonLight & Sky
Mirage
A mirage is an optical illusion in which distant objects appear displaced, distorted or replaced by the image of sky or other scenery. A common example is the shimmering ‘water’ seen on hot roads.
The science
Mirages occur when layers of air at different temperatures have different densities and refractive indices. Light bends as it passes through these layers, causing the eye to trace the rays back to an apparent but misleading location.
Where to see it
Did you know?
A mirage is a real optical image formed by refracted light, not a hallucination.
RareLight & Sky
Fata Morgana
A Fata Morgana is a complex, rapidly changing mirage that can make ships, coasts or ice appear stretched, stacked or floating above the horizon. The scene often looks layered or castle-like.
The science
It forms when strong temperature inversions create sharply curved paths for light in the lower atmosphere. Multiple refracted and inverted images are stacked and distorted, producing the characteristic towering shapes.
Where to see it
Did you know?
The name comes from Morgan le Fay of Arthurian legend because the illusion was once thought to resemble enchanted castles.
OccasionalLight & Sky
Cloud Iridescence
Cloud iridescence is the display of pastel greens, pinks, blues and golds along the edges of thin clouds near the Sun. The colours are softer and more patchy than those of a rainbow.
The science
It is caused by diffraction of sunlight by tiny water droplets or ice crystals of nearly uniform size in thin cloud. Different wavelengths spread by different amounts, producing delicate colour bands or patches.
Where to see it
Did you know?
Iridescent colours are often strongest in young clouds because their droplets tend to be more similar in size.
Very RareLight & Sky
STEVE
STEVE appears as a narrow mauve or purplish ribbon of light, sometimes accompanied by green picket-fence structures below it. It shows up at lower latitudes than typical auroral arcs.
The science
STEVE is linked to strong flows of hot charged particles in the upper atmosphere associated with geomagnetic activity, but it is distinct from ordinary aurora in appearance and location. Research indicates that different physical processes from standard particle-precipitation aurora are involved, especially for the mauve arc.
Where to see it
Did you know?
The name STEVE began as a playful label used by aurora watchers and was later turned into the backronym Strong Thermal Emission Velocity Enhancement.
Celestial & Night Sky
12 phenomena
RareCelestial & Night Sky
Total Solar Eclipse
A total solar eclipse turns day briefly into twilight as the Moon completely covers the Sun and the Sun’s pale corona shines around the dark disk. Bright stars and planets can appear, and the landscape often takes on an eerie, silvery light.
The science
It happens when the Moon passes directly between Earth and the Sun at new moon and its apparent size is large enough to hide the Sun completely for observers inside the narrow path of totality. The alignment must be very precise because the Moon’s orbit is tilted relative to Earth’s orbit around the Sun.
Where to see it
Did you know?
Totality at any one place usually lasts only a few minutes, even though the entire eclipse event can take several hours from first partial phase to last.
OccasionalCelestial & Night Sky
Lunar Eclipse
During a lunar eclipse, Earth’s shadow slowly darkens the full Moon, which can turn a muted coppery red at totality. The change is gradual and can be watched safely with the naked eye.
The science
A lunar eclipse occurs when Earth passes between the Sun and the full Moon so that the Moon moves into Earth’s shadow. The red colour comes from sunlight bent through Earth’s atmosphere, which filters out much of the blue light and sends redder light into the shadow.
Where to see it
Did you know?
A lunar eclipse is visible from the entire half of Earth where the Moon is above the horizon, so many more people can see it than a total solar eclipse.
OccasionalCelestial & Night Sky
Supermoon
A supermoon is a full Moon that appears a little larger and brighter than average because it occurs near the Moon’s closest approach to Earth. The difference is subtle to casual observers but noticeable in photographs and when compared with smaller full Moons.
The science
The Moon follows an elliptical orbit, so its distance from Earth changes during the month. When full moon happens near perigee, the Moon’s disk looks larger and it reflects slightly more light toward Earth than a more distant full Moon does.
Where to see it
Did you know?
The dramatic “huge Moon” effect near the horizon is mostly a psychological Moon illusion, not the supermoon itself.
OccasionalCelestial & Night Sky
Blue Moon
A blue moon is an extra full Moon that falls into a calendar pattern rather than a change in colour. Most blue moons look like ordinary full Moons, bright and silvery white.
The science
In modern common usage, it is either the second full Moon in a single calendar month or, in the older seasonal definition, the third full Moon in a season with four full Moons. The Moon is not usually blue, because the term refers to timing, not appearance.
Where to see it
Did you know?
A Moon can look genuinely blue only rarely, usually when unusual atmospheric particles such as smoke or volcanic ash scatter red light more strongly.
OccasionalCelestial & Night Sky
Meteor Shower
A meteor shower sends repeated streaks of light across the night sky as tiny bits of space debris burn up high in the atmosphere. Under dark skies, the best showers can produce meteors every few minutes, sometimes more.
The science
Meteor showers happen when Earth passes through streams of dust left behind by comets, and sometimes asteroids. The particles hit the atmosphere at high speed, heating the air and themselves until they glow and leave bright, short-lived trails.
