“8/6/82 Morning. I was sitting here with my coffee, my thoughts turning to continental drift, the various bands of sea-floor basalts and sediment scraped up against the edge of the North American plate, when suddenly I felt a memory tug at me, of a dream I had many years ago, a dream about faults etc., so I went and got some old journals out and started leafing through them in search of a record of this dream. Couldn't find it.
What I did find was a record of the days just before I actually moved out here, in early ’76. The Yelping Bird of Mystery was mentioned—that I only figured out this summer to be a Spotted Owl—and the large flocks of band-tailed pigeons near the springs. Winter of ’75-’76.
My fears of the development of Moody Ridge have all come true, right down to the worst one […]”
[Russell Towle's journal]
“8/6/83 ~ Saturday morning. [...]
Mosquitoes worse this year by far than any year I remember up here.
~ Evening. A few quesadillas for dinner. An hour was spent out on the cliffs before sunset. The day was hot, and it is possible to spend time outside at the cliff without being chomped by mosquitoes. Clouds had built up over the Sierra crest; and as they drifted across the sky upon them I gazed, with delight and fascination, the shapes and shades were noted; a few rain-streaks were [indecipherable] from their bases. I watched and waited and hoped, and all my dreams came true; a rainbow, a majestic glowing rainbow, lasted some twenty or thirty minutes. An outer bow was noted, and within the upper part of the inner (main) bow, four subsidiary bows were seen, close-aligned, and yet suggesting, by the fact that they faded before reaching the lower outer parts of the main bow, that perhaps they were not perfectly concentric ~ as the main and outer bows are ~ but are almost so, with an infuriatingly small, nearly unquantifiable increment of convergence with the main bow in its lower regions.
I waited and watched, so thrilled to see this miracle, and at last, some five minutes after sunset, it waned to nothing, a blue-grey ruffled sky that seemed pregnant and fertile and almost about to really rain, just as the arcs were almost but not quite concentric.
I returned to the cabin for lunch at three-thirty. Aside from a round at dawn, no hydraulicking today ~ no, I did another round at five ~ … ”
[Russell Towle's journal]
Date: Mon, 6 Aug 2001 22:37:44 -0800
From: Russell Towle
Subject: Geology of Sailor Meadow
I remarked upon the "especially thick" section of young volcanics exposed at Sailor Meadow, but neglected to put that into context, other than remarking that generally, all the ridges in this part of the Sierra are capped by these young volcanics. By the way, the volcanics—andesitic mudflows and rhyolite ash layers—are young in comparison with the underlying bedrock, which is not exposed at all at Sailor Meadow. The generalized stratigraphic column, as the geologists put it, is as follows, with youngest at the top, oldest at the bottom, age in millions of years (m.y.).
Basalt. Only locally present, as at Devils Peak. 3 (6?) m.y.; Pliocene.
Andesitic mudflow; the Mehrten Formation. 5 to 20 m.y.; Mio-Pliocene.
Rhyolite Ash; the Valley Springs Formation. 20 to 30 m.y.; Miocene.
Auriferous river gravels; 50-55 m.y.; Eocene.
—a profound unconformity separates the younger rocks above from the older rocks below—
Bedrock; Jurassic and Cretaceous granites, granodiorites, slates, serpentines, and metamorphic rocks of many types, from Jurassic through Triassic and Paleozoic ages, down to near the base of the Paleozoic, as in the Ordovician Shoo Fly Complex, exposed in the North Fork from just west of Sailor Canyon, down to Green Valley. Except for the granitoid intrusives, all these rocks are tipped up on edge, and form linear belts roughly parallel to the Central Valley and Sierra crest.
There is no basalt near Sailor Meadow; it would be found on the highest ridge crests were it present. The Mehrten Formation andesitic mudflows are more a "complex" than a single "formation," since there are many different mudflows, from many different volcanos, which were located near the present crest. These volcanos have been wrecked by erosion, and only remnants remain. The mudflows—also known as lahars—are thickest near the crest, and thin towards the Central Valley, but may still be found even in the lowest foothills, locally, as near Sierra College Boulevard at Rocklin. A typical section in the elevational range of Sailor Meadow might be about 300 to 400 feet thick; at Sailor Meadow, the mudflows are over 1000 feet thick.
It is important to realize that these mudflows came within a hair of burying the entire ancestral landscape. Only a few ridges of bedrock escaped burial. Then came the uplift of the Sierra, and the rapid entrenchment of our present canyons, under the combined impetus of steeper slopes (from the uplift) and increased precipitation (from the Ice Age). So, there was a plateau of mudflow, into which our present canyons were incised; and the remnants of this plateau are the flat-topped ridges so prevalent in this part of the Sierra. I will come back to this below.
