Here is another true statement: “Conservatives did not invent taxes.”

As far as I know, both of these statements are correct and historically accurate. They are both true.

Combined together, by simple addition: “Liberals did not invent taxes and conservatives did not invent taxes.” Another way to say it is “Neither liberals nor conservatives invented taxes.” But these two statements are not quite the same.

Each true statement, taken separately, can be described as a half-truth (½T). The question is how to put them together, by addition or by multiplication. Does a half-truth plus a half-truth yield a whole truth (½T + ½T = T) or does a half-truth times a half-truth yield a quarter truth (½T x ½T = ¼T²), only we also have multiply the units and get square-truth. What??

Multiplication can be thought of as a mathematical metaphor for two different kinds of experience, repeated addition or a blending of properties. So, 3 inches time 2 equals six inches, and 2 inches time 3 also equals 6 inches. But 3 inches times 2 inches yields six square inches. Fortunately, we have a clear physical picture of what a square inch is, so the blending of the two dimensions is not confusing. Square truth??

The power of language lies in its ability to create virtual worlds by the simple manipulation of grammar and vocabulary. That is true of mathematical language as well as cultural language. It is a power that is dangerous if the mind gets too absorbed and intoxicated by the unreal intensity that is easily generated, particular by modern technologies.

Back to square truth. Here is a word combination that flows strictly from the rules of algebra. Is there a way to put ordinary meaning into these words? The second combining statement above, the one that starts with “Neither..”, does this. This statement points to the possibility of something larger than the simple polarity of liberals and conservatives, putting these two contending groups into a larger historical framework. Like √-1, symbolized by i, we know the number exists though we cannot write a numeral for it.

Square truth. It’s just that for which the truth is the square root of! Like many radical ideas, it may not be expressible in numerals. Mathematicians call that irrational. Perhaps it is irrational to think that there is something beyond the polarities of argument about “who’s better than who” (see Seuss:The Big Brag (Yertle the Turtle)).

I have argued elsewhere in the blog that the mominalization of the adjective “true” into the noun “truth” is something that should not be done casually. I would go on and assert that “truth” is always partial, and therefore subject to the multiplication of fractions rules. As a direct consequence, as we learn more and more about the world, the fraction of knowledge we have, compared to the implied whole, gets smaller and smaller! That’s a little scary, and humiliating.

Even in the parlance of the street, the contradiction is clear. “You talk the talk! But can you walk the walk?”

Philosophy is talk about talk. It is talk about the difference between “talking the talk” and “walking the walk”. In philosophy, all you can do is talk about it. In the actual world, you can shut up and walk away. But then, there is nothing left to say. The ones who get their power from talking are left speechless.

I just got up and walked away- to get a glass of water. You couldn’t know this without my telling you because we are not sharing real space and time. We are only virtually together.
I am here in my now and you are somewhere else in the future of my now. In a non-literate world, one without written words, we could only communicate when sharing space and time. Gradually, mechanisms developed for communicating across time and ultimately space, leading to written words. So now we can pretend we are sharing space and time and experience. That pretending creates a “virtual” world, a world of essences derived from walk-world but is still only in the talk-world.

In this virtual world, we also lie to each other. Of course, people can be deceptive face to face, but they can also be discovered or suspected. We can also be honest, face to face. But the written word is always a lie. That may seem a strong thing to say, so let me follow up on it a little.

“I just got up and walked away..” I wrote several lines above here. While that was a true statement, it was not the whole story. It was not everything I did or thought. It did not place my action in any kind of meaningful frame of reference. I left that all up to you. If I had set about to fill all that in, I would still be writing about the glass of water! To completely exhaust the subject, I would need to write forever for after I finished writing about the glass of water I would have to write about the writing about the glass of water and… Let’s not go there. Only computers are stupid enough to chase their own tails into logical oblivion.

So I employ my own internal editor to decide what to write and what not to write. Now, I am an honest fellow and altruistic in the extreme. So in the editing that I do while I am writing this for you, you can be assured that I am not forwarding my own personal agenda or lust for social prominence, or any other kind of lust. Trust me on this one!

One can communicate the real world only in a limited way. You can throw a stone only so far. But one can communicate virtually a great deal more. Even so, what is left out of the communication is greater than what is included. How the communication is shaped is determined by the internal editor of the communicator. That editor is subject to the conscious and unconscious impulses of the human being doing the communicating. Like all other human beings, the communicator lives in social setting that is, one way or another, a dominance hierarchy. Our communication skills have been shaped and honed not just to send signals about our environment, but also to facilitate our struggles for our desired place within that hierarchy.

