Sunday, June 14, 2015

Why, Hello, There!


Apologies for the two-week hiatus. If you follow me on Twitter, you know we had about five days over that interval that were hot enough to knock me down and out- hot weather destroys my appetite, so poor nutrition was likely a factor too. I finished the Upper McKenzie stretch of the Geo series, and I just lost motivation- coinciding with the first of the hot days. Then my co-presenter for the Oregon Master Naturalist Willamette Valley Geology workshop had to cancel, so instead of planning half of that day, I'm planning all of it. And I got called for jury duty tomorrow (Update: Yay!). And on and on. I make no promises either way on the continuation of the Geo series, though I have hatched an idea that could allow for a quick catch-up with minimal work. On the "maybe not" side, Dana is also suffering from a series of set-backs (pitch in if you can), I haven't been out in the field since October, and I don't have a whole lot more trips to choose from in terms of photo series.

And yes, I am still tagging stuff for Sunday Funnies. Both the last two Sundays have been beastly, and finishing this up today means I won't have time this Sunday either. But never fear, they'll be back. Sigh... okay, here's a good one:

On the flip side, I did do a scouting trip for next Saturday's field trip (too busy taking notes to take photos, though) so here's the result. For those doing this trip on their own, it would likely be easiest to reverse stops 1 and 2, starting in the parking area, then going two to three tenth miles back to the Tyee soil, then subtract 4.9 miles from the mileage at each subsequent stop. (In other words, no need to start at OSU, just start at Chip Ross Park.)

Marys Peak Field Trip Route and Stops

Players in the story, oldest to youngest:
·                     Siletz River Volcanics- sea-floor and Hawiian-island type basalt, about 60 to 50 million years old (Ma = "mega-annum," or million years.)
·                     Kings Valley Siltstone- formed from erosion and marine redeposition from one or more islands of SRV. Toward the end of same span as SRV.
·                     Tyee Formation- Turbidites, vast underwater "sand and dust storms" that settled out in distinctive sand->mustone couplets, from erosion of granite to the east, in or near the Idaho Batholith. About 48 to 38 Ma.
·                     Corvallis Fault- A fracture in the earth's crust creating the boundary between the Willamette Valley floor and Coast Range foothills in the Corvallis area. Probably active around 35 Ma for a few million years, but does not appear to have been active since the following intrusive activity.
·                     Marys Peak sill (along with numerous similar intrusions of about the same age and composition in central Coast Range)- Gabbro, similar in composition to basalt, but slower cooling, so larger mineral grain size. Quite resisitant to weathering and erosion. 30 Ma.

We will be walking along the roadside at several stops. Be alert for traffic, and make safety your first priority.

Mileage Location/Stop Number/Feature

0.0 Depart Richardson Hall. Zero odometer as you turn onto 30th Street northward.

-At intersection with Harrison Blvd., turn right, and jog over a block to 29th.
-At 29th, turn left and continue north to Walnut Blvd.
-At Walnut, turn right, and continue east to Highland Dr.
-At Highland, turn left and wind up the hill to the ridge crest.
-Just before Highland descends into Crescent Valley, turn left on Lester Avenue. There's a small brown sign pointing to Chip Ross Park on the right (Correction: left- this is an unusual case where I really did recall right, rather than making a sloppy mistake) berm.
-We didn't get accurate mileages until noted, so the first two stop mileages are estimates from Google Maps

4.6 Stop 1 Lester Ave. Roadcut. Soil developed from Tyee Formation- note light yellow color. The Corvallis Fault cuts across the lower saddle between here and the Chip Ross parking area. As we move from stop 1 to stop 2, look for nice views to the southwest of Marys Peak and Alsea Pass, where this same fault cuts across the Coast Range crest.

4.9 Stop 2 Chip Ross Park Parking lot. Soil developed from Siletz River Volcanics- Note dark red color. Why are we going up Marys Peak to look at the geology of the "Willamette Valley?"

-Return to Highland, and turn right.
-At Walnut, turn right.
-Follow Walnut roughly 5.5 miles to Philomath Boulevard. The line of hills to the north and west of this drive is more resistant Siletz River Volcanics, uplifted by offset along the Corvallis Fault. The less resistant Tyee (and overlying Spencer) Formation form, at most, low hills to the south and east.

11.8 -(At this intersection, we figured out how to get tenth-mile accuracy on our exploratory vehicle.) At Philomath Boulevard, turn right and procede through Philomath.

15.6 - Route 20/34 split. Turn left, and follow route 34 to Alsea Pass.

24.5- Marys Peak Road- turn right, and drive to the Marys Peak Summit Parking area.

