There was a bit of confusion at this stop. Dana didn't realize that "Bridge of the Gods" referred to both the landslide-created "bridge" AND to the engineered steel truss bridge. Nor did she realize "Cascade Locks" referred to both the town and the now-disused shipping locks. I think we got that all straightened out, though. This bridge is the one I've crossed the Columbia on most often, probably more than all the others put together. The reason is that I was a student worker in Forest Soils during much of my undergrad time at OSU, and especially early on, one of our field sites was at Wind River Experimental Forest, which is upstream from here a bit, then north from Carson, Wa.
And in the center mid-ground, more of our friends the geese.
Back to the cliffs I've pointed out in earlier posts, this slide was very likely due in part to oversteepening caused by incision during the Missoula Floods. Indeed, the many waterfalls in the gorge, particularly along the north-facing Oregon side, are thought to have their origins in these monstrous floods, which left nearly vertical cliffs in many places. The nice thing about this shot is that you can see both the headwall- the slide's source- and the runout into the river. I don't recall the view from Beacon Rock terribly well, but that's probably the best ground-based view of this feature that one is likely to find. Though come to think of it, the view from either of those peaks might be even better. But there's little doubt in my mind that the clearest views are from above. Here's a crop from a FlashEarth satellite map that shows the overall layout well:
The cliffs in the panorama at top show up as the lighter areas to the left of the word "Headwall," and the "x" in "~Photo location" is approximately where I was standing to shoot the photo.
This is the view downstream from the footbridge across the former ship channel at Cascade Locks. The "toe" of the Bonneville Landslide, if you want to be picky, is really the outer perimeter of the whole debris lobe. However, I've been tending to think of it as the point where it's closest to the south shore. I'm pretty sure there's no narrower portion of the river downstream from here, and suspect it's quite a ways upstream before you'd find a similar neck, so this is indeed a good spot for a bridge. The well-known Pacific Crest Trail crosses the river at this point.
Not exactly geology, but I've always been fond of Canadian geese. These are technically dusky Canadian geese (or so I'm told), but I'm not really sure what distinguishes the subspecies. These appeared to have established permanent residence here, and were quite unperturbed by humans wandering toward them. It's a situation to be careful in. Geese can be quite mean, and that's more likely to happen when they've lost most of their fear of people. They'd slowly amble away from us as we approached, and we took it slow and gave them time to do so.
To the extent that there is geology in this photo, the flat area looks as if it's a fluvial terrace, but given the geology of the area, it's oddly wide, and really, too flat. But keep in mind, this was a heavily engineered area for shipping infrastructure, and I suspect that this lawn is mostly artificial, not a natural landscape.
See the bridge? No, not the steel truss cantilever bridge on the left, but the land bridge that extends out to it. According to the latter link, there is considerable disagreement in the radiometric carbon dates obtained for the landslide's age, with the most recent measurements suggesting a date of about 1450, but ranging from 1060 to 1760 AD. My take on these wide ranges is that it's not likely due to inaccuracy of lab measurements, but difficulty ascertaining which wood samples are directly related to the Bonneville Slide.
This photo doesn't illustrate the reason for the locks here well, but I'm not sure others will do a better job. As you can see from the toe of the slide behind the human-constructed bridge on the left, the river was pushed and constricted to the south side of the gorge. Prior to construction of the Bonneville Dam in 1957, this was an area of rapids, which are now submerged in the pool behind the dam. Construction of the locks at this point allowed boat and shipping access to the Columbia Channel upstream from here.
This is more similar to the last post than I'd like, but it's a panorama composed of two more zoomed shots, so looking at the full-size version should allow you to see more easily the rocks composing the two major cliffs here. The amphitheater-like headwall I pointed out in the previous post is the source of a large landslide that occurred maybe one or two centuries before the first European explorers come through this area. Native American legend has it that it blocked the Columbia River at this point (actually, just a bit down stream), allowing easy travel from one side to the other. I can't imagine this being a stable situation for too long- weeks to a month or so at most- before the river overtopped the debris, leading to rapid failure of the "bridge."
Looking across the Columbia River at Cascade Locks, the peak on the right, the same as in yesterday's shot, appears to be sedimentary rock. The peak on the left looks like Columbia River Basalt. Given the essentially horizontal bedding in both exposures, it seems pretty certain there's a significant fault between the two, close to the left peak. In closing, note that the pair of cliffs seems to create an amphitheater-like wall, curving around to the south (we're looking close to west, in this view) on the far left.