Like the Mehrten mudflows, the older Valley Springs rhyolite ash reaches its greatness thickness near the crest, and thins towards the Central Valley, becoming increasingly patchy in the foothills. Here too many different ash layers exist. Some are unequivocally welded tuffs, from nuee ardentes, or glowing avalanches of incandescent ash which solidify into rock the instant they stop moving. The sources appear to have been east of the present crest, with one known vent near Carson City, Nevada. Other ash layers are more like mudflows of ash, but lacking the bouldery, cobbly component of a mudflow. Still others appear to be lacustrine (lake) deposits. This was the first of the formations to bury the ancestral Sierra's bedrock landscape, so it is natural to imagine rivers being dammed, at least transitorily, and huge masses of the powdery ash being moved here and there by erosion. Then this partially re-worked landscape would be buried by still more ash, which would settle deep in the valleys and thin on the ridges; and then this would be again buried. And so on for millions of years. The process of deposition, erosion, renewed deposition, renewed erosion, characterizes the entire volcanic period. Thus there are many "fossil" erosion surfaces within the volcanic section.
Only near the Sierra crest, and thus near the source(s) of the rhyolite ash, are the unequivocal welded tuffs found. Sailor Meadow is part of a broad bench or terrace, which resulted from glaciers stripping away the more weakly-consolidated mudflows above, down to the level of the welded tuff. This welded tuff is often pinkish in color. It is exposed at Sugar Pine Point, and near Soda Springs, and actually at many places, including, of course, all around Sailor Meadow.
Finally, though the volcanic section is unusually thick at Sailor Meadow, over 1200 feet rather than 300 or 400 feet, it should be noted that not all ridges are capped by these volcanics. Just across the canyon to the north stands Snow Mountain, which has no cap now and likely never was capped; it stood too high. There are vestiges of the volcanics on its lower slopes, but none whatsoever on the summit. Probably the safest observation is simply to state that, so far as the pre-volcanic, bedrock landscape of the ancestral Sierra goes, Snow Mountain was high ground, and Sailor Meadow, low ground. The Eocene gravels in Sailor Canyon, just below the level of the meadow, showed that a small river flowed here in Eocene times. This river may have been a tributary of the Eocene river which flowed through Gold Run and Dutch Flat.
Although in the middle elevations, remnants of the mudflow plateau are common, forming the flat-topped ridges, in the somewhat higher elevations near Sailor Meadow they are much less common; here the effects of glaciation were too intense, and the ridges have been lowered beneath the level of the mudflow plateau surface.
The bedrock geology is complicated. Imagine a layer cake tipped up on edge. Carve a nice little landscape into its new top (the layer edges). Pour liquid frosting of many types over this and do a little smoothing between pours. Now cut some trenches through the frosting into the cake, at right angles to the layers. And voila. You have a little model of the Sierra. The granite is missing, but, well, just forget it for now.
Now, what these upturned layers of cake actually are, how old, how they came to be upturned, and so on, is all very difficult and still a subject in flux. With continental drift we have a situation wherein one layer might have come from the south, another from the north, another from the west, and so on; they were rock units "rafted" here from somewhere else and accreted to the continent. But I cannot go into all that now. This was meant just to be some final remarks about the young volcanics—the thick frosting, of Sailor Meadow.
Date: Wed, 6 Aug 2003 07:02:19 -0800
To: North Fork Trails
From: Russell Towle
Subject: Lost Camp: Emergency
The fledgling North Fork American River Alliance (NFARA) has been largely concerned, so far, with the proposed Capitol-to-Capitol Trail. Our next meeting is scheduled for Tuesday, August 19, 7:00 P.M., Dutch Flat Community Center, during which we will hear from TNF District Ranger Rich Johnson and Placer County Parks staffer Vance Kimbrel. The proposed trail will be among the subjects discussed. Be there or be square.
However, upon studying the Timber Harvest Plan for the Lost Camp area, I am convinced that a far more immediate issue demands our attention. We should contact CDF at once and ask for an extension of the public comment period and also that CDF officials meet with us at the Dutch Flat Community Center, to more fully explain the scope and impacts of the timber harvest.
Call either CDF Auburn/Bowman at (530) 889-0111, wait through the recorded options, press "0", and ask the operator to speak to Kelly or another forester, about THP 2-02-040-PLA.
Call CDF Archeologist Rich Jenkins at CDF Redding, (530) 224-4749. Even if you have never set foot on Lost Camp, tell Rich that you have heard that a historic Placer County townsite (Lost Camp), its associated mining sites, ditches, and reservoirs, and at least one trail (the China Trail) are threatened by this timber harvest, THP 2-02-040-PLA, and that you question whether an adequate archeological survey has been performed. Ask for an extension of the public comment period; ask for a thorough archeological site examination by professional archeologists.
