GeezerHiker

February 23, 2010

Mounts Erie and Sugarloaf, and the Fidalgo Ophiolite

Filed under: Geology, Hiking — geezerwriter @ 10:29 pm

Last Thursday we were scheduled to hike to Mount Erie and Sugarloaf Mountain on Fidalgo Island, near Anacortes. For a change I remembered to check the geologic map and found that those “mountains” (merely 1300′ and 1100′ high, respectively) are part of a structure called the “Fidalgo ophiolite”. That set me to searching and reading up on ophiolites, and yes, you will be learning about them, too! (Fair warning.)

An ophiolite is not a kind of rock but a series or sequence of related rocks that pops up in a number of places around the world. While the Fidalgo ophiolite is certainly not unique, it belongs to a pretty rare family. An ophiolite sequence can consist of sedimentary rocks, various kinds of volcanic rocks, an intrusive igneous rock called gabbro, all piled on stuff like serpentine and dunite which are actually part of the earth’s mantle. We’ve run into most of those types of rocks (except the gabbro) many times on our hikes in the North Cascades, and most are pretty nondescript, but I was all fired up to see if I could find any of this stuff in real life. Especially the gabbro – I’d learned of it over fifty years ago when I was a freshman geology major at Notre Dame and seen pictures in books, but I’d never encountered it in the wild. [The big black cliffs on the flank of Mount Sefrit that tower over Ruth Creek and the Hannegan Pass trail are reportedly made of gabbro; I’ve intended for years to bushwhack across the creek to the base of the cliffs to snag a sample but haven’t done so, yet.]

The Olympics over Admiralty Inlet

We had another beautiful day for our hike – sunny and chilly as we started out, but quickly warming into the fifties. The hike runs mostly through the woods, with no grand views. We weren’t going terribly fast, and I wasn’t leading, so I could pay some attention to the rocks as we went.

Another reason that I was glad not to be leading: I didn’t know where we were most of the time! The area is a virtual rabbit warren of intersecting and overlapping trails. It is all part of the ACFL, the Anacortes Community Forest Lands, which was acquired and retired from active forestry (i.e., clear-cutting) by the fine folks of Anacortes, who had the generosity and foresight to see that forest lands could have some value beyond that of the potential toilet paper in the tree trunks. It is a wonderful resource for which we should all be grateful, and a hiker might ask, “Can you ever have too many trails?”

I think the answer may be “Yes.” We had a pretty big group (18) so it was inevitable that, despite our modest pace, we would get a bit spread out; there were so many trail intersections that we had to be almost constantly on guard to see that the slower hikers came the right way.

Mount Baker

But still I could keep my eyes on the rocks much of the time. As usual, most of the lower-lying places were filled in with glacial till from the recent (geologically speaking) continental glaciers, and some parts of the trail were old roadways that had been built up with rock that might have been trucked in from anywhere, so the only rocks worth looking at, from my ophiolite-centric point of view, were bedrock exposures. And as usual, again, when there was a big enough chunk to be pretty sure that it had been around for more than a few thousand years, it was likely to be covered with enough moss and lichen to turn any kind of rock into a bland greenish-gray lump.

Actually, though, that’s what I was looking for. According to the geologic map, we would be moving across various kinds of volcanic (i.e., lava) rocks, which are themselves pretty pretty dull and nondescript. Now volcanos are certainly interesting, even exciting sometimes, in themselves (e.g. Mount Saint Helens, ca. 1980) and lava flow sequences can tell interesting stories, but the individual chunks of rocks are kind of boring. They were extruded onto the surface where they cooled very quickly, not allowing time for the individual minerals to gather together into the pretty little crystals that you see in intrusive rocks like granite. Has anyone ever tried to sell you a lovely basalt countertop for your kitchen remodel? I didn’t think so.