We're standing inside the Cascade Locks visitor center here; you can see the fuzzy reflection of the chandelier in the window in the top center. There's a sight-seeing paddlewheel boat departing in the foreground. I haven't done that excursion, and likely won't, so I have no idea if they discuss the geologic events the led to the creation of this scene. It would be a shame if they didn't; the geology is beautifully laid out. The large cliff to the left of center plays a major role. Given the distance, I can't be certain, but I think most of the cliff is sedimentary rock of some kind, but the high point above its center is a much darker gray, and is probably the base of the Columbia River Basalt flows here. So why a cliff? Stay tuned...
Last Wednesday, we puny humans landed on a comet- kudos and sincere admiration to ESA. I fully expected that I would lose a day or two focused entirely on that, and I did. Then, due to the (hilarious) foibles of the landing, as I was struggling to get caught up with my reading Friday, Philae was sputtering out of battery power, and was apparently headed into "hibernation mode," or as one wag put it, "a coma." So again I was largely distracted, watching breathlessly to see if the last batches of data were uploaded to Rosetta for later transmission back to us. They apparently were.
So all in all, an incredible success, with the proviso that a hoped-for extended mission looks unlikely to happen. That's why they call them "extended missions:" everything has to go perfectly, and this landing, while it had me alternately laughing and shaking with suspense, did not go perfectly.
Saturday, I was within range to not only get my reading finished, but probably get started catching up on the Geo 730 posts, possibly even get an early start of the Sunday Funnies, which are now more than two weeks in arrears.
But Interzone's wireless router had different ideas. It's been problematic for years, but when the students returned this fall, it was an utter disaster, lasting for, at best, an hour or two, or at worst, a few minutes before needing to be reset. Saturday, it was lasting seconds before crashing again. At times, I can get onto the OSU visitor network, but it's slow and intermittent, and also prone to losing signal. I was able to get out a few Tweets, but as far as internetting goes, Saturday was a complete loss. I went home before 3 PM, which both my cat and I found a little odd-feeling. Apparently, a new router was purchased and installed later that day.
The problem is that the routers that have been in use here are intended for homes, not small businesses, and there's just too much traffic for a home router to handle here. I'm told that within the next day or two, they will be acquiring an "access point," which I'm led to understand will be more capable of handling the traffic of a busy coffee shop with (aside from yours truly) a high turnover rate. That is, people who pop onto the web for a few minutes while they consume their drink, head out, and are replaced by others in rapid succession.
So long and short, *I'm* fine, just behind, and I'm hoping to get some Geo posts done this afternoon. Eventually, I'll try to put together a post on Philae, because it truly is a wonderful story, with many unexpected twists. I'm keeping my fingers crossed that this new-fangled high-tech contraption works well, because I can't tell you how much time I've wasted this fall waiting for the information superhighway to overcome gridlock.
For those who've seen and recall the opening scene of "The Fifth Element," you may be amused to know that I've worked out a code with a couple of the barristas: "Aziz! Router!"
At some point, I'll copy over some tweets and retweets from the past couple of hours, but for the time being, science people on Twitter are being like this. And I'm one of them. I'm not sure that anything else will be happening today. Thanks, ESA!
Above is a closer shot of the same general area on the petrified log at the Cascade Locks Visitor Center as in the previous post. Looking even more closely in a crop from this photo, there's some very pretty agate with a botryoidal (grape-like) texture.
I've been meaning to discuss just why these ash-rich sedimentary environments tend to have such rich and well-preserved fossils. This is not just a feature of the Cascades; many renowned fossil localities are in ash-rich sediments, including Petrified Forest National Park in Arizona. Volcanic ash is, in large part, simply broken glass. Glass is geologically unstable- it would "rather" be in the form of quartz and feldspars. In other words, those minerals are more stable. If there is organic material nearby, SiO2 (silica) will dissolve from the glass and re-precipitate as quartz in and on the organic material. I'm not familiar enough with the geochemistry of silica and organic matter to say why the latter is a preferred nucleation site for the former, but my petrology professor said that silica is more soluble in bases, while organic matter tend to decay to acidic end products. This would mean silica tends to dissolve in areas away from the organic material, and precipitate nearby. I can say from experience that in ash-rich environments, preservation appears to be rapid, thorough, and with exquisite retention of cellular-level detail.
No, not a redwood, but there's a fair chance this was a dawn redwood, or Metasequoia. Peavy Hall, the Forestry building at Oregon State, has a living dawn redwood near the north entrance, and two petrified logs of it, one near the east entry, and another in the atrium. Both were from the Eagle Creek Formation, as I suspect the above is. Not a terribly informative photo, but I love the color, and the contrast with the fern below.