Now, unfortunately, I am fairly well sure that many on this list are not acquainted with Lost Camp, and the China Trail. I will lead a hike down to the North Fork of the North Fork American on that trail this coming Saturday, August 9, for anyone interested in seeing what is at stake. Let's meet, 10:00 A.M., at the Alta Store (take the Alta exit from eastbound I-80, turn left, drive up the hill .25 mile, turn right on the road to Alta, cross the tracks, store is on left; park across the street in lot below Fire Station; I will be in the lot in my little Subaru Outback).
We will explore some of the historic town site and mining areas around Lost Camp before walking down to the river. Please call or email me if you wish to attend.
It is quite likely that, however many and loud the objections we will make, the timber harvest will go forward. However, our experience with a somewhat similar, but smaller, timber harvest near Dutch Flat has shown that the plan of operations can be modified. In this particular harvest, several new roads are proposed, totaling in the thousands of feet of length, and one in particular would cross Texas Canyon to the ridge between Texas Canyon and Fulda. We may be able to stop construction of the several new roads, and we may be able to expand the area of helicopter logging, and diminish the area of tractor logging. Suppose we succeed in all these objectives: the Lost Camp harvest will still be a mess.
I am going to survey as much of the site as possible today. More later.
Moraines in the East Fork
[North Fork Trails blogpost, August 6, 2007:Early Saturday afternoon Gay Wiseman and I drove up to Emigrant Gap and then south on Forest Road 19 towards the North Fork of the North Fork of the American River (NFNFAR).
There is a Tahoe National Forest campground where The Nineteen crosses the NFNFAR, a popular campground, and yet one often sees cars parked along The Nineteen, near the campground.
They park along the road in order to walk downstream to a beautiful waterfall and swimming hole. A close examination of the USGS 7.5 minute quadrangle reveals several of the 40-foot contour lines crossing the river near the falls; but for quite a ways further downstream, the gradient lessens, ergo, no waterfalls, and a cursory exploration twenty years ago or so had confirmed what the map suggested.
However, around a mile downstream, several more 40-foot contours cross the river in fairly close succession; hence, there ought to be more waterfalls, perhaps bigger and better waterfalls, with deeper and more dramatic swimming holes.
One always wants more drama while swimming—there can never really be enough—so Gay and I set out to find these supposed waterfalls, and their exciting pools.
While staring at the map, with its many contour lines, I noticed two strange spur ridges, one on either side of the river, one farther upstream, closer to the campground, the other farther downstream, close to Sailor Point. The area lies within Township 16N, Range 12E, in sections 7 and 18.
What drew my attention to these two ridges was their geometry. Imagine if you will a generalized canyon following a straight course. Let the typical cross-section be a simple "V" in shape. Now imagine the contour lines in such a canyon; they roughly parallel the river; they have a "global" direction which is nearly parallel to the length of the canyon.
Now further imagine that the walls of the V-shaped canyon are scored by ravines, and ribbed by intervening spur ridges, which are more or less at right angles to the river, to the length of the V-shaped canyon. Hence although the "global" direction of the contour lines parallels the river, locally, the contour lines bend in around the ravines, and bend out around the little spur ridges. We have defined the ridges and ravines as perpendicular to the river, and the "global" direction of the contour lines as parallel to the river. If we place a ruler so that it intersects all the little local outward bends in the contour lines, where a spur ridge is crossed, or so that it intersects all the little local inward bends, where a ravine is crossed, our ruler will itself be at right angles to both river and canyon.
However, these two little ridges which caught my eye do not exhibit this geometry. If one places a ruler so that it crosses all the little outward bends in the contour lines, it is far from being at right angles to the river. In fact, in both cases, the ruler would lie at approximately a 45-degree angle to the line of the river, to the trend of the canyon at large.
They are both moraines, portions of terminal moraines from a recessional stage or "stade" in the most-recent, "Tioga" glaciation. I say, recessional, because it is fairly clear to me that Tioga ice extended well down the canyon, miles down the canyon, during its maximum extent. The Tioga is somewhat poorly-defined in time: it is well known to have ended about 12,000 years ago, which is a geologic and climatologic blink of an eye, but its beginning point is harder to specify. We would not be drastically amiss, I think, to set the beginning of the Tioga to "about" 20,000 years ago.
To illustrate why the beginning of the Tioga becomes problematic, research has been conducted in recent years in which the sediments of Owens Lake, on the east side of the Sierra, were cored to a depth of a couple hundred feet, and the cores carefully analyzed. During periods of intense glaciation, one type of sediment reached the lake and was deposited. During interludes between glaciations, a different type of sediment reached the lake and was deposited. The sediment cores are longitudinally striped with these alternating types. All that remains is to attach a date to each stratum. This was done.
