The Lava River Cave exhaled chilled air.

I put on my sweatshirt, despite the hot July day. Though I'd been warned about the sudden drop in temperature to a crisp 42 degrees, it was hard to believe I'd soon be shivering instead of sweating.

Small mammals, mainly chipmunks, skittered around the rocky entrance, enjoying the unseasonably cool climate.

The escaping cold air forms a bustling ecosystem at the cave sink, said my guide, Sophia Zoll. But when we entered the darkness, that diversity would soon disappear.

“As we go further, it’ll just be us and the bats,” Zoll said.

This was the start of a mile-deep hike into the Lava River Cave, located in the Deschutes National Forest outside of Bend.

While visiting looks a bit different this year, with a timed reservation system and altered o

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