Whenever we speak or write, we have as part of our agenda how that speaking or writing affects our struggles within the social hierarchy. And it is so much easier to lie when I don’t have to look you in the face! Trust me on this one!

I’m not sure all of this hangs together very well. Maybe you have something to say?

Blue gem mineral

A couple of weeks ago the very prolific Callan Bentley at Mountain Beltway raised some speculative questions inspired by the concept of mineral evolution, the idea that the mineral suite of the Earth has changed over time. I’ve been mulling over this proposition since, more or less in the back of my mind as more pressing personal happenings have been going on.

First, there is a terminological issue. The word “evolution” has meant very different things to different people over the centuries. Like most, if not all words, you cannot be assured that the etymological roots are anything other than a guide to the history. In today’s world, the word automatically brings up the name Darwin, even though it meant very different things to Erasmus than it did to his grandson Charles, who used it only sparingly.

Taken as its roots imply-unfolding in time-, the concept of mineral evolution would follow directly from logic of thermodynamics and an expanding Universe. Particular minerals, such as the one shown above, will form in environments wherein they are stable, or at least closer to equilibrium than whatever was there before. The parameters of the environment, as far as minerals are concerned, are temperature, pressure and composition. Consequently, in a Universe where energy is constantly dissipating, temperatures will constantly fall, and new, conceivably unique patterns of temperature, pressure and composition come and go. Predictably then, mineral suites will  change with time, with or without life!

Which takes me to Kelvin.

Geologists typically know Kelvin in the context of the age of the Earth debate. Geochemists and others whose curriculum involves thermodynamics know that aspect of his work: entropy, Kelvin scale, so forth. Never the twain should meet! But, in fact, they do. Albritton, in his book The Abyss of Time points out that the late 19th century debate between Kelvin and the geologists centered not so much on the age of the Earth as on the nature of geologic history. Kelvin’s  argument was not with Darwin the geologist, but through Lyell, with Hutton and his memorable phrase “no vestige of a beginning…” that we have all read, somewhat uncomprehendingly.

We read Hutton with difficulty, but not because of his writing style. You can check it out for yourself ( Theory of the Earth)   . What makes him difficult to understand is that he was writing in a thoroughly Aritotelian frame of reference that has eternalism at its base. Furthermore, he had no chemical atomic theory, no way to distinguish between fire, heat and phlogiston. No oxygen in his vocabulary. What he did have was the awesome ghost of Newton and the image of an eternally revolving system of Sun and planets. In short, at least according to historians of Geology like Martin Rudwick (Worlds Before Adam), no sense of geologic history as a series of unique events unfolding in a unique, non-repeating sequence.  This was the Huttonian foundation for Lyell’s cyclical uniformatarianism which made such difficulties for his admirer, Charles Darwin.

The mineral at the top of this page illustrates mineral evolution in the sense that it almost doesn’t exist. The conditions of temperature, pressure and composition that it requires are rarely achieved in the Earth, so it occurs in only one or two places on Earth. Fortunately for me, few people prize it as much as I do, so the price for this small example was within my wife’s birthday budget for me when I turned 65. I wore it as an ear stud until she passed.

Most of what I know factually about the Bucks Batholith is in the literature referred to. My fantastic ideas about how it came to be the way that it is can correctly be left to expire on their own.

But if you are interested in what happens inside an intruding body of  magma, particularly near the top, there is a fact or two here you might find interesting and that are not reported in the literature to my knowledge. Plus a bit for the paleomag buffs.

GDT

I have raised the question that one should be careful in the use of language, suggesting that some easily and commonly made word conversions, like nominalizations, are correctly critisizable on the basis of whether or not they map something that actually happens in the world. Here is a another opinion:

“Once the human intellect creates  symbols from reality, those symbols or words can be manipulated and catalogued to increase our understanding of reality. “(The Trivium: The liberal arts of logic, grammar and rhetoric : Sister Miriam Joseph  (Paul Dry Books Edition 2002)) p.24

I think this statement is true, but I’m sure it is not the whole story.

Unfortunately, when you try to tell the whole story, the language begins to bend around on itself, like the proverbial snake biting its own tail. We can find our way out of the confusion with a map.

