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What Is the Difference Between a Crevice and a Crevasse?

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The difference between a crevice and a crevasse is more than just a few letters. It’s the difference between geology and glaciology. While both terms come from the Anglo-French word crevace, to break, they mean two different things. Crevices are cracks or splits caused by a fracture of a rock, while a crevasse is a deep fracture in a glacier or ice sheet.

Crevasses in a glacier. Image Credit: G310ScottS via Wikimedia Commons // CC BY-SA 3.0

 
Crevasses form in the top layers of a moving glacier, usually because some parts of the massive body are moving at a different pace than the rest. If a glacier is moving over varied terrain (over mountains and down valleys), for instance, the glacier can stretch and fracture. The part of the glacier moving over a mountain will move more slowly, while the part that’s flowing down through the adjacent valley will gain speed. As the ice pulls apart at the stress points between those two portions of the ice, cracks form. Crevasses can also form when the glacier turns a corner, since the ice on the outside moves faster than the ice on the inside as it goes around a bend, or in open areas where ice begins to spread out horizontally (as it often does at its front end).

Often covered by snow, crevasses pose a great threat to mountaineers as they traverse the surface of a glacier: That snow can give way, leading to a steep fall. While the intense pressure at the bottom of a glacier typically squeezes a crevasse closed long before the crack reaches bedrock, the opening between the two parts of the ice can still reach as far as 100 feet down. As a safety precaution, climbers undergo crevasse rescue training in which they learn how to attach themselves to each other using a rope; should one of them fall into a crevasse, the other can pull them to safety on the ice.

A glacier may have more than one crevasse, and when they come together, they form a kind of free-floating column of glacial ice separate from the rest of the glacier. Called seracs, these pose yet another risk to climbers, because they can topple easily.

One big crevice (and many smaller ones). Image Credit: upyernoz via Wikimedia Commons // CC BY 2.0

 
Meanwhile, a crevice doesn’t always pose a threat. These are formed when brittle rocks crack under stress, and the two sides begin to pull apart (rather than sliding past each other). While you wouldn’t want to fall down a large one, they’re not always dangerous—they can be as small as a crack you’d see in the sidewalk or as deep as a canyon. These rock formations are not typically a threat to hikers because they're typically easy to see; in fact, they can often be a great help to rock climbers. The small ones are great for hand-holds or to attach bolts to, and larger crevices can be scaled. They’re also habitats: In western North America, there are dozens of bat species that use crevices as roosts [PDF].

If you're wondering in the middle of a conversation whether to use "crevice" or "crevasse," it's probably safer to go with crevice—unless you spend a lot of time talking about glaciers. While it's technically a geological term, the word crevice is used much more generally to describe cracks and gaps, whether in rock or in other materials. For instance, engineers use the word to describe the gap between two joined metals. Weeds might grow in the crevices of a sidewalk or between bricks. Colloquially, you could describe the gaps in your couch cushions where all your change accumulates as crevices.

In short, if it's not ice and you aren't making a glacier metaphor, it's a crevice.

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Big Questions
How Long Could a Person Survive With an Unlimited Supply of Water, But No Food at All?
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How long could a person survive if he had unlimited supply of water, but no food at all?

Richard Lee Fulgham:

I happen to know the answer because I have studied starvation, its course, and its utility in committing a painless suicide. (No, I’m not suicidal.)

A healthy human being can live approximately 45 to 65 days without food of any kind, so long as he or she keeps hydrated.

You could survive without any severe symptoms [for] about 30 to 35 days, but after that you would probably experience skin rashes, diarrhea, and of course substantial weight loss.

The body—as you must know—begins eating itself, beginning with adipose tissue (i.e. fat) and next the muscle tissue.

Google Mahatma Gandhi, who starved himself almost to death during 14 voluntary hunger strikes to bring attention to India’s independence movement.

Strangely, there is much evidence that starvation is a painless way to die. In fact, you experience a wonderful euphoria when the body realizes it is about to die. Whether this is a divine gift or merely secretions of the brain is not known.

Of course, the picture is not so pretty for all reports. Some victims of starvation have experienced extreme irritability, unbearably itchy skin rashes, unceasing diarrhea, painful swallowing, and edema.

