For some — whether by dint of practice or natural talent — reading poetry comes easy. This is not the case for me, however. While I’ve poured over lots of poems in my years on Earth, it seems like I always have to go over the same lines again and again before I can pry any sense out of them.
Hermeneutics Of Caving
Caves are the same way to me. Utterly inscrutable at first, but repeat visits lead to a gradual orientation. You figure out which way is north, which crawl leads where. Protrusions of rock become familiar landmarks. You even start to piece together how the void you’re in might have formed.
Again, though, as with the hermeneutics of poetry, the hermeneutics of caving is for me a rather protracted process. As a ranger, I walked through the ornately decorated halls of the Timpanogos Cave System hundreds of times last summer, and I was still making discoveries all the way up to the season’s very last tour.
Since I’m not a natural-born caving guru, I supplement my practice of repeated visits with insights from experts who’ve been going underground for a lot longer than I have. I like the combination of trying to figure things out on your own first and then getting opinions from those who really know their stuff.
As part of our ongoing mission to learn as much about the insides of our planet as we can, Mag and I joined a few members of the Sandia Grotto for an excursion into Alabaster Cave, which is located northwest of Albuquerque on the Zia Reservation.
The team leader was a geologist named Dave. As has been the case with every other caver I’ve come into contact with over the course of this last year, he’s not only extremely knowledgable, but he’s also extremely generous in sharing his knowledge with rookies. As we scrambled down into the main entrance, slipping under fractured and sharply-tilted layers of variegated gypsum, I asked for a quick geology lesson and got a fantastic one.
Around 160 million years ago, during the Jurassic era, there was a shallow lake in what would eventually become north-central New Mexico’s Todilto Basin. After awhile, all the water evaporated, leaving strata of eponymous gypsum behind to be buried in sediment. This is what we were crawling around in today — the Todilto gypsum.
Somewhere in the ballpark of 90 million years later, the Laramide Orogeny would begin to build the southern Rocky Mountains. As the subducted Farallon Plate scraped the underside of North America, long hidden layers of stone were re-exposed, becoming susceptible once again to the forces of surface weathering.
This re-exposure is extremely important because water from rain and snow is what carved out Alabaster Cave.
Vadose And Phreatic
Once you’ve gone a ways into Alabaster’s few thousand feet of tortuous passage, you start to notice a couple of details. The first are small scallops rippling the ceiling with tiny “frozen” whitecaps. The second is a very distinct line of sculpting running parallel to the floor. Each of these, Dave explained, represents a different phase in the cave’s development.
The scallops predate the line and tell of a time when the gypsum was at the water table — or “phreatic zone” — soaking and dissolving. Because they are small, water must have been moving pretty fast.
The line, meanwhile, indicates that the cave was eventually lifted out of the water table into what’s called the “vadose zone.” During this time, Alabaster had a decent stream flowing over its floor at least every now and then. This stream may also be responsible for sections of the cave that are tall and narrow and wending like a southern Utah slot canyon.
Open For Interpretation
As coherent and aesthetically pleasing as this story is, I’m sure the cave admits endless interpretations the way any poem does and the way the universe at large does.
A really far out archeologist, for example, might conclude Alabaster was hewed out by a member of the Clovis Culture with an obsidian chisel in accordance with an architectural ethos we today couldn’t possibly comprehend let alone reconstruct. (There’s a guy who does this sort of thing today in sandstone outside of Las Vegas, New Mexico.)
But being something of a fallibilist — a person who’s happy to provisionally believe science I find compelling — I’m going to stick with Dave’s account for now. Nevertheless, I’ll definitely keep my mind and eyes open. I’ll definitely keep re-reading.
- A Video Of Yours Truly Squeezing Through A Small Hole In Alabaster Cave (YouTube)
- Caving In El Malpais National Monument, Part 1: Xenolith Cave (Farther Still)
- Holding True, Come What May (Farther Still)
(Today’s photo of selenite crsytals — a form of gypsum — is courtesy of the Wikimedia Commons.)