In fact, that is where I got started in this whole business, talking about maps with students in the classroom. First, draw a map of how to get from home to school. Then go on to written messages versus maps, visual and verbal problem solving, right brain and left brain, algebra and geometry, grammar and vocabulary of maps. It took two class periods altogether. Toward the end I would ask who drew a perfect map. Usually no response. Sometimes “What do you mean by perfect?”

My response: If it solves the problem of instructing someone how to get to your place, it is perfect. Now several people volunteer that their maps were perfect in that sense. But still imperfect in two basic ways: uniformity of scale, and suppression of detail. So I point out that the utility of the map for solving a real world problem is directly dependent on those very distortions. A map that was free of all distortions and that fully recorded every detail of existence, were it possible to construct such a map, such a map would be useless for guiding the person to your place. It would be like pushing them out the door and saying Try!

So is the map true? Most student said yes. If it solved the problem, it was true.

The ethical question comes up when you ask “What if you made this map and somebody used it and got lost because of some distortion you put on the map, and suffered harm because of getting lost. Whose fault is it? Now there is some debate

But if the map were the Truth, there is no debate. It’s the traveler’s fault for getting lost.

A map, which is a statement in visual language, can be true. A statement in verbal language can be true. The word “true” is an adjective, and as such, in my limited understanding of such matters, in the jargon of Aristotelian thought, is an accident that is a property of a substance, like the blue color of the mineral azurite. The nominalization of the adjective to the noun, “Truth”, brings forth a substance, something that exists in and of itself.

But would Aristotle approve of this switching from accident to substance? In conversation with a knowledgeable friend, I was reminded that nominalization was introduced into English by the Norman Invasion (1066 CE).  Before that, the Anglo-Saxons who were uttering the forerunners of English had no such word as truth! No wonder they lost.

Which brings up the always underlying historical question:”When did it come to be the way it is now?” Could Aristotle conceivably approve the moving of an idea from one kind of Platonic entity (accident) to another (substance)?

The substance , being substance, can be possessed by some, and not by others. Those that possess it are exalted in power and held blameless for the execution of that power, no matter how hurtful. Those that do not possess it are debased and held responsible for their own misery.

One could become cynical about it all. I prefer to remain a skeptical optimist. I am skeptical of all maps, visual, verbal, mathematical, whatever, knowing that they can only imperfectly capture the actuality of the existent world. I am optimistic that the human community will continue its quest to create ever more precise and subtle maps to solve the problems that bear down on us in our actual existence.

The virtual world created by words has enthralled us for millenia.

Once upon a time....

But somewhere there is a baby crying.

Enough of this eclectic plagiodoxic rambling!

One learns about fractions, proper and improper, somewhere in grade school, along with how to convert the improper ones into proper ones. After grade school, no one worries about their propriety anymore.

In other words, “improper”, in the sense I am trying to use here, does not mean you should never, never do it. It’s more like “it isn’t quite what it seems to be- so be careful”.

Consider these two statements:

• The sky is blue.

• There is blueness in the sky.

In the second statement, the adjective “blue” has been changed to the noun “blueness”. This is the process of nominalization, the conversion of a word, usually a verb or an adjective into a noun.

The core of my assertion is that the conversion of the adjective “true” into the noun “truth” produces something that is not quite what it seems to be, so be careful!

Back to the blue sky. Here is a photo of a really blue sky.

Blue Sky at the Four Corners

Here is something else that  is blue.

Moki in hand

The object I am holding here is known in the trade as a moki marble. Usually they are white. I bought a bag of them in a shop in Moab, Colorado, on the same trip that I took the Four Corners photo of the Blue Sky.

The following statements are valid:

The sky, in the photo, is blue.

The moki marble, in the photo, is blue.

No problem.

In the photo, there is blueness in the sky.

In the photo, there is blueness in the moki marble.

Now we have a problem.

Geologically speaking, the moki marble is an azurite concretion, a small stone weathered out of a larger mass of sandstone as a spherical body because a spherically shaped zone within the sandstone was particularly tightly cemented, oddly, in this case by the blue mineral azurite, and so this zone was resistant to erosion. That means that the blueness in the moki marble is due to a substance, the azurite, that can actually be physically separated out and possessed by someone. So the abstraction and conversion of the adjective blue into a noun blueness is paralleled by the real-world action of dis-aggregating  the azurite from the sand.

Can the same scenario play out with regard to the blue sky? Or the blueness of/in the sky? Is the sky blue because it contains a blue substance?