Where to see it
Did you know?
The meteors in a shower seem to radiate from one point in the sky because of perspective, like railway tracks appearing to meet in the distance.
OccasionalCelestial & Night Sky
Fireball
A fireball is an exceptionally bright meteor, often dazzling enough to outshine Venus and sometimes leaving a glowing trail that lingers for seconds or minutes. Some fragment dramatically as they race across the sky.
The science
It is caused by a larger-than-usual meteoroid entering Earth’s atmosphere at high speed and heating intensely through compression of the air in front of it and ablation from its surface. If any pieces survive to reach the ground, they are called meteorites.
Where to see it
Did you know?
A very bright fireball can sometimes be heard minutes later if it produces sound waves that reach the ground as sonic booms.
CommonCelestial & Night Sky
The Milky Way
The Milky Way appears as a faint, cloudy band arching across a dark sky, mottled with bright star fields and dark dust lanes. It is the combined light of vast numbers of distant stars in our home galaxy.
The science
We see the Milky Way as a band because we live inside a flattened spiral galaxy and look through its crowded disk. Dense interstellar dust blocks some starlight, carving the dark rifts that stand out against the glow.
Where to see it
Did you know?
The bright central bulge seen in southern summer skies does not mark the exact galactic centre visually—the true centre is hidden behind thick dust in the direction of Sagittarius.
RareCelestial & Night Sky
Zodiacal Light
Zodiacal light is a soft, triangular glow that rises from the horizon before dawn or after dusk along the zodiac. In very dark skies it can look like a ghostly extension of twilight.
The science
It is sunlight scattered by countless tiny dust particles spread through the inner Solar System, many shed by comets and collisions between asteroids. The glow follows the plane of the planets because that dust is concentrated near the ecliptic.
Where to see it
Did you know?
Under exceptionally dark conditions, the zodiacal light can connect with a faint band across the whole sky called the gegenschein and the zodiacal band.
RareCelestial & Night Sky
Great Comet
A great comet is a rare comet that becomes bright enough to dominate the sky, often with a striking head and long tail or tails visible to the naked eye. Some are seen in daylight or remain obvious for weeks.
The science
A comet brightens when sunlight heats its icy nucleus, releasing gas and dust that form a glowing coma and tails. A comet appears especially impressive when it is both intrinsically active and favourably placed relative to Earth and the Sun.
Where to see it
Did you know?
Comets often show two distinct tails: a dust tail curved by the comet’s path and a straighter ion tail pushed by the solar wind.
OccasionalCelestial & Night Sky
Planetary Conjunction
A planetary conjunction happens when two or more planets appear close together in the sky, creating a striking pairing or grouping. They may look almost side by side even though they remain far apart in space.
The science
Conjunctions occur because the planets orbit the Sun in nearly the same plane, so from Earth they sometimes line up along similar lines of sight. The effect is geometric rather than physical: the planets are not actually near one another.
Where to see it
Did you know?
Very close conjunctions can be mistaken for a single bright object with the naked eye, but binoculars usually separate the planets clearly.
RareCelestial & Night Sky
Noctilucent Clouds
Noctilucent clouds are delicate, electric-blue ripples or filaments that glow after sunset or before sunrise, very high in the summer twilight sky. They look luminous because they are still lit by the Sun when lower clouds are in darkness.
The science
They form in the mesosphere at about 76–85 km altitude, where temperatures become cold enough for ice crystals to grow on tiny particles. They are visible only when the Sun is below the horizon for the observer but still shines on these extremely high clouds.
Where to see it
Did you know?
Noctilucent clouds are the highest known clouds in Earth’s atmosphere.
RareCelestial & Night Sky
Nacreous Clouds
Nacreous clouds, also called polar stratospheric clouds, shimmer with pastel iridescent colours like mother-of-pearl in deep twilight. They are rare and often appear as smooth, lens-like sheets or billows.
The science
They form in the lower stratosphere when temperatures drop extremely low, allowing tiny particles of water, nitric acid and sulfuric acid to form clouds. Their vivid colours come from diffraction and interference of light by very small, similarly sized droplets or crystals.
Where to see it
Did you know?
Some polar stratospheric clouds help drive chemical reactions that activate chlorine compounds involved in polar ozone depletion.
Weather & Storms
17 phenomena
CommonWeather & Storms
Lightning
A lightning flash is a sudden, brilliant electrical discharge in the atmosphere, often branching across storm clouds or striking the ground. It heats the air so rapidly that the shock wave is heard as thunder.
The science
Collisions among ice particles and supercooled water inside thunderstorms separate electric charge, leaving different parts of the cloud and ground electrically imbalanced. When the electric field becomes strong enough, the air breaks down and a discharge races through it as lightning.
Where to see it
Did you know?
A lightning channel can heat the air to about 30,000°C—hotter than the surface of the Sun.
Very RareWeather & Storms
Ball Lightning
Ball lightning is a rare, short-lived luminous sphere reportedly seen during or just after thunderstorms, drifting, hovering, or moving unpredictably. Accounts describe it as ranging from pea-sized to several tens of centimetres across.
