PLATES D Magnetic polarity

 

Continuing my personal reflections on the birth of plate tectonics…..

During my graduate years at Stanford (1957-60) continental drift/seafloor spreading were much discussed elsewhere, but not – as I recall – by my own faculty.  Bill Dickinson was there and must have been mulling mobilist concepts – but my only contact with Bill was field camp which, for me, was a near-total bust.  Emphasis at Stanford at the time was almost entirely “classical”: how to use the petrographic microscope, make a map, find mineral deposits, etc.  Fortunately there was one “big picture” guy for me to lean on – George Thompson.  As I believe I mentioned earlier, George taught a wonderfully broad graduate course called Theoretical Structural Geology.  George’s course it was that entrapped me into what became the rest of my career – magnetism.

So, in about 1960 here is what definitely was known about rock and earth magnetism:

(1)             The earth had an intrinsic magnetic field, as had been demonstrated for thousands of years by the usefulness of the magnetic compass.

(2)             Some rocks were magnetic, as could be shown by merely waving a large stone (preferably basalt) near a reasonably sensitive compass.

(3)             Some rocks were magnetized in an anti-parallel direction – that is, north-seeking needle pointing south.  This had been shown by a guy named Brunhes early in the century.

(4)             These “reversely” magnetized rocks could not all be explained by mineralogical peculiarities, although some – a tiny minority. It turned out – could be.

(5)             Ergo, whatever caused the earth to be magnetic had the property of spontaneous reversal – north and south magnetic poles changing places.  Moreover, the exchange of polarity was accomplished swiftly – no more than ~ 2 ky, and often much less.

So, knowing all this (say, early 1960s), all hell was justified in breaking loose.  Take seafloor spreading, for instance.  It had been determined previously that there was a young, seismically active, occasionally volcanic ridge in the middle of the Atlantic Ocean (and similar ridges were known in other oceans).  It also was known that the age of the ocean floor increased monotonically away from the ridge, but that no ocean floor older than Jurassic existed anywhere.

SO, enter Fred Vine, Drummond Mathews, Alan Cox, Dick Doell, Don Tarling – and a huge mob of others.

First, Vine and Mathews drove the final, irrefutable nail into the coffin of fixist dogma by showing that heretofore mysterious linear magnetic anomalies that had been found running parallel to the mid-Atlantic ridge were symmetrical – that is, if you found a broad one so many kilometers east of the ridge, you would find an identical one that many kilometers west of the ridge.  And so forth.  Vine and Mathews drew the obvious, but paradigm-shattering conclusion: hot magma was continuously being extruded at oceanic ridges, acquiring a magnetic direction when cool enough – thereby recording the polarity of the geomagnetic field – then being passively carted away to either side by seafloor spreading.  Moreover, simultaneous studies were underway to determine an absolute age for each polarity transition – I will describe them next time, it’s time for my nap!

But, one last thing…  The oldest ocean floor rock was only Jurassic in age.  Did that mean that seafloor spreading only began ~ 200 Ma ago?  Seems unlikely, no?  Thus began the study of what came to be known as subduction zones.  Your homework:  Google Hugo Benioff and read about Benioff Zones.

PLATES C: Ocean floor spreading

                                           Ocean floor spreading

Continuing my tale of confronting plate tectonics….

Here I plan to record what I can remember of my wrestling match with the second of my three stages – ocean-floor spreading.  It wasn’t much of a struggle; I succumbed immediately.

There were lots of heroes who contributed to this stage; I remember particularly Harry Hess, Bob Dietz, and Fred Vine.

I am writing now about the latest 1950s and the very early 60s.  By that time I had ripped through Stanford’s rather stodgy undergraduate curriculum and was taking graduate seminars, reading on my own, and talking to my fellow grad students.  Most of them simply wanted to finish up, get a good job, and get on with life.  However, a few were as speculative and impractical as I turned out to be.  I remember in particular Bob Speed (later professor at Northwestern), and Dave Scholl (later with the USGS).  I also should mention George Thompson who taught a wonderful advanced seminar called Theoretical Structural Geology.  As for the rest of the Stanford faculty, well – they definitely were not on the cutting edge.

So what was going down at the time?  Well, Harry Hess was reporting results from a series of systematic surveys of the depth of the oceans.  With regard to the Atlantic, he found that there was a ridge running down the middle, and that it got deeper as you approached the bordering continents.  He could do that thanks to instrumentation developed during WW2; Hess had been a naval officer.  As a Princeton professor he also noted, and puzzled over, the abundance and distribution of strange suites of rocks in orogenic belts.  These were called, of course, ophiolites.

At the same time Bob Dietz was working for for the Coast and Geodetic Survey.  He also pondered the meaning of the pattern of ocean bathymetry being revealed at that time.  I believe that Dietz coined the term ocean floor spreading, although Hess and quite a few others must have been thinking along those lines.

