Snow and Language

C. P. Snow famously noted the inability of scientists to communicate with their liberal arts colleagues at Cambridge. As a scientist, he tended to blame the other side for not keeping up.

The problem isn’t so much that they have different interests and that those of science have become much more difficult to grasp since Einstein, but that the two groups use language differently.

In the liberal arts, there is some attempt to write in the current lingua franca, albeit, often a highly artificial and convoluted form. But words still tend to have meanings that can be deduced from context.

In science, there is a deliberate attempt to appropriate words and give them arcane meanings. As an example, they discuss secular trends in temperature in the mantle.

Now, to someone with any exposure to western civilization, secular is usually contrasted with religious, meaning that controlled by the civil or political world. Try to apply that to previous sentence.

After searching a bit in Google, I found economists had used the term secular to refer to long term trends, probably from some discussion of those events outside the control of the church hierarchy in the middle ages. That was enough. Scientists like to appear au courant. They adopted a word used by the movers and shakers of the world.

Graduate school is a time for adapting to new rules of discourse where many want, nay actively conspire to make an aspirant fail. Make a comment about the social background of Hawthorne to an English professor influenced by William Empson and you’re guaranteed a poor grade. Quote some fact from your historical geography text to an economics history professor who thinks it’s wrong and watch him look at you with dismay.

But these misadventures are nothing compared to what must happen when people enter into science. It begins in high school with never spelling out a word, but using abbreviations. One never says water when H₂O will do. One couldn’t possibly say the year 2000. Those zeros, that extraneous word thousand had to disappear. We all learned to say Y2K. For an historian it became the label for a technological crisis and the date remained a date. I’m not sure what happened in science, but so far I haven’t seen Y2K11.

It’s rather like science became captive to a group of men who never outgrew the thrill of using Pig Latin in their boyhood tree house sanctuaries. The primary initiation ritual was speaking obfuscation. And so, scientists and social scientists make proficiency in jargon their badge of identity.

Snow wasn’t the first to recognize the problems with language. It was an Oxford mathematician, Charles Ludwig Dodgson, who used the pen name Lewis Carroll to write:

'When I use a word,' Humpty Dumpty said, in rather a scornful tone, 'it means just what I choose it to mean - neither more nor less.'

'The question is,' said Alice, 'whether you can make words mean so many different things.'

'The question is,' said Humpty Dumpty, 'which is to be master - that's all.'

Notes:
Carroll, Lewis. Through the Looking Glass, 1871.

Snow, C. P. “The Two Cultures,”1959.

Photos: Jemez behind badlands with (top) far arroyo in front.

Mantle Structure

The mantle is the cream filling between a silicon-rich crustal meringue and an iron-rich core base. Unlike a common pie, however, it’s composed of layers detected by seismic wave tests and is not some separate ingredient like lemon or coconut, but a transition from silicon to iron in mixtures that includes oxygen, magnesium, aluminum, calcium, sodium, potassium and hydrogen in combinations that change by layer.

Starting at the top, the beginning depths, temperatures and distinguishing characteristics of these layers are:

Crust
Moho - 7 km - 500 C - increase in seismic velocity
Lithosphere - 50 km - 900 C - low viscosity, rigid
Asthenosphere - 200 km - 1100 C - flowing, low velocity
Transition Zone - 410 km - 1800 C - distinctive seismic patterns
Lower Mantle - 660 km - no agreement - high viscosity
Anomalies - 1700 km - no agreement - lateral velocity anomalies
D” Layer - 2891 km - 4000 C - ultralow velocity, distinctive seismic patterns
Core

Olivine, a compound of iron, silicon, magnesium and oxygen [(Mg,Fe)₂SiO₄], is identified as the most important component in the asthenosphere. In the lithosphere, it combines with elements like calcium and aluminum to produce pyroxene. Above that, in the Moho, pyroxene replaces the calcium and aluminum with potassium to become amphibole. That, in turn, replaces the potassium with calcium, sodium and hydrogen (water) to create biotite.

The ratio of iron and magnesium in olivine can vary, which is why they are represented by a comma, rather than a more specific number in the formula. The permutations of both olivine and pyroxene produce many of the silicon rocks found on the surface that have created the perception that the mantle is predominately composed of silicon.

Below the asthenosphere, in the transition zone, the forsterite-fayalite form of olivine changes its crystalline structure into wadsleyite [(Mg,Fe²⁺)₂(SiO₄)], which in turn becomes ringwoodite [(Mg,Fe²⁺)₂(SiO₄)]. The important feature of their structures is that changes in oxygen create spaces for water molecules which are being released as parts of the crust sink into the transition zone. Eli Ohtani thinks the presence of water trapped in these two forms may explain the layer’s seismic properties.

