Archive for the ‘Teaching Geology’ Category

No defenders of “Truth”?

March 7, 2010

I am not terribly surprised. But it is surprising. “Truth” is a very popular word. You can say the most awful thing about some one and should you be queried why, the most common defense is “It’s the Truth!” Scientists claim it. Relgionists claim it. But no one will defend it?

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!


Meandering acrosss the digital divide III: Pedagogy of a meandering stream

November 9, 2009

My teaching was clearly rooted on the other side of the digital divide from here and now. In it I developed a fairly consistent program for using meandering streams as a means of teaching how geology goes about answering its basic question (how did the Earth get to be the way it is?) by bringing to bear the non-historical sciences, in this case physics.

I started with an in-class problem. The students got a piece of paper with a meander loop drawn on it, and a data set with depth and water velocity. As I recall now I stole the data from something of Strahler’s. Actual stream gauge measurements. That required some explanation of measurement and operationalism. The students plotted the depth profile and the velocity profile across the meander loop. Needless to say, there was a close correlation: deeper water on the outside of the curve, running faster where deeper. Generalizing from this, I showed them how to draw the thalweg down the length of the stream shown on the map, completing the three-dimensional view of the  inter-relationship of process and form.
The next step was to, hypothetically, dump a load of mixed size sediment into the river at the thalweg on the cross-section and follow it downstream, using the stream competency diagram (particle size vs stream velocity). I had to resort to drawing my own version, even if there was one in the text. With it by interpolating velocity at max at the thalweg to zero at the bank, the students could figure out where to look for the sediment: on the next point bar downstream on the same side of the thalweg it started from and sorted out by size.
In the interests of saving time during the term, I dropped the in-class problem aspect and just lectured my way through these ideas. That doesn’t work nearly as well, but I needed to save the time for my other problems that I thought were more fundamental to geology- eight in all. The mysteries of log-scaled graphs, interpolation, and diagrams that show process but are too easily conflated with form just took too long to unravel.

After I felt that I had the students mind thoroughly into the stream, I went back to the cross-section and started talking about the actual point to point velocity and how that could be measured. I re-introduced the turbulence, showing where it maxed out on the outer part of the curve, below the surface, not at the bottom, sometimes with some helical flow. Then, with the bald assertion that the velocity plotted in the competency diagram was a surrogate measurement for the degree of turbulence, which we did not know how to measure, I further asserted-teachers in a classroom can get away with crap like that!-that if the stream was eroding, the point at which the erosion occurred was where the turbulence was maximum where, in turn, velocity changed the most in the shortest distance. That is, below the water surface, on the outside of the  curve, not at the bottom. Sediment removed from that point would leave the unconsolidated material above it un-supported, and it would collapse into the stream. All this stuff would be carried downstream to the next loop and depositied on the point bar, sorted out according to size. Frequently there were students who had swum in rivers, knew where the beach was and where the swimming hole was, and could testify about walking into the water over increasingly coarse sand, pebbles, etc.

The net result of these processes operating was the migration of the asymmetric profile sideways, leading to the side-cutting action of the stream and the accentuation of the meander loop, etc. By introducing some speed-up and slow-down of velocity around the loop, down-valley migration can be accounted for. Oxbow lakes, clay plugs resisting erosion(back to the competency diagram): it fits together beautifully. Occasionally you can see the click on the face of the student when all the various pieces of the puzzle fall into place.

All of this leads easily to saying that once the form of a meander is established, the process that occupies the form will re-create the form continually. The only remaining question was what caused the stream to wiggle in the first place.
I then went through the familiar examples from Leopold’s work of melt water streams on glaciers, the Gulf Stream, the jet stream in the atmosphere, even adding my own favorite examples, streams flowing across beaches, like at Alamere Falls. I could say at that point that meandering seemed to be an inherent property of fluids in turbulent flow, so we have to await a further understanding of turbulent flow from the people who are responsible for that sort of thing, the physicists.

Uncomfortably, the above development implies that all streams should meander. So that required some work on the conditions that rule in non-meandering streams: braided streams (variability of sediment load and discharge) and riffle and pool streams in canyons (flowing water can’t cut sideways into bedrock- the cutting tools are all in the bottom. They are doing the best they can.).

Meanwhile, geologically speaking we could say that the observational evidence indicates that we need refer to nothing beyond the current on-going process to explain the existing form. The independent variables in a stream system are the discharge and sediment load, which are both determined basically by climate. The internal dynamics of the process adjust the form to meet the needs of uniform dissipation of energy. While the process can approximate balance or equilibrium or steady state at the local time scale, so long as there is land above water, the planet Earth is not gravitationally in a stable configuration, and will continue to change at the global time scale. The internal energy residual and generated within the Earth is now, and has for nearly 5 billion years, acted to counter the force of gravity, fueling the continuing and shifting interactions at the surface of the Earth that we call geologic history.