There is one important wrinkle here that puzzles me: Who was it that determined the age of the ocean crust, and how did they do it?  Somehow it became known at this time that the crust was very young at the mid-ocean ridges, much older near the continents – but, compared to continental rocks, very young overall.  This thickened the plot immensely.  I assume that K-Ar dating was somehow involved.

So, it became obvious by at least 1962 that young oceanic crust (in the form of basaltic magma) somehow appeared at ridges, and then spread out laterally.  The obvious motor for such behavior was some kind of thermal convection in the mantle.  Confronted in the early 1960s by this body of evidence it became an act of heroic stubbornness to deny that Wegner had been right all along – but, amazingly, the majority of geologists still did.  It took the work of Fred Vine and other dabblers in rock and earth magnetism to drive in the final nail in  the fixist coffin.  That’s where, finally, I got involved.  I will write about it next time.

PLATES B: Continental Drift

                       Bullard's best (computerized) fit

This is the second of a series of blogs in which I will describe how I dealt with the birth of the plate tectonics paradigm, which now of course now completely dominates geotectonics.  I was in the perfect place to observe: I was at a major university, studying geology, totally absorbed by it, old enough to be skeptical – and completely ignorant!

Well, the paradigm came about in three installments: continental drift, ocean floor spreading, and finally plate tectonics proper.  I will begin with the initial phase.  

In the late 1950s, at Stanford, here is what some of us were mulling over, concerning drift: the “fit” of the Atlantic-bordering continents, geologic “matches” on either side of that ocean, the Glossopteris flora of what came to be known as Gondwana, and evidence of Permian glaciation in those same Gondwana continents but not elsewhere.  The heroes of this stage were Alexander Dutoit, Sir Edward Bullard, and others:  and of course Alfred Wegener, who initiated the whole thing.

Wegener’s evidence basically consisted of the statement that the fit of continental outlines, as well as geologic and fossil similarities, on Atlantic-bordering continents were to exact  to be coincidental.  For instance: the geology of the Caledonian mountains of northern Europe is an excellent match to the geology of the Appalachian mountains of North America.  Moreover, a peculiar and distinctive fossil flora was known to be present, along with glacial deposits, in Africa, India, South America, and Antarctica – but not elsewhere.  The overwhelming precision of the Bullard fit (shown) should alone have proved the case but, of course, it didn’t.

In the meantime, I was tearing through my elementary classes as quickly as possible, going to all our guest lectures, and reading on my own.  By the time the next stage in the revolution rolled around I was pumped and raring to go!

If you want my guess as to why every geologist of that era didn’t welcome continental drift with open arms and a kiss on the cheek, click on: 

https://frivilousessays.blogspot.com/2020/10/s-warren-carey-part-2.html 

THE BIRTH OF PLATE TECTONICS, A

 

This is the first of a number of blog entries concerning my recollections of the early development of what has become the dominant paradigm of modern geotectonics – plate tectonics.  You might call it “viewing the birth of modern tectonic thought, from way back in the bleachers”.  I will explain.

I became seriously involved with geology in 1957, when I already had attained the advanced age of 24.  After graduating from Stanford with what proved to be a well-nigh useless degree in Economics, and then whiling away two years in Germany with the United Stated army, I had returned to Stanford to study geology.  As I had only completed a single course in the subject previously (oddly enough – taught by Bill Dickinson, who later became my principal antagonist) - I was essentially a freshman,  Consequently, I enrolled in Geology 1a, or whatever they called it – general physical geology.  As I recall, it was taught by Art Howard, who was essentially a classical geomorphologist. 

For me, the most exciting topics in that course were big-picture things; the origin of continents, ocean basins and mountain ranges.  (I have always enjoyed big-picture speculation: to hell with the details!).  I do not recall Dr. Howard spending much time on such topics.  He lectured that mountain ranges probably were the result of contraction of the earth due to cooling.  If he mentioned continental drift at all,  I don’t remember it.  The text book did cover drift, in two short paragraphs; the first a half-assed summary of Wegener’s ideas, and the second a scornful rejection.  The main lines of counter argument were that (a) drift was impossible, given the properties of the earth’s interior*, and (b) Wegener’s evidence was inexact and/or could be explained otherwise.

Well, two years later I was an all-in drifter.  I will describe why, next time.  

*see https://frivilousessays.blogspot.com/2020/10/s-warren-carey-part-2.html 

EGYPT 2. SOME READING

         Linda didn't really like camels a whole lot

You would think that, at my age, a person would have learned how not to become voluntarily self-overburdened with “projects”.  You might think that – but you would be wrong.  At present I am juggling my cancer blog (MyrlsBlog), as well as several other topics, “The minimum you need to know in order to get the most out of a trip to Egypt”, and a collection called ‘Terranes”, supplemental to  Nick Zentner’s You Tube geotectonics lectures (“Nick from Home”).  Now has arisen another topic, one which I really want to pursue – my personal recollections and reflections on the birth of what became plate tectonics.  I was an observer, not (until much later) a participant – but my observations may be of some little historical value someday, and with luck will be interesting right now.  I will post them on my “Frivolities” blog, maybe under the title of “The birth of plate tectonics, as virerd from way up in the bleachers”.

