Saturd80's: Au Pairs

Two or three years ago, I went looking for this song on the innertoobz, without any luck. I was reminded of it again recently, and booyah! Paydirt! Yeah, it's a still photo, but I really like this song a lot, and I'm happy to hear it again, after a decade or more of missing it.

So while we're on the topic, here's a couple more from that group. "Come Again" is from "Urgh! A Music War." If you like post-punk/new wave music of the early 80's (and I do, you may have noticed), this movie is must-see. Go over to that wiki link and take a look at the artist/song listing to see what I'm talking about.

Finally "Sex Without Stress." Au Pairs had only two studio albums, but in them, they focused heavily focused on the politics of sexual relationships- a topic I find fascinating, even while I choose not to engage in those politics, for the most part.

Geo 365: March 16, Day 75: Looking Back

Looking back to the far end of the amphitheater at Fort Rock, you can see that the far, higher-based walls have not been as modified by erosion as much as the cliffs at the "mouth" of the feature. They're above the high stand of the pluvial lake. I've always kind of assumed that the lower mound visible in the center, which stands farther out from the tuff ring than you can see in this photo, represents the last dying gasp of this eruption, but I never mapped it carefully enough to get real evidence for or against that conjecture. I will say, though, the feature overall shows the same circular structure, and strike-and-dip patterns, as Fort Rock overall. Had we an hour or two to spend here, there's a rough dirt road (not open to private vehicles) that circles the internal perimeter of this park, and is a moderately easy walk- that is, there are some decent grades in places, which may have one or two hundred feet elevation change, max, but overall, it's a pretty flat stroll. And with the road, you're not fighting through or weaving around the ubiquitous sage and rabbit brush. Even as out of shape as I am, I wouldn't hesitate to set out on the loop.

For the more adventurous, just out of frame to the left, there's a long, not-too-steep slope that allows safe and relatively easy access to the top of the rampart on its west flank. I didn't get a photo of that spot, but it's a pretty obvious and heavily used path, visible here. It's safe enough that we took high school groups up there (after a quick talk about common sense and sudden death); the views out over the valley floor are very much worth it. But at this point, between the physical exertion, growing fear of heights, and increasing difficulties with balance, I have a feeling it's not a spot I'll get back to.

Photo unmodified. August 20, 2011. FlashEarth Location.

Geo 365: March 15, Day 74: More Pluvial Features at Fort Rock

Yesterday's view was shot looking approximately east; today's is turned to approximately southwest, looking toward the opposite end of the amphitheater. Again, there is an excellent example of a wave-cut notch at the foot of the cliff, and at least one distinct step a bit below that- for scale, I'm guessing that step is about the height of a typical adult, maybe 5-6 feet. There is also a hint of fossil shorelines on the low hill in the mid-distance; those are more distinct in the full-size view.

The fact that the "fort" at Fort Rock is open to approximately the south-southeast suggests that during pluvial times, at least, that is the direction from which prevailing winds came most often and most strongly. Thus wave erosion was most effective against that sector of the tuff ring. However, even in the areas where the edifice is largely removed, bare surfaces of the eroded rock provide plenty of opportunity to see structural clues as to what once existed overhead.

Photo unmodified. August 20, 2011. FlashEarth Location.

Geo 365: March 14, Day 73: Wave-Cut Notch and Structure

Here we've climbed up from the parking lot to just below the high stand of pluvial Fort Rock Lake, which filled this basin during the Pleistocene. A prominent notch can be seen on the flank of Fort Rock, just below the line of the horizon, but numerous other horizontal lineations suggest that lake levels varied quite a bit above and below the level of that shelf.

I didn't think to document the structure of this tuff ring as well as I could have (kicks self), but as I said, this was a stop that was much more rushed than I'd have liked- we scrambled up to this spot, stuck our noses up against the outcrop, snapped a few photos, and buzzed off again. However, if you enlarge the photo to full-size (right-click, "open link in new tab"), you can easily see that the layers of palagonite tuff are dipping toward the interior. However, if you look carefully at yesterday's photo (taken near the parking lot, near the base), it's more subtle, but especially looking along the top of the tuff ring, you should be able to see the layers are dipping toward the exterior. This allows some insight into what this feature may have looked like before wave erosion started tearing it up, and how it formed. This diagram, from USGS Circular #838, may help clarify. A somewhat more detailed description, and the source of that diagram, can be found in this road log at mile 36.1.

