Saturday, January 31, 2015

Geo 1095: January 31, Day 761: Old God Underground

Given yesterday's sepulchral introduction to the afterlife, it should come as no surprise that one of the first residents to greet us bore an uncanny resemblance to Cthulhu.

I mentioned a few days ago that carbonate rocks are uncommon in Oregon. There are several reasons for that. First, Oregon is overwhelmingly dominated by fairly young (Cenezoic) volcanic rocks. That doesn't necessarily preclude carbonates, but it does mean older rocks are largely obscured under the various younger volcanic products. Second, the sedimentary rocks we do have are overwhelmingly terrigenous (derived from land erosion) in origin. Carbonates tend to occur in areas or time intervals with little terrigenous deposition, and tend to be obscured when that input is large. To be clear, many of our shallow water sedimentary rocks have plenty of calcite and such minerals in them, but they're a tiny fraction of the overall rock mass. Third, because carbonate minerals have a gas, carbon dioxide, as a major component, they're less soluable- that is, more likely to precipitate out of solution- when the water is warmer. As a general rule of thumb, large deposits of bedded carbonate rocks indicate warm, tropical marine environments. For most of Oregon's history, the region has been too far north to be a hospitable environment for large scale carbonate deposition.

The exceptions, largely here in the Klamath Mountains, and in the northeastern portion of the state, in the Blue Mountains, consist of bits of plate that originated closer to the tropics, then drifted north on plate tectonic conveyors, and were accreted as terranes to the region we now call Oregon. As a result, much of what was originally limestone was metamorphosed during accretion to marble. Many people are familiar with limestone caverns, but this is a marble cavern.

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.)

Friday, January 30, 2015

Geo 1095: January 30, Day 760: No Cerberus

At the entrance to Oregon Caves, one goes in on a metal grate walkway, with the stream "River Styx," flowing the opposite direction underneath. In Greek and Roman mythology, after death, one entered the gate to the underworld, which was guarded by Cerberus, a three-headed dog. Its purpose was two-fold: to keep the dead from escaping and the living from entering. After passing through the gate, the deceased would cross the River Styx with the ferryman Charon, to reach the final destination, which was overseen by Hades/Pluto. We're crossing Styx on a bridge, so I guess Charon is morosely unemployed. But I was grateful that the park rangers had restrained Cerberus somewhere away from us tourists.

Photo run through's "autolevel" routine for contrast and saturation. May 9, 2013. FlashEarth Location.

Thursday, January 29, 2015

Geo 1095: January 29, Day 759: Stygian Pool

Continuing the walk to the Visitor's Center at Oregon Caves National Monument, here is a better view of the pool and patio behind the lodge. The cave entrance is directly above the waterfall, and is the source of that water. The stream flowing through the cave has been dubbed The River Styx, hence the post title. Astute readers may notice there's no outlet to this pool. So where does the water go? That's a topic for future posts, but it'll be a while; tomorrow we're going spelunking!

Photo unmodified. May 9, 2013. FlashEarth Location.

Wednesday, January 28, 2015

Geo 1095: January 28, Day 758: Off to Oregon Caves!

I never did get around to writing a "reflections" post for this past year, but one item that was on my mind was that, while doing chronologically ordered photos from a single trip (or multiple trips to the same spot) makes it much easier to make each day's choice, it also makes for a certain monotony on my end, and, I worry, also on the reader's end. With that in mind, I'm breaking off from Silver Falls State Park, and skipping off to a rather unusual type of geology in Oregon: carbonate rocks. I'll get back to South Falls some other time.

After a short walk from the parking area (which comes after a long, winding drive up the mountainside from Cave Junction), this is what it looks like when you reach the lodge and headquarters. The cave entrance is hidden behind the trees and their foliage, but the outflow of the cave's "River Styx" cascades into a pool behind the lodge, on the right side. Western US Parks are known for their rustic architecture, but this lodge goes one further, with the bark siding of the building blending in wonderfully with the surrounding forest.

Photo unmodified. May 9, 2013. FlashEarth Location.

