Water loving willows hug the edges of the shore. Lost Lake, at its peak, is around 79 acres. Right now, it is draining away.

About half way around from the lake entrance, a sharp eye might spot a footpath leading out onto the grassy, muddy lake bed. Follow that and soon the sound of rushing water is audible.

Then, there it is. The hole.

Dave Kretzing has a pretty good grasp on the mystery of Lost Lake. He’s a retired hydrologist with the U.S. Forest Service and he’s spent years thinking about what happens here and why.

“Whether it’s a lava tube or whether it just is a sink hole into a buried channel, we don’t know unless we did (sic) some kind of seismic investigation,” Kretzing said.

“This hole is around 7 to 8 feet in diameter. It’s about 6 feet deep. It’s got rubble in the bottom. The water is passing through the hole and its passing underneath lava into a buried channel of a tributary of the McKenzie River.”

Kretzing says geologists believe the McKenzie was formed in the Pleistocene era. More than 2,000 years ago, the Sand Lake Volcanos began to erupt. The cones buried one of these ancestral channels—creating an underground river.

Oregon's Lost Lake, near the Santiam Pass Highway, is a seasonal alpine lake with a unique trait: a drain-like hole. Each summer, as the water supply dries up and stops feeding the lake, the water drains out into an underground river.

Oregon’s Lost Lake, near the Santiam Pass Highway, is a seasonal alpine lake with a unique trait: a drain-like hole. Each summer, as the water supply dries up and stops feeding the lake, the water drains out into an underground river.

Tiffany Eckert/KLCC

Kretzing: “And these eruptions blocked the channel and buried it and created Lost Lake. And of course that ancestral channel still existed it was just buried not destroyed. And so we believe the water is flowing through this hole in the bottom of the lake down and accessing that original channel and flowing on downward, eventually coming out at Clear Lake.”

Kretzing said it’s easy to think of Lost Lake as a sink with a drain that isn’t completely closed. When you turn the tap on full strength, it fills up. If you turn the tap down enough, the water starts to empty down the drain.

In the rainy wintertime, when stream flows are high, Lost Lake fills. When rainfall and stream flows drop during summer months, the amount going in becomes less than the capacity of the hole to drain the water. So the lake drains. Fast.

“I know that it was reported to us in 2003 in fact at that time we went up and found a gentleman and his two grandchildren frantically shoveling material, rocks in to block the hole to save the fish. We didn’t really want them to do that but their hearts were in the right place,” Kretzing said.

Kretzing said this is an interesting natural phenomenon and that piques curiosity. He hopes that when people come here to look at Lost Lake, they enjoy it and leave it as they found it.