Thursday, September 29, 2016

Geo 902: Jefferson Looms on the Horizon

A last shot from Ochoco State Park: I turned around to face west, and there was a nice view of Mt Jefferson. I promise, it's right there, kinda behind the middle of the three electric poles in the middle of  the photo. It's not the darker, more visible one in the right middle.

I had forgotten Jefferson is the second tallest mountain in Oregon (after Hood). More basic information on the mountain can be found on its USGS page. It's also the Cascade Volcano that's most reliably visible from Marys Peak, and thus the one I've seen most often. I have climbed most of the icefield visible in this photo, but it got steep enough that, without crampons, I decided to stop and turn around.

Photo unmodified. September 7, 2016. ZoomEarth location.

Monday, September 26, 2016

Geo 901: Prineville, Oregon

Looking northeast from the Ochoco State Park Viewpoint, Prineville sits almost entirely on alluvium of the Crooked River. I don't have a whole lot geological to say about this photo, but I liked it. For more about the geology of the area, I commend yesterday's PDF link, which I found while fact-checking myself, to you. I skimmed over the field trip briefly, and for people who want details of the area, it's a great resource!

Photo unmodified. September 7, 2016. ZoomEarth location.

Sunday, September 25, 2016

Geo 900: Ochoco State Park

Looking a bit south of east from Ochoco State Park, we see a variety of rimrock basalts of varying ages. The one on the right has been named the Basalt of Meyers Butte, which has been dated at 5.42 +/- 0.11 Ma, and erupted west of this location. (Glad I looked it up: I had been under the impression these came from Newberry Volcano, which is way to the south.) This PDF (see page 4) has a very similar photo to the one above, with the various basalt units labeled, and a field guide going into great depth about the volcanic stratigraphy of the area.

There are numerous reasons I wouldn't live in eastern Oregon, but the views and excellent, less weathered rock exposures make it a favorite place to visit.

Photo unmodified. September 7, 2016. ZoomEarth location.

Saturday, September 24, 2016

Geo 899: Three Fingered Jack and Cascade Crest

I've been trying to find a name for the peak on the left-middle skyline; at 6200 feet plus, it must have a name. However, I've been unsuccessful. The rubbley and shaded area on the left is the quarry northeast of, and the base of, Hogg Rock, and TFJ is the peak on the right. My sense, when I was there, was that we were looking at the transition between an icefield and a valley glacier in terms of the valley landforms, and the Google topo map below seems to support that somewhat. The black dot is the approximate location where the above panorama was taken. The patch of blue on the map's lower left edge, above Route 20, is the east end of Lost Lake.
Directly south of Hogg Rock, and not pictured, is Hayrick Butte, another tuya, and Hoodoo Butte, a post-glacial cinder cone, and the closest ski area to the mid-valley region.

Panorama stitched in Hugin. Photos unmodified. September 7, 2016. ZoomEarth location.

Friday, September 23, 2016

Geo 898: Three Fingered Jack

From a quarry on the north side of Hogg Rock, the view to Three Fingered Jack is excellent. Three Fingered Jack is described on OSU's Volcano World page as a stratovolcano in the leading basic information, then in the first sentence as "a deeply eroded basaltic shield volcano." I don't know which it is, but I guess I'd lean toward shield rather than stratovolcano. The Oregon Cascades were heavily glaciated during the Pleistocene, and the fact the volcano is so deeply incised shows that it hasn't been active- or at least hasn't had any major lava-producing eruptions- since the end of the ice age. Mt. Jefferson, the next major peak north of it, shows the same style of faceted glacial erosion.

Route 20 winds around the west and south side of Hogg Rock, a tuya (a sub-glacial eruptive landform, where the lava erupted under ice), much too close to get any decent photos, and the rock here in the quarry seemed too nondescript to bother with. The best photo of Hogg Rock on this trip was the one I took at Lost Lake. As noted in the post at that link, the pass area burned a few years ago, killing many, many trees.

Photo unmodified. September 7, 2016. ZoomEarth location.