One last thing to notice: the lake sediments here hold abundant groundwater. So while annual precipitation is more appropriate for semi-arid grassland, and approaching desert-like conditions, water is being mined for agriculture, in particular, center pivot irrigation, which in satellite views dominates the flat lake floor. Such a plot is visible just below the horizon on the right.

Photo unmodified. August 20, 2011. FlashEarth Location.

Geo 365: March 13, Day 72: Fort Rock

Looking up at Fort Rock from near its base, the precipitous cliffs of the tuff ring jump out. It's difficult, not just in this photo, but in real life, to get a sense of scale here- there's little but sagebrush for context. However, this spot is the one with the highest relief, and the Wikipedia page says the prominence is nearly 350 feet, so this is by no means a trivial edifice. The cavernous weathering over this surface is terrifically appealing to raptors. They nest and roost in those little hollows, which afford both protection from the elements, and, I'd imagine, an excellent vantage point to watch for prey in the surrounding agricultural flats.

As I've mentioned, Fort Rock is a smaller version of Table Rock, examined in detail over the past couple weeks, but without the final effusive basalt flows. It's also much better known, and has been designated a State Park. It's day-use only, but it does have bathrooms with running water, and shelters for picnicking. The facilities are minimal, and as the day was moving along quickly, we didn't spend as much time here as the feature warrants. However, we did manage to squeeze in some highlights, which I'll showcase in coming days.

Photo unmodified. August 20, 2011. FlashEarth Location.

Geo 365: March 12, Day 71: China Hat and Pine Mountain

Approaching Fort Rock State Park (which is out of view, just to the left), we stopped to admire the horizon to the north for a moment. The middle-left peak (left-most) is China Hat, which I think is a cinder cone, though I'm not really sure, just guessing from its shape. The next peak to the right is Pine Mountain, a rhyolite dome complex, and home to an astronomical observatory, I think run by the University of Oregon. It's another one of those spots I've never been to, but would like to visit eventually. I'm not sure what the low peak on the middle right is, but that's starting to get into the neighborhood of the Devil's Garden, a field of younger basalt flows, so it may be associated with that feature.

Photo unmodified. August 20, 2011. FlashEarth Location.

Geo 365: March 11, Day 70: Semi-Stabilized Dunes

Headed north from Table Rock into the Fort Rock-Christmas Lake Valley, unfarmed landscapes often have a sort of hummocky appearance. Here we see why: dunes. During dry periods, the vegetation dies back, possibly burning off, and dunes start to migrate. During moister periods, vegetation takes hold and stabilizes the moving sand. Here we see an example that's right on the cusp.

At the east, down wind, end of this basin, there's a fairly large tract of open dunes, which are interesting for a variety of reasons. In particular, they're composed largely of Mazama Ash.

Photo unmodified. August 20, 2011. FlashEarth Location.

Sunday Funnies: Daylight Savings Edition

"When my time course runs through the daylight savings time change (and then I don't know what to do)." What Should We Call Grad School?

Bits and Pieces

Tastefully Offensive -LongCat's nemesis, ShortDog...

Are You Talking to Meme?

 Darius Whiteplume's Tumblr

Tastefully Offensive

Funny to Me

"What I told everyone I was going to do..."

"What I really did." (After submitting my mapping project.) Geology is Hard

Criggo

Sober in a Nightclub

 "Star Trek Logic" Sober in a Nightclub

Cheezburger

Doghouse Diaries

"Stephen Colbert finds the perfect candidate for today's GOP." What Would Jack Do?

Very Demotivational

Bits and Pieces

Historic LOLs

Cheezburger

First, take a look at this optical illusion (original, full-size here works much better for me), then watch this video:

I find this not only funny, but very interesting: it seems to show that cat's visual perception system, with respect to this illusion at least, is similar to our own.

Criggo

Tastefully Offensive

Buttersafe

Julia Segal

"How trees are made." Senor Gif

"Dreaming about pipetting" What Should We Call Grad School?

Bless whoever it was wearing that costume. Wil Wheaton's Tumblr

 Matt Bors

Sofa Pizza

Geo 365: March 10, Day 69: Farewell to Table Rock

Looking out the window as we depart Table Rock, you can see the dirt road leading up to and into the complex. The area I've always parked in is in the junipers to the left, but the road continues into the interior and all the way up to the flat summit on the right. A target for future exploration...

But we had a number of other things planned for the day, and actually ended up doing a number of things we hadn't planned on as well. Time to go.

Photo unmodified. August 20, 2011. FlashEarth Location.