But, in the meantime, if you are planning to visit Egypt any time soon, in lieu of personal advice I suggest several books:

Mertz, Barbara, Temples, Tombs and Hieroglyphs.

Perhaps a little dated, but beautifully written

Tyldesley, Joyce, Egypt: How a lost civilization was rediscovered.  History of Egyptology

Clayton, Peter, Chronicle of the Pharaohs.  Probably more than you really wanted tp know about 3000 years of Egyptian history.

Christmas Letter, 2020

                    Damn, how I miss these people!

                         Well, not Santa Claus, necessarily 

Well, not much good one can say about the year 2020, other than that it’s almost over,  My adventures for the year have consisted mainly of trips to the doctor; my health remains pretty good for a man of my advanced years (currently 87 7/12), but numerous consultations with medical science seem to be required.  Like a good boy I am staying home to avoid giving/receiving our friendly local virus.  The only people I ever see, other than my two daughters and my cleaning lady, are happy, mainly be-masked dog owners (through the window), transporting their pets to and from the dog-pooping grounds a few blocks away.  Makes me appreciate cats, especially on rainy days.

But, of course, I have good family news to report.  I have two new great grandchildren to make me smile and give me hope for the future of the human species:  Thomas Robert Moreno, only a few months old, and Hugo Wilde Weise, who is a half-year or so older.  Both cute as buttons, of course.  Add them to Evelyn and Seamus, both seven and in school, for goodness sake, and Finnegan, not far behind – and you have proof that I have done my part to replenish humanity.  Now if this damned virus would only let me go see them…..

For the last few months I have been thinking about geology, a little bit, anyway.  This is mostly owing to the fact that there seems to be renewed interest in some ideas I wrote about 40-50 years ago.  In essence, I apparently am regarded as a kind of interesting archeological specimen!  Anyway, to see how it all started, go to Google and ask for Nick Zentner You Tube * 13, and don’t be dismayed at how old I look.

So, anyway, I hope that your holiday season is as nice as can reasonably be expected, and that 2021 proves to be much better than our current unhappy year.  Hang in there.

 

SUGGESTED READING

 MAGNETIC LINES OF FORCE OF A GEOCENTRIC AXIAL DIPOLE

I have a suggestion for all of you who follow Nick Zentner’s lectures, as well as any other people out there with an active, if perhaps comparatively non-professional, interest in geology and, especially, geotectonics.  Much of current discussion surrounding Cordilleran tectonics revolves around data from the field of paleomagnetism.  Thus it would be very useful to understand how rocks acquire a permanent magnetic direction, as well as what that direction can tell us.  Bob Butler has written an excellent book on those and related subjects which is available free on line.  However, I suspect that Bob’s treatment of rock and earth magnetism may be a bit beyond the average non-professional reader.  For that reason, I suggest that you go to your local library and bully them into obtaining a copy of Paleomagnetism and its application to geological and geophysical problems, written by E. Irving and published by John Wiley and Sons  in 1964.  Section 2 explains rock magnetism in a way that is easy to comprehend, and the rest of the book – while outdated in some areas, of course – is also worth studying.

You might even think about buying a copy.  Although currently out of print, there is a used one for sale listed on the web site www.abebooks.com,  But I warn you – it’s not cheap!

ANCIENT REFLECTIONS

 

As read by Nick last night

  For what they may be worth, here are some of my reflections on the state of geotectonic thinking about the Western Cordillera during the 1970s and 80s.  Note that they are MY reflections and recollections: other players such as Ted Irving and Davey Jones may have had somewhat different views; too bad they’re not around to comment.

Well, first and foremost, I didn’t regard the bulk of displaced crustal blocks as in any way “exotic”.  Without much thought, I casually assumed that they had originated as part of North America itself, and had been transported relatively north by the north-oblique nature of subduction of the Farallon plate.  In fact, I spent inordinate amounts of time and energy pondering the circumstances under which this would occur.  It turns out that, theoretically, what is needed are:  a shallow subduction angle, a high angle of obliquity – and a mysterious factor measuring  the “stickiness” between the interacting plates, which I never figured out how to measure.  I wrote several papers on the subject which you can find very easily; the most cited one appeared in the 1991 volume of Physics of the Earth and Planetary  Interiors. 

Another player in the northward-transport game was, of course, the Kula plate – but we didn’t know how far south it had ever extended.  Clearly, detach a chunk of crust and attach it to the Kula – and northward displacement would be very fast.  But we didn’t know how, when, or even if this (might have) occurred.

