What Is the Difference Between a Crevice and a Crevasse?


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.

Why Are Mugshots Made Public Before a Suspect is Convicted by the Court?

Jennifer Ellis:

Several reasons.

1. Mugshots can help find people when they have absconded, or warn people when someone is out and dangerous. So there is a good reason to share some mugshots.

2. Our legal system requires openness as per the federal constitution, and I imagine most if not all state constitutions. As such, this sort of information is not considered private and can be shared. Any effort to keep mugshots private would result in lawsuits by the press and lay people. This would be under the First and Sixth Amendments as well as the various Freedom of Information Acts. However, in 2016 a federal court ruled [PDF] that federal mugshots are no longer routinely available under the federal FOIA.

This is partially in recognition of the damage that mugshots can do online. In its opinion, the court noted that “[a] disclosed booking photo casts a long, damaging shadow over the depicted individual.” The court specifically mentions websites that put mugshots online, in its analysis. “In fact, mugshot websites collect and display booking photos from decades-old arrests: BustedMugshots and JustMugshots, to name a couple.” Some states have passed or are looking to pass laws to prevent release of mugshots prior to conviction. New Jersey is one example.

a) As the federal court recognizes, and as we all know, the reality is that if your picture in a mugshot is out there, regardless of whether you were convicted, it can have an unfortunate impact on your life. In the old days, this wasn’t too much of a problem because it really wasn’t easy to find mugshots. Now, with companies allegedly seeking to extort people into paying to get their images off the web, it has become a serious problem. Those companies may get in trouble if it can be proved that they are working in concert, getting paid to take the picture off one site and then putting it on another. But that is rare. In most cases, the picture is just public data to which there is no right of privacy under the law.

b) The underlying purpose of publicity is to avoid the government charging people and abusing the authority to do so. It was believed that the publicity would help protect people. And it does when you have a country that likes to hide what it is up to. But, it also can cause harm in a modern society like ours, where such things end up on the web and can cause permanent damage. Unfortunately, it is a bit of a catch-22. We have the right to know issues and free speech rights smack up against privacy rights and serious damage of reputation for people who have not been convicted of a crime. The law will no doubt continue to shake out over the next few years as it struggles to catch up with the technology.

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

What Happens When You Flush an Airplane Toilet?

For millions of people, summer means an opportunity to hop on a plane and experience new and exciting sights, cultures, and food. It also means getting packed into a giant commercial aircraft and then wondering if you can make it to your next layover without submitting to the anxiety of using the onboard bathroom.

Roughly the size of an apartment pantry, these narrow facilities barely accommodate your outstretched knees; turbulence can make expelling waste a harrowing nightmare. Once you’ve successfully managed to complete the task and flush, what happens next?

Unlike our home toilets, planes can’t rely on water tanks to create passive suction to draw waste from the bowl. In addition to the expense of hauling hundreds of gallons of water, it’s impractical to leave standing water in an environment that shakes its contents like a snow globe. Originally, planes used an electronic pump system that moved waste along with a deodorizing liquid called Anotec. That method worked, but carrying the Anotec was undesirable for the same reasons as storing water: It raised fuel costs and added weight to the aircraft that could have been allocated for passengers. (Not surprisingly, airlines prefer to transport paying customers over blobs of poop.)

Beginning in the 1980s, planes used a pneumatic vacuum to suck liquids and solids down and away from the fixture. Once you hit the flush button, a valve at the bottom of the toilet opens, allowing the vacuum to siphon the contents out. (A nonstick coating similar to Teflon reduces the odds of any residue.) It travels to a storage tank near the back of the plane at high speeds, ready for ground crews to drain it once the airplane lands. The tank is then flushed out using a disinfectant.

If you’re also curious about timing your bathroom visit to avoid people waiting in line while you void, flight attendants say the best time to go is right after the captain turns off the seat belt sign and before drink service begins.

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