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Do Earthquakes Affect an Aircraft Flying Above?

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Ron Wagner:

They sure do, and I experienced it once. It was pretty scary, too.

BLYTHEVILLE AFB CIRCA 1978

I was flying a VIP jet transport from Andrews Air Force Base in Washington, to Blytheville Air Force Base, Arkansas to pick up someone, probably a member of Congress. It was night and there was a solid cloud overcast with a ceiling at about 3000 feet.

We were talking to and being vectored by approach control and inside the clouds we saw nothing but black—in those conditions, cockpit windows look like they’ve been painted black.

Suddenly, we broke out of the cloud base. Below them, it was crystal clear and we could see lights for many miles, including the runway lights and rotating beacon on the base. We reported to approach control that we had the airport in sight, we were cleared for a visual approach, and we turned toward the runway.

Just as suddenly as the lights had appeared, everything went black again.

When the windows went black again, we assumed we’d flown back into a cloud, so we called approach to tell them we’d lost the visual and wanted to continue vectors.

No reply.

We then checked our position on our navigational instruments but noticed they had red flags on them, which meant that the ground signal had been lost.

We called again. No reply.

We then noticed our transponder wasn’t blinking anymore, which meant we weren’t being painted by radar.

We called again. No reply.

We began to ponder climbing and switching back to our last en route frequency but first we called again. No reply.

Just as I was about to change frequency, a very excited controller called us.

They’d just had a big earthquake, which knocked out all power. It had taken a couple of minutes to get running on their emergency backup, but he now had his radio working.

He asked us to orbit visually on our own while they got things up and running again. That was the scary part because we saw nothing but black.

We could only hope there wasn’t a tall antenna out there—now unlighted due to the power outage. We called him and he verified he didn’t have his radar back yet, but he knew the area well and we were in the clear at our altitude. We continued to orbit—seeing nothing else in the whole world but the red glow from our flight instruments.

Finally the runway lights came back on. The controller then told us to continue to orbit while they sent some trucks down the runway to check for cracks.

A few minutes later we were told the runway was fine, so we finally went in visually and landed.

So, yes, earthquakes can absolutely affect pilots!

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

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Big Questions
What Causes Sinkholes?
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This week, a sinkhole opened up on the White House lawn—likely the result of excess rainfall on the "legitimate swamp" surrounding the storied building, a geologist told The New York Times. While the event had some suggesting we call for Buffy's help, sinkholes are pretty common. In the past few days alone, cavernous maws in the earth have appeared in Maryland, North Carolina, Tennessee, and of course Florida, home to more sinkholes than any other state.

Sinkholes have gulped down suburban homes, cars, and entire fields in the past. How does the ground just open up like that?

Sinkholes are a simple matter of cause and effect. Urban sinkholes may be directly traced to underground water main breaks or collapsed sewer pipelines, into which city sidewalks crumple in the absence of any structural support. In more rural areas, such catastrophes might be attributed to abandoned mine shafts or salt caverns that can't take the weight anymore. These types of sinkholes are heavily influenced by human action, but most sinkholes are unpredictable, inevitable natural occurrences.

Florida is so prone to sinkholes because it has the misfortune of being built upon a foundation of limestone—solid rock, but the kind that is easily dissolved by acidic rain or groundwater. The karst process, in which the mildly acidic water wears away at fractures in the limestone, leaves empty space where there used to be stone, and even the residue is washed away. Any loose soil, grass, or—for example—luxury condominiums perched atop the hole in the ground aren't left with much support. Just as a house built on a weak foundation is more likely to collapse, the same is true of the ground itself. Gravity eventually takes its toll, aided by natural erosion, and so the hole begins to sink.

About 10 percent of the world's landscape is composed of karst regions. Despite being common, sinkholes' unforeseeable nature serves as proof that the ground beneath our feet may not be as solid as we think.

A version of this story originally ran in 2014.

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Big Questions
How Are Speed Limits Set?
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When driving down a road where speed limits are oppressively low, or high enough to let drivers get away with reckless behavior, it's easy to blame the government for getting it wrong. But you and your fellow drivers play a bigger a role in determining speed limits than you might think.

Before cities can come up with speed limit figures, they first need to look at how fast motorists drive down certain roads when there are no limitations. According to The Sacramento Bee, officials conduct speed surveys on two types of roads: arterial roads (typically four-lane highways) and collector streets (two-lane roads connecting residential areas to arterials). Once the data has been collected, they toss out the fastest 15 percent of drivers. The thinking is that this group is probably going faster than what's safe and isn't representative of the average driver. The sweet spot, according to the state, is the 85th percentile: Drivers in this group are thought to occupy the Goldilocks zone of safety and efficiency.

Officials use whatever speed falls in the 85th percentile to set limits for that street, but they do have some wiggle room. If the average speed is 33 mph, for example, they’d normally round up to 35 or down to 30 to reach the nearest 5-mph increment. Whether they decide to make the number higher or lower depends on other information they know about that area. If there’s a risky turn, they might decide to round down and keep drivers on the slow side.

A road’s crash rate also comes into play: If the number of collisions per million miles traveled for that stretch of road is higher than average, officials might lower the speed limit regardless of the 85th percentile rule. Roads that have a history of accidents might also warrant a special signal or sign to reinforce the new speed limit.

For other types of roads, setting speed limits is more of a cut-and-dry process. Streets that run through school zones, business districts, and residential areas are all assigned standard speed limits that are much lower than what drivers might hit if given free rein.

Have you got a Big Question you'd like us to answer? If so, let us know by emailing us at bigquestions@mentalfloss.com.

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