Also, in those days I thought of northward displacement as occurring piecemeal, along a series of moderate-sized strike-slip faults and shear zones.  Then Ted introduced the concept of Baja BC, which seemed to imply existence of a San Andreas-type super through-going break.  That really got the geologists stirred up!

I said earlier that I thought of these allochthonous terranes as originally part of North America:  not “exotic” by today’s terminology.  The one universally acknowledged, indubitably exotic terrane was of course Wrangellia, which contained rocks that must have originated in the ocean.  Davey Jones, being a paleontologist, may have thought more along “exotic” lines, but I don’t recall him talking about it.

The next exotic terrane to be discussed in those early days was, I think, Stikinia, but by that time I had departed for the relative simplicity (and excellent cuisine) of the Central Andes.

 

EGYPT 1: GENERAL ADVICE

                       Linda at a fancy hotel in Cairo

Egypt 2:  General advice

Do you speak Arabic?  Do you take pleasure in intense bargaining on all retail occasions?  Does it please you to have people dogging your every footstep, trying to extract money by whatever means?  Can you ride a camel?

If you answered “no” to most of those questions, better go with an established tour.  I know one family that winged it on their own:  they saved a little money, but never got out of Cairo.  Hell, its only money; nothing to worry about.  Right?

So, take a tour.  An excellent plan would be to email an experienced Egyptological guide and go with what he/she has on offer.  My personal recommendation is to contact Amr Shahin  (amrhotep@gmail.com).  He is friendly, knowledgeable, and greatly experienced.  Linda and I loved him, and if she were still alive and I weren’t such a physical disaster we would be doing another trip with him as guide, just as soon as Covid lets up.

Also, be sure to work in a Nile cruise of four or so days.  It’s an ideal way to visit temples and such along the river, as well as a great sightseeing and culinary experience.  For Linda, our cruise was the highlight of the trip.  Sure, it will add to the expense, but who cares?  Only money, right?

Later on I will conjure up a list of things you absolutely must see, if you are to obtain your Junior Egyptologist badge.  One piece of advice now, however.   The rock-cut temple of Abu Simbel is a substantial plane ride to the south, and may not be worth the time and effort (not to mention the cost, which we are agreed to ignore.)  It is big, that’s for sure, but rather clunky.  Ramses II built it to frighten the Nubians; apparently he didn’t have art critics in mind.  Most good tours offer it, but you might be better off spending your days elsewhere.

Finally, a tip almost none of you will follow.  Go to your public library and  locate a copy of A Thousand Miles up the Nile, by Amelia Edwards.  Ms. Edwards explored the Nile near the end of the 19^th century, and produced a delightful cultural experience for generations thereafter.  Come to think of it, you probably can find it on your computer.  For Free!

 

Egypt, into

  Two things everybody knows about ancient Egypt

Why Egypt?

There are older civilizations (Sumer, by a whisker) and plenty of dead cultures close by to assuage one’s curiosity (Incas, Mayans, Aztec, etc.), so why fly half-way around the world to get your antiquarian rocks off?  Well, the answer is crushingly obvious.  Egypt – the Pharaonic culture we associate with the pyramids and King Tut – lasted about 3000 years, far, far longer than any other ancient civilization.  Moreover, it built and sculptured in hard, erosion-resistant stone, thereby leaving behind multitudes of objects for us to gawk at and wonder about.  Additionally, this richness of surviving artifacts has generated an enormous amount of study and exploration, by persons ranging from sober academic scholars to shifty-eyed tomb-looters.  Europeans began messing around in the Nile valley more than two centuries ago.  All this attention has churned up a meaty and complex story, as well as quite a few mysteries, for us to ponder.  And, blessing of blessings, they are still digging stuff up!

But seriously, the ancient Egyptians were the first, or almost the first, to tackle the important, universal questions of human life: Where did we come from?   Where do we go after death?  Are there entities superior to us who influence our daily lives?   How should we behave – and why?  Ancient Egyptians confronted these questions long before any of our extant religions came Into existence The answers they came up with are deeply absorbing.

So – that’s why you need to go to Egypt.  Moreover, the food is good, the mid-winter weather excellent, and prices are reasonable – compared, say, to Norway. Furthermore, there are non-Pharaonic pleasures to be had, especially in Cairo and Luxor.  But bring your own whiskey.

 

THE J2 CUSP

                                                   EDGE EFFECT

                                              Main forces that move plates

Here is my choice for “paper I wrote that’s most difficult to         understand”:

Beck, M. E., and B. Housen, Absolute velocity of North America during the Mesozoic from paleomagnetic data, Tectonophysics, v. 377. pp 33-54. 2003.