Geo 365: March 9, Day 68: Rhythmic Surge Deposits

There are some faults to be seen in this photo, and the "splort" mentioned yesterday is to the right middle edge. But what I want to draw attention to is the nature of sedimentation in the block to the left of the fault running diagonally from top right to bottom left. Starting from the bottom, overhanging, bit and working up, we first see some pretty well-sorted, finely stratified, fine-grained deposits. This would indicate a period of relative calm. Above that, a layer that is suddenly chaotic, poorly sorted, and much coarser overall. In addition, I'm seeing a suggestion of reverse grading, that is, it looks as if the clasts *may* be getting larger upwards- this would indicate an increasingly energetic environment. I'm very tentative on this point, though- it's just not as clear-cut as I'd like it to be. This coarser layer would indicate a burst in activity at the vent, creating a debris-laden wave, or surge, that was capable of carrying those large, cobbly clasts quite a distance- I don't think those are bombs. They're too angular and too abundant for that.

That paired sequence of fine (low energy)/coarse (high energy) then repeats three more times, and is capped with a final low energy interval, before switching to a period of moderate energy deposition. Lapilli-sized debris was consistently deposited, the finer material being overwhelmed by it, but the coarse large gravel to small cobbles are absent. Then a period of quiescence, followed by more of the moderate energy environment, a short period of peace, then more moderate energy, and we're off the top of the photo.

I don't really know enough to be totally confident in my interpretation here, but it seems logical enough- I'd love to hear from someone who knows more than I do about this kind of volcanoclastic sedimentation. Also, I'd caution that thickness is not equivalent to duration... it's difficult for me to make any guess about relative rates of deposition. I would have a hard time accepting the above sequence was deposited in less than days, nor that it took more than months, but that's simply a gut-level feeling, rather than based on any empirical evidence.

Whatever the reality of this spot is, I find it exhilarating to visit, find bunches of wonderful structures, and speculate wildly about just how they came to be. The esthetic appeal is pretty well up there for me, too.

Photo unmodified. August 20, 2011. FlashEarth Location.

Geo 365: March 8, Day 67: In the Neighborhood of the Splort

As I've been emphasizing the last couple weeks, there's a heck of a lot going on at Table Rock. There's plenty going on at Fort Rock, too, but the latter is well known, commonly if not heavily visited, while the former is largely unknown outside of a few intrepid, geologically-inclined, souls. And Table Rock records fine details, as well as a plethora of volcanoclastic sedimentary features, that Fort Rock simply does not. Table Rock deserves more attention, and this past couple week's photos have been my attempt to give it a bit of time in the spotlight.

Let's consider this environment as the eruption and deposition occured:

• Sedimentation and erosion were both occurring quickly, as shown by poor sorting, angular grains, rapid changes in dominant grain sizes, and common disconformities.
• Overall, though, the pile was accumulating much faster than consolidation and lithification; it probably wasn't until long after the eruption stopped that much of the material could be considered to be "rock."
• During the episode, the pile of debris would be subject to frequent, likely locally powerful, seismic shock from two sources: earthquakes related to magma moving underground, and frequent phreatic blasts as ground and surface water interacted with hot basaltic magma and lava.
• I picture this situation as a rapidly growing "circular delta," with the central vent as the metaphorical sediment source. It seems likely that with such rapid accumulation, oversteepening and slumping were frequent. This would lead to tensional regimes in the topset beds, normal faulting in the foresets, and compression in the bottomsets. Because sedimentation was so rapid, the stress regime was almost certainly changing rapidly and constantly. This may have been exacerbated by rapid shifts from loading to unloading, and back, as sites of deposition became sites of erosion.
• Add on top of all this that the alteration of basalt to palagonite results in a net increase in volume. I'm not sure by how much, but in a pile like this, that effect probably shouldn't be ignored.

Given the above, it's not really surprising to me that the rock is as disrupted as can be seen above, but still, very mesmerizing. And below, I've annotated most of the major features that pop out at me. (I just realized I neglected to mark the common examples of graded bedding, but see the concluding link in this paragraph for a good example of that.) Clear, sharp faults are marked with solid yellow lines. Faults that look more like ductile shear, or are so minor as to make it difficult to tell where they begin and end are marked with dotted yellow lines. A sequence of strata that I'm pretty sure is correlative across the largest fault, running diagonally through the photo, is marked at the top and the base with solid blue lines. And finally, I'm not really going to say much about the "splort," highlighted with a black circle, because I've already written it up- you can see that post here.

Photo unmodified. August 20, 2011. FlashEarth Location.