Thursday, September 22, 2016

Geo 897: A Last Glance at the Lost Lake Drain Hole

I'd say the hole is about 4-5 feet across, less than the 6 foot diameter reported in most of the stories I've read, and 2-3 feet deep. As I mentioned in the first post about this location, the layers of ash and lapilli are probably responsible for creating a tough and poorly permeable lake bed. It does seem likely to me that this is some kind of sinkhole, but I don't have any sense of what might have created the void that the rock collapsed into. The mafic lava flows in the area have enormous amounts of void space in their rubbly surfaces, and I don't feel that a lava tube is a necessary conclusion, though it might be the correct one. Perhaps someday we'll find out.

To put this in a broader context, if you're traveling across Santiam Pass, and you have a little time, this is well worth the rugged, pot-holey drive in (I'd say okay for smaller cars, just take it slow.) at least once. It's not something I'm going to feel I need to do every summer, but I'd like to visit in the late spring sometime, and given the new hole, it might be worth stopping every few years or so, to see if the area evolves further.

Photo unmodified. September 7, 2016. ZoomEarth location.

Tuesday, September 20, 2016

Geo 896: Drain Oregon!

Drain, Oregon is an actual town off I-5, south of Eugene. But these two holes actually help drain Oregon. With Gary for scale, you can get a sense of how large the holes are, and their relationship to each other.

Photo unmodified. September 7, 2016. ZoomEarth location.

Monday, September 19, 2016

Geo 895: Lost Lake

Looking more or less west from its newest "drain hole." The old one is just out of the frame to the right. It's an odd spot, even without the drains: the basin was almost certainly covered in glaciers during the Pleistocene, but more recent volcanic activity blocked the outlet. As I mentioned on Friday, much of this area is covered with very permeable lava flows. Rain and snow melt goes directly into the ground, to re-emerge as springs at Clear Lake and elsewhere along the Upper McKenzie River. Here, apparently, the tephra seen in Fridays post, and the lacustrine sediments visible in the sides of the hole above, create a less permeable cap and impounding the lake's water. I can't say what portion of the lake's summer water loss goes down these holes, and what infiltrates directly through the lake bed and into the underlying bedrock, but I doubt the holes account for all of it. That is, I expect the lake bed isn't entirely impermeable.

Route 20 runs through the notch in the horizon on the left, and along the south side of the lake.

Photo unmodified. September 7, 2016. ZoomEarth location. (Location approximate- can't resolve hole.)

Sunday, September 18, 2016

Geo 894: Lost Lake Has a Falling Out With Itself

The sediment forming the edge of the second hole appears to be more like lake mud and silt than the ash and lapilli in the first, older, hole. However, I didn't look all that carefully at the stratigraphy here- the same mud and silt (which appears to be more easily eroded) may have been removed over the years since the original hole opened up. In other words, given a few years of erosion, this hole may come to look the same as the old one.

Also, as you can see, this hole is still draining the lake in early September. We had our first significant rain of the season yesterday and this morning, and I'd bet the pass area got much more rain than we did down here in the valley. While the next week is forecast to be dry and very pleasant, it won't be too long before both holes are submerged again.

Photo unmodified. September 7, 2016. ZoomEarth location. (Location approximate- can't resolve hole.)

Saturday, September 17, 2016

Geo 893: A New Drain for Lost Lake

When I looked up from peering into Lost Lake's "drain hole" yesterday, Hollie and Gary had wandered over to another hole- this one still actively draining the edge of the lake. They had been up here the previous summer, and assured me it was new in the past year. Cool!

Many the the articles I've read since this spot hit public awareness have well over-stepped the edges of what we actually know about what's going on here. They've confidently claimed there's a lava tube here. The are tubes in the area, and that's certainly a possibility, but I saw nothing that I would say is good evidence of one here. The bottom of both holes are rubble-choked, and both are relatively shallow. Articles have claimed there are vast "underground rivers." This reflects a common misunderstanding about groundwater: most often (except in karst terrain) the water travels in pore spaces and fractures between the fragments that make up the rock or aggregate, rather than in one or more defined channels, which are intrinsic in the concept of "river."