Well, no. For a fuller story of the blueness of the sky, I emphatically recommend Peter Pesic’s delightful little book Sky in a Bottle (MIT Press, 2005). Art, religion and science chase each other around. “The sky is blue! Calculate Avogadro’s  number”.  “The night sky is black. Calculate the age of the Universe!”

There is no substance  in the sky that makes it blue the way the azurite is a substance that makes the moki marble blue. Even so, both the statements about each having blueness are true statements. But is either statement the truth? What can we say that is true-blue?

Along the timeline of existence words came into being, phyllogenetically, some sooner than others, just as they do in our individual lives, ontogenetically. “Truth”, a noun, came from “true”, an adjective, by the process of nominalization. That the word “true” came before the word “truth” is indicated by how they are defined. “Truth” is defined by using the word “true”, but “true” is defined in a way that does not use the word “truth”.Therefore, “true” came before “truth” chronologically. Just like sand comes before sandstone.

We know that statements can be true, or false, just as we know, in a more personal way, that people can be honest or not in what they say to us. But is there a substance-like thing that can be properly called by a noun-name, the truth? If it is substance-like, like the azurite in the stone, it can be segregated out and possessed by some, and not by others.

Perhaps I should pause here to see if you have any comments to make?

www.geolsoc.org.uk/spkl

on the above titled subject, at the end of which the question was asked.

The Montclair store had a persistent problem with plumbing and damage to the floor in the meat department, which ran along the southern wall. After noticing this for several months, it occurred to me that the problem could be related to movement on the Hayward Fault, which might pass through the building.

Apparently, that was the case. The Lucky corporation decided to re-locate the store in a new building- the present site- and conducted a series of trenching studies, so they could place the new building completely on one side of the trace of the fault. The economics were such that they could take care of the persistent problem, but would not be too concerned about the long term exposure to seismic problems.

Following this process, I fully expected that the original building would be torn down. No way! It now houses the Rite Aid store. I have shopped there, just as I continue to shop at the Lucky Store. While I am aware of the hazard-shall I park in the basement or on the roof?- it does not impact my daily life.

When I was in the building, I took notice and sometimes pointed out to people, the ongoing deformation of the floor tiles. You can’t see this now as remodeling of the store covered the old floor with carpeting. I happened into the store while this remodelling process was getting started, got my camera, and took these photos of the deformed floor tiles.

Faulted Floor Tile I

Faulted Floor Tile II

The damage was confined to a zone running through the middle of the store. The floor at the entrance, and near the rear wall was undamaged.

The fault dominates the landform in the area, meaning that the basic street grid is laid out parallel and perpendicular, happenstancially, to the fault. That is, the trenchlike cleft in the landscape along which the freeway runs is the result of erosions of the shattered rock along the fault. Of course, the streets, like Mountain Boulevard, were there before the freeway, just as earlier “transportation corridors”- paths, trails, dirt roads- were their before the streets. The result of this cultural heritage is that the building the Rite Aid occupies today is oriented such that the fault slices straight through the building and the floor tiles are very close to being rectilinearly lined up.

Of course, the building structure spreads the stress and strain, so making the exact connection been fault movement and tile deformation would be pretty complicated. But the right-lateral shear (sides compressed together, opposite side sliding to the right) is nicely shown.

I don’t know the age of the building, which would tell us when the tiles were laid. Nor can I calculate the actual amount of displacement the deformed tiles represent. With these two numbers, one could calculated the movement on the fault, and compare it other studies.

Outside, on Medau Place, you can see the effects of the fault in the street.

Painted curb

Faulted Curb: Montclair

Here is a photo and a “painted” blowup  of the offset of the curb. I just took this photo a few days ago. It is across the street (Medau Place) from the building; the line of sight up the curb was better, not obscured by a refuse bin.

This site presents a different problem.
You can readily see the off-set of the curb, measureable in inches, much more than inside the store, that is across the street,to the left. Of course, the building is younger than the street. We know this from documents, and also because the building lines up with the street, which likely shows the street came before the building. So we would expect the curb to show more displacement.

But there is a problem. The curb shows a smooth bending, rather than a sharp break and displacement. We can see a break-and-slip at one place along the curb at a joint in the concrete (Actually, there are several little places along the curb, which you can see if you click on the photo and enlarge). But the majority of the off-set seems to be taken up in the smooth flex part. Rocks, and concrete is a kind of synthetic rock, can bend and flow into smooth shapes like this, but not in the environmental conditions of the Earth’s surface- not even in Oakland! Put that curb under the confining pressure of a few miles of rock, and heat it up accordingly, and it could take that form. But not on Medau Place in the 20th century.

