Some places and natural events look so strange that people assume a photo has been doctored. A wave that surfs up a river for half an hour. Flames that burn electric blue. A lake that leaves birds looking like stone statues. Every example in this gallery is real, and each has a clear scientific explanation, which in most cases is even more interesting than the illusion.
The twenty wonders below are grouped by what drives them: moving water, fire and weather, living things, and unusual land and ice. For each one you will find where it happens, what causes it and, where it matters, a correction to the myths that tend to travel with the pictures. A few of these sights can be visited with a little planning; others need luck, the right season or a very specific moment of light. Several of them are also fragile, threatened by pollution, invasive species or a changing climate, which is a good reason to reconnect with nature and protect it rather than simply scroll past.
Waves, whirlpools and holes in the sea
The never-ending wave of the Amazon
The pororoca is a tidal bore: when a strong incoming tide meets the outflow of the Amazon and nearby rivers, the sea pushes upstream as a single breaking wave up to about 4 metres high. It can travel as far as 800 km inland. It is strongest at new and full moons, especially around the March and September equinoxes. Surfers love it; in 2003 Brazilian Picuruta Salazar rode one for 12.5 km over 37 minutes.
Maelstroms: whirlpools made by the tide
Powerful tidal whirlpools form where huge volumes of seawater are forced through narrow straits as the tide turns. Norway is famous for them: Saltstraumen near Bodø is counted among the strongest tidal currents in the world, and the Moskstraumen off the Lofoten Islands gave literature the word "maelstrom." They can be dangerous for swimmers and small boats, but stories of them swallowing ships are mostly legend.
The Great Blue Hole, Belize
This near-perfect circle of deep blue sits in the middle of Lighthouse Reef, about 70 km off the coast of Belize. It is roughly 318 metres across and 124 metres deep. It began as a limestone cave system during the ice ages, when sea levels were far lower; stalactites inside show the cave was dry at several points in the last 150,000 years before rising seas flooded it. Jacques Cousteau's ship Calypso charted it in 1971, and it is now part of the Belize Barrier Reef UNESCO World Heritage Site.
The "underwater waterfall" of Mauritius
Off the Le Morne peninsula in southwest Mauritius, the sea appears to pour over a cliff into the deep. It is an optical illusion. Sand and silt drifting along the island's underwater shelf and down its slope create streaks that, seen from the air, look like a cascading waterfall. The water itself is not falling anywhere, which makes it one of the best natural tricks of the eye on the planet.
Fire, light and wild weather
Blue fire at Kawah Ijen, Indonesia
Often described as "blue lava," the glow at the Ijen volcano on Java is actually burning sulfuric gas. Gas escaping through cracks ignites on contact with air at temperatures up to about 600 °C, producing flames as high as 5 metres; some condensed sulfur also burns as it runs downhill. The crater also holds one of the most acidic lakes in the world, and local miners carry heavy loads of solid sulfur out of the crater by hand.
Volcanic lightning
During large explosive eruptions, ash particles and ice crystals collide inside the plume and separate electric charge, much as in a thunderstorm. The result can be spectacular bolts flickering through the ash cloud. Photographers captured striking examples during eruptions in Chile, Iceland and elsewhere in recent decades, but the phenomenon is old news: Pliny the Younger described it during the eruption of Vesuvius in 79 AD.
The "everlasting storm" of Catatumbo, Venezuela
Where the Catatumbo River flows into Lake Maracaibo, thunderstorms build on about 140 to 160 nights a year, often lasting around nine hours. Warm, moist air from the lake meets the surrounding Andes, which hem in the plain on three sides, and storms form night after night. The area has one of the highest lightning densities on Earth. It is not literally endless: a drought paused it from January to March 2010.
Lenticular clouds
These smooth, lens-shaped clouds form when stable, moist air flows over a mountain and sets up standing waves in the atmosphere downwind. Cloud forms at the crest of each wave and evaporates in the trough, so the cloud seems to hover in place even in strong wind. Their saucer shape has led to more than a few UFO reports, while glider pilots seek them out for the lift they signal.
Horsetail Fall, Yosemite's "firefall"
For about ten minutes at sunset on certain days in mid to late February, the low sun lights up Horsetail Fall on the east side of El Capitan so that it glows orange like flowing lava. It needs three things at once: enough snowmelt for the fall to run, a clear sky and the right angle of light, so it does not happen every year. Ansel Adams photographed it in 1940, and Galen Rowell's 1973 picture made it famous.
Steam towers under the northern lights
In volcanic regions such as Iceland, steam from hot springs and geothermal vents rises into the cold night air in tall white columns. When the aurora is active at the same time, the scene looks like science fiction. The aurora itself is caused by charged particles from the Sun striking the upper atmosphere, while the steam comes from groundwater heated by magma below; the two simply happen to share the same sky in high-latitude volcanic areas.