To me, this type of reporting doesn't seem so much "sensationalist" as it does "poorly informed." I don't know that either is better or worse, but the latter seems more tolerable in my mind, since I can add corrections in posts like this. The former just exasperates me. The world we live in is an amazing and astonishing place. Reporters don't need to add fireworks, bells, and whistles to make it more so- in fact, that behavior distracts from the wonders in front of our faces.

Photo unmodified. September 7, 2016. ZoomEarth location. (Location approximate- can't resolve hole.)

Friday, September 16, 2016

Geo 892: Lost Lake's "Drain Hole"

The hole is both smaller and shallower than I expected, and at this time of year, well back from the water's edge. The lake bed appears to be composed of relatively thin laminae of ash and lapilli, and well lithified. This isn't surprising, given its location near the crest of the active section of the Cascades, but it isn't what I was expecting. Rubbly basalt and basaltic andesite dominate much of the central Oregon Cascades between our location here, along Highway 20, and McKenzie Pass along Rte. 242. However, my suspicion is that under these layers of tephra, the lava rubble is present; that would allow the water draining through this sinkhole to move to the water table, and, ultimately, re-emerge at Clear Lake.

Photo unmodified. September 7, 2016. ZoomEarth location. (Location approximate- can't resolve hole.)

Thursday, September 15, 2016

Geo 891: Lost Lake Basin and Hogg Rock

The basin the the foreground fills with water during late winter into spring, then slowly drains into the ground over the summer- there is no surface outlet. I've thought for years that Hogg Rock, in the back, looked like a tuya- a subglacial volcanic landform- in terms of its shape, and a couple months ago, I was informed by Adam Kent, a volcanologist at Oregon State, that it is.

Over the past year, there have been a number of stories in Oregon news sources about Lost Lake's "drain hole," starting with one in the Bend Bulletin. Even though I had never stopped here before, I was able to get a general sense of its location from the shape of the landscape in photos accompanying the articles. However Hollie and Gary had visited the site previously, so we didn't have to search it out. Nevertheless, my "general sense" turned out to be quite accurate. We're looking pretty much right at it, but from this angle, it's hidden in the grass and willows.

The countless dead trees on and around Hogg Rock were killed in a nasty fire a few years ago.

Photo unmodified. September 7, 2016. ZoomEarth location.

Wednesday, September 14, 2016

Geo 890: Saber-Toothed Nimravid and Trip Outline

Cast of saber-toothed Nimravid display along the Island in Time trail, John Day Fossil Beds National Monument, Sheep Rock Unit. Nothing for scale, but I think box is ~3 feet on the sides. In terms of representing the area, the above, to me, is perhaps the most iconic fossil photo of the trip
Interpretive sign associated with the fossil cast above. (Open pics in new tab for larger size and readability.)

I've got this written up, and I'm going to go ahead and post it, but I need to double check and clarify a few things in the outline below, so I may make some minor changes and expansions in coming days

