Saturday, November 13, 2010

Another Day in the Sierra Foothills: The Sierra Underground

I had another marvelous day exploring the Sierra Nevada foothills, this time a Geology Club journey underground in a series of wild caves in the Stanislaus River Drainage. The host rock was marble of the Calaveras Complex, which originated as carbonate shelf and reef deposits in a late Paleozoic sea off to the west. The caves occurred high above the river and have not been active in a long time, being well above the regional water table. They would have formed when the adjacent canyon was more shallow, and the water table much higher. Minor formation growth can occur in the present day during the rainy season, but most of the formations show little evidence of activity.

Wild caves are one of the precious geological gifts we have in our region, and one of the most fragile of environments. There are developed caves, which I have featured in previous posts, six or so, but around 1,000(!) caves are known in the Sierra, including some that exceed 20 miles in total explored passages. Their locations are kept out of public attention because of the ease with which they can be vandalized (and vandalism is a huge problem). Our trip today was one of education and building an appreciation for these rare environments. Our college students were accompanied by a group of local high school students who joined us in the exploration.

We did an exploration of a small cave that required crawling and scooting through a narrow passageway to prepare them for the adventure of the larger cave a few hundred yards away. All of our explorers wore helmets and carried three lights for safety, but they also wore gloves to preserve surfaces in the caves. Any visit will impact a cave and the life within it (even clothing lint), so our purpose was to teach how to explore with the least amount of impact. They did well, as I saw no gratuitous touching of formations (although that may have had something to do with not one, but three "wrath of God" speeches before entering any of the caves).

The largest cave we explored had a challenging squeeze through a very narrow passageway into a large room about 70 feet long (I tried not to think about the fact that it was the ONLY way out; what if someone got stuck? I have phobias...). It is festooned with some glorious stalactites and columns that hang in thick masses from the high ceiling (click on both pictures above for a better view).
In some sections, water flowing from cracks in the wall has formed flowstone and rimstone pools (above). The cave formations (collectively they are called speleothems) are mostly composed of crystalline calcite (calcium carbonate), which is the reason the formation is sparkling.
Although not quite so spectacular as those at Black Chasm Cave, there are helictites that have formed on the ceiling of the big room. Helictites are basically stalactites on LSD, paying no attention to gravity as they grow.

Living organisms have a tough time of it in caves, with a general lack of food sources, but there is a surprisingly rich collection of creatures that live there, and which are adapted to life in total darkness. We saw quite a few spiders on this trip, but I was especially watching for salamanders, as I have seen them in this cave twice on previous trips. I didn't see any this time, but I've never had a good excuse to show a picture of one of them, so here it is. Anyone want to tell me the species?

Update: Helena Heliotrope provides an example of the horrific damage that can occur in caves when morons and idiots find them. This sort of thing has ruined many caves in the Sierra, and elsewhere across the country. Cave vandalism is a serious problem, and the perpetrators deserve stiff fines and imprisonment. Hopefully education can overcome the tendencies people can have towards this sort of crime. Certainly a great deal of damage occurs through simple ignorance, too (not to mention injuries; I took a hard hit on the head this last weekend that made me see stars, and put a gash in my helmet).
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