Living wonders
The pufferfish that draws circles in the sand
Divers first noticed these delicate geometric patterns on the seabed off Amami Ōshima in southern Japan in 1995, without knowing who made them. The builder turned out to be a small male pufferfish, only about 10 cm long, later described as the species Torquigener albomaculosus. Working with its fins for seven to nine days, it shapes a circle about 2 metres wide to attract a female, which lays her eggs in the centre.
Living rocks of Chile
What looks like a rock split open to reveal red flesh is Pyura chilensis, a sea squirt (tunicate) that lives fixed in place on the coasts of Chile and Peru. Locals call it piure and eat it raw or cooked. It has unusual biology: its blood can carry high levels of the metal vanadium, and it starts life male, becoming hermaphrodite as it matures.
The red crab march of Christmas Island
Every year, usually after the first rains of the wet season in October or November, millions of red crabs leave the forests of Christmas Island, an Australian territory in the Indian Ocean, and head to the sea to breed. Older reports put the population at around 120 million, but recent surveys estimate about 43.7 million adults, after an invasive species, the yellow crazy ant, killed millions. Rangers close roads and have built crab underpasses and a crab bridge to help them cross.
The "black sun" of Denmark
In spring and autumn, vast flocks of migrating starlings gather over the marshes of southwest Jutland at dusk. Their swirling formations, called murmurations, can be dense enough to darken the sky, which is why Danes call it sort sol, or black sun. Flying in tight, shifting groups makes it hard for falcons and other predators to single out one bird.
Monarch butterfly migration
Each autumn, monarch butterflies from eastern North America fly up to roughly 4,000 km south to spend the winter clustered on fir trees in the mountains of central Mexico. No single butterfly makes the round trip; it takes several generations to return north in spring. Numbers have fallen sharply in recent decades due to habitat loss and fewer milkweed plants, the only food of monarch caterpillars.
Rainbow eucalyptus
The bark of Eucalyptus deglupta peels off in strips, revealing fresh bark that is bright green and slowly ages through blue, purple, orange and maroon, so the trunk shows many colours at once. Despite the "eucalyptus" name, this tree is not Australian: it is native to the Philippines, Indonesia and Papua New Guinea, and is planted as an ornamental in frost-free places such as Hawaii.
The flowering desert of Chile
The Atacama is one of the driest places on Earth, yet in years with unusually heavy rain, often linked to El Niño, seeds that have waited in the soil for years germinate almost at once. Between about September and November, stretches of desert turn purple, pink and yellow with flowers. Chileans call it desierto florido, and visitors are asked to stay on paths so the plants can set seed for the next bloom.
Strange land, stone and ice
Lake Natron, Tanzania
Lake Natron is extremely alkaline, with a pH that can rise above 12 and water temperatures above 40 °C, because evaporation concentrates sodium carbonate minerals washed in from volcanic rock. A common myth says it turns animals to stone the moment they touch it. In reality, birds and bats that die in or near the lake can become calcified and preserved, as in photographer Nick Brandt's famous images. The same lake is the main breeding ground for lesser flamingos in East Africa.
Rainbow mountains of China
The striped hills of Zhangye in Gansu province formed from layers of sandstone and siltstone with different minerals, laid down over millions of years. Tectonic forces later tilted and folded the layers, and erosion exposed them in bands of red, yellow and orange. Similar red-bed landscapes across southern China, known as China Danxia, were named a UNESCO World Heritage Site in 2010.
Hair ice
These silky white strands grow from moist, rotting broadleaf wood on humid nights just below freezing. It is often credited to bacteria, but a 2015 study in Biogeosciences showed that a fungus, Exidiopsis effusa, is the key: it was present in every sample, and killing it stopped hair ice from forming. The idea goes back to the meteorologist Alfred Wegener, who suspected a fungus as early as 1918.
Seeing these wonders responsibly
Many of these sights depend on narrow conditions: a tide at the right phase of the moon, a few days of February light, a rainy year in the desert. That is part of their magic, and also part of their vulnerability. The red crabs of Christmas Island are threatened by invasive ants, monarchs by habitat loss, and Lake Natron's flamingos by any change to the water that feeds the lake.
If you plan to visit, go with local guides, follow park rules and never take "souvenirs" from fragile sites. At places like Kawah Ijen, sulfur fumes are a real health hazard, so check current safety advice and carry a proper gas mask. And when a picture seems too strange to be true, it is worth looking up what is really going on. The science is usually the best part of the story.
Sources: Wikipedia: Pororoca; Wikipedia: Torquigener albomaculosus; Wikipedia: Kawah Ijen; Wikipedia: Lake Natron; Wikipedia: Hair ice; Wikipedia: Horsetail Fall; Wikipedia: Pyura chilensis; Wikipedia: Rainbow eucalyptus; Wikipedia: Christmas Island red crab; Wikipedia: Catatumbo lightning; Wikipedia: Great Blue Hole. Photographs are by various photographers and were widely shared online; the Lake Natron image appears to come from Nick Brandt's series of calcified animals.
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