Unoccupied Cars Sliding Backwards in Paradise Lot

Has anyone here noticed that sometimes after parking your car in the Paradise parking lot on Rainier (and maybe even in other lots) that your unoccupied car has moved backward by several feet during the course of the day while you were gone? Sometimes far enough to touch the bumper of the car behind it?

Amazingly, this seems to happen en masse on some days, when the parking lot is covered in snow and ice but the day is warm enough to melt it. Numerous unoccupied cars slide backwards by various amounts, up to several feet over a few hours, and even 8-10 feet in some cases (over half a car-length). The parking lot is slightly sloped to the south, but not much. I was shocked when I discovered this happening a few days ago. Is this actually a well-known phenomenon? It's certainly news to me.

I've written a script to grab various webcam images, such as the ones at Paradise. When we got home from our trip to Muir on Feb 15 ( see TR ), I looked at the webcam images from earlier that same day and was amazed to see our car (and several others) slowly moving backwards by several feet over a few hours.

Don't believe me? Click the image below to watch a brief video (3 MB MP4, 1280x720), which has 27 frames of the Paradise east webcam, every 10 minutes from 9:40am to 2:00pm.

ParadiseSlidingCars.mp4

Watch the cars in the row beside the white pickup at right. Almost all are slowly moving backward by several feet over those 4 hours, but come to a halt once the ice is mostly melted (around 2pm). The 5th car in the row (Subaru Forester?) slides back about 8-10 ft! The white minivan slides back for a while, then suddenly moves forward at 12:00pm when the family has returned (they moved it to get in the rear hatchback), then it continued sliding backward after they left again.

Meanwhile, cars in other rows (such as the ones at left) are not moving at all.

What on earth is going on? Are the tires simply sliding on the melting, water-lubricated ice? Must be . . . can't think of any other explanation. Maybe someone out there has a better explanation. I'd like to hear about any other examples or anecdotes of this phenomenon if people have seen it.

I've had the same thing happen to me at Longmire--ice on pavement at warm temps. I had to move my truck twice one day to keep it from slipping into the next car.

Ha! That's great

It's a car glacier.

That's funny, Amar. All this time I thought the moron in front of me had moved his car at lunch.

The pavement is moving south, not the cars. This also explains why everything is getting warmer.