In the lower mantle, the crystalline structure changes again, this time to magnesium silicate perovskite [(Mg,Fe)SiO₃]. Water is lost and iron becomes more important. With an atomic weight of 26, it has a partially filled third orbit. In its ferrous form [F²⁺], it has two electrons available to bond with other atoms; in its ferric form [F³⁺] it has three.

As pressure increases, the spin speed within the atom changes from high to low. Ferric iron changes its spin at 70 gigapascals which is about 1700 kilometers down in the area where seismic anomalies have been detected. Ferrous iron changes its spin pattern at 120 gigapascals which is about 2600 kilometers down, just above the D” layer where the crystalline structure changes again to one called post-perovskite.

The two valences can appear in the same compound in different ratios, while the amount of iron relative to magnesium also varies. Such differences explain why detectable seismic patterns are hard to replicate with current technology: the deeper one goes into the mantle, the greater the amount of iron that has changed its spin cycle.

Neither of the transition zone compounds are known from samples from the mantle. Wadsleyite was found in the Peace River meteorite from Canada. Ringwoodite was first identified in the Tenham meteorite in Australia and has since been seen in other meteorites from other parts of the world. It’s the laboratory conditions under which the two were synthesized that suggests they are the primary components of the transition zone.

A team headed by James Brado put samples of magnesium silicate perovskite through laboratory tests to produce evidence of spin changes and the deep mantle conditions that could produce them. They didn’t indicate where they obtained their raw material.

Notes:
Brado, James, Guillaume Fiquet, and François Guyot. Thermochemical State of the Lower Mantle: New Insights from Mineral Physics.

Ohtani, Eli. Recent Progress in Experimental Mineral Physics: Phase Relations of Hydrous Systems and the Role of Water in Slab Dynamics.

Both appear in Earth’s Deep Mantle: Structure, Composition and Evolution, 2005, edited by Robert D. van der Hilst, Jay D. Bass, Jan Matas and Jean Trampert for the American Geophysical Union.

Diamonds

I’m sure this is a simple minded question, but if the mantle is homogenous why aren’t diamonds found everywhere?

When I was a child, this wasn’t a question. I was told in fourth grade that all the ferns in the swamps got covered by debris and turned into coal in the Pennsylvanian period. I don’t know if I was also told that all you had to do to create a diamond was add more pressure, or if I make the connection later when I heard a diamond is simply a form of carbon.

I was wrong about coal and diamonds, but it’s a common enough conclusion. All you have to do is enter the two words in a Google search to see how many others have the same idea. Indeed some of the first men to try to make synthetic diamonds began with charcoal. The ones who succeeded used graphite in a belt press able to producing pressures beyond 10 gigapascals at temperatures above 2000 degrees Celsius.

Once scientists at General Electric had produced that first synthetic stone it became possible to know, fairly precisely, the conditions required to make a diamond. But first, it was necessary to understand more about carbon.

The carbon atom is created from helium in a giant or supergiant star which is then scattered as dust in a supernova explosion. That dust is then coalesced into planets in third generation stars like our solar system.

The number of carbon atoms on Earth was set at creation, although some have since been introduced by meteorites. The carbon atom is particularly promiscuous, able to join with other elements like oxygen and hydrogen in long chained molecules. Perhaps ten million have been identified so far, and more are possible.

However, carbon atoms can also combine with themselves into crystalline structures. Graphite has a hexagonal structure, diamond a cubic one. These are the two main allotropes of carbon. Moving between them, means converting the crystalline pattern of one into the structure of the other.

I suppose it made little sense to believe coal could somehow become a diamond. Coal is mined. The first diamonds were found in alluvial expanses in India, then in Brazil. It wasn’t until the late nineteenth century that men in South Africa found diamonds beneath the surface deposits they were exhausting.

Then it became possible to know something about their origins. They had come up to the surface through volcanic pipes made of kimberlite. The ones in India and Brazil had eroded away, leaving a false impression of their provenance. The ones in South Africa still existed.

Diamonds are believed to be formed at pressures between 4.5 and 6 gigapascals and at temperatures between 900 and 1300 degrees Celsius, both lower than conditions in the first belt press.

The only parts of the mantle that meet the conditions for a diamond lie between 140 and 190 kilometers beneath the thickest, oldest parts of continental crust. Ocean bottom crust is thinner so temperatures rise more quickly with depth. The requisite condition never materializes.

Diamonds today are found in India, Brazil, South Africa, Siberia, and parts of Canada and Australia. These lie under the Indian, Amazonian, African, Angaran, Canadian and Australian shields. The last two are near areas where the oldest known rocks have been found.

Neither a view of a homogenous mantle nor one with two reservoirs explains the appearance of diamonds. The first view would have to be amended to suggest the chemistry was the same throughout the mantle, but varied by location from weight from above. The other looks for the reservoirs near the upper and lower heat sources, not somewhere above the boundary between the upper and lower mantles.