I'll spare you the bulk of the photos I took of this beautiful petrified log we found at the visitors' center at Cascade Locks. I'm pretty confident this is from The Eagle Creek Formation, which contains a lot of petrified wood and leaf fossils, and has been dated as early Miocene in age. So it's younger than similar-looking plant fossils in the Sweet Home-Quartzville area, which are Oligocene. I haven't found a good on-line reference to The Eagle Creek Formation, but Interzone's wi-fi is having another difficult day, so I haven't been able to review some possibilities. I will post another shot of this log tomorrow, and I'm hoping by then I can find some more useful information.
Sitting below and a bit to the right of the peak on the central skyline, Beacon Rock, a Washington State Park, rises nearly 850 feet from the edge of the Columbia River. Despite the post title, this is actually a pretty clear view, and if our recent experiences with the smoke and haze hadn't been so frustrating, we might have considered crossing the river and climbing it. There a crazy system of trail segments, staircases and switchbacks that allow non-climbers like me to get right up to the summit. It's a strenuous hike but the views- on a clear day- are well worth the effort. In particular, features from the Missoula Floods, the landslide at Bridge of the Gods, the Dalles Dam and the Oregon side of the Gorge are well displayed.
It was here that the second consequence of a late, dry autumn made itself evident: the waterfalls were mere trickles. So both of the outstanding scenic qualities of the Columbia River Gorge, the vistas and the waterfalls, were at low ebbs. We parked in the central island of I-84, and walked over to Multnomah Falls for a couple quick photos, but we decided that this was not really a good day to spend in the gorge. Dana wanted to get a better look at Bridge of the Gods, which I was familiar with, but had not spent much time looking at in any detail. So we quickly set off with new plans.
Incidentally, you can get a sense of the size of the upper falls by looking near the bottom center of the photo, where there's a bridge with a couple of people sightseeing.
The Columbia River Gorge is rightly famous for two scenic aspects: its incredible vistas, and its waterfalls. Above we almost see Crown Point, and if you know where to look, and for what, you can make out the silhouette of the Vista House at its summit. The vistas were not so incredible on this day. Shifting winds had brought smoggy haze from Portland, and smoke from fires in eastern Oregon. Dana and I were disappointed.
Even though, as I mentioned in the previous post, the water level was quite low for mid-October, the Willamette River is substantial even in dry conditions. Here we're looking at the upper portion of the amphitheater-shaped falls, and there's plenty of water moving.
This is an easy pullout on north-bound Route 205, which bypasses downtown Portland, and takes those of us from the Willamette Valley to PDX and The Columbia Gorge without dealing with the downtown's congestion. I don't believe there's access to this stop for those coming southward. It was the Gorge, in fact, that was our intended destination on this crisp fall day.
On October 10, 2012, we hadn't had anything but a few sparse showers, and those were in early to mid-September, so the water was quite low. As you can see, the fall colors were pretty nice, by Western Oregon standards, but we were definitely antsy for our fall rain. The lack of precipitation would shortly play a major role in changing what we had decided to do on this day. The size of the driftwood logs resting on the falls, though, gives a sense of what a more swollen river can accomplish. During the great flood of 1996, the falls were barely visible as a riffle in the torrent. See, for example, this photo (several other good ones at this page). As I mentioned yesterday, the bedrock here is Columbia River Basalt.
The factor that drew settlers to Oregon was its rich farmland, but the factor that shaped the first incorporated city west of the Rocky Mountains was geology. Skipping inland and north from the previous post, we find... Yes! More basalt. Specifically, more Columbia River Basalt. Here it forms a resistant lip over which the Willamette River pours, creating the largest waterfall by volume in the Pacific Northwest (see note). That sort of hydraulic head is a wonderful source of cheap power- early on, mechanical, later, as you can see from the sign, electrical.
Note: Celilo Falls, in the Columbia River Gorge, was the most voluminous in the PNW, and it certainly deserves the title, but it was inundated by the construction of the Dalles Dam. I'm very sorry to have missed it. Among other interesting trivia, "Celilo was the oldest continuously inhabited community on the North American continent until 1957..."
In this final photo from our mid-July coast trip, it's clear that the contact between the Columbia River Basalt and the underlying Astoria Formation is not conformal- that is, the basalt is not resting on a single bedding surface, but cuts across them. In particular, if you look at the contact just above where the small wave is breaking on the left, you can see the basalt protruding down into the sediments, but just a bit to the right, at the water's edge, the contact is significantly higher.