Gabbro makes a good bench

The map had promised, however, that if we went far enough south we would to get to the intrusive part of the ophiolitic sequence: that elusive gabbro. But would I find it before we got the the very steep cliff that drops off the south side of Mount Erie and attracts to hang gliders, parasailors and rock climbers to the area? It made sense that I would: the developed crystal structure of gabbro, like other intrusive igneous, gives it great hardness and durability – if anything could survive the scraping and gouging of the glaciers, this would be it. So as we neared the summit I was taking my time and peering closely at every outcrop. I saw nothing that would tell me that the rock wasn’t gabbro (it was pretty dark colored, but by no means black; it didn’t show any flat spots, like slate or schist) but the lichens continued to homogenize everything.

But just as I almost caught up to others at the lunch spot on the summit, I saw a spot that looked different. It was right near the edge of paved trail, and perhaps someone had broken off a piece when building the forms. (I should mention that there is also a road that leads up to the summit, and a big communications facility of some sort.) On closer inspection, I could see a dark, sort of greenish rock with a definite crystal structure – just what I’d been looking for! I stupidly forgot to take a picture of it – the nearest thing I have is one of Cindy and Janet sitting on the gabbro and gazing at the view.

Did I mention that it was a beautiful day? I had never seen the Olympic Mountains so clearly without actually being on the Olympic peninsula with them. But the big surprises were the views of Mount Rainier and Glacier Peak. The latter is always a special treat, since it is so far back toward the Cascade Crest, and so far from what passes for civilization, that you hardly ever get a good look at it. Indeed, the summit of Mount Erie is, to my knowledge, the only place anywhere where you can drive and get a good look at Glacier without a significant amount of hiking.

Glacier Peak and Whitehorse Mountain

On the way back we took a slightly different route, visiting the summit of Sugarloaf Mountain (if I dare use as grand a word as “summit” for the top of this hill). As you can see from the picture below, the exposed bedrock is a bunch of lumps. [Now, I am only talking about the rocks, to be sure.] They are typically lichen-encrusted and I wasn’t able to find any pieces with fresh faces [Really, just the rocks!] so I can’t say anything about their composition, but I’m betting that these are the pillow basalts that also a typical component of an ophiolite. That made it a very good day for me, geologically speaking.

Pillow basalt(?) on Sugarloaf (with hikers)

On the way back we ran slightly afoul of the “too many trail” phenomenon, but as always, Pat led us back to our cars. I really don’t know how he does it in places like this and in the Chuckanuts – I would be in deep doo-doo without my GPS

Epilog

And if you think that was a lot of geology talk, you ain’t seen nothing yet. Once I got started writing about ophiolites, the professor-that-refuses-to-die inside me took over and just wouldn’t shut up. Figuring that not everyone is enthralled by the niceties of orogeny and geologic history, I decided to split most of the ophiolite talk off into a separate posting with a clear “reader discretion is advised” warning.

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The fair ophiolite of Fidalgo Island

Filed under: Geology, Hiking, North Cascades — geezerwriter @ 10:18 pm

This posting is an addendum to one about our hike last week to Mounts Erie and Sugarloaf on Fidalgo Island. Most of that island, which includes the city of Anacortes, gateway to the San Juan Islands, is built on a bedrock base that is called the Fidalgo Ophiolite. Ophiolites have played an important role in a part the history of geology that has some special meaning for me. so the amateur geologist in me, who always likes to rattle on about geological points of interest, got carried away on this one. So I pulled out most of the general talk about ophiolites so that it wouldn’t completely submerge the hike.

So be warned: This is almost entirely about geology and science history, and my experiences with them, and not about hiking.

Another warning: I have absolutely no credentials in the field of geology, just a lifetime of interest in same and a one year sequence of college courses in 1958-9. My main reason for writing all this is to test my own understanding – one of the best ways of testing your understanding of a subject is to try to explain it to someone else. [If you are a REAL geologist, I would appreciate your letting me know if there is any serious BS in here.]

If you can tolerate some pretty heavy geology lingo, the Wikipedia entry on ophiolites has some nice drawing and photos. It was the first place I looked when I started this investigation, and the density of the jargon also was factor in making me want to explain this stuff in simpler language.