Note: Most of the information came from Wikipedia entries on carbon, diamond, kimberlite and synthetic diamond.

The Mantle

The mantle is the great terra incognita. Contra Jules Verne, no one has actually visited it. We have no rocks pulled directly from it, only those thrown out through volcanos or those that have seeped from cracks in ocean bottoms.

What we absolutely know has come from modern technology. We know its approximate thickness, 2890 kilometers or 1800 miles, which is the difference between the calculated size of the core and the external perimeter observed from space.

Seismic wave tests have identified areas with radically different patterns. One, the D” or D double prime layer, sits between the core and the mantle. Another, the Moho or Mohorovičić discontinuity, lies between the mantle and the crust.

Beyond that, nothing is agreed upon.

In the face of such massive unknowns, scientists, like the rest of us, have fallen back on what they do know, in this case, that the laws of physics never change. If they ever yielded on the absolute truth of the patterns of heat and effects of temperature, there would be no way to calculate or predict anything. They would be thrown back into something akin to medieval wonders.

Geophysicists have created an image of the mantle as an homogenous mixture slowly stirred by convection. The only disruption comes from the crust of the earth sinking down in a subduction zone. The materials are absorbed into the mix, and prepared for the next eruption. The mantle remains unchanged from its primordial state.

The second absolute for geologists is that rocks never lie. They may tease and mislead, but they never outright lie. Therefore, the actual components of rocks summarized in the periodic table have not changed. The proportions and distributions may have changed, one may have been transformed into another, but oxygen has always been oxygen, samarium has always been samarium.

They focus on the mantle rocks the earth is currently displaying, the basalt from mid-ocean ridges and the basalt from ocean islands. They have different chemical signatures, so therefore must have different sources. Seismology has defined two boundaries. Therefore, the first is thought to come from the top of the mantle, the other from somewhere near the bottom generated somehow from crust that has fallen there from the surface. Whatever exists between is so much unimportant, dark matter, rather like the liquid that survives in a vacuum pack of pickles.

Since seismologists revealed more discontinuities in the mantle that correlate with changes in the structure of olivine, geochemists have begun to apply the laws of physics to rocks themselves and have been asking the effects of heat and temperature on the atomic structure of the matter that makes up the mantle. They are developing a view of the mantle as one of layers, albeit each composed of the same matter under different conditions. So far, they can only define the first thousand kilometers. The rest, nearly two-thirds of the mantle, awaits future research.

All these views are ahistorical. When asked how the mantle evolved from that gaseous mass we’ve always been shown into the stable planet we know, they tend to fall into the von Däniken trap. Erich von Däniken is the one who, when confronted with evidence of ancient new world civilizations that contradicted the long held view that man has been progressing in a straight line from primitive life to the present with no lost knowledge or relapses, argued in Chariots of the Gods? that monuments like those found in Peru were the result of contacts with aliens from outer space.

The outer space concept now is a bit more sophisticated. Since we’ve brought back rocks from the moon, scientists have become aware of the effects of the constant bombardment that must have been occurring before the atmosphere developed to protect us. But, it’s still a bit of a deus ex machina, a type of solution even Horace knew was suspect.

None of their views ultimately make sense.

The only model I have for the effects of heat is boiling chicken soup. The globs of fat in water break into smaller units until they turn into an edible suspension. As soon as you turn off the heat, the fat begins reseparating out. Continents form and unform, as it were. The underlying soup is irrelevant. Plate tectonics makes sense.

The only model I have for mixing is making a cake. Even with the most efficient mixer, lumps of flour will remain if you don’t keep smashing them and redirecting the pieces back toward the beaters. A complete blend cannot be left to a machine.

I have a hard time visualizing how the mantle became completely homogenous. But, I’m willing to accept that’s the case, if someone can suggest when that occurred. Scientists have been trying. The best have created mathematical models, but most end projecting absurdities. One group has suggested how two reservoirs of magma could have been formed 2500 million years ago in conditions that existed prior to the development of plate tectonics.

If I latch onto their explanation, it’s because I want to know what are events that occurred before the North American plate began forming after the break up of the Kenorland supercontinent 2500 million years ago.

However, I know that accepting an answer that meets my expectations is dangerously naive. The alternative is to accept ignorance which is always difficult, but apparently necessary in this case.

I can only assume the mantle was evolving, that something happened between the iron catastrophe that accompanied the formation of the core and the formation of Laurentia, and move on to trying to understand the origin of the next layer, the oceans.

Notes:
Anderson, Don. “Self-Gravity, Self-Consistency, and Self-Organization in Geodynamics and Geochemistry,” has a readable explanation of the various views of the mantle, with a chart showing the layers in the first thousand kilometers.

van Thienen, Peter, J. van Summeren, Robert D. van der Hilst, A. P. van den Berg and N. J. Vlaar. “Numerical Study of the Origin and Stability of Chemically Distinct Reservoirs Deep in Earth’s Mantle.”