Day 1 (Wednesday, Sept. 7): Travel to Dayville, Oregon, stops at
  1. Lost Lake to see "drain hole." There are *two* of them now.
  2. Gravel quarry on back side of Hogg Rock.
  3. Overlook viewing area, Prineville. (Whole trip was in OR.)
  4. Roadcut of Clarno Fm. near milepost 53 on Rte 126 (Folds, faults, leaves)
  5. Mascall, Picture Gorge Overlooks, 4 miles west of Dayville.
  6. "Home" for four nights: house rental in Dayville.
Day 2: Exploration of two of three John Day Fossil Beds National Monument Units, Sheep Rock and Painted Hills. Stops/hikes:
  1. Mascall Overlook to check out morning (vs. evening) light.
  2. Blue Basin, Island in Time trail. (Photos above)
  3. Foree, Story in Stone trail and Flood of Fire trail.
  4. Thomas Condon Paleontology Center. (Holy Cow! My head was swimming!)
  5. Visitor Center, Painted Hills Unit.
  6. Red Scar Knoll trail.
  7. Painted Cove trail.
  8. Lower Meyers Canyon- mostly to fritter away daylight until early evening at next stop. (Outside JD Fossil Beds NM.)
  9. Painted Hills Overlook Trail. (Wished we'd been there an hour later, but still awesome.)
Day 3: Return to Painted Hills Unit for morning light, then on to Clarno Unit, and Nut Beds in Fossil.
  1. Painted Hills Overlook for morning light. ( Not *quite* as spectacular as evening, but still...)
  2. Leaf Hill trail. (Meh)
  3. Caroll Rim Trail. (OMG overwhelmingly gorgeous! For n=1->infinity, repeat.)
  4. Drive to Clarno Unit, several roadside stops to puzzle out stratigraphy.
  5. Clarno Unit, Geologic Time trail and Trail of Fossils
  6. Fossil, OR High School, digging in famous Nut Beds- found some leaves.
  7. Return to Dayville through Sheep Rock Unit. Stopped to photograph Sheep Rock. (Lighting is poor midday.)
Day 4: Baker (ophiolite) and Izee (Crazy metamorphosed and folded seafloor sediments atop Baker) Terranes.
  1. Two stops in Baker Terrane on Rte. 395 just south of (City of) John Day.
  2. Five stops in Izee Terrane between mileposts 11 (I think- need to check) and 15 on Rte. 395.
  3. Return to John Day and explore ultramafics and associates of Baker Terrane from Forest Service roads (This had a number of stops, and is complicated. But a companion GPS'd 'em all, so I'll get better info.)
  4. Home.
Day 5: Return to Corvallis. Stops at:
  1. Smith Rocks State Park and a hike. I was too tired and sore to really enjoy this, misinterpreted a map, resulting in an extra mile or two of hiking, and lost my lens cap to the Crooked River. But better than I'm making it sound, plus I'd never been there before.
  2. Crooked River Gorge. A nice, easy amble, with a spectacular gorge 300 feet deep, and sheer basalt walls.
  3. Niagara County Park along N. Santiam River.
  4. Yay! Back in Corvallis.

Wednesday, August 24, 2016

Geo 889: Stranded Terrace II

A shot from nearby yesterday's, which zooms in a little closer to the small remnant of stranded terrace deposits. I like the framing of the foliage and old man's beard.

Photo unmodified. July 21, 2016. ZoomEarth location.

Tuesday, August 23, 2016

Geo 888: Stranded Terrace Deposits

Overlooking a small cove just north south of Sunset Bay, one can fairly easily spot the buff-colored layer of semi-consolidated sand, about six feet thick, overlying the tilted Eocene beds of the Coaledo Formation. It's a beautiful spot, and a nostalgic one for me. When I was young and hale, I clambered down into this cove a few times; there are some gorgeous sedimentary structures in the strata here. But at this point, with poorer balance and limited endurance, there's no way I'll be down there again unless a decent path is constructed. I have no reason to think that has been, or will be, done. The routes down were precarious, with tree roots and vines, mostly, as the only hand-holds, and the climbs back up were often scary, or worse if I had taken samples (one ten-pound block, in particular, comes to mind).

There's a modest fault running through the cove; this is particularly apparent in the ZoomEarth satellite image. I'm pretty sure the sandstone bed running from the middle toward the lower right is the same as the one on top of the tilted slab on the middle left.

However, the feature the sprang out at me on this trip was the isolated bit of terrace material on top of the anvil to the far right. There a tension between subsidence and uplift in this area. On a scale of millennia, there can be subsidence, as demonstrated by the dead tree stumps on the inner south shore of Sunset Bay. On a longer scale, tens of thousands to millions of years, terraces like this (and six more higher up tentatively identified) clearly show a pattern of tectonic uplift. That little pile of stranded terrace deposits will soon fall as the latest victim to the ongoing ups-and-downs of this area's coastal elevator.

Photo unmodified. July 21, 2016. ZoomEarth location.

Monday, August 22, 2016

Geo 887: Wave Refraction

As an ocean wave approaches shore, it reaches a point where the decreasing water depth causes it to slow and pile up. Wave frequency (number of waves in a period of time) remains more or less unchanged, but wavelength (distance between waves) is shortened, and amplitude (height between crest and trough) increases. Shortened wavelength and increased amplitude finally renders the wave unstable, and it breaks.

