
A view of the jelly fish-like forms of the “Paradise Lost” cave. (image via Flickr user Meghan Nazer)
PORTLAND, Ore. — A label like psychedelic sculpture, for what it’s worth, does justice to the gnarly stalactites and unorthodox mineral deposits of the Oregon Caves National Monument. Seriously, it’s like walking through a three dimensional Grateful Dead album cover.
Tucked away underneath a remote hill near the Oregon/California border, this subterranean sculpture garden is worth the long drive down its twisting winding road that ventures far off from the highway.

Entrance sign, Oregon Caves National Monument (image via Flickr user oregon ducatisti)
The most stunning cavern in the cave system is called “Paradise Lost” after John Milton’s epic poem. It looks like a school of petrified jelly fish with all those long tentacles of what’s referred to as calcite drapery. Like Milton, it’s gorgeous in a dark and creepy way.
In another room, known as the “Banana Grove,” the mineral deposits, as might be expected, resemble a stoney version of banana bushels. Yet in others caverns deposits take the form of a necklace or appear more linear with small straw-like forms flowing down from the ceiling.
Slight differences in geological conditions can lead to jellies, produce, jewelry, or soda straws. When you look at these different shapes forming, you start to get curious about geology and how this all happens.
The short answer is a leaky limestone roof. Rain drops fall from the sky, hit the topsoil, and then seep down (at which point we usually stop thinking about it.) But some raindrops dig deep, find their down way into a micro-cracks in the cave’s ceiling, and then fall into the cave.
But after filtering through all that soil, the raindrops are no longer pure. They’re now carbonic acid – the carbon in the ground molecularly bonds with the water. This weak acid does little to most rocks. But limestone is peculiarly sensitive and vulnerable to the compound. In some places, the acid colludes with other geological effects to carve out vast caverns. In other spots, marvelous formations begin to form as these drops of acid slowly warp, cavort and twist the limestone.

Cave stalactites at the Oregon Caves National Monument (image via Flickr user jshyun)
And with all the rain that makes Oregon notorious, you just need a limestone cave in the right place with the right amount of time for a gnarly sight. And the Oregon Caves is it.
Sometimes, we just find a big room without the sculptural formations. But it can be just as cool. In the case of the “Belly of the Whale Room”, this hallowed out space actually makes you feel like Jonah stuck inside the wale.
Old graffiti in the cave has actually been preserved by the mineral deposits. In a room that was the end of the caves in the 19th century and early 20th century, visitors wrote in the year and made other scribbles. By the time efforts were made to remove the graffiti, limestone from the roof had already rained down enough to create a thin transparent mineral layer over the surface, making the insignia impossible to remove.
One final peculiarity in the caves is the “Imagination Room.” It’s the one room where moon milk has occurred. It’s a strange bacteria that grows in certain moist limestone caves under the right conditions. Although the moon milk no longer grows in the room, the dead moon lends itself to imaginative shape finding. One looks like a rabbit from the right angle. Another resembles George Washington’s head.
The Buddha once remarked that jars fill drop by drop. It’s a proverb about patience and the power of drops over time. Over thousands of years, those little drops of carbonic acid have helped carve out caverns and twisted limestone into entrancing forms. All it takes is a leak in the roof to get started. Who knew such good sculpture could come from bad plumbing?
The Oregon Caves are nestled deep inside the Siskiyou Mountains in Southern Oregon but there is a (long) road from the highway to get there. The National Park Service operates a visitor center on the site and rangers lead tours of the caves from late March until early November.