Thursday, May 19, 2022

Moaning Caverns adventure tour


Moaning Caverns is a limestone-marble solutional cave in Vallecito, California. It is about 200 kilometers east of San Francisco, on the foothills of the Sierra Nevada mountain range. The main show cave attraction is the 165-feet high massive hole, but the cave extends further down in smaller passages under the big room, getting to a depth of 410 feet or 120 meters. An adventure tour explores some of these parts, which is why I was here. But there are other interesting aspects of the cave as well -- at the bottom of the main room there's a large pile of animal and human bones, presumably from whoever fell down to their fate here.

Bones covered by calcite deposits:

The main room has a staircase welded together from stairs of an old warship. Scary, but regularly inspected:

The cave is also interesting in that it has both limestone and marble parts. One of the tight squeezes on the adventure tour is actually between two beautiful slabs of white and blue marble, polished smooth by previous cavers. The slabs slope upwards and are spaced just barely far enough apart that a helmet fits in. Not much room:


Other squeezy parts of the adventure route include the Birth Canal, is a tight climb out of a hole right after managing to pull yourself out from between the marble slabs. There's also the "Meat Grinder", where you need to negotiate inconveniently placed rocks, like a puzzle where you have to fit your body just the right way to pass through. It turns out that this can involve painful grinding of the sensitive parts of cavers.

There's more, chimney climbs, rope-assisted descents and ascents, and smaller detours that require climbing skills.

What I found particularly interesting was a small room opening through a hole from the Lower Mud Flat. This room is decorated by helictites. These are small cave forms, like stalactites but which changed their direction of growth in different stages of their development, for reasons that are not fully understood even today. Direction changes might be due to capillary forces, wind, bacteria, or other reasons. 

Here's a picture of the helictites:

I ended up continuing my quest for 3D scans from caves. The entire cave is too big for my iPhone lidar sensors, which has only 4-5 meter range, when the big hall is 50 meters across. But I did scan two smaller rooms from the cave, the Lower Mud Flat and Helictite Rooms.

There's a nice rotate-on-your-screen version of these 3D models here and here. The corresponding 3D models can be downloaded in GLB format here and here, and in Blender format here and here.

Here's a snapshot of the Helictite Room model:

There's also a video of the models rotating around:

Nice cave forms:

But boy, do they have rules in the Moaning Caverns. Check this out:

And an advertisement for the expedition tour. $95, or with tax $115:

And here's me on site:

The Moaning Caverns website is here, and the wikipedia article here. If you decide to take on the adventure tour, ask for Tyler -- he's an expert guide and can take you to all places that you could possibly want to go to, and more :-)

This article has also been published at TGR. Read more urban exploration stories from, and other underground stories from Read the full Planetskier series at, or all blog articles from Blogspot or TGR. Photos, videos, and text (c) 2022 by Jari Arkko except where otherwise indicated. All rights reserved.

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