I say this because I picked it up lately and, after 17 years, could barely get through it myself!  However, it may have some relevance to Nick Zentner’s discussion of exotic terranes, so here goes:

First we need some basic assumptions:

1)    A paleomagnetic study of rocks of a particular age and geographic location gives an accurate approximation of the location of that area at that time with respect to the spin axis of the earth – the geographic pole.

2)    As a continent moves with respect to the spin axis it will, in effect, paint a path of apparent polar wander in the form of a string of paleomagnetic poles that reflects that motion.  These are called curves of apparent polar wander (APW).

3)    Continents, like everything else, move in response to the sum of forces applied to them.  If the sum of forces remains constant so does the motion, in direction and speed.

4)    North American APW can be described as a series of intersecting paths.  Each path should represent a period of constant applied external forces; intersections of these paths accordingly should represent episodes at which the sum of applied forces changed.  This has been discussed previously by Ted Irving, Richard Garden, and Alan Cox. 

5)    External forces that may influence plate motions include subduction zones, rifts and strike-slip faults.  It follows that events such as initiating or choking off of large subduction zone might be expected to alter the velocity of plate motion.

AND NOW, finally, I get to the point.  The incomprehensible paper cited earlier recognizes a half-dozen or so “cusps”, defined as times when North America abruptly changed its direction of motion with respect to the spin axis.  One of the better defined of such cusps occurs at about 160 Ma, the J2 cusp.  Could that represent the effect of cramming the Intermontane Superterrane into a west-dipping subduction zone?  I suggest an alternative in the 2003 paper – but who knows?  I need to study the damned thing again!

 

 

TERRANES C: WRANGELLIA

                                    WRANGELLIA, NORTH

THE WRANGELLIA PALEOMAGNETIC CONUNDRUM

In the earliest days of terrane excitement the name most prominently discussed was “Wrangellia”.  As Nick has explained, Wrangellia is an accreted terrane outboard of most of the current version of the western North American collage of terranes.  Rocks comprising Wrangellia show it to be latest Paleozoic and earliest Mesozoic in age.  Wrangellian-type rocks occur in bits and pieces from Alaska to – possibly – northeastern Oregon.  A big chunk is exposed on Vancouver Island.  The largest, as you might expect is located in the Wrangell Mountains of southern Alaska.

Lucky for paleomagnetists,, Wrangellia contains some volcanic rocks that have survived with their magnetic signal mostly intact.  These have been investigated in several places, notably the Wrangell Mountains proper (Talkeetna Fm; Jack Hillhouse & USGS crew) and Vancouver Island  (Karmutsen Fm Ted Irving & Co).  I am going to drastically over-simplify what these two studies found.

The rocks in question are roughly 230 Ma on age.  Their direction of magnetization is - very approximately -   shallowly upward, to the north.  This gives rise to the conundrum:

As you certainly know, the geomagnetic field has two steady states (polarities); we call them normal (N), and reverse (R).  In an N field, a rock magnetic direction of northward and up indicates origin in the southern (geographic) hemisphere.  However, given an R field the upward magnetic direction indicates origin in the northern (geographic) hemisphere, but with the magnetic vector pointing SOUTH.  

Thus, the paleomag data, which are nearly  impeccable, leave us with two choices:  either Wrangellia was in the southern hemisphere 230 Ma ago, hence has been transported many, many  thousands of km northward, OR it was in the northern hemisphere at that time and subsequently has moved much less further northward -  but has rotated 180 degrees in the process!  One of these is almost certainly correct.  What to do?*

Well, in the 80s it was common to yield to ones innate fixist bias and opt for whichever scenario required the least relative displacement, so the second alternative tended to be favored.  At that time however, I was a wild-eyed mobilist (still am), so I favored the southern hemisphere alternative (still do).

What do you think?

*See diagram in Jones et al, 1980. p 78

 

 

S. WARREN CAREY, PART 2

                     VISCO ELASTICITY MODEL

Did you ever wonder why it was so hard for the geological community of the early and middle parts of the 19^th century to accept the concept of continental drift?  Probably not, but now’s your chance.  After all, Wegener, du Toit and others had presented a varied body of evidence that it HAD occurred which, nowadays, appears totally conclusive.  So, why did so many prominent geologists disagree?

Well, human cussedness obviously played a part.  If you grew up instinctively harboring  fixist ideas, and those ideas had served you well throughout your career, damned if you were going to let a bunch of  Johnny-come-latelies turn everything upside down!

However, if you rejected drift you needed some scientific argument to back you up.  And such, you thought, existed – from the field of seismology!  Continental drift couldn’t be true because it was impossible!

Early drifters had at best a bunch of crude ideas about HOW drift occurred, and all of them required some degree of mobility in, at least. the upper mantle.  Nay-sayers could point to seismic evidence that indicated that the mantle, far from being the least bit soupy, was more rigid than steel!  Hence, no drift.  It was all an illusion.  Here is how that works. 