Having spent the last four decades in front of a classroom, dealing with the structured ignorance of the students, I am a little intimidated by the staggering amount of new knowledge the scientific community has compiled while my back was turned, facing away from learning and toward teaching. To be a little more precise, I have been learning, but the thing I have been learning about is hidden behind that phrase “the structured ignorance of the students” and how that clashes with the fundamentals of science. In this process, I have been forced to re-learn those fundamentals again, but trying now to look at them from the point of view of someone who is, consciously or unconsciously, committed to a radically different frame of reference. But that’s not this story!

Alamere Falls 2006

The last Alamere: no beach, no stream

High school earth science: Is it a good thing??

June 8, 2009

I have been “away” for the last few months coping with a birthday (77) and a diagnosis of Parkinson’s disease.  I ran into a piece at Oakland Geology on the subject of earth science courses in high school, particularly Prof Eldridge Moores efforts. That bounced me into writing the current post.

From the Preface: Physical Geology; Longwell, Flint and Sanders (1969) John Wiley.
“We believe the text will be readily comprehensible by students with no more than secondary-school background in physics, chemistry and mathematics.”

In 1969, secondary-school earth science courses were rare to non-existent. But the movement was on, rationalized in many ways, including the currrent ones. I was involved in this period with an NSF project at San Diego State College in training high school teachers in geology.

Then the Law of Unintended Consequences reared its ugly head. We all thought of earth science as being an enrichment of the high school curriculum. But it became a substitution, and that during a time when high school curricula were becoming generally impoverished, particularly in science. My own graduation from a basically average public high school in 1950 required four years of science in the academic track. But that has subsequenty been cut in half.

Thirty years later, when I surveyed my community college students in Physical Geology, nearly half had taken only an earth science course in the physical science category. Another 40% had taken chemistry, 10% had taken physics and all of those had also had chemistry. The remaining  group had nothing at all to report. Perhaps that was in part sampling error or simply due to the fact that a high school diploma is not required for community college entrance in California.

The consequences were as you would reasonably expect. The students who had only earth science were the least well prepared for a college level geology course.

Of course! The students were in my geology course, not in a physics course or a chemistry course, even though these courses also fulfilled the degree requirements. The “average student” avoids math based courses, in high school and in college, and arrives in the geology course with the expectation that nothing particularly challenging is ahead of them. There was occasional outrage at even the necessary reference atoms or elements or equations for gravity or seismic velocity. The students who had no background were at least aware that they were in for some work.

But the “average student” that graduates from a California high school does NOT end up taking Physical Geology at a prestigious University. The entrance requirements screen out “average students”. The aspiring elite students know that to get in to their first choice schools, they have to show high grades in hard courses, so they very well may meet the requirements stated above by Longwell, et alli., wherever they ended up (sometimes in my classes for personal reasons).

I urge you to take these circumstances into account. I am heated about the subject because my own career path took me from average grades in the average high school through a community college to the prestigious University. It is a well travelled path; a high percentage of university graduates follow it- perhaps half. Requirements are coercive. The aspiring elite student is already coerced by aspiration itself. Coercing the less aspiring into learning skills that open up posssibilities is not a bad thing. And in science, chemistry and physics are basic skill courses!

The unintended consequences of adding earth science to the high school curriculum has been the subtraction of basic science skill courses from their study lists by many students, to their ultimate detriment. In the long run, it hurts students and is counter-productive to enlarging the geological perspective that we so desperately need to cope with the problems the world community now faces.

Teaching geology

October 21, 2008

This morning I put that title into Google and hit the button. A typical response followed: a zillion things to sort through. Adding one more to the zillion does not seem significant, one way or the other.

I started in the Fall of 1963, the term wherein JFK got shot. The Free Speech Movement at Berkeley followed the next year, and we were off and running through the 60’s. The question hung over my head for many years: In the face of all that was going on, what was the relevance of teaching geology? Was there any significance beyond being a decent way to make a reasonable living for my family. The answer to that question emerged slowly over the decades. But that’s not my path this morning.

My first teaching assignment was in two courses: Introductory Geology and Physical Science. The latter course was basically physics, for which I was only marginally qualified to teach. Oddly enough, it was that course that was easier for me to handle than the Geology course, for which I was highly “qualified”.  The unfolding of physics from Aristotle to Newton to Einstein follows an historical narrative path that can be followed with only a little algebra. But the geology course just seemed to be a hodge-podge of assorted facts about the Earth, in spite of the then-new Gilluly text. Modern texts have Plate Tectonics commonly as an organizing theme, but I found that only marginally better. The texts present the answer without asking the question!

The physical science  course, and textbook, presented the material along an historical line, the way it was learned in the first place. The pedagogy followed the phyllogeny, so the ontogeny of the individual student unfolded in the same way. Or at least it seemed so to me as I was both learning and teaching the subject. Paradoxically, we don’t teach geology that way. Paradoxically because we ignore our own history when introducing the first historical science. “The mind grows giddy…” said Playfair. Giddy, and perhaps more than a little afraid of the abyss of time.