Outside The Interzone: Feb 8, 2015

Saturday, February 14, 2015

Geo 1095: February 14, Day 775: Heart-Shaped Rock

All Apologies, Nirvana. I don't recall the name of this feature, but it's something predictable, like "Lover's Grotto," or "Valentine Rock," or something along those lines. Chronologically, it fell between the posts of Feb. 10 and Feb. 11, but it was too perfect for Valentine's Day, so I put it on hold until now. I'm amused that my set of photos from Oregon Caves just happened to coincide with this holiday. It's not a holiday I'm terribly fond of, and I certainly wasn't thinking about it when I started this set, but hey, here you go.

Photo unmodified. May 9, 2013. FlashEarth Location. (Since we're underground, I have only a vague idea where this is with respect to the surface.)

Geo 1095: February 13, Day 774: Niagara Falls

Most guided cave tours lean heavily on (what I often feel are) cutesy names for specific rooms or features. Given that attitude, it's easy to understand why I most often don't register or recall those names. The downside, though, is that I can't use the generally accepted name of the room/feature when I post a photo of it. Enter the interwebz. I was trying to track down the name (without success) of the feature I'll post for the Valentine's Day photo, and found a photographic tour of Oregon Caves. According to page 16 of this PDF tour, this spot is called "Niagara Falls." It was a mostly white surface of flowstone, next to the path, and early tourists were encouraged to autograph the spot, and often added dates and other notes. According to the description of the feature, "The Forest Service tried to erase the signatures in 1917 but enough calcite formed over them by then that they could not be erased." It's unsightly graffiti, but the dates allow precise measurements of the rate of deposition here... eyeballing it, it looks like less than a millimeter per century.

Photo unmodified. May 9, 2013. FlashEarth Location. (Since we're underground, I have only a vague idea where this is with respect to the surface.)

Thursday, February 12, 2015

Geo 1095: February 12, Day 773: Quake-Cracked Columns

Standing and zooming closer to the middle of yesterday's photo, we can see the answer to that post's "dance floor" puzzle. The stalagmites and columns are dancing a stately waltz of tectonics. We appear to be looking at a very low-angle normal fault, dipping to the left, with the top offset to the left. Speleothems are notoriously slow-growth features, and highly variable in different locations within the same cave. The fracture across the columns here has clearly been resutured, but not heavily enough to obscure it or its offset. This suggests fairly recent seismicity. I'd hazard a guess that this quake was in the neighborhood of hundreds to a few thousands of years ago, not recent in human terms, but recently enough that I wouldn't rule out more such quakes in the future. In terms of hazard? This is probably a safer environment than many in which to experience an earthquake, and the offset is quite small, which suggests a tiny quake. I'd bet it'd be startling to tourists, and terrifying to few, but the likelihood of injuries or fatalities is really pretty minimal (for a quake of this sort, anyway), in my non-professional estimation.

Photo unmodified. May 9, 2013. FlashEarth Location. (Since we're underground, I have only a vague idea where this is with respect to the surface.)

Geo 1095: February 11, Day 772: Stalagmites on a Flowstone Dance Floor

When calcite-saturated water droplets fall from the ceiling, not only can they slowly build stalactites from there, but when they hit the ground, the agitation causes more calcite to precipitate. This leads to the development of stalactites' counterparts, stalagmites. In this case, the slow flow of groundwater is still saturated with enough calcite that it has created a lower, flatter platform of flowstone. The high points on that "dance floor" represent the impact sites of steady drips from the ceiling, while the broad slope is deposition from a thin sheet of run off from those point sources.

The choice of "dance floor," in this case, is chosen for two reasons. First is the simple esthetic imagery: it pleases me to imagine these features dancing over the millennia, at rates so slow, we could never hope to perceive the pattern. The second reason is that they are! Can you spot what I'm talking about? Here's a hint: look for a dark, nearly horizontal (but small) feature near the center of the photo, and try to figure out what it is... Answer in tomorrow's post, which is really today's, since I'm a bit behind. I'm hoping to get it done before I go home tonight.

Photo unmodified. May 9, 2013. FlashEarth Location. (Since we're underground, I have only a vague idea where this is with respect to the surface.)

Geo 1095: February 10, Day 771: Cracked Ribs

I suppose I'd call this a solution fissure. It seems evident that the diagonal fracture in the top left middle was the weak zone allowing solution along its plane, though whether that's a joint or a fault is unclear from the photo. The features I find interesting, though, are the "ribs" along the sides of the fissure. They look close to horizontal, but that could be misleading. They could just happen to align with whatever direction my camera was pointing, which might not have been horizontally. If we assume that I was shooting horizontally, the most likely explanation for the ribs is that they represent intervals where groundwater levels were dropping rapidly compared to periods where water levels were stable for longer times. Putting it another way, the deeper furrows along the sides may represent periods when groundwater levels were stable, allowing more time for solution to occur.

On the other hand, if I wasn't looking along a horizontal plane, but up or down at some angle, those ribs may represent impurities in the marble, such as silt and/or mud, which would have gone to various silicates such as wollastonite during metamorphosis, rendering those layers less soluble than the purer calcite bands.

Photo unmodified. May 9, 2013. FlashEarth Location. (Since we're underground, I have only a vague idea where this is with respect to the surface.)

Tuesday, February 10, 2015

Twitter Is Being An Asshole

What exactly I did that "appears to have exhibited automated behavior" is ever-so-helpfully unaddressed, but the real assholiness appears when I clicked the "Unlock my account button."

No e-mail option. In fact, NO other option than entering a phone number. Entering "I don't have a phone" doesn't work, because it has the "incorrect number of digits." Furthermore, if I DID have a phone, I most certainly would not be posting it online to some god-damned bot which appears to be exhibiting automated behavior. "We will not store your phone number." Oh, yeah, and there's that bridge in Brooklyn you might want to buy some stock in. What a pain in the fracking butt.

Followup, 4:50 PM: I have been unlocked.

Geo 1095: February 9, Day 770: Faulty Wall?

I think what we're seeing here is a pair of faults, or possibly a brecciated fault zone, but I'm not positive about that. The fact we're seeing flowstone and draperies originating along the top fracture, but not elsewhere, suggests that the middle block is not permeable. The guide on this tour pointed out several faults, and I know I spotted a few others, but I'm uncertain as to why I took this particular photo. This whole region is tectonically terribly chewed up- faults are everywhere! And as we'll see a few posts on, there's some very strong evidence that the area has seen continued activity in the relatively recent past.

Photo unmodified. May 9, 2013. FlashEarth Location. (Since we're underground, I have only a vague idea where this is with respect to the surface.)

Monday, February 9, 2015

Geo 1095: February 8, Day 769: Groundwater, Underground

I was planning on skipping this photo of Oregon Caves' "River Styx," but I realized it's a sight seen only under unusual circumstances, such as in a cave. One doesn't often actually see groundwater that is still technically "groundwater." We see springs, and streams largely sourced with groundwater, by the time we see it, it's normally surface water. So there's a lesson in this: if you want to actually see groundwater, you have to go underground. It's a hipster thing... you wouldn't get it. (BTW, the white swath along the left side is flash glare, reflected from the walkway.)

Photo unmodified. May 9, 2013. FlashEarth Location. (Since we're underground, I have only a vague idea where this is with respect to the surface.)