In most cases, death comes when the organs begin to shut down after six to nine weeks. Usually the heart simply stops.

(Here is a detailed medical report of the longest known fast: 382 days.)

This post originally appeared on Quora. Click here to view.

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Big Questions
Why is Friday the 13th Considered Unlucky?
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Today, people around the globe will feel uneasy about getting out of bed, leaving their homes, or going about their normal daily routines, all because of a superstition. These unfortunate folks suffer from “paraskavedekatriaphobia,” a common neurosis familiar to us all: the fear of Friday the 13th. But just where did this superstitious association come from, and how did it catch on?

The truth is that no one is absolutely sure where the idea that Friday the 13th is unlucky originated. Donald Dossey, the founder of the Stress Management Center and Phobia Institute in Asheville, North Carolina, suspects the fear can be traced back to a Norse myth about 12 gods who had a dinner at Valhalla—the fabled hall where legendary Norse heroes feasted for eternity after they died—that was interrupted by a 13th guest, the evil and mischievous god Loki. According to legend, Loki tricked Höðr (the blind god of winter and son of Odin, the supreme god in Norse mythology) into shooting his brother Baldr (the benevolent god of summer who was also a son of Odin) with a magical spear tipped with mistletoe—the only substance that could defeat him. Thus the number 13 was branded as unlucky because of the ominous period of mourning following the loss of such powerful gods by this unwanted 13th guest.

For whatever reason, among many cultures, the number 12 emerged throughout history as a "complete" number: There are 12 months in a year, 12 signs of the zodiac, 12 Gods of Olympus, 12 sons of Odin, 12 labors of Hercules, 12 Jyotirlingas or Hindu shrines where Shiva is worshipped, 12 successors of Muhammad in Shia Islam, and 12 tribes of Israel. In Christianity, Jesus was betrayed by one of his 12 Apostles—Judas—who was the 13th guest to arrive for the Last Supper. Surpassing the number 12 ostensibly unbalances the ideal nature of things; because it is seen as irregular and disrespectful of a sense of perfection, the number 13 bears the stigma of misfortune and bad luck we know today.

WHY FRIDAY?

Friday joins in the mix mostly because all of the early accounts of Jesus’s crucifixion agree that it took place on Friday—the standard day for crucifixions in Rome. As Chaucer noted in The Canterbury Tales, "And on a Friday fell all this mischance." Yet perpetuating Friday as an unlucky day in America came from the late 19th-century American tradition of holding all executions on Fridays; Friday the 13th became the unluckiest of days simply because it combined two distinct superstitions into one. According to the Oxford University Press Dictionary of Superstitions, the first reference to Friday the 13th itself wasn’t until 1913. (So despite actually occurring on Friday, October 13, 1307, the popular notion that the Friday the 13th stigma comes from the date on which the famed order of the Knights Templar were wiped out by King Philip of France is just a coincidence.)

The repercussions of these phobias reverberated through American culture, particularly in the 20th century. Most skyscrapers and hotels lack a 13th floor, which specifically comes from the tendency in the early 1900s for buildings in New York City to omit the unlucky number (though the Empire State Building has a 13th floor). Street addresses sometimes skip from 12 to 14, while airports may skip the 13th gate. Allegedly, the popular Friday the 13th films were so-named just to cash in on this menacing date recognition, not because the filmmakers actually believed the date to be unlucky.

So, is Friday the 13th actually unlucky? Despite centuries of superstitious behavior, it largely seems like psychological mumbo jumbo. (One 1993 study seemed to reveal that, statistically speaking, Friday the 13th is unlucky, but the study's authors told LiveScience that though the data was accurate, "the paper was just a bit of fun and not to be taken seriously." Other studies have shown no correlation between things like increased accidents or injuries and Friday the 13th.)

And Friday the 13th isn't a big deal in other cultures, which have their own unlucky days: Greeks and Spanish-speaking countries consider Tuesday the 13th to be the unluckiest day, while Italians steer clear of Friday the 17th. So today, try to rest a little easy—Friday the 13th may not be so unlucky after all.

Additional Source: 13: The Story of the World’s Most Popular Superstition.

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