We know how concrete is formed. It is an aggregate fluid and is poured into a form. What the bend in the curb shows is the bend in the form the concrete was poured into. So why was the concrete form bent that way? Why would they do that?

Well, there is a reasonable explanation. Curbs are laid out in relation to surveyed centerlines of streets, as are property lines. After the 1906 earthquake, it became obvious that the legal system would need to deal with the relation between property lines and moving earth. The conclusion was that property lines are displaced along faults along with the earth itself.

When the original survey of the Monclair District was done, probably in the late 1800′s, the centerline of Medeau Place was presumably a straight line, with property lines parallel. Later on, when the curb was laid out, the surveys would disclose the off-set of the centerline, and the laying out of the curve in the curb accordingly. The displacement since then can be seen in the slip at the joint.

But that means that the slip along the fault was known, or should have been known, to the builders of the Lucky Store building. Of course, they could have discounted the danger. Even such an “expert” as Andrew Lawson, in studying the 06 quake, assured the populace that they did not need to worry about any recurrence. The built up stress was dissipated. Danger would not return for many centuries, according to the then experts. It took the uncovering of the trace of the San Andreas Fault in the pit being dug for a nuclear reactor at Bodega Head to prompt a reevaluation of the theory.

From the damaged tiles to the off-set curbs we get inches of off set in perhaps a century of time. The next step is more difficult. If we had artifacts or natural structures that were formed over the last thousand years, we could work with that. But the next thing to look at here is in the range of tens of thousands of years: Palo Seco Creek.

Palo Seco Creek emerges from the groundwater in the gullies and ravines of Joaquin Miller Park, flows through those same declivities northwesterly, crosses the Hayward Fault zone and joins Shephard Creek just below the Montclair Country Club at the head of Dimond Canyon. Thence, now called Sausal Creek, the stream flows through the canyon, across the flatlands parallel to Fruitvale Avenue, and sinks underground close to the bay.

Streams crossing faults is a sport unto itself. Streams are not fixed things, and neither are active faults. Unraveling the intricacies of process and form with two dynamic processes leaves a lot or room for differences of opinion. Given that, and having walked both Dimond Canyon and Palo Seco Creek, and dined at the Montclair Country Club, even hit a few golf balls, every time I walk along Monterey Road, past the country club, creek on my right in that steep little gully, up to the cross-walk where, just as the pedestrian underpass leads under the freeway to the Joaquin Miller trails on the other side, the creek tunnels under the freeway, and borrowing some data from UC, I think of 32,000 years of displacement and what has happened in the world in that time.

Palo Seco Right Lateral: I have "painted" the creek a darker blue in the photo of the map. I am NOT asserting that the offset has been as simple as it appears on this little map.

A roll of adding machine tape stretched out along the street between the country club entrance and the cross-walk would give us a time-line upon which we could note the significant events-significant to us.

• Walking your dog along, the complete history of dog domestication and breeding.
• The extinction of various large mammals in the world, including cousin Neanderthalensis.
• The perhaps complete history of polar bears from the time of their divergence from Grizzly stock 20,000 years ago to their imminent demise due to loss of North Polar sea ice.
• The domestication of the horse, the invention of the wheel, chariot warfare.
• Written language- spoken language had been around a lot longer- words and numbers.

• The retreat of the ice following the Last Glacial Maximum. The subsequent diversification of at least the northern races of humans who followed the retreating ice.

I don’t want to give the impression that I am attempting to prioritize this listing. They are just things that happen to come into my conscious mind as I write this. Obviously, except for the landscape, the world of 32,000 years ago would be frighteningly different from today. I can walk this route today while thinking about getting something to eat without worrying about what other creature might be on the path, perhaps a not-very-Golden-Bear grizzly bear, with the same motivation but with me as a target!

The mind does indeed grow giddy, looking only a little way into the abyss of time, while staring at some damaged floor tiles in a drug store.

Meandering in Vicksburg, Mississippi, 1945

This is the image I had in mind when I read the post at Highly Allocthonous early last month, that started me off on my own meanderings about the digital divide, that I am now closing the loop on.