34.0- Stop 3 Marys Peak Summit Parking area. Lunch. Depending on interest, some of the group may choose to hike to the summit. (We budgeted about an hour here.) This, to me, is one of the most profound viewpoints in Oregon. There are quite a number that are more scenic, but I can think of few that have such a mental wallop. We're standing on the Coast Range crest, the divide of the Cascadia forearc ridge. To the east, if we have decent visibility, a few to many of the Cascade Peaks are visible. Normally, Mount Jefferson and Three Sisters can be seen, and Mount Hood can be picked out more often than not. On rare days with near perfect conditions, one can see from Mount Rainier in the north to the vicinity of Crater Lake to the south. To the west, the Pacific Ocean can be seen, taking on different appearances as the light changes through the day. With help from trigonometry, you can calculate that the distance to the horizon is about 75 miles, which is close to where the Juan de Fuca Plate begins its long slide into the earth's interior. It's that slide that has created the forearc ridge of the Coast Range, the more-or-less vertically stationary forearc basin of the Willamette Valley, and water "sweating" off the subduction slab causes melting in the upper mantle, creating the magma that produces volcanism in the Cascades. My favorite metaphor to describe what we're seeing is that here, we have an overview of one piston in the engine that drives earth's plate tectonic activity!

Before departing, be sure to make use of the sanitary facilities at the south end of the parking lot. There will be no further opportunities for actual restrooms until we return to Richardson Hall.

35.1 Stop 4 (Possible, depending on how time looks) This meadow provides a long parade of wildflowers from mid-spring into mid-summer, but in terms of rocks, a short walk up the road to the closest cut will reveal a metamorphic rock called hornfels, created when heat from the underlying Marys Peak Sill baked the overlying Tyee formation. This is similar in nature and effect to what happens when you fire a raw clay pot in a kiln; it becomes harder, stronger, and more dense.

36.7 Stop 5 Parker Creek Falls. This is the dense, tough, and extremely resistant to weathering and erosion Mary's Peak Sill, a rock called gabbro, and a good illustration of how Marys Peak sits about a thousand feet higher than any other Coast Range mountain. Note that most of the weathered, and lichen/algae coated cut face looks like basalt. But if you look carefully, a more recently broken surface will show a typical "salt-and-pepper" appearance. Those light and dark grains are the minerals making up the rock. Individual mineral grains are not visible to the naked eye in "typical" basalt. (There are exceptions beyond the scope of this workshop.)

37.1 Stop 6 We'll pull off a bit up the road from the outcrop, as there isn't safe space at the spot itself, and walk down the road to a nice outcrop of horizontally-bedded Tyee Formation. Note the abundant mica flakes and fragments of plant material- these two features can help distinguish this rock unit from others. A bit farther on, there is a fairly chaotic outcrop of Kings Valley Siltstone, which is derived from erosion of Siletz River Volcanics. As we saw at Chip Ross Park, the color difference between these two units is striking. Given that the Tyee is horizontal, there must be a fault between these two exposures, even though we can't see it. Walking across the road to the guard rail, we see another effect of the hidden fault: a fairly large landslide. The fault created a zone where the rock was broken up, and water and air had better access to the rock, speeding weathering and further weakening it.

39.9 Stop 7 Parking lot. Park here and walk back about a quarter mile or so to a quarry exposing spectacular pillow basalts of the Siletz River Volcanics. Keep in mind, these were erupted on the ocean floor. Here, they've been uplifted to thousands of feet above sea level.

40.5 Stop 8 (Possible, depending on how time looks) Columnar basalt is common in Oregon, which is no surprise, given how much of the state is covered with that rock. These are the best examples I know of on Marys Peak.

40.7 (In passing; we'll try to slow down a bit to get a look, but we won't be stopping.) Slickensides. The vertical scratches, or striations, you see on this wall were created as a fault ground the two opposing surfaces. The orientation of the "slicks" gives you two possible directions for fault offset: up or down, parallel to the scratches. Continue back to Route 34, and turn left (east) back toward Philomath and Corvallis.

45.1 Stop 9 We will not be crossing the road here. Both we and oncoming traffic have very poor visibility. Tilted beds of the Tyee Formation. Unlike the flat-lying beds of Tyee we saw near the top of the peak, these are steeply tilted. Now off the Siletz River Volcanics, we've crossed the Corvallis Fault again, but it's very close by, probably crossing through the clear cut up the valley. Deformation and folding near major faults is common, and explains why these beds are tipped over to such a degree.