It transpires that some physical properties of the interior of the earth can be deduced by what happens to earthquake waves as they pass along their paths.  In particular, how rigid a material happens to be is reflected in how rapidly the energy contained in a seismic wave is dissipated – converted to heat.  Precise seismic measurements showed conclusively that the mantle was extremely rigid.  Voila!  The mantle had the properties of hard, cold steel – and continental drift, Q.E.D,  was out of the question.

Well, S. Warren Carey blew that particular ship out of the water with an important paper that nobody reads any more:

Carey, S. W., 1953, The rheid concept in geotectonics, , Journal  of the Geological Society of Australia, Volume 1, Issues 1, 2.

In this paper, the old Tasmanian Devil points out the fact – that should have been obvious – that the response of a material to an applied force depends in large part on for how long the force is applied.  Look at the model at the top of the page.  If a force is applied for only an instant,  the spring will show significant (elastic) displacement but the piston will not have time to respond very much.  Hence the material will appear to be totally elastic.  However, apply the force for a geological significant time and the “dashpot” (think a cylinder filled with goop) will deform so much that the elastic contribution can be totally ignored.  In other words, on a tectonic time scale, the mantle behaves very much like a soupy, viscous fluid!  Among other things, this makes thermal convection not only possible, but likely.

If you have trouble with this concept, try a thought experiment.  Mentally strap on your crampons, grab an ice ax, and find a nice steep glacier to climb.  On the time scale of your ascent you can treat the glacial ice as a fine, trustworthy solid – even though, as a good geologist, you know that, on a time scale of weeks or even days, it is flowing steadily  downhill!

 

S WARREN CAREY; PART 1

                           S. Warren Carey and an expanding earth

S. Warren Carey, the Tasmanian  Devil, Part 1

I am going to describe the work of one of the most important geotectonic thinkers of the early and middle years of the 20^th century.  S (Sam) Warren Carey was a professor at the University of Tasmania; although he had visiting appointments at prestigious universities elsewhere.  He is sometimes described as an early advocate of continental drift – but that, while true, requires an asterisk, and a big one.  Carey certainly believed that the sialic continents of the earth had once been together and have separated subsequently, creating ocean basins in between.  However, Carey knew nothing (or cared not much) of mantle convection.  Instead, he proposed that the earth once had a much smaller diameter – about half as big as now, if you must know – and had a complete sialic shell!  Then, as the earth expanded, the sialic shell broke into pieces and moved apart, creating relatively young oceanic crust in between.

This was not as wild an idea in 1930, say, as it seems today.  After all, the astrophysics people had shown that the universe itself is expanding.  So, people mused, what if Newton’s “universal constant, K – as featured in his equation F = K(m1Xm2)/r² was actually a variable)?  If gravitational attraction decreases, do objects get farther apart?  Would the earth expand as a consequence?

Well, as it happens, probably not – but Carey had good reason to think otherwise, before Vine and Mathews and the plate tectonics scientific revolution.  It can be shown (has been shown) that Carey’s specific model doesn’t work - but that is a topic in itself, which I may get into someday.

So if Carey was so wrong, why do I maintain that he was an important figure in geoscience?  That will be argued extensively in my next blog.  However, note that terms defined by Carey on the basis of his expanding earth hypothesis are in common use today.  Who has not heard of “oroclines” – bent linear crustal features – first defined by the Tasmanian Devil?  Less commonly used are “rhombochasm” (the Atlantic Ocean basin could be so described}, or “sphenochasm” – the Arica depression in the western edge of South America could be one of these – although I doubt it.

Here is Dr. Carey, pleading his own case:

https://www.youtube.com/watch?v=Othb0xsvZb4&list=PLRA8S2qijlkE9bJe69VlglZuU-ppoxVAU&index=2&t=0s&app=desktop 

TERRANES B

                                                    Lopez Island

EARLY EVOLUTION OF THE “TERRANE” CONCEPT

Early on, when I first began to believe that large chunks of crust were allochthonous* with respect to interior North America I simply referred to them as “displaced crustal blocks”.  Some others interested in this line of work called them “micro-continents”, but that particular awkward terminology  quickly disappeared, although it left the term “microplate tectonics” behind as a memento.

The “official” terrane definition arose out of a GSA Penrose Conference held on Lopez Island, Washington, in the summer of 1980.  A report on that conference was published in the GSA journal later that same year:

            Beck. Cox and Jones, Mesozoic and Cenozoic microplate tectonics of western North America, Geology, v. 8, pp. 454-456, 1980.

The order of authorship is alphabetical; Davey wrote most of it.

Anyway, this “official” definition arose from three fun-filled days of argument, field trips and liquid refreshment.  Here it is::

A tectonic (or tectonostratigraphic) terrane is a fault-bounded geologic entity characterized by a distinctive stratigraphic sequence  and/or structural history differing markedly from its adjoining neighbors ….