Structure

An ophiolite is not a kind of rock, but a series of different kinds of rocks appearing together in one mass. It consists of all or most of these elements:

  • Sedimentary rocks
  • Pillow basalts
  • Basalt dikes
  • Gabbro
  • Mantle rocks

How did all these very different kinds of rocks come to be clumped together in one mass? There are two situations that could account for it, and there seems to be some disagreement about which is more prevalent, but either will do for our purposes:

  1. Rift zones like the Mid-Atlantic Ridge, where the seafloor is being stretched; It cracks and new material wells up from the earth’s mantle to fill the crack and form new crust.
  2. Volcanic island arcs like Hawaii, where a hotspot in the mantle causes volcanoes which grow up into islands.

But in either scenario, the main point is that they originated somewhere far out in some ocean, and that is widely agreed upon.

I find it easier to picture the island arc situation, so I’ll base my explanation on it.

Volcanic Island Arc Ophiolites

So picture Hawaii. Not so much the hulas and Waikiki Beach but rather the big volcanos that have grown, and continue to grow, thousands of feet above the surrounding seafloor, all the way up to the surface of the ocean and beyond. They emit lots of lava, and lava that cools in water, whether it is extruded under water or runs down off the newly formed land, forms into hummocky mounds called “pillow basalts”. And remember that most of the mass of the islands is below the surface, so there could be a lot of pillow basalts down there.

Some lava doesn’t gush out onto the surface, but rather seeps into cracks in the nearby crust, forming flattish plates called dikes. And after millions of years, there would be a lot of those, too.

And the main culprit in the island formation is a big, fat ball of magma (a “magma chamber”) extending down into the mantle, below the crust. (“Magma” just refers to molten rock that has not reached the surface; it is not called “lava” until it erupts.) Magma is a mixture of a number of different minerals, and over time the heavier (and coincidentally darker-colored) minerals tend to sink to the bottom; the lighter ones rise to the top and are more likely to erupt. Oceanic rocks don’t generally have huge amount of the lighter minerals, but the magma does get darker and heavier with time. When and if the volcanic activity quiets down and the magma cools, it forms a rock called “gabbro” which is coarse-grained and crystalline like granite, but much darker in color.

And the magma chamber is either in the mantle or resting on it.

So all but one of the components of the typical ophiolite are accounted for by undersea volcanic activity. What about the sediments? Remember that all of the volcanic activity takes place over an enormous period of time, likely with lots of time between eruptions, during which time the new rocks that are at a higher elevation would begin to erode and wash sediments down onto lower ones.

But nothing goes on forever, so at some point the hotspot cools down or moves away, erosion and sedimentation continue, and the whole thing becomes a docile island archipelago.

The plot thickens

Now as long as all this stuff stays on the bottom of the ocean, it would just be run-of-the-mill ocean bottom that no one would ever have reason to comment on, or even see. One of the key aspects that I neglected to mention earlier is that the term “ophiolite” refers not to just any old clump of oceanic crust, but one that shows up on dry land as part of a continent.

The most likely scenario is this: Two sections of the crust are moving towards one another. If one side is composed mainly of lighter weight continental rocks and the other of heavier oceanic stuff, the oceanic plate will sink and be shoved under the continent, making a “subduction zone”. This is what is currently going on just off our coast, where the Pacific Ocean is giving the west coast a massive wedgie.

When two pieces of continental crust collide, however, there will likely be a huge smashup and the crust will crumble and fold and make a great big mess of everything, such as when India crashed into Asia, forming the Himalayas.

Suppose we are looking at a subduction zone with the ocean floor sliding under a continent. [Of course “sliding” is a ridiculously gentle word to describe a process that is enormously violent and goes on for thousands of years.] Now suppose that an old island arc or an old piece of mid-oceanic ridge is carried by the oceanic plate toward our subduction zone. Being at least partially composed of lighter material, it might not slide willingly down into the trench but rather just jam up the works. The forces that are causing the plates to move toward each other are not likely to give up so easily, causing a smaller (but still huge) scale version of the Himalayan thing.