58.3 Return to Richardson Hall.

Postscript: The sequence we've seen here, ocean floor volcanics, overlain by marine sediments, and modified by later events, such as magma intrusions and faulting, varies in details from place to place in the Willamette Valley and the Coast Range, but as a general outline, is consistent across the region. In other words, if you were to drill a hole on the Willamette Valley floor, you would go through a few to a few hundred feet of  Missoula Flood and Willamette River sediment, then you'd hit marine sedimentary rock of one formation name or another. (From the Albany-Salem area north to Portland, you'd also encounter Columbia River Basalt interfingered with the uppermost marine sedimentary rock.) Eventually you'd go through the Tyee, which is the lowermost of those sedimentary units, and pretty much ubiquitous in the region. Finally, you'd hit basalts of the Siletz River Volcanics. Those basalts are not continuously exposed on the surface, so they have different names in different areas (Roseburg Volcanics and Crescent Volcanics, for example), but they were all formed the same way in a geologically short period of time, and they are believed to be all the same unit, connected underground where we can't see it. Climbing nearly four thousand feet off the valley floor has allowed us to see rocks that lie thousands of feet below it. Furthermore, as we saw at the first two stops, due the the milder climate of the lower elevations, rock that is exposed in the valley is often too weathered to get much information from.

Saturday, May 30, 2015

Geo 1095: May 30, Day 880: Spring Surprises

Here's a final shot from the Upper McKenzie drainage, for now, another from "Lost Springs," as I informally named it in the previous post. The best story that Anne told us about her dissertation work up here was that in the first few years of the 2000s, someone had done a project similar to hers, working out the volumes and characterizing springs forming the headwaters of the Metolius River in central Oregon. One aspect of that work was comparing the annual rate/volume of water flow, from the springs, out of the presumed hydrological basin, extending from those springs to the Cascade crest, to the modeled annual volume of water equivalent precipitation. When all was said and done, the conclusion was that there was an excess of spring flow amounting to 12 cubic meters per second! In other words, 12 cubic meters (~424 cubic feet, a bit short of 3200 gallons) of water per second more than could be explained by precipitation was flowing out of the east side springs. Needless to say, over the course of a year, some 31.5 million seconds, that's quite a bit of water.

Now I don't know how that scientist, or the committee, reacted to that result. I would have been frantically puzzled, wondering where I'd messed up, or where the incorrect assumption(s) was/were, or whether the precipitation model was anything approaching realistic. I would have not been a happy camper, because that really is an awful lot of unexplained water.

Then Anne did her dissertation work in the latter part of the same decade, and did a similar estimate of precipitation input versus spring output. The result? The west side springs appeared to have a 12 cubic meters per second deficit with respect to the amount of water equivalent precipitation it receives.

Those balancing numbers delight me. What it suggests is that the Cascade hydrological divide in the central portion of Oregon is, at least in some areas, well to the west of the topographic divide. Given the extensive covering of this portion of the High Cascades by young lava flows, cinder cones, and other tephra, that's certainly plausible. And I'm not going to fault the east side for hijacking "our" water. They need it much more than we do.

Photo unmodified. October 9, 2014. FlashEarth location.

Geo 1095: May 29, Day 879: Lost Springs

I don't know if this system of springs has a name, but the outflow drains down Lost Creek to the McKenzie River, so it seems reasonable to call it "Lost Springs." They're easy to find, but from the road, there's no clue to what most people sail past on their way to or from the pass. So perhaps a better name would be "Missed Springs." In person you can see fish- I'd guess trout; I'm not a fish person, so that is a guess- swimming languidly in the crystal-clear water, but they're not easy to pick out in these photos. I think I'm seeing a few over the lighter sand, and under the long pole across the middle of this shot:
Dana got some video of the fish swimming, but I don't know if she ever posted it.

Photo unmodified. October 9, 2014. FlashEarth location.

Thursday, May 28, 2015

Geo 1095: May 28, Day 878: Where the Water Goes

As we left Proxy Falls during our July 2013 (my first) visit, I asked Anne if she knew where the water came back out. She grinned and nodded "yes." I don't know if she had intended to stop at this spot or not, but it's gorgeous, and I'm awfully glad we did. This is merely the edge of a vast area where water reemerges as springs and pools, so it's not just where the water from Proxy Falls comes back to the surface, but likely the main set of springs for this entire drainage, up onto the western portion of the High Cascades Platform. To find it (It's maybe 6 or 7 miles down the road from the Proxy parking area.), look for a large field on the north side of the road, with a large Douglas fir standing out from the rest of the forest toward the back. There's a dirt road across that field, which circles the tree. The path to the springs is pretty much directly opposite the tree from the highway, and it's a very short and easy walk from the field to the pools. The FlashEarth view should make it pretty clear, and drag the view to the WNW to get a sense of the extent of these springs.

Photo unmodified. October 9, 2014. FlashEarth location.

Wednesday, May 27, 2015

Geo 1095: May 27, Day 877: Simple Contact, or Channel?