The Owens Lake sediment cores revealed no fewer than sixteen separate glaciations within the past 52,000 years. Sixteen!
And yet, it is a commonplace among Sierran geologists to refer to the Tioga glaciation of 12-20,000 years ago as having been preceded by the Tahoe II glaciation of 65,000 years ago. Clearly the glacial history is much more complicated, in detail. It is exciting to think that the story will continue to unfold as research progresses.
There is an important reason why geologists remain "stuck" in the Tahoe-Tioga model of glacial sequence: one the east side of the Sierra, so much drier than here, many terminal moraines are well-preserved, and in canyon after canyon after canyon one can see two principal terminal moraines: an older, more blurred moraine, farther down the canyon, and a younger, sharp-crested moraine, farther up the canyon. Sometimes only a little distance separates them. The younger, sharp-crested moraine is Tioga; the older, blurred moraine, farther down the canyon, is Tahoe.
Direct observation leads to the Tioga-Tahoe model.
Of course, as a glacier melts away it retreats up its canyon, and leaves a series of terminal moraines. Actually, if its retreat is steady and rapid, it may leave a formless mass of glacial till slathered over everything. On the other hand ...
It may well happen that during this retreat up its canyon, a retreat which may require well over a thousand years, the glacier stops retreating for a century or two. During such a "stade" the glacier will deposit a much more strongly marked moraine along its terminus.
My two ridges-of-odd-geometry, in the canyon of the NFNFAR, represent two such stades, the younger one half-a-mile up the canyon from the other. The upper, younger ridge-of-odd-geometry is in the SE 1/4 of Section 7, T16N R12E, near the word "Fork" as seen on the 7.5 minute quadrangle, and is on the southeast side of the NFNFAR. The other ridge-of-odd-geometry is to the west, in the NW 1/4 of Section 18, T16N R12E, near the surveyed elevation of 5137'. This moraine is northwest of the river, and The Nineteen cuts right through its upper end.
Both are really rather minor ridges. On the topographic map, they are expressed as a series of kinks in the contour lines.
It is not nearly as easy, here on the well-watered west slope of the Sierra Nevada, to see moraines. They do exist, but they are often inconspicuous. I have a rather short list of such moraines, in my mind: there is a fine figure of a moraine north of Lake Spaulding, visible from I-80 at a distance of several miles. There is a long, brushy moraine complex on Black Mountain, also visible from I-80. Red Mountain has a blurred-into-till portion of a lateral moraine of the Fordyce Glacier, high above Fordyce Creek. And there is quite a distinct moraine at the lower end of Bear Valley. And there are others.
So, having noted the two ridges-of-odd-geometry, I was excited to see whether I was right, or wrong, when I actually got out there on The Nineteen and passed Sailor Point, entering the NFNFAR canyon.
Of course I was right.
It is a very beautiful reach of river and canyon, with pretty stream-polished exposures of the Shoo Fly Complex metasediments, and the giant-leafed Indian Rhubarb all along the water, and many many many giant granite eggs left there by the ice, 12,000 years ago. During our explorations we discovered several old narrow-gauge logging railroad grades which had been pressed into service by Tahoe National Forest as skid trails, twenty-five or thirty years ago. In fact, I was fuming quietly to myself as Gay and I finally climbed back up to the good, the old, the huge Bradley & Gardner, the Placer County Canal. A bulldozer skid trail angled steeply up the slope, and we followed it for a time. Under what possible pretext did Tahoe National Forest allow the canyon wall to be thus scarred for the next thousand years or more?
I can forgive the glacier, in fact, I rather admire its scars.
I can forgive the loggers of the 1890s, who made a few carefully-thought-out railroad grades and rolled logs right down onto flatcars. The loggers of the 1890s lived in an era of rapacity, in which rapacity was so universal that "everyone" did it. But to come along in the 1980s, and make scars on the canyon walls which will easily last a thousand years? If it was Sierra Pacific Industries, whose only view is the bottom line in a ledger, well, that would at least be intelligible.
But since the scarring was on public land, under the management of Tahoe National Forest, I can't shake the feeling the the public trust was violated. It's not a new feeling. When I stop and wonder how it could be that Tahoe National Forest either itself orchestrated the destruction, or stood by and did nothing to avert the destruction, of so many historic trails, in this same area: the Burnett Canyon Trail, the Monumental Creek Trail, the Mears Meadow Trail, the Big Valley Trail, the Sugar Pine Point Trail, the China Trail, et cetera, well, when I recall all that, I am worse than displeased.