The science
Ball lightning has been reported for centuries, but it is not yet fully explained and has been only rarely documented instrumentally. Proposed mechanisms include plasma sustained by electromagnetic energy or vaporized materials such as silicon from soil after a lightning strike, but no single theory accounts for all reports.
Where to see it
Did you know?
Because reliable measurements are so scarce, ball lightning remains one of the least understood reported atmospheric phenomena.
Very RareWeather & Storms
Red Sprites
Red sprites are huge, faint flashes of red light that bloom high above powerful thunderstorms, often shaped like jellyfish or carrot-like columns. They last only milliseconds and are usually invisible from brightly lit places.
The science
Sprites are triggered by intense positive cloud-to-ground lightning strokes that abruptly change the electric field above a storm. This field excites nitrogen molecules in the mesosphere, roughly 50–90 km up, producing the red glow.
Where to see it
Did you know?
Sprites occur far above ordinary lightning—high in the mesosphere, well above the tops of thunderclouds.
OccasionalWeather & Storms
Tornado
A tornado is a violently rotating column of air that extends from a thunderstorm to the ground, often visible as a funnel cloud or a swirling debris cloud. Sizes and shapes vary from thin ropes to broad wedges.
The science
Tornadoes form when strong instability, moisture, and wind shear create rotating updrafts inside severe thunderstorms, especially supercells. If that rotation is tightened and stretched downward to the surface, a tornado can develop.
Where to see it
Did you know?
Not every visible funnel is a tornado—a circulation only counts as a tornado when it is in contact with the ground.
OccasionalWeather & Storms
Waterspout
A waterspout is a rotating column of air and spray over water, looking like a slender funnel beneath a cloud. Some are relatively weak fair-weather whirlwinds, while others are tornadoes that have moved over water.
The science
Fair-weather waterspouts usually develop beneath growing cumulus clouds when warm water and light winds help a small vortex stretch upward. Tornadic waterspouts form the same way as land tornadoes, within severe thunderstorms, but occur over water.
Where to see it
Did you know?
Most waterspouts are the fair-weather type and are much weaker than the tornadic kind associated with severe storms.
OccasionalWeather & Storms
Supercell
A supercell is a powerful thunderstorm with a deep, persistent rotating updraft called a mesocyclone. It can produce giant hail, destructive winds, intense rain, and sometimes tornadoes.
The science
Supercells develop when strong wind shear causes rising air to rotate, and the storm’s updraft becomes organized enough to maintain that rotation for a long time. This structure separates the updraft from the downdraft, helping the storm persist and intensify.
Where to see it
Did you know?
Supercells are the thunderstorm type most commonly associated with the strongest and longest-lived tornadoes.
OccasionalWeather & Storms
Tropical Cyclone
A tropical cyclone is a large, spinning storm system over warm ocean water, with bands of heavy rain, strong winds, and a low-pressure centre. Depending on the ocean basin, it may be called a hurricane or typhoon.
The science
These storms draw energy from warm sea surfaces and the release of latent heat as moist air rises and condenses in deep thunderstorms. Earth’s rotation helps the inflowing air spin around the low-pressure centre, allowing the cyclone to organize and strengthen if wind shear stays low.
Where to see it
Did you know?
Tropical cyclones cannot form right at the equator because the Coriolis effect there is too weak to organize rotation.
OccasionalWeather & Storms
Mammatus Clouds
Mammatus are pouch-like lobes hanging from the underside of a cloud, often dramatic beneath the anvil of a thunderstorm. They can look smooth or lumpy and are especially striking in low-angle sunlight.
The science
They form when sinking air within a cloud layer becomes cooler or more moisture-laden than the air below, creating rounded downward bulges. Mammatus are most often linked to thunderstorm anvils, but can also occur under other cloud types such as altostratus or volcanic ash clouds.
Where to see it
Did you know?
Although they often appear after severe storms, mammatus themselves are not a separate storm type.
OccasionalWeather & Storms
Lenticular Clouds
Lenticular clouds are smooth, lens- or saucer-shaped clouds that often seem stationary while air flows through them. They commonly form in stacked layers near mountains.
The science
When stable, moist air flows over mountains, it can set up standing atmospheric waves on the downwind side. Air cooling at the wave crests condenses into smooth clouds, while evaporation in the sinking parts keeps them sharply defined.
Where to see it
Did you know?
A lenticular cloud may stay in the same place for hours even though the air inside it is constantly moving.
OccasionalWeather & Storms
Shelf Cloud
A shelf cloud is a low, wedge-shaped cloud attached to the leading edge of a thunderstorm or gust front. It often marks the arrival of cooler outflow air and a sudden wind shift.
The science
Rain-cooled air spreads out from a storm as a density current, lifting warm, moist air ahead of it. As that air rises and condenses, it forms the broad, arcing cloud along the storm’s front edge.
Where to see it
Did you know?
Shelf clouds are often mistaken for wall clouds, but shelf clouds form on outflow while wall clouds form on a storm’s inflow side.
RareWeather & Storms
Morning Glory Cloud
A Morning Glory is a long, rolling tube cloud that can stretch for hundreds of kilometres, often advancing as a dramatic solitary line across the sky. It is most famous for appearing at dawn in northern Australia.