Geo 365: March 7, Day 66: Hammer for Scale

Dana holds a hammer for scale over a set of normal faults forming a tight horst at Table Rock. Directly over the hammer, near the top of the photo, is a clast (actually two, the obvious one and another, smaller, to its right) that is much larger than anything around it. I suspect that was lobbed by an explosive blast at the actual vent, which would have been something like a mile and a half away.

Talk about nasty weather.

Photo unmodified. August 20, 2011. FlashEarth Location.

Geo 365: March 6, Day 65: Palagonite Tuff

When a basaltic melt encounters water at or near the earth's surface, several things may happen: if the flow is gentle and gas poor, pillow basalt may form. Likewise, if the flow is under high confining pressure, such as an ocean ridge, under thousands of feet of water, that pressure prevents brecciation, and again pillows will form.

With lower pressures, though, and especially if the magma interacts with water below the surface, and erupts with a very high gas content, breccias of one type or another will form. In the case of Table Rock, the basalt was likely interacting with water in the ground, as well as erupting into a shallow lake. The basalt shattered and quenched upon eruption, but remained hot- at least warm- for some period of time. In these conditions, the very fine-grained or glassy volcanic rock altered quickly- you can think of it as accelerated weathering- to form the clay-like material, palagonite.

There are a large number of volcanic features around the Fort Rock-Christmas Lake Valley formed from water/lava interactions, and are largely composed of palagonite tuff such as that shown above. Fort Rock is the most famous, but none of the others I've seen have the variety that Table Rock does.

Photo unmodified. August 20, 2011. FlashEarth Location.

Geo 365: March 5 Day 64: Fault and Aerie

A fault runs through the cliff, offsetting the lighter buff sandstone in the lower portion of the exposure. Toward the top of the cliff, a splash of white and some sticks reveal the nest of some sort of raptor. It wasn't occupied at the time, so I have no idea what kind of bird it was. Raptors love this sort of cavernous weathering on cliff faces for nesting sites, but we would have been better off in the late spring to early summer to catch its inhabitants.

Photo unmodified. August 20, 2011. FlashEarth Location.

Geo 365: March 4, Day 63: Faulty Overhang

The last four photos in this series were taken looking at the fairly flat surface under the overhang visible above. The lighter-colored layer under the hammer's head is probably fine enough to be called sand, but it's marginal; the grain size is verging on lapilli. And, as you can see, just to the right of the hammer, a small fault offsets that layer by a few inches. The reason for that flat area I'd been looking at so closely for a few minutes is likely that it broke off from that small fault. Which, in turn, means that all that overhanging rock is likely to fall off itself, sometime in the not-too-distant future. Now the chances of that happening during the few minutes I was standing there were quite low, but the consequences would have been quite nasty, and easily fatal.

The moral? Pay attention to your surroundings!

Photo unmodified. August 20, 2011. FlashEarth Location.

Sunday Funnies: Mad World Edition

I came across a couple links to this on Friday before I finally took a few minutes to watch/listen to it. The lyrics changes and expressions are perfect, hilarious, and yes, precious. Also, don't ignore the guy in the background playing keyboard. Genius!

Cheezburger I may have already posted this, but I love it.

Walking From Work

 Are You Talking to Meme?

"Before my defense." What Should We Call Grad School?

Historic LOL

Bits and Pieces

Tastefully Offensive

This would be Halloween perfection. Derpy Cats

Tastefully Offensive

"Riding in the back of the field trip van on an unpaved road driving to the outcrop." Geology is Hard

Wondermark

Cheezburger

 Bits and Pieces

Sober in a Nightclub

Senor Gif "Gandalf Style"

Bits and Pieces

Mark Stivers

Bits and Pieces

Shirtoid, via Wil Wheaton's Tumblr. (Tees for sale at Shirt Woot! Only $15.)

Sofa Pizza

"Apex Predator" Tree Lobsters

Sober in a Nightclub

What Would Jack Do?

Blackadder

Jennifer Lawrence seems very cool, based on what I've read- granted, not a lot, but this is a good example of her type of comment. Wil Wheaton's Tumblr

The Far Left Side

STOP POKING ME! Senor Gif

Bits and Pieces

Criggo

Tastefully Offensive

Tastefully Offensive

Bits and Pieces

Lunar Baboon

"When my professor goes on and on about the importance of stromatolites" Geology is Hard

This cat doesn't even have the excuse it was cleaning its belly. It's back leg is just a dick. Sober in a Nightclub

"Hold me closer, tiny dancer." Senor Gif

Are You Talking to Meme?

Senor Gif