Many times the offending arc is probably forced down under the continent, where it will be remelted, maybe appearing later in volcano somewhere on the land. But now and again the arc might break off from the oceanic plate and be shoved up onto the continental plate and we have an “emplacement” of an oceanic formation onto dry land – an ophiolite is born.

Plate Tectonics and Me

When I took Physical Geology in 1958, the whole idea of “continental drift” (now called “plate tectonics”) was dealt with in my textbook in one paragraph and treated as a childish fantasy; ten years later it was well on its way to being accepted as the principal mechanism of landscape formation on earth. Structures like the “Ophiolite of Fidalgo Island” were an important part of that major achievement in the history of geology and all of science. Ophiolites had long been identified and studied in mountain ranges like the Alps, Andes and Himalayas, but once their mid-oceanic origin had become clear the question became, “How in heaven’s name did they come to be in mountain ranges, especially ones far from any ocean?” Of course I should have said “any present-day ocean” but in those ancient times, it was believed that oceans and mountains tended to stay put and didn’t go gallivanting about the planet! The idea that a chunk of oceanic crust could break off in a collision between continents and end up on dry land would have been quite fantastical.

I was one of those childish types for whom drift made a whole lot of sense. I found the conventional schemes for explaining mountain formation to be contrived and even preposterous. They would have required that rocks go up and down, forming synclines and anticlines, but with no mechanism to explain that movement. Why was it respectable to suppose that rocks were going up and down, but childish to think that they move from side to side? Especially given the whole “gravity” thing? I was more than a little insulted by this. This caused a lack of respect for geology and geologists that contributed in no small way to my changing my major from geology to mathematics. (The fact that I was studying geology in northern Indiana, where they don’t have any geological formations more exciting than a sand dune, also contributed to my disaffection. For our big field trip, we had to travel almost 100 miles to find an exposure of bedrock: a limestone quarry.)

You can imagine my surprise when, just about 10 years later, I was browsing in the Natural Science Library at the University of MIchigan (trying to avoid working on my thesis) when I saw the words “Continental Drift” in large letters on the spine of a thin volume, and found that some of my fellow “childish fantasists” were actually able to get books published on the subject. And there was no small amount of undeserved smugness involved, as you can also imagine. Much later I learned that a very distant relative of mine (about a 7th cousin, with the common ancestor living in the 18th century) named Bruce (or Bruus) Heezen was an oceanographer who had led the first oceanic expedition that actually succeeded in measuring the expansion of the sea floor in the Atlantic Ocean.

Epilog

Scientists make lots of mistakes, but science generally gets it right. Eventually. There is no particular reason to think that any scientist’s opinion is any better than anyone else’s, and even a well designed scientific study can sometimes result in bad conclusions, especially in “soft” sciences like sociology but even in “hard” sciences like geology where it is often difficult or impossible to run controlled experiments, because of the enormous scale of the phenomena being studied. But the broad body of scientific investigators, testing and bickering and fighting and challenging each other’s results, ultimately filters out the nonsense. The process is often not very pretty (e.g., the recent hullaballoo caused by some climate scientists questionable handling of data) and is often confusing to the lay observer (e.g., the aforementioned hullaballoo) and can take a very long time (Galileo is a good guy, now. Right?), but the results are ultimately more reliable than reading Tarot cards or chicken entrails.

February 21, 2010

Coal Mine Snowshoe

Filed under: Geology, Hiking, Mining, North Cascades — Tags: , — geezerwriter @ 1:14 pm

I hadn’t been out on the snowshoes for awhile and was feeling the onset of a case of cabin fever, and the weather forecast was good, so on Monday I went up into the mountains to see what conditions were like on Coal Pass Road. I hadn’t been up there in quite a long time since there has been too much snow at low elevations for the last few years – you have to be able to drive up to an elevation of about 2500′ in order to make it a reasonable hike up to the end of the road in the vicinity of Coal Creek, where there are some great views of Mount Baker.