The seas on this day at Sunset Bay were quite calm, but the narrow opening to the bay at low tide meant that what waves were coming in off the ocean were well defined. Despite the curvature of the shore, you can see the waves are approaching it nearly perpendicularly across its length (despite the pesky botanical material in the way).

Photo unmodified. July 21, 2016. ZoomEarth location.

Sunday, August 21, 2016

One Year From Today

The blue line across the middle represents the mid-line of the August 21, 2017 total solar eclipse. The shaded area around that line represents the area of totality, where the sun's disk will be completely obscured for a period of time as the moon passes in front of it. The closer an observer is to the mid-line, the longer the sun will be obscured.

I've been excited about this for years; I've never seen a total solar eclipse. I've seen partials that were total or annular elsewhere, but I've never been in the path of totality. For viewing, all I really need to do is be awake and standing in view of the sun, but I'd like to get to a decent elevation. I understand that if you're in a spot with a good east-west vista, you can see the shadow of the moon approaching and receding before and after totality. In Corvallis, the umbral speed will be 1.310 km/sec, or 2929 miles per hour-- which is to say, the fastest predictable thing I will ever see. This interactive map (from which the above screen shot was taken) is the best resource I've found for planning, with extensive details about the event. Simply click the crosshairs on a point of interest, and a table of data will pop up, telling you everything you could want to know about the eclipse at that position.

I have some ideas about where to watch it, but I hope to have opportunities to do some scouting between now and then. It may be that I can get up to the Santiam Pass area and do geology for much of the remainder of the day. In the end, I suspect I'll play it by ear. This time of year, fires and smoke can muddle an otherwise glorious view. However, the chance of rain- or even heavy clouds- in mid-late August is next to nil.

Sunday, August 14, 2016

Geo 886: View of a Broken Shoreline

You can see (barely) the two beds from yesterday's photo behind Gary, and the fault in that photo is the nearly horizontal dark line extending east-west. Less obvious, but quite clear when you recognize what you're seeing, is a larger fault just behind him. The prominent sandstone bed behind Hollie is the same as the one on the far right side of the photo. If the offset on the closer fault is horizontal, and I'm not sure it is, it looks to be about 30-35 feet. Some three and a half years ago, I posted and annotated a shot of this same area, but looking approximately the opposite direction.

On that previous visit, in early March, the wind and chilly temperature combined to make not-so-pleasant conditions. On this visit, apparently, warmer temperatures and less energetic summer waves in July combined to deposit a couple inches of disgusting, sulfurous, black, slimy mud in certain areas of the intertidal zone. We had to walk through that to cross the larger foreground fault. I'm honestly not sure which "downside" was more unpleasant, but in both cases, it was well worth the discomfort. Though if I'd slipped and fallen in that awful mud, I have no doubt I'd prefer March.

Photo unmodified. July 21, 2016. ZoomEarth location.

Saturday, August 13, 2016

Geo 885: Lovely, But Not Without Fault

Sunset Bay is gorgeous, but not without fault. In fact, the whole thing is eroded around a major (inferred, but not directly observable, as far as I can tell) fault that slices through the middle of it. That major fault has quite a number of smaller, directly observable, subsidiary faults, such as the one above. This photo could have been framed a little more clearly; the prominent bed in the lower left correlates with the one on the far right. The bed running through the upper middle correlates with the tiny bit on the left middle. This spot is easily found in what is now called "Zoom Earth." (See crosshairs)

Photo unmodified. July 21, 2016. ZoomEarth location.

Sunday, August 7, 2016

Geo 884: Not Just a Pretty Face

As I predicted in yesterday's post, today's is a bit to the left, and without scale. The cobble in the lower right is the same one my foot was resting on in that photo. Just to the right of that cobble, there are some laminations with cross-cutting features, but they're obscure and poorly focused, so let's look at a crop from yesterday's shot.
Here I've highlighted a couple of the beds that cut across other beds. The principle of superposition tells us that younger beds are on top of older beds, and the principle of cutting tells us the feature doing the cutting-- whether that's bed forms, as here, a fault or a dike-- is younger than the rocks it cuts. The highlighted horizons are cutting the other beds nearby, so those horizons are younger. Since they're younger, we can infer they're on top. Thus stratigraphic "up" is the opposite of the orientation in these two photos. Which is to say (at the risk of being confusing) that "up" is down.