The science
It forms from a moving atmospheric wave, often linked to sea-breeze interactions and stable layers of air, that lifts moist air into a long band of condensation. The cloud marks the crest of the wave, while air sinks and clears behind it, giving the impression of a rolling motion.
Where to see it
Did you know?
Glider pilots have used Morning Glory waves to gain lift and travel long distances alongside the cloud.
RareWeather & Storms
Asperitas Clouds
Asperitas clouds have a striking, rough underside with dramatic wave-like ripples, as if the sky were a choppy sea seen from below. They are usually dark and textured rather than smooth.
The science
They are thought to form when layers of cloud are disturbed by atmospheric gravity waves, wind shear, or turbulence, often after convective weather. The effect comes from uneven cloud bases shaped by waves in stable air rather than from a separate cloud genus.
Where to see it
Did you know?
Asperitas was formally added to the International Cloud Atlas in 2017 as a supplementary cloud feature.
OccasionalWeather & Storms
Haboob
A haboob is an intense dust storm that sweeps forward as a towering wall of dust and sand, sharply reducing visibility. It often arrives suddenly ahead of or beneath a thunderstorm.
The science
Strong downdrafts from thunderstorms or collapsing rain-cooled air spread outward across dry ground, lifting large amounts of loose dust into the advancing outflow. The densest dust is usually concentrated near the leading edge, where the gust front is strongest.
Where to see it
Did you know?
The word “haboob” comes from Arabic هبوب, meaning “blasting” or “drifting” wind.
CommonWeather & Storms
Dust Devil
A dust devil is a small, spinning column of air that picks up dust, sand, or debris from the ground on hot, dry days. Unlike tornadoes, it usually forms beneath clear skies.
The science
Strong surface heating creates pockets of rising air, and if that rising air begins to rotate, the vortex can tighten and stretch upward. The visible column appears when the whirl lifts dust and loose particles from the surface.
Where to see it
Did you know?
Dust devils also occur on Mars, where orbiters and rovers have photographed and recorded them.
CommonWeather & Storms
Virga
Virga is streaky precipitation that falls from a cloud but evaporates or sublimates before reaching the ground. It can look like soft grey or silvery trails hanging beneath a cloud base.
The science
It forms when raindrops or ice crystals fall into a layer of very dry air below the cloud. As the precipitation evaporates or sublimates, it cools the air and can sometimes help generate downdrafts.
Where to see it
Did you know?
Virga can contribute to dangerous microbursts when evaporation cools the air enough to make it plunge downward.
CommonWeather & Storms
Hailstorm
A hailstorm is a thunderstorm that produces balls or irregular lumps of ice, sometimes small as peas and sometimes much larger. Hail can fall suddenly and damage crops, vehicles, roofs, and windows.
The science
Hail forms inside strong thunderstorm updrafts where supercooled water freezes onto ice embryos and grows in layers as it is carried up and down through the cloud. If the stones become too heavy for the updraft to support, they fall to the ground.
Where to see it
Did you know?
The layered interior of a hailstone records repeated journeys through different parts of a storm.
OccasionalWeather & Storms
Microburst
A microburst is a compact but powerful downdraft that slams into the ground and spreads outward, producing sudden, damaging winds. It can occur with heavy rain or, in dry air, with little rain reaching the surface.
The science
Rain, hail, and evaporative cooling inside a storm can make a parcel of air colder and denser than its surroundings, causing it to accelerate downward. When that descending air hits the ground, it bursts outward in all directions, creating intense straight-line winds.
Where to see it
Did you know?
Microbursts are especially hazardous to aircraft during take-off and landing because the wind speed and direction can change abruptly over a short distance.
Water & Ocean
10 phenomena
RareWater & Ocean
Bioluminescent Waves
At night, breaking waves and splashes can flash electric blue as the water seems to light up around moving surf, boats or swimmers.
The science
The glow usually comes from bioluminescent plankton, especially dinoflagellates, that emit light when they are mechanically disturbed. The light is produced by a chemical reaction inside the cells involving luciferin and the enzyme luciferase.
Where to see it
Did you know?
Many bioluminescent dinoflagellates flash as a defensive response, and the light may help expose or startle their predators.
OccasionalWater & Ocean
Red Tide
Red tide is a harmful algal bloom that can stain coastal water red, brown or green, though some blooms are nearly invisible.
The science
It happens when certain microscopic algae multiply rapidly in favourable conditions such as warm water, sunlight and available nutrients. Some species release toxins that can kill fish, contaminate shellfish and irritate human lungs when sea spray carries them ashore.
Where to see it
Did you know?
Not all red tides are actually red, and not all harmful algal blooms are caused by dinoflagellates.
OccasionalWater & Ocean
Tidal Bore
A tidal bore is a moving wall or surge of water that travels upstream in a river or estuary as the incoming tide pushes against the river flow.
The science
It forms where a large tidal range is forced into a narrowing, shallow estuary or river channel. The incoming tide steepens into a wave front because the funnel-shaped channel concentrates the water and slows its passage.