The road is one of several in the area built back in the 1930’s by the Civilian Conservation Corps. I attended a presentation about the CCC several years ago sponsored by the WWU Lifelong Learning program where these roads were discussed. Lately I have seen it referred to as “Coal Creek” Road, but that seems to be another bit of the local geographical silliness – anyone would expect a road with such a name to travel up the valley of the eponymous creek (e.g. Canyon Creek Road) but this road runs up a ridge between Davis Creek and Deep Creek for most of its seven mile length before it even approaches Coal Creek. The road does lead to Coal Pass (or it did at one time) so the old name makes at least some sense.

I was able to drive to 3200′ before the snow covered the entire width of the road. After parking the car I packed up and carried my snowshoes, assuming that this first patch of snow wouldn’t stretch very far. And in fact it extended just beyond the next curve in the road. Aside from one more pretty good snow patch at a creek crossing, it was just bare road for almost a mile, where I was within spitting distance of the end of the road. The snowshoes were still optional at this point, but at least there was enough snow to justify hauling them up the road. (BTW this is at an elevation of 3800′, considerably above the level of the White Salmon lodge at the Ski Area.)

Coleman Glacier Area

The first viewpoint was a bit disappointing. The trees have grown a bit, and although the day was lovely and sunny, Mount Baker was mostly obscured by clouds, with just a few peek-a-boos up into the Heliotrope Ridge / Coleman Glacier area.

I called this “the end of the road” but it is just decommissioned at this point – the old roadway continues on toward the site of the old coal mine that gives the creek and the pass and the road their names. Since it was still quite early and I hadn’t gotten much exercise yet, I headed up toward the mine. It is a bit of a slog since, in addition to the young alder saplings and the occasional fallen tree, the roadway is cut several times by ditches marking the sites of removed culverts.

Chute leading up from mine site

Chute leading up from mine site

A hundred yards or so from the mine, you have to leave the roadway and go downhill for awhile. The tangle of alders gets worse at this point and the trek devolves into a true bushwhack. Not in the sense of getting lost, since you can see the destination all the while – you just have to whack a lot of bushes. And all of a sudden I came across a cleared out channel running right down to the mine site – almost like a mini-half-pipe. (The picture looks back up the “pipe” from the mine.) I have no idea why it it there, but I took advantage of the absence of “bushes” and headed on down.

Part way down the chute the snow had melted from one side, exposing a pile of shiny black rock with brownish-gold frosting on some surfaces. I’m no expert, but I took this to be coal of the high-sulfur persuasion. It didn’t look very much like the stuff we had in our coal bin when I was a kid, but who knows how much that had been processed before I saw it? (And then there is just the remotest possibility that my recollections, sixty-odd years later, might be ever so slightly less than perfect.) I brought home a couple of small pieces with the intention of trying to see if it burns, nut I haven’t gotten around to that.

Coal?

I had intended to poke around the mine site but it all of a sudden dawned on me what a stupid idea it would be to walking around near a place where there might be very deep holes with the ground obscured by snow, even if seemed to be only a few inches deep.

So I kept to the high ground as I headed back to the old roadway and further on up toward Coal Pass. But the roadway quickly turned into such an impenetrable thicket that I couldn’t be sure if I was still on it. At one point I even circled back onto my own tracks. So I acknowledged defeat and headed back down.

Mount Baker summit in the clouds

Back near the “end of the road” there is a spur that heads up to a logging yard and provides another marvelous viewpoint. By this time the clouds had thinned out a bit but the view was still quite limited.

So the trip was a bit of a bust by a number of objective assessments – very little actual snowshoeing, no exploring the mine, no trip to Coal Pass, not much in the way of photography – it was still wonderful to be out in the sun and the fresh, chilly air. And whenever I stopped clattering around on the crusty snow, the silence was almost perfect, except for a brook here and there or the rare birdsong. That’s something you’re not likely to enjoy at Heather Meadows.

February 7, 2010

Cub Creek, Schmub Creek

Filed under: Hiking, North Cascades — Tags: — geezerwriter @ 12:12 pm

What has been a pretty boring hike took on several new aspects on Thursday. It is called the Cub Creek Trail, but that has never made any sense to me. Neither “cub” nor “creek” nor even “trail” is particularly apt for describing this hike.

