Scientists have spent centuries uncovering the many mysteries of the natural world, yet some phenomenon still baffle even the sharpest of scientific minds.
From strange lights in the sky following earthquakes to rocks that spontaneously glide across the ground, these naturally-occurring events from around the world seem to have no purpose or meaning.
Science Uncovered‘s Hayley Birch has compiled a list of the top 10 most strange, cryptic and incredible naturally-occurring events from around the world.
1. EARTHQUAKE LIGHTS: Ethereal lights that appear in the sky before and during a quake
For mystery, controversy and epic scale, nothing beats earthquake lights – the unexplained illuminations in the sky that can accompany a seismic shudder.
The mystery: what causes them? The controversy: do they even exist? And the epic status? Well, it’s like an earthquake and a lightning storm all rolled into one. It’s beyond Biblical.
Italian physicist Cristiano Ferugia assembled a complete account of earthquake light reports dating back to 2000BC. For a long time, however, geoscientists remained sceptical about the strange phenomena. It wasn’t until 1966 that hard evidence emerged, in the form of photos from the Matsushiro earthquake in Japan.
Now, of course, you have only to head to the internet to come across hundreds of pages full of earthquake light photos, many of dubious authenticity.
But the lights appear in so many different colours and forms – from red to white to blue, and in globes, flickers and glows – that it’s difficult to spot a fake.
The various theories include heat caused by friction, radon gas and piezoelectricity – an electric charge accumulating in quartz rocks as tectonic plates move.
In 2003, NASA physicist Dr Friedemann Freund carried out lab experiments, which suggested that earthquake lights are caused by electrical activity in rocks.
He said shockwaves from earthquakes can change the electrical properties of silicon and oxygen-containing minerals, allowing them to transmit currents and emit light.
But Professor David Brumbaugh, at the Arizona Earthquake Information Center in Flagstaff, Arizona, thinks the theory can be considered only a ‘possible explanation’ at best.
‘Although Freund’s theory seems promising, the answer may be a bit more complicated,’ he said. Brumbaugh, however, admits he’s not aware of any new research that would be as useful as Freund’s.
2. THE NAZCA LINES: Vast shapes drawn in the Peruvian sand by an ancient population – but no one knows why
Covering a 450km2 expanse of coastal desert, the Nazca Lines are oversized artworks etched into the Peruvian plains. Including large geometric designs as well as pictures of animals, plants and rarer human-like figures, they are visible from the air as giant line drawings.
They are thought to have been created by the Nazca people over a 1,000-year period between 500BC and 500AD, but no one knows why.
Despite World Heritage status, the Peruvian authorities have trouble protecting the Lines from squatters. According to Peruvian law, which protects the landless, squatters only have to stay for a single day in order to be able to stake a claim.
Last year, reports emerged of Peruvians raising pigs on the artworks. In their view, the site is simply an expanse of wasted space in a region with a rapidly growing poor population.
Meanwhile, archaeologists are trying to study the Lines before they are destroyed. Early claims that the designs formed part of an astronomical calendar have been discredited and, since 1997, researchers working as part of a Peruvian-German collaboration have turned their attention to the history and culture of the people who created them – how they lived and what happened to them.
In 2012, Yamagata University, in Japan, announced that it would open a research centre at the site as part of a 15-year project to study more than 1,000 drawings.
3. INCREDIBLE BUTTERFLY NAVIGATION: Monarch butterflies find their way thousands of miles to specific mountains
Each year, millions of North American monarch butterflies migrate 2,000 miles south for winter. For years, no one knew where they ended up.
Then, in the 1950s, Norah Urquhart and her husband Fred, a zoologist, began tagging and tracking the creatures. In 1976, tipped off by a local woodcutter, they climbed to the top of the ‘Mountain of Butterflies’. All the butterflies in North America, it seemed, were in a mountain forest in Mexico.
That’s not where the story ends. While we know the monarchs target just 12 to 15 Mexican mountain sites, we don’t know how they navigate there.
Studies suggest they use the position of the Sun to fly south, adjusting for the time of day through circadian clocks in their antennae. But the Sun only gives them a general direction. What guides them towards the Michoacan mountains?
‘They are funnelled in, probably by landmarks as they reach the overwintering site,’ said Professor Steven Reppert, a monarch expert at the University of Massachusetts. ‘But how they home in is still a mystery.’
Landmarks such as the Gulf of Mexico couldn’t provide enough information to take butterflies all the way, so they must use other short-range navigation systems.
One theory is that a geomagnetic force attracts them, although, says Reppert, ‘that’s never really panned out’. Scientists only recently acquired some of the genetic tools needed to probe the details of their navigation systems. Now they have a full genetic code, they are starting to knock out genes to see how this affects the animals’ sense of direction.