The video shows the remarkable annual event at Lost Lake in Oregon, which fills up every winter and empties like a bathtub in summer through a two-metre laval tube.
It empties so completely that the lake becomes a meadow until the winter rains return.
But the effect is deceptive. The lake is actually draining gradually all the time but as there is less rain in summer to replenish the lost water it becomes completely dry.
The water travels through porous volcanic rock underground and into an aquifer before emerging at nearby springs.
A lava tube is formed as a natural pipe by flowing lava which moves beneath the hardened surface of a lava flow. When extinct, they leave a long, cave-like channel.
Read science facts, not fiction...
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