Where to see it
Did you know?
Some tidal bores are followed by a train of secondary waves called whelps that can continue upriver behind the main front.
OccasionalWater & Ocean
King Tide
King tides are the highest regular tides of the year, when the sea reaches unusually high levels along coasts and estuaries.
The science
They occur when the Sun, Moon and Earth line up in ways that maximise tidal forces, especially around new or full moon when the Moon is near perigee. Local weather and ocean conditions can raise water levels even further.
Where to see it
Did you know?
King tide is a common term rather than a formal scientific one, but these tides are useful for showing how modest sea-level rise can worsen coastal flooding.
RareWater & Ocean
Rogue Wave
A rogue wave is an unexpectedly large, steep ocean wave that towers above surrounding seas and can appear suddenly in open water.
The science
Rogue waves can form when wave energy is focused by several processes at once, including constructive interference, strong currents opposing waves and instability within wave groups. These mechanisms can briefly concentrate energy into a single extreme crest.
Where to see it
Did you know?
The Draupner wave, measured in the North Sea in 1995, provided one of the first clear instrumental records confirming that rogue waves are real.
OccasionalWater & Ocean
Whirlpool
A whirlpool is a spinning mass of water that forms a visible vortex, sometimes with a depressed centre and fast-circulating flow.
The science
It develops when currents, tides or flowing water move past each other, around obstacles or through narrow channels, creating rotation. Conservation of angular momentum can intensify the spin as water is drawn inward.
Where to see it
Did you know?
Most natural whirlpools are hazardous because of strong currents and turbulence, not because they form a deep hole that swallows large vessels.
OccasionalWater & Ocean
Geyser
A geyser is a hot spring that intermittently erupts, shooting jets of hot water and steam into the air.
The science
Groundwater is heated by hot rock or magma below the surface and becomes trapped in a natural underground plumbing system. Pressure allows the water to become superheated; when some of it flashes to steam, the sudden expansion drives an eruption.
Where to see it
Did you know?
True geysers are rare because they need a precise combination of heat, abundant water and the right kind of subterranean plumbing.
CommonWater & Ocean
Hot Spring
A hot spring is groundwater that emerges naturally at the surface warmed above the local average by heat from within the Earth.
The science
Rain and surface water seep underground, are heated by geothermal gradients or nearby magma, and then rise back to the surface through cracks. Dissolved minerals from the surrounding rocks often give the water distinctive colours and deposits.
Where to see it
Did you know?
Some hot springs deposit travertine or silica as they cool, building terraces and rims around the spring over time.
RareWater & Ocean
Blue Hole
A blue hole is a deep, steep-sided water-filled sinkhole or cavern that appears dark blue against shallower surrounding water.
The science
Most form in soluble limestone when caves and sinkholes develop on land during lower sea levels and are later flooded by rising seas. Their great depth and clear water make them look much darker than the nearby seabed.
Where to see it
Did you know?
Some blue holes contain sharply layered water with very low oxygen at depth, preserving chemical records and, in some cases, delicate sediments.
CommonWater & Ocean
Sea Foam
Sea foam is a mass of bubbles that collects along shores and on the sea surface, sometimes piling up in wind and surf.
The science
It forms when waves churn seawater containing dissolved organic matter such as proteins, fats and decaying algae. These substances act like natural surfactants, helping bubbles form and persist.
Where to see it
Did you know?
Sea foam is usually natural, but unusually persistent or discoloured foam can also signal pollution or heavy organic runoff.
Earth & Fire
12 phenomena
OccasionalEarth & Fire
Volcanic Eruption
A volcanic eruption sends lava, ash, gas and rock out of a vent in Earth's crust. It can range from gentle outpourings of molten rock to towering explosive ash plumes.
The science
Eruptions happen when magma and dissolved gases rise because they are buoyant and pressure changes as they approach the surface. If gas escapes easily the eruption is often effusive; if gas is trapped, pressure can build and drive explosive fragmentation.
Where to see it
Did you know?
Volcanic ash is not soft ash from fire—it is made of tiny sharp fragments of rock, glass and crystals.
RareEarth & Fire
Lava Lake
A lava lake is a pool of molten rock sitting in a volcanic crater or vent, often crusted over in places and glowing through cracks. Its surface can circulate, crack and overturn like a fiery skin.
The science
Lava lakes form where a steady supply of magma reaches the surface and remains pooled in an open vent. Heat from below keeps the melt mobile while cooling at the top forms a crust that repeatedly breaks and sinks.
Where to see it
Did you know?
A lava lake can rise and fall as gas pressure and the level of magma in the volcanic plumbing system change.
OccasionalEarth & Fire
Lava Flow
A lava flow is a stream or sheet of molten rock moving across the ground after an eruption. Some flows creep slowly in thick blocky masses, while others spread more fluidly in glowing rivers.
The science
Lava flows because erupted rock is still hot enough to behave as a liquid, though its viscosity varies with temperature and composition. Basaltic lava is usually runnier and can travel farther than silica-rich lava, which is generally stickier.
Where to see it
Did you know?