Tuesday, January 27, 2015

Geo 1095: January 27, Day 757: A Bit Closer

This photo is a little bit closer to the cliff than yesterday's shot of Winter Falls, and the ovoid forms look a little bit more pillow-like, but there's still just too much moss and other vegetation for me to be very confident about identifying them. It's more like "suspicious." During the Miocene, when these basalt flows erupted, there was definitely still a marine inlet in the Willamette Valley, though my sense is that sediment deposition wasn't as heavy as during the Oligocene, so pillows in Columbia River Basalt flows are not out of the question, and indeed might be expected. In this instance, though, the exposure is just not defined or clear enough for me to feel any conviction about their identity.

Photo unmodified. August 30, 2012. FlashEarth Location.

Monday, January 26, 2015

Geo 1095: January 26, Day 756: Winter Falls Pillows?

This is Winter Falls, on the next drainage south from North Falls, so named due to the fact it's more of a steady drip than a waterfall by mid summer. There are at least two Columbia River Basalt flows, with the boundary visible as the recess through the upper middle of this view of the cliff. About halfway up from that is another boundary, but I'm suspicious that's a textural change within a single flow- from hackley jointing to columnar jointing, for example, rather than a third lava flow. Something I hadn't noticed until reviewing the photos, though, is that the upper portion of the lower flow and lower portion of the upper flow appear to have a pillow-like aspect to them... but I can't... quite... tell... at the best resolution of this shot. It's also at a spot where hikers are making a prolonged, steep climb, and all they can think about is "Get me to the top, now!" So not the best spot for thinking about what you're seeing, geologically. But if I ever get back here, pillow basalt is definitely something I'll seek evidence for or against in outcrops closer to the trail where I can get a better look at textures.

Photo unmodified. August 30, 2012. FlashEarth Location

Sunday, January 25, 2015

Geo 1095: January 25, Day 755: Another Pool

Another pretty pool on the hike from North Falls to Winter Falls at Silver Falls State Park. I quite possibly wouldn't have posted this one, but Anne liked yesterday's shot and sent me a couple links to relevant papers (both PDFs) on pool and riffle morphology. I haven't had time to look them over carefully (Honestly, I've just read the abstracts thus far.), but the first discusses how large woody debris (notice the lack of such in today's and yesterday's photos, compared to the left side of this one) influences characteristic pool spacing. The second involves an idea I hadn't heard before, "velocity reversals," but which makes intuitive sense to me. It's the idea that at low water, pools are lower velocity, but experience higher velocity than riffle areas during high water. This means that pools get scoured during high water, but riffles are depositional environments in those conditions. When the stream returns to a lower stage, it no longer has the competence to move the debris deposited in high water.

Photo unmodified. August 30, 2012. FlashEarth Location (pretty much guessing on this one too, but right general area).

Sunday Funnies: Muzzled Edition

Bird and Moon
Gone Into Rapture
"Kitty remembers stupid thing you did just yesterday." Senor Gif
Wil Wheaton
"Has science gone too far?" Tickld
Dierdre Treacy
Yeah? I'd take that job. Bad Newspaper
"I made soy milk." Tastefully Offensive
"A recap of the State of the Union Address." Tastefully Offensive
Tastefully Offensive
Blue Gal
Tastefully Offensive
Senor Gif
Two of many "brilliant shower thoughts," at Tastefully Offensive
Tastefully Offensive
"Gotta pee. Gotta pee. Gotta pee." Sober in a Nightclub
Cyanide and Happiness
What Would Jack Do?
"Sesame Street has gotten really wild..." Senor Gif
"If Bryan Cranston and Neil Patrick Harris had a baby." Tastefully Offensive
Darius Whiteplume
Darius Whiteplume
Scariest. Beer. Ever. Senor Gif
Toothpaste for Dinner
Sober in a Nightclub
Pregnancy announcement. Wil Wheaton
Sarah Walker
Very Demotivational
Cyanide and Happiness
Spud Comics
Tastefully Offensive
Sober in a Nightclub
Chaos Life
Fake Science
Senor Gif
"She unmatched me pretty quick." Tastefully Offensive
Sober in a Nightclub
Very Demotivational
"Catzilla" Tastefully Offensive
 Funny to Me
Tastefully Offensive
Funny to Me
Funny to Me