Later, of course, new terms arose:

            Suspect terrane:  A chunk of crust that may fit the definition given above, but not for sure.

            Exotic terrane: A tectonostratigraphic terrane that didn’t originate as part of North America.

*Two useful words that geologists toss around:

            Autochthonous:  Formed right where it is now.

            Allochthonous:  Formed somewhere else than where          it is now.

Thus, the B.C. terranes Nick is describing are allochthonous, whereas the young cover rocks that partially hide them are autochthonous.

 

 

TERRANES A

                                  major terranes of nw north america

This will be presented by Nick Zantner as part of one of his UTube geology lectures - next Friday, I believe.

I am going to record what I remember about the early days of the terrane concept.  My memories are 40 or so years old, thus subject to a high degree of mental erosion.  Also, at the time I was concerned almost exclusively with the North American Cordillera, and with rocks that were younger than early Mesozoic; similar thinking may have been going on elsewhere, and with older rocks, but I would have been largely unaware of it.  I am sure that Dutch geologists – Zijderveld and van der Voo for instance – were thinking along similar lines with regard to the tectonics if the Mediterranean region.

Anyway, the undisputed godfather of Cordilleran “microplate tectonics”, as we called it then, was David (Davey) Jones.  Davey worked for the USGS, and his specialty was radiolarian paleontology.  Clearly he went far beyond the little siliceous bugs, though, because he came up with the terrane idea while doing geologic field work in Alaska.  As I remember the story, Davey and his crew were mapping – probably central Alaska – and they were frustrated by the exposure problem.  Their field area apparently consisted of a bunch of elevated ridges, separated by deep valleys filled with dense vegetation.  When it was possible to see rock in the valleys it consisted of dark colored, organic-rich shale and mudstone – over beer, Davey referred to it as the “black crap”.  Pretty clearly, the valleys housed faults.

The most puzzling aspect of the geology, however. was that neighboring ridges suggested completely different geological histories; their rock suites were dissimilar in lithology and/or age, as were their structural histories (faulting, folding, etc.).  You couldn’t correlate across the black crap!  So Davey began to refer to these isolated ridges as “terranes”, probably to reserve the alternate spelling “terrain” for more descriptive uses – volcanic terrain, basin and range terrain, etc.  It would have been obvious to Davey and others that these terranes had been juxtaposed by movement along the bounding faults.  Fortunately, at about that time paleomagnetism began to show that big blocks of crust had been displaced by hundreds or even thousands of kilometers.  That’s how I got into the game.

 

 

• 
  

BUMMER!

                                                          both gone

Let me share today's foul mood with you: I doubt that you have enough of your own.  Here are my complaints:

Too much smoke.

Not enough worthwhile to do.

Damned few human contacts.

Too cold to drink beer with the boys on the back deck.

Lonesome.

Too many birthdays*.

BUT, on the other hand, the Seahawks looked pretty darned  good!

*Probably the root cause of it all. 

AM I SAPPY, OR WHAT?

A cute little girl

A long time ago

Yesterday I spent several hours sitting on a park bench in Zuanich Point Park, experiencing  beautiful sunshine and views – but still filled up with sour,  gloomy thoughts and pessimistic  speculations.  To boil it all down the way my Beaumont family would have done, it just seems like the world is going to Hell in a handbasket.  Fast. You  know what mean.

And then a marvelous thing occurred.  

A little girl, all dressed up, rode by on what obviously was a new bike – and flashed me a big smile.  Her smile clearly meant that she was proud of herself and her new toy, happy to see me look up and, startled,  smile back – and that she was simply filled with joy.  Poof! went all my black and ugly thoughts.  Poof!  They'll come back, but for the moment - Poof!

Lucky are the parents of that beautiful little girl. Lucky is society that such innocence and goodness still exist in the world. – and lucky was I to be so thoroughly booted out of my foul mood.  Thank you , little girl.

Maybe there’s hope for us, after all.

THE MYSTERY OF DNA PACKING

Have you ever lain in bed at night, unable to sleep because your brain insisted on wrestling with the eternal, vital  question, to wit “How can you stuff a human DNA molecule that is six feet long into the nucleus of a single cell”?  Probably not too often.  Well, Dr. Collins gives you a colorful hint, here:

https://directorsblog.nih.gov/2020/08/13/a-new-view-of-the-3d-genome/

Of course, now you have to cope with the equally important conundrum:   how in hell does the copying mechanism find the right spot to do its job, in all that knotted-up, colorful mess?

There’s lots we don’t know – and, I suspect, lots we will never know.

Nuts!

Abu Becker ibn Myrl al Beaumonti

has some irritating news

Google, in its infinite wisdom, has seen fit to "improve" the program I use to post my blogs.  This means that I must wrestle with new complications and, so far, I have lost.  So postings may be irregular and look peculiar for awhile.  Please bare with me.