From my side of the divide there is a certain amount of sediment that is being transported by the river of flowing time. I was 13 in 1945, living in Los Angeles, having been moved there with my family from a little town not far from Charlotte, North Carolina. My mind was certainly not on meandering streams.

Vicksburg, Mississippi is indelibly associated in my mind with images of the  civil rights struggle subsequent to 1945 that my wife and I were involved with, just as Dow corporation is associated in my mind with images of napalm and agent orange from later years.

All of which should have nothing to do with doing geology or teaching geology or being a scientist or blogging about any of these. Even so, it prompts me to wonder what was in the minds of those people in the photo. Men, apparently. Perhaps even Friedkin himself.

Individual motives cannot be read from photos, but institutional rationales are a little safer to surmise. That is, the people who payed for this research I think we can be confident about. They were out to control the river. First understand, then control.

We understand from this side of the divide that achieving that goal is not only undesirable, but is quite likely impossible. Perhaps a little too easily we attribute to the people in the photo aspects of vanity, arrogance,  even hubris. Perhaps a little too easily, I reacted the same way to the Post and its comment stream.

But a question lingers. Does restoring the river come down to controlling it, to making it move backward through historic time to some earlier ideal state?

Ideal state? Whose ideal? Who has the authority to define the ideal? Whence comes that authority? Questions as old as the human community itself.

In my mind, streams follow a sinuous course, in single channels or multiple, even within fixed walls, because the flow is turbulent, perhaps following some demands of  chaos theory.

So I wondered what new stuff has developed over the years about sinuous fluid flow, turbulent flow versus laminar flow, chaos theory and so forth. I can’t remember how I got there, but I was looking at a map that showed the avulsion of the meandering channel of the Owens River. So I had to look up avulsion. Great word!
It led me to the book “Tectonic Geomorphology”: Burbank and Anderson (2001), which I went to Amazon and ordered, along with “California Rivers and Streams”: Mount(1995). I also have “Braided Rivers”: Best & Bristow ed (1998) coming from the Geological Society of London.
Going in the other direction, I dug out my Leopold “Fluvial Process….” (1964), and some other stuff:(Russell-”Rivers, Streams and Seacoasts”1967; Birot “The cycle of erosion in different climates” 1968). I guess there are two places I tend to go to for answers:old books in my basement and new stuff through my computer. Meandering I go, back and forth across the digital divide.

But what causes it to wiggle in the first place?

From Longwell, et alli; 1969 Physical Geology

I searched for Prandtl, not knowing anything about him. He was a pioneer in aerodynamics in the early 20th Century. Boundary layers and separations thereof, subsequent forces.

Wikipedia has a nice piece on turbulent flow and laminar flow. I clicked on a “See Also” topic titled “swing bowling”. It sounded too much like swing dancing to pass it by. Turns out it is a cricket phenomena where the bowler causes the ball to deviate sideways (wiggle?)  by heaving it at just the right speed to keep the airflow over half the ball turbulent and the other half  laminar. The ball, which has an equatorial seam, is kept half rough and half smooth by the players in the field. The sideways force comes about because the separations of the boundaries layers on the turbulent side and the laminar side don’t line up. I think I have that right.

In a stream, what corresponds to the two sides of a cricket ball? I taught that in a stream one can distinguish a laminar flow layer at the contact with the un-moving bed of the stream. As velocity increases away from this surface, at a specific velocity, the flow abruptly changes to turbulent. Then, as flow velocity continues to increase, the flow again changes abruptly to jet flow.  Typically, this occurs at the surface along the thalweg.

Rethinking this now, I wondered what was jet flow, the flow that produces those smooth standing waves on the surface of even small streams, like the one at Alamere Falls? Of course it looks like laminar flow, but it is going too fast, faster even than the turbulent flow.

But fast relative to what frame of reference? For a packet of water moving down the thalweg, the source of friction that would produce turbulence is not the bed of the stream, but the water packet immediately beside it, which is traveling at nearly the same velocity! The jet flow portion of the stream is an elongate lake being carried downstream on the rollers of turbulence. Any flow within it is laminar!

Somewhere in there in the separation of boundary layers on the two sides of the turbulent flow zone sandwiched between the laminar flow at the bed and the laminar flow at the thalweg, those swing bowling side-wise forces arise to start the stream to wiggle! I believe it!

But then I’m just an old igneous petrologist from the geosynclinal era gone to seed in the classroom, now out to pasture.