Water Mystery: Why an Oregon Lake Disappears Each Year

— -- It's not a magic trick but it sure seems like one.

A mysterious lake in Oregon fills up every winter and then as the season changes, water disappears through a 6-feet-wide hole on the shore, leaving the area dry before it later fills up again.

There's a geological explanation for the phenomenon, which has been happening for as long as people can remember.

Lava tubes, which are tunnel-like structures created to drain lava from a volcano during an eruption, are abundant in the area.

A video taken by the Bend Bulletin shows the incredibly process.

After the lava flow stops, the underground conduits can harden leaving behind a long, cave-like system with an opening to the surface.

"In Lost Lake, this particular lava tube collapsed and became the drain hole for that lake," Jude McHugh, a spokeswoman for the Willamette National Forest, told ABC News.

The lake is likely constantly draining, she said, but its most evident in the drier months when the rate of draining exceeds the input from precipitation, turning the lake into a meadow.

McHugh said it wasn't clear where the water goes after traveling through the lava tube, but she said since volcanic rock is porous, it like seeps into the subsurface, adding to an aquifier that feeds into springs on both sides of the Cascade mountain range.

"Eventually that same water pops up out and I'm having it in my morning coffee right now," she said.

Some locals have attempted to plug the hole, but McHugh said the efforts have been unsuccessful. Even if they succeeded, she said, it would mean the lake could flood, causing problems for a nearby road.

A few miles from the Lost Lake, a similar disappearing act is also pulled each year by "Fish Lake."

McHugh said a lava tube isn't seen on the surface and that the water is likely soaked up by porous rocks beneath the surface.