The rough ʻaʻā and smooth ropy pāhoehoe textures are two classic surface types of basaltic lava.
Very RareEarth & Fire
Volcanic Lightning
Volcanic lightning flashes through dark ash clouds above an eruption, sometimes branching repeatedly through the plume. It can look like an ordinary thunderstorm embedded in volcanic ash.
The science
Ash particles, ice and rock fragments in the turbulent plume collide and separate electric charge. When the charge difference becomes large enough, the air breaks down and a lightning discharge occurs.
Where to see it
Did you know?
Lightning can occur close to the vent within seconds of an explosive eruption, even before a plume grows into a large cloud.
RareEarth & Fire
Fire Whirl
A fire whirl is a spinning column of flame, hot gases and smoke that forms over intense heat. Small ones can look like twisting fire devils; larger ones can become dangerous and erratic.
The science
They form when rising hot air from a fire begins to rotate, often because of wind shear or airflow around obstacles. The spinning motion tightens the vortex, drawing in more oxygen and stretching the flames upward.
Where to see it
Did you know?
Most fire whirls are short-lived and relatively small, but some have been strong enough to loft burning debris and spread fire.
OccasionalEarth & Fire
Fumarole
A fumarole is an opening in the ground that vents steam and volcanic gases, often staining nearby rocks yellow, white or red. It can hiss, roar or shimmer with heat.
The science
Groundwater and volcanic gases are heated by magma or hot rock below the surface and escape through cracks. The vapor is commonly rich in steam, with gases such as carbon dioxide, sulfur dioxide and hydrogen sulfide.
Where to see it
Did you know?
Bright yellow crusts around fumaroles are often sulfur deposited as hot gases cool.
OccasionalEarth & Fire
Mud Pot
A mud pot is a bubbling pool of hot mud that blorps, spits and heaves as gas escapes through it. The surface can range from thin gray slurry to thick, sticky paste.
The science
Mud pots form in geothermal areas where hot acidic water and steam break down surrounding rock into fine clay. With limited water supply, the heated clay and water mix into mud that is churned by rising steam and gases.
Where to see it
Did you know?
Their consistency changes with rainfall and groundwater supply—after wet periods a mud pot may become much thinner and more watery.
OccasionalEarth & Fire
Earthquake
An earthquake is a sudden shaking of the ground caused by movement in Earth's crust. It may last only seconds, but the motion can range from a gentle sway to violent jolts.
The science
Most earthquakes occur when stress builds up along faults as tectonic plates move. When the rocks finally slip, stored elastic energy is released as seismic waves that travel through the ground.
Where to see it
Did you know?
The point inside Earth where rupture starts is the focus, while the point directly above it on the surface is the epicenter.
RareEarth & Fire
Tsunami
A tsunami is a series of long ocean waves that can race across entire ocean basins and then rise dramatically in shallow coastal water. At shore it may arrive as a fast-rising flood, a powerful surge or multiple waves.
The science
Most tsunamis are triggered when an undersea earthquake suddenly lifts or drops part of the seafloor and displaces a large volume of water. They can also be caused by submarine landslides, volcanic eruptions or, rarely, meteorite impacts.
Where to see it
Did you know?
In deep ocean, a tsunami may be only tens of centimeters high and pass unnoticed by ships, despite moving at jet-aircraft speeds.
OccasionalEarth & Fire
Sinkhole
A sinkhole is a depression or hole in the ground caused when the surface collapses or gradually subsides. Some open suddenly, while others form slowly as the land sags.
The science
Many sinkholes develop in karst terrain, where groundwater dissolves soluble rock such as limestone, gypsum or salt and creates underground voids. If the roof over a cavity weakens or sediment is washed downward, the surface can drop or collapse.
Where to see it
Did you know?
Some water-filled sinkholes in limestone regions are cenotes, formed when cave roofs collapse and expose groundwater.
Very RareEarth & Fire
Sailing Stones
Sailing stones are rocks that leave long tracks across a flat, dry lake bed as if they had moved by themselves. The trails can curve, cross or run parallel over the cracked mud surface.
The science
At Racetrack Playa and similar sites, movement occurs when a thin sheet of ice forms during cold nights and then breaks up in daytime sun and light wind. The floating ice panels push stones across the wet, low-friction mud, carving tracks behind them.
Where to see it
Did you know?
For decades the stones' motion was a mystery, but direct observations in 2013–2014 confirmed that thin ice and light winds can move them.
RareEarth & Fire
Pele's Hair
Pele's Hair consists of delicate golden strands of volcanic glass spun from lava like windblown fibers. It often collects in tangles on the ground or drapes over vegetation near active lava fountains.
The science
It forms when blobs of very fluid basaltic lava are stretched into thin threads by wind and by the force of escaping volcanic gases during fountaining or spattering. The strands cool so quickly that they solidify as glass before they can fall apart.
Where to see it
Did you know?
Despite its hair-like look, Pele's Hair is made of sharp volcanic glass and should not be handled with bare hands.
Ice & Snow
11 phenomena
CommonIce & Snow
Snowflakes
Delicate ice crystals that fall from clouds as tiny stars, plates, columns or branching patterns. To the eye they look white, but individual flakes are transparent ice.