The first time I did the hike, it was a steepish slog up an old road called the Wickersham Truck Trail, which runs from the so-called North Lake Whatcom trailhead (located, in the spirit of geographical confusion so common around here, near the southeast end of Lake Whatcom) up and over the southern end of Stewart Mountain to Highway 9 near the small town of Wickersham. It is gated now and its main use is as an access road for a set of high-tension power lines that carry BPA power between stations in places like Sedro Woolley and Monroe to the south and Bellingham and Custer to the north.

No one seems to know where the eponymous “Cub Creek” is. The local legend is that someone once saw a bear cub near a creek somewhere around here. But this route does not follow any creek at all. Early on you can look down on and hear Smith Creek, a sizable stream, to the north, and the map shows a small intermittent stream to the south, but the road actually climbs up a ridge. There is nothing “creeky” about the trip at all.

A few years ago there appeared at the edge of the parking lot a new path which is an honest-to-goodness trail, winding through the woods for about a half a mile until it rejoins the Truck Trail. This year Pat and Ron discovered a couple more new trails that leave the road and rejoin it higher up. One of them is, in part, apparently an old road, probably for logging, that has been decommissioned long enough for some substantial trees to have grown in the old track, some with trunks approaching a foot in diameter. Other parts of the trails have been built more recently by local mountain bikers. The upshot is that most of the first two and a half miles of hiking can now be spent on actual hiking trails, rather than winding amongst the power lines on a gravel road.

Change can always be difficult, but everyone was quite pleased to be spending more time in the woods, even if some of the trail segments were a bit on the steep side. (I guess fat-tire bikers like stuff like that.) After a couple of miles on the road we came to a fork where we had to decide how to complete the hike. Last year we had taken the left fork, which led to a pretty horrendous slog through heavy snow along another decommissioned road that was choked with alders, but led to a broad logged-off summit with nice views out toward the water and the Canadian mountains, and a decent view of Mount Baker. But that Baker view was partially obscured by another summit, slightly higher and also recently logged, which has been beckoning to me ever since.

Mount Baker and the Sisters

I knew how to find the road leading to that summit, too, but we had never gotten within a mile of it in previous years. But we had gotten an earlier start than usual for this hike, so I talked the group into going for it. The road stayed fairly level for well over a mile but then climbed rather steeply up the last 400′ or so. After almost six miles and 3000′ of elevation gain, we came out on a broad, unbroken view of Mount Baker and the Twin Sisters Range. From that point of view they seemed almost to merge into one massif, although Baker is 4000′ taller and about ten miles further away.

Beaver Lodges?

The only things interfering at all with the view were a line of enormous piles of logs and sticks. Some thought they might be lodges built by some very thoughtful beavers in anticipation of a rise in sea level due to global warming; others thought they might slash piles left from the recent logging operations. That will have to remain a mystery for now.

The Sentinel

But as often happens, the piles/lodges, while not particularly lovely to look at in themselves, did provide some foreground interest. In particular, there was one forlorn little tree that stood proudly on the corpses of its fallen brethren and framed the distant mountains.

The return trip was uneventful, and more pleasant than in the past. The new trails were a great relief to the legs after pounding along for many miles on the hard-packed roadway.

Another improvement would be to find a route from this “new” summit back to other summit and back to the fork in the road, giving the trail a “lollipop” form, rather than just out-and-back, and cutting out even more of the road.

And I propose that we rename this hike to something more suggestive of its new character. Perhaps “Stewart Summit Trail” or “South Stewart Trail”?

Old Stuff

In early January a bunch of us went snowshoeing up at the Heather Meadows / Artist Point area. I got lazy and never wrote anything about it, and now I’ve forgotten whatever is was I might have written. But I did get some pictures that I liked, so I will just tack them on here, without further comment:

The North Cascades

Gary, recumbent

Camp Robber

Fred, Cindy and Amy framing Shuksan

Pillow drifts by Table Mountain

Baker

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