Back to today's photo, just a quick comment: who says rocks aren't pretty? There are some interesting details, but take a moment to enjoy to appreciate the esthetic quality of the exposure.

Here's a crop from above ("below") the cobble:
I'm guessing that the round clast on the upper left was able to roll into place, then draped with subsequent sediment. The bump (keep in mind, stratgraphically, that's a divot) in the right middle looks like a burrow of some sort. And toward the upper right, the tent-like form *may* be a very small flame loading structure. And I'd be remiss in failing to point out that all three of those are informed guesses, with varying degrees of confidence.

Another structure, which puzzles me a little, is visible in both yesterday's and today's shots. (The crop is from yesterday's.)
I *think* that's a dewatering structure; as saturated sediment compacts, the interstitial water can escape along a channel and disrupt the sediments it's passing through. However, I think it's also possible that it might be a burrow instead.

Photo unmodified. July 21, 2016. FlashEarth location.

Saturday, August 6, 2016

Geo 883: Riddle Me This

In this photo from Sunset Bay State Park, north is to the right, west toward the top, and so on. Which direction is stratigraphic "up?" This should be a pretty easy question if you have any experience with geology, but as a hint, look carefully at the cross-beds in the lower right.

I mostly took this photo because it's purdy, but it will reward close inspection. This one has my foot and boot for scale, but the one I'll post tomorrow overlaps this one on the left, albeit without scale. More details then.

Photo unmodified. July 21, 2016. FlashEarth location.

Sunday, July 31, 2016

Geo 882: More Ball and Pillow... But Wait! There's More!

The more I look at this photo, the more little details I'm spotting. Starting with the colorful band of sediments near the top, one can tell from cross-cutting relationships that stratigraphic "up" is to the right. That gray, elongate blob on the bottom of the colorful package looks like a rip-up, a clot of semi-consolidated mudstone ripped from one spot and redeposited in another. It looks awfully big for the flow regime indicated by the surrounding sand, but I can't think of a better explanation.

In the crop below, I've highlighted one of maybe a half-dozen of ball and pillow structures in the photo, and a flame structure- the latter tend to be pointy in the stratigraphic upward direction. While ball and pillow represents denser sediment sinking, flame structures represent less dense sediment rising or being displaced upwards as ball and pillow structures form. Also, above and below those two structures, tafoni or honeycomb weathering can be seen. (We'll be seeing a LOT more of this in days to come.)
If you open the top photo up to full size and look around, you can find numerous small examples of minor soft sediment deformation.

Photo unmodified. July 21, 2016. FlashEarth location.

Saturday, July 30, 2016

Geo 881: Ball and Pillow

Hey boys and girls! Remember me? I'm that guy who used to talk about rocks all the time! I finally got out last weekend to re-familiarize myself with some of them near Charleston, Oregon, at three state parks: Cape Arago, Shore Acres, and here, Sunset Bay.

The main feature I wanted to illustrate here is called ball-and-pillow structure, and makes up the downward lobate features above the lens cap. This happens when denser sediment is deposited on less dense sediment layers. The denser sediment sinks down into the less dense layers. The underlying sediments often push upward to form flame structures, but in this case, subsequent re-erosion has beveled off the upper layers, creating a disconformity. Above that horizon, you can see more or less laminar bedding, punctuated by imperfections created by burrowing creatures, referred to as bioturbation.

Below the lens cap, and just above the toe of my boot, there's another disconformity where flowing water carved out a small channel then refilled it. I should probably brush up on my sedimentary structures vocabulary, but I refer to these sorts of things as "cut-and-fill structures." There's a lot going on here.

My mindset on this trip was to take photos to show how beautiful the rocks and their colors are, but that certainly doesn't mean I missed the science!

By the way, I'm not going to commit myself  to the one-a-day regime I've done previously, but I figured I'd quit referring to years-worth of days, change the name to "Geo Series," and start the numbering after 880, which was the last of the Geo Series posts I finished, on May 30 of last year.

Photo unmodified. July 21, 2016. FlashEarth location.