Down in those vine maples, you can see the contact between the edge of the Collier Cone Lava Flow (right) and the older, glacially carved, volcanic rock of the valley floor (left). The question is, has this contact been modified by rare to occasional burst floods from above the valley? It seems clear to me that there has been no such activity recently; the thick-bedded moss would not be so consistent. Likewise, there's some down logs in pretty advanced states of decay near the center of the photo. Any recent (past decade or so) would have left both of those features more chewed up. The contact seems rounded, which might indicate erosional modification... but look at all that living and dead plant material! Surely that might be the explanation for the apparent rounding.

In the end, as is so often the case, the answer is, "I don't know; I need more information." I'm okay with that. It means I have a reason to go look again.

Photo unmodified. October 9, 2014. FlashEarth location.

Tuesday, May 26, 2015

Geo 1095: May 26, Day 876: Upper Proxy Notch

Looking back down the path from Upper Proxy Falls (i.e., the falls are behind us in this view), The Collier Flow is on the right, and the southern edge of the valley is on the left. Has this notch been reworked by running water? It's not clear, but it seems possible. It would certainly fit with the idea of burst floods contributing soil components (clastic sediment and plant debris) to the surface of the lava flow, and fostering an environment for rapid recolonization and reforestation. I have a few more photos of this notch, and I'll post at least one more, but looking over them, I see nothing convincing either way. Next time I get back here, I should see if I can spot rounded gravel farther down the notch- it drops quickly just past that saddle.

Photo unmodified. October 9, 2014. FlashEarth location.

Monday, May 25, 2015

Geo 1095: May 25, Day 875: Collier Flow Berm

My camera's flash has a tendency to go off at times I think it's unnecessary, but it can lead to some interesting shots, such as this one. One has to clamber over the root system of this Doug fir to get at the rubbly hillside- the south edge of the Collier Cone Lava Flow- where you can see Anne and Chris in the upper left corner. It might be interesting to come up here with a couple bottles of food coloring to see if you can actually find the area(s) where the water is leaving the pool. It's shallow, and the volume is fairly small compared to the rate of flow from Upper Proxy Falls into it, so I'd bet the residence time of water in this pool is in the range of ten minutes or less.

Photo unmodified. July 6, 2013. FlashEarth location.

Geo 1095: May 24, Day 874: Upper Proxy Runout

Sitting up on the berm of the Collier Cone Lava Flow, looking down to the runout of Upper Proxy Falls is a peaceful experience. I love the little Doug fir that has managed to get established on a tiny island in the pool... I think I'll call it The Little Prince. As I mentioned in the previous post, this pool has no outlet. However, looking at the shape of the gap between this little cove and the lower valley, where the trail leads to this spot, I'm pretty confident this stream does overflow its basin from time to time. This may be related to the burst floods that (rarely) make it into channels up on the flow behind us here.

Photo unmodified. July 6, 2013. FlashEarth location.

Sunday, May 24, 2015

Sunday Funnies: Bizarro Edition

Dan Piraro, the comic-artist who does BIzarro, announced earlier this week that sometime in the not-too-distant future (1-2 year range), he'll be dropping his syndicated comic for other art projects. I'm saddened; I've been a fan from very early in his career. One of the Eugene (OR) alt-papers featured his work for several years before it was more widely distributed. Nevertheless, I wish him luck on his new path. I avoid swiping more than one funny from any single post, but I'm breaking that rule here. Every single comic in his set this week is funny-worthy, and I seriously recommend you click over to see the others. It wasn't easy to select only two. Regarding that last comic, it occurs to me that there have been three distinct ages of humanity: Prehistoric, Historic, and looking at news the last decade and a half or so, it's clear we've entered a new age, the Antihistoric.
Tastefully Offensive
Blackadder
Wrong Hands
Cyanide and Happiness
Blackadder
Bad Newspaper
Funny to Me
SMBC
Bad Newspaper
Tastefully Offensive
Savage Chickens
Senor Gif
"Reading comments from reviewer two." What Should We Call Grad School?
Shannon Wheeler
Lunar Baboon
xkcd
LLment
Funny to Me
Funny to Me
"Oh, the irony." Sober in a Nightclub
"Salvador Dali drawing a penis on the forehead of a woman and signing it with Picasso’s signature." "Let’s all take a long second to appreciate this." Funny to Me
Gemma Correll
Bug
Very Demotivational
Buttersafe
Tree Lobsters
Jim Benton
Real Clear Science (The other two "shortest sciences" are pretty good, too.)
SMBC
Senor Gif
Tastefully Offensive
A monkey accustomed to oranges tries a lemon for the first time. Senor Gif
 
Obvious Plant
Funny to Me
SMBC
Jen Sorensen

Matt Bors
xkcd
What Would Jack Do?
Senor Gif
Funny to Me
Funny to Me
Very Demotivational
Wondermark