Lost Lake: Why a small body of water in the US vanishes every year

The lake in Oregon has an lava tunnel underneath it which drains water away

The lava tunnel in Oregon (Bend Bulletin, via YouTube)

It is one of the more unusual natural features of central Oregon in the United States: a lake that every years drains away and “disappears”.

Known as the “Lost Lake”, the small body of water near Hoodoo Ski area in Oregon caused endless trouble for early settlers and explorers as the landmark that kept disappearing.

But there is a simple explanation for the lake’s mysterious ability to vanish: a lava hole.

Jude McHugh, a spokesperson for the Willamette National Forest, said that the hole – itself a result of an open lava tube – drains the lake each winter.

Melting ice from the nearby mountains keeps the lake high in the summer and spring months, but during the coldest part of the year – when the water on the Cascade Mountains freezes – the lake is not topped up and drains.

Open lava tubes form during volcanic eruptions when the surface of the lava flow cools and solidifies, but underneath remains warm and fluid. As the warm lava departs, a shell is left creating a tunnel.

Where exactly all that water disappears to remains unknown but one theory is that it seeps into a huge aquifer underneath the Cascade Mountains, replenishing groundwater.

But Ms McHugh said stopping the lake draining could have dire consequences.

“If anyone was ever successful at plugging it — which we’re not sure they could do — it would just result in the lake flooding, and the road; it’s an important part of how the road was designed,” she explained to the Bend Bulletin.