The science
Snowflakes grow when water vapour freezes onto a tiny particle in a cold cloud and the crystal enlarges as more vapour deposits on it. Their shape depends mainly on temperature and humidity as they fall through different layers of air.
Where to see it
Did you know?
A snowflake’s six-sided symmetry comes from the hexagonal arrangement of water molecules in ice.
CommonIce & Snow
Hoarfrost
A feathery white coating of ice crystals that forms on grass, fences, branches and other exposed surfaces. It often looks spiky or fern-like in calm, cold weather.
The science
Hoarfrost forms when water vapour in the air deposits directly as ice onto a surface that is below 0 °C. It grows best on clear, still nights when surfaces cool strongly by radiation.
Where to see it
Did you know?
Hoarfrost does not come from frozen dew; it forms directly from water vapour turning into ice.
OccasionalIce & Snow
Rime Ice
A rough, milky-white ice coating that builds outward on trees, wires, rocks and summit structures in freezing fog or cloud. It often points into the wind like a frozen plume.
The science
Rime forms when supercooled water droplets in fog or cloud hit a surface below freezing and freeze almost instantly. Air bubbles get trapped in the ice, making it opaque and brittle.
Where to see it
Did you know?
Because it grows from wind-driven droplets, rime ice usually thickens on the windward side of objects.
RareIce & Snow
Hair Ice
Fine, silky threads of ice that sprout from dead wood like white hair. The strands are extremely delicate and can curl into soft tufts.
The science
Hair ice forms when moist, decaying broadleaf wood contains liquid water that is drawn out through tiny pores and freezes in subzero air. A winter-active fungus, Exidiopsis effusa, helps keep the ice in very thin strands by influencing the crystallization process.
Where to see it
Did you know?
Individual hairs are often only about 0.01 mm thick, yet they can grow several centimetres long.
RareIce & Snow
Ice Spikes
Narrow, needle-like towers of ice that sometimes rise from the surface of freezing water, often in ice cube trays or shallow puddles. They look like tiny frozen chimneys.
The science
As water freezes from the edges inward, expanding ice can leave a small opening above liquid water trapped below. Pressure then pushes water up through the hole, where it freezes around the rim and lengthens into a spike.
Where to see it
Did you know?
Ice spikes are much more likely to form in pure water than in water containing dissolved salts or other impurities.
RareIce & Snow
Penitentes
Tall, thin blades and pinnacles of hardened snow or ice that can cover high mountain snowfields in rows. Their fields can look like a crowd of white figures, which gave them their name.
The science
Penitentes form mainly by sublimation, when strong sunlight and very dry air cause snow to turn directly into water vapour. Small hollows absorb more radiation and deepen faster, gradually exaggerating the surface into spikes and troughs.
Where to see it
Did you know?
Some penitentes grow several metres high in the driest, sunniest high-altitude environments.
RareIce & Snow
Pancake Ice
Round, flat pieces of young ice with raised rims that bob and jostle together on rough water. From above they resemble overlapping lily pads or giant floating pancakes.
The science
It forms in cold, turbulent seas where slushy frazil ice and thin sheets are churned by waves. Repeated collisions round the edges and pile up rims of softer ice.
Where to see it
Did you know?
Pancake ice is often an intermediate stage in the growth of a more continuous sea-ice cover.
RareIce & Snow
Frost Flowers
Fragile, petal-like ice crystals that curl and spread across new sea ice or sometimes young lake ice. They form intricate white clusters that look more like blossoms than frost.
The science
When very cold air sits over much warmer newly formed ice, water vapour rises from salty brine at the surface and deposits as ice crystals. The crystals can wick up brine, which makes them chemically distinctive from ordinary hoarfrost.
Where to see it
Did you know?
Frost flowers are not true flowers of frozen seawater; they are ice crystals grown from water vapour above the ice surface.
RareIce & Snow
Diamond Dust
A glittering fall of tiny ice crystals that sparkles in sunlight or streetlights, often in otherwise clear air. It can make the atmosphere seem full of drifting dust made of glass.
The science
Diamond dust occurs when very small ice crystals form in extremely cold, stable air near the ground and slowly settle out. It is especially common when the air is moist enough for ice to grow but too cold for liquid droplets.
Where to see it
Did you know?
Diamond dust can create halos, light pillars and other optical effects because the crystals act like tiny prisms and mirrors.
Very RareIce & Snow
Snow Rollers
Naturally rolled cylinders or hollow tubes of snow that look like mini hay bales scattered across open ground. They are made when the wind pushes a sticky top layer of snow along the surface.
The science
They form when a thin, cohesive layer of wet or lightly crusted snow can peel away and roll under strong, steady wind. Conditions must be precise: snow sticky enough to hold together, but not so wet or deep that the roll collapses.
Where to see it
Did you know?
Many snow rollers are hollow because the first layers can blow away or crumble as the roll grows.
RareIce & Snow
Aufeis
Layered sheets or terraces of ice that build up over winter along stream valleys, springs and river margins. They can spread across the ground in broad, frozen masses.
