Some people might think humans have mastered the Earth. Clearly, those people aren't paying attention. Sure, we might have built concrete jungles and sent people to the moon, but for every landmark achievement, the world has some creepy natural phenomena up its sleeve to put us in our place — and give us nightmares, because seriously? A waterfall of blood (well, rust-colored water) oozing out of a glacier in Antarctica? A whirlpool so vast and deadly it terrified Edgar Allen Poe into writing a story about it? You can't tell me this stuff doesn't make you want to live in a nice, secure room safe from Mother Nature's sadistic streak.
The good news is that while the following phenomena are unsettling at best, they also have totally rational explanations. Take the apparently-bloody waterfall (appropriately named Blood Falls) I mentioned above. First discovered in 1911, it looks like something out of an unsubtle horror movie, but within a few decades, scientists figured out that the water's macabre color comes from iron oxide. Recently, they were even able to determine where all that iron comes from: a salty lake trapped beneath the glacier for nearly a million years. Once the iron-rich water is exposed to oxygen in the air, it turns red, producing what appears to be a waterfall of blood.
I don't know about you, but that's the kind of information that lets me sleep at night. Here are eight other creepy phenomena with totally reasonable explanations.
1The Door To Hell
Near the village of Deweze in Turkmenistan, visitors can find a 230-foot-wide pit in the earth that has been burning steadily since the '70s. The Darvaza Crater, also known as the Door to Hell, is the result of human and natural intervention. In 1971, Soviet scientists were drilling in the Karakum Desert when their rig collapsed into a natural gas pocket. To prevent the sinkhole from releasing poisonous gases, the team set the crater on fire, expecting it to burn itself out within a few days.
Instead, more than 45 years later, it continues to burn merrily, and efforts to fill in the hole have fizzled. Sometimes, it supposedly gives off a stench of sulfur. Never let it be said Mother Nature doesn't have a sense of drama.
Anything that inspires Edgar Allen Poe ("A Descent into the Maelstrom") and Jules Verne ("Twenty Thousand Leagues Under the Sea") is bound to be terrifying, and the Moskstraumen delivers. Found off the coast of Norway, the maelstrom is one of the strongest series of currents and whirlpools in the world; according to a 16th century bishop, it's stronger than the famous Sicilian whirlpool Charybdis. Although there's no official record of its death toll, the maelstrom is known to be extremely dangerous, especially for small boats that are easily caught in its powerful currents.
So what's the explanation for the area's treacherous waters? It's not divine forces or some hole in the ocean floor. According to a 1997 study, the Moskstraumen owes its existence to enormous tidal differences between the mainland and the Lofoten island chain. The difference in sea level can reach up to 20 inches over a distance of just a few miles, creating the powerful currents and eddies that make up a maelstrom.
3The Bolton Strid
In Yorkshire, England, the Bolton Strid looks like any other stream in the area. About six feet across, it's surrounded on either side by grassy banks, trees, and signs warning passersby of hidden danger. Underneath the surface, you see, runs a current so powerful it's said to have claimed the lives of everyone who has fallen in, and it's too dangerous to reclaim their bodies. In fact, nobody is quite sure how deep the caves underneath the Strid's water goes.
If you take a quick walk, the reason for the stream's force is obvious: It's not a stream at all. Just upstream, the waterway is a churning river about 30 feet across. When it reaches Bolton Abbey, all that water is forced into a narrow gap — essentially, the river goes from horizontal to vertical. The waters may only be six feet across, but they're far deeper (and more dangerous) than they appear.
Imagine you're wandering the snowy fields of Antarctica when you come across what appears to be a giant chimney made of ice. Oh, and it's smoking. It's an unsettling sight, and the explanation isn't much better.
These formations are known as ice fumaroles, and they can be found where the heat of a volcano melts the snowpack above, creating a cave. When steam escapes from that cave, it freezes in the icy environment above, building what some call "ice chimneys."
5Underwater Crop Circles
Crop circles aren't exclusive to land; they can be found on the ocean floor as well. First noticed in 1995, these elaborate, geometrically-patterned circles creeped people out for years until the rather prosaic explanation was discovered. Apparently, underwater crop circles are created by male pufferfish attempting to woo the ladies. Say it with me: Awwww.
6The Great Blue Hole
Off the coast of Belize lies a massive underwater chasm hundreds of feet deep, known for its deep blue waters. Perhaps unsurprisingly, it's become known as the Great Blue Hole over the years. I can't speak for anyone else, but I have no desire to know what's lurking in its depths. (Cthulhu. Definitely Cthulhu.)
According to Atlas Obscura, the Great Blue Hole is a sinkhole formed from an ancient limestone cave. As sea levels rose with the end of the last glacial period, the cave filled with water, creating the Lovecraftian horror seen above.
Watch the video above and tell me that doesn't look like a sign of the apocalypse. Although I would consider them cause to batten down the hatches and prepare for the incoming alien invasion, these clouds are apparently totally normal, natural formations. Just last month, asperitas clouds were officially recognized by the World Meteorological Society; they're caused by weather fronts causing atmospheric waves.
As if Death Valley wasn't already disquieting, it's home to a phenomenon that's baffled scientists for years: sailing stones. These large, heavy rocks appear to be moving across a dry lake bed called Racetrack Playa — without any outside help. We know this because the rocks leave a trail behind them as they move, although nobody's actually witnessed them move.
In 2011, scientists finally solved the mystery. As researcher Ralph Lorenz explained to Smithsonian in 2013, the sailing rock is part of a "small floating ice sheet." When the ice sheet moves, so does the rock, dragging a trail behind it in the mud. Not so creepy now, is it?