Hiroshima & Bataan

Today is August 6^th, 2020, the 75^th anniversary of the U.S. bombing of Hiroshima.  I always felt that the bombing was justified and necessary.  Without a demonstration of our overwhelming military superiority Japan almost certainly would have fought on, with the consequent death of thousands of Americans and possibly hundreds of thousands of Japanese.  But, like most people Hiroshima continues to trouble me.

It so happens that, quite by circumstance, today I have been reading an account of the Bataan death march and the subsequent treatment of our soldiers by the Japanese army.  I confess that I have to struggle against the impulse to regard Hiroshima and Nagasaki as condign retribution for Bataan.  But I shouldn’t feel that way, and I know it.  However, it is difficult.

As someone surely must once have said, “An eye for an eye, and a tooth for a tooth eventually must lead to a blind, toothless humanity”.  So I am going to stop reading about Bataan,  and watch something mindless on TV.  Moral cowardice, I guess, but then, that’s me

If God really did create us, He shouldn’t be too proud of His handiwork..

CREAMPUFF, MY LAST KITTY

Creampuff and Linda

IN PRAISE OF THE COMMON COLD

Our Enemy

This is not a “Frivolity” by any stretch of the immagination, but as it isn’t about ovarian cancer I stuck it here,

https://directorsblog.nih.gov/2020/07/28/immune-t-cells-may-offer-lasting-protection-against-covid-19/

You probably know more about how the immune system works than I do; it wouldn’t take much.  Well, Francis Collins has provided us with a blog concerning Covid 19 - more specifically about how we might combat it - that I found very interesting.  The gist is something like this:  

The virus we now are contending with is a member of a “family”; specifically, the coronavirus family.  Other members include SARS, MERS, and several of the bugs responsible for the common cold.  All members of this family are structurally and/or biochemically similar.  Seems that “memory” T cells activated by these various coronavirus-type diseases hang around for decades – and sometimes, somehow, under some circumstances, may be effective against our current tormentor.  This was discovered by some guys in Singapore; it may lead to an effective vaccine.  Much work is ongoing, in Singapore and elsewhere.  Let us fervently hope.

So maybe those childhood "colds" were a blessing in disguise.  Well, probably not.

BAD NEWS

CORONAVIRUS, BUBONIC PLAGUE, EARTHQUAKES

and Donald Trump

You’ve all heard of the Four Horsemen of the Apocalypse, right?    We’ve been dealing with two of them, Donald Trump and Covid 19, for some time.  Well, this morning I was startled to learn of signs of  the remaining two: Black Death has arisen again, in Mongolia, and earthquake activity in Yellowstone could indicate an imminent civilization-destroying super-eruption!

Note that I’m not predicting the end of the world, but. . ..

If you have some wine that you’ve saved for a special occasion – drink it now.

TWO WOMEN I WISH I HAD KNOWN

Two women I wish I could have known.  Unrelated, except rhrough Ancient Egypt.

Amelia Ann Blanford Edwards.  (1831 – 1892).  Ms Edwards was a well-heeled Englishwomen who played a vital part in the development of scientific Egyptology.  She already was a writer and illustrator of some note when, in 1871, she made a journey up the Nile, in an old fashioned sailing boat, with a half-dozen companions.  The result was a true literary triumph, A Thousand Miles Up The Nile, published in 1877.  That trip kindled a passion for ancient Egypt in her of such intensity that she went on to found the British Egyptology Association and helped finance the career of Flinders Petrie, the absolute father of scientific Egyptology.  Ms Edwards herself wrote one volume of Egyptian history; sadly, it is dreadful.  However, A Thousand Miles is a masterpiece, which you can read off your tablet for free.

Barbara Mertz.  (1927-2013).  Dr. Mertz earned a Ph.D. degree in Egyptology  from the University of Chicago, then and perhaps now the top school in the field.  However, probably owing to her sex (my guess here) she did not settle down in some quiet academic grove, but rather became a writer of mysteries- and a wonderful one, in my opinion.  Early on she wrote two useful and entertaining nonfiction books on Egyptology:  Red Land, Black Land and Gods, Graves and Hieroglyphics, both still available.  Then she turned to fiction and, Lord, what a flood!  She wrote under several pseudonyms and in several different genres, but the collection I recommend most strongly is her Amelia Peabody series, written under the name of Elizabeth Peters.  There are 20 books in all, each detailing  the adventures of a family of Egyptologists around the turn of the last century.  The stories, all involving crime – usually murder – are fun, but it is the characters that make Ms. Peters tales absolutely sparkle!  If you haven’t met Amelia yet you are in for a treat.

My guess is that the fictional Amelia Peabody Emerson is based, at least loosely, on the very real Amelia Ann Blanford Edwards.   Somewhere, Ms. Peters says that isn’t true, but my doubts remain.

And here is Barbara Mertz