The science
Aufeis forms when groundwater or stream water repeatedly flows onto an existing ice surface in freezing weather and freezes in successive layers. The process can continue all winter where water keeps emerging despite the cold.
Where to see it
Did you know?
The word 'aufeis' comes from German and is often used interchangeably with the Russian term 'naled'.
Living World
8 phenomena
RareLiving World
Synchronous Fireflies
Thousands of fireflies flash in near-unison, turning dark forest edges into waves of blinking light. The display is most famous on warm early-summer nights in parts of the eastern United States and Southeast Asia.
The science
In some species, males use rhythmic bioluminescent flashes to attract mates, and large groups gradually synchronize their timing through visual cues from nearby individuals. The light is produced by a chemical reaction in special abdominal organs involving luciferin, oxygen and the enzyme luciferase.
Where to see it
Did you know?
The best-known North American synchronizing species, Photinus carolinus, is one of only a few firefly species in North America known to coordinate its flashes so closely.
OccasionalLiving World
Starling Murmuration
A murmuration is a shifting, cloud-like flock of starlings that twists and folds across the evening sky. The flock can change shape in seconds, forming dense ripples and sweeping curves.
The science
Each bird adjusts its speed and direction in response to nearby neighbours, and simple local interactions can create large, coordinated patterns across the whole flock. Gathering in dense flocks may also reduce predation risk and help birds share information about safe roosts.
Where to see it
Did you know?
Studies suggest starlings track the movements of a limited number of nearest neighbours rather than responding to every bird in the flock.
RareLiving World
Coral Spawning
On a few nights each year, corals release huge numbers of eggs and sperm into the sea, often making the water look as if it is filled with drifting pink or cream-coloured beads. The event can involve many coral species spawning within a narrow time window.
The science
Mass spawning is timed by environmental cues including sea temperature, day length and the phase of the Moon, which help synchronise reproduction across reefs. Releasing gametes together increases the chance of fertilisation and can overwhelm some predators by sheer numbers.
Where to see it
Did you know?
Many reef-building corals are broadcast spawners, releasing eggs and sperm into open water rather than fertilising internally.
RareLiving World
Foxfire
Foxfire is a faint blue-green glow seen on decaying wood or forest litter at night. It is caused by bioluminescent fungi, so the wood itself is not producing the light.
The science
Certain fungi emit light through chemical reactions in their tissues, probably involving luciferin-like compounds and oxygen. The glow is usually associated with fungal growth in damp, decaying wood where the organisms are breaking down lignin and cellulose.
Where to see it
Did you know?
The term "foxfire" is old, but the glow has nothing to do with foxes; it refers to luminous wood colonised by fungi.
OccasionalLiving World
Monarch Migration
Each autumn, millions of monarch butterflies travel south in a long-distance migration, with eastern North American monarchs funneling toward mountain forests in Mexico. In spring, subsequent generations spread north again across much of the continent.
The science
Shortening day length and cooler temperatures help trigger migratory behaviour and reproductive delay in autumn monarchs. They navigate using a time-compensated Sun compass, and magnetic cues may also help when sunlight is unavailable.
Where to see it
Did you know?
No single eastern monarch completes the full annual round trip; the northward return takes several generations, while the southbound autumn generation is exceptionally long-lived.
OccasionalLiving World
Sardine Run
The sardine run is a vast movement of sardines along South Africa’s east coast, often accompanied by dolphins, sharks, seabirds and whales feeding on the shoals. Near the surface, the fish can pack into dense bait balls under attack from predators.
The science
The run is linked to seasonal ocean conditions, especially cool water moving northward along the coast that allows sardines to enter areas that are otherwise often too warm for them. Predator behaviour then concentrates the shoals into tight formations, making the event highly visible.
Where to see it
Did you know?
The sardine run does not occur with equal intensity every year; ocean temperatures and currents strongly influence its size and timing.
OccasionalLiving World
Red Crab Migration
On Christmas Island, millions of red crabs leave the forest and march to the coast in a striking seasonal migration. Roads, drains and shorelines can become carpeted with moving crabs as they head to breed.
The science
The migration begins with the onset of the wet season, when higher humidity reduces the risk of the crabs drying out on land. Breeding is timed so that females release their eggs into the sea at a particular phase of the Moon, improving the chances that larvae are carried away by suitable tides and currents.
Where to see it
Did you know?
Christmas Island’s red crabs are land crabs, but they still depend on the ocean to complete their life cycle because their larvae develop in seawater.
RareLiving World
Periodical Cicadas
Periodical cicadas emerge in enormous numbers after spending either 13 or 17 years underground as juveniles. For a few weeks, woodlands ring with the loud buzzing and whirring calls of adult males.
The science
The nymphs feed on fluids from tree roots below ground and develop very slowly, emerging when soil temperatures near the surface rise to about 18 °C in late spring. Prime-number life cycles of 13 and 17 years may help reduce overlap with predators and with other cicada broods.
Where to see it
Did you know?
A "brood" is a geographically distinct population on its own schedule, so different broods emerge in different years across the eastern United States.