Both appear in Earth’s Deep Mantle: Structure, Composition and Evolution, 2005, edited by Robert D. van der Hilst, Jay D. Bass, Jan Matas and Jean Trampert for the American Geophysical Union.

A Rock Is a Rock Is a Rock

The young man in the mineral shop who dismissed my gray rock as “just a rock” with none of the special characteristics of a recognized mineral was wrong.

Rocks aren’t just rocks. To begin with, there are only eight elements that go into the composition of most: oxygen, silicon, aluminum, iron, calcium, sodium, potassium and magnesium. They represent great permutations on matter.

Basalt is some combination of oxygen, silicon, aluminum, calcium, sodium and magnesium. The percentages of silicon and sodium are often used to define the type.

Granite is formed from magma and contains oxygen, silicon, aluminum, sodium and potassium.

Quartz is essentially oxygen and silicon.

Rocks don’t limit themselves to just the eight fundamental elements. Basalt, pyroxene and perovskite can contain titanium. Zircons are silicon and oxygen with zirconium.

More important for geologists interested in the history of the planet are their trace minerals. The half-lives of radioactive isotopes of elements like uranium, neodymium and samarium are used to date them. Zircon crystals are the oldest found above ground.

Rocks, as pieces of matter, do have definable characteristics. In the early twentieth century, Norman Bowen crushed them so he could heat the powders until they melted, then heat them more until they boiled. He let them cool in controlled steps.

He ended with iron-magnesium bearing olivine which was formed at a high temperature and pressure. At a specific lower temperature it becomes pyroxene. At another temperature, pyroxene becomes amphibole, and that, in turn, becomes biotite. In contrast, plagioclase gradually transitions from a rock rich in calcium to one rich in sodium without the abrupt phase breaks.

At a set point, they become potassium feldspar, which becomes muscovite, which becomes quartz. These are the three major components of granite, with quartz the least likely to weather away because it was formed in conditions closest to those of the present.

In the past few decades, new technologies like diamond-anvil presses have allowed geologists to return to experiments like those of Bowen, only now they are looking at how rocks are altered at the higher pressures and temperatures deep in the mantle. Instead of changes in elemental chemistry they’re interested in changes in crystalline structure.

When pressure increases, the O^2- ions in olivine are altered into a spinel structure. At even higher pressures, the spinel structure converts to one found in perovskite and another found in periclase.

Near the earth’s surface, enstatite combines silicon, oxygen and magnesium. It too converts to a perovskite-like structure at higher pressures, then near the bottom of the lower mantle to a post-perovskite structure.

All of this makes terminology a bit confusing, since the same thing is identified by its elements, its crystalline structure and its origins. What one thought was just a rock isn’t. There are at least 11 forms of olivine, including basalt which is further broken into five groups. There are 24 types of pyroxene, including enstatite, and 37 varieties of mica, including biotite and muscovite.

It doesn’t help that only some of these can be seen. Anything with a post-perovskite structure immediate changes to something else when the pressure relents which it must if it’s to make a journey from the center of the earth where it may end up as simple quartz in my arroyo.

Mica (top) from near Albuquerque; granite with bands of gray quartz and shining specks of mica (middle) and a thin piece of quartz (bottom) from the far arroyo.

Quartz

My bookshelf is beginning to resemble something hidden in the backroom of a museum. Sedimentary rocks kept from crumbling on my floor lie in baggies. None are particularly attractive. They simply will be informative if I ever put them side by side to learn the differences in the different sediments in this area.

My camera doesn’t like any of them. I fantasize about the silicon chip rebelling at such ugly dates and give it nicer silicon oxide to look at.

White colored quartz is common in the arroyos, usually as pebbles, but sometimes in larger hunks. But more aesthetically pleasing are the small, broken ones with exposed facets that capture light.

The Ways of Water

On my way back from the Barrancos I followed the path left by water. This was less a point of curiosity than the easiest way to negotiate broken land. The rivulet began somewhere in the hillocks below the fan before the cliffs.

From there the water wound through low hills.

The water reached more gently sloping ground, where its path was marked by the lack of vegetation. Once in a while, the bottoms was littered with gravel it had recently picked up, but mainly it was a slightly shinier, more level continuation of the banks.

When it reached a more level area where sedimentary gravel covered the ground, it spread wider. Juniper trees grew along both sides.

Below the junipers softer soils appeared. The line was crossed between Tertiary and modern alluvium. Water was no longer able to define a specific course. It spread into a flood plain, leaving areas bare of vegetation. The only clues for where water had flowed were gravel deposits.

The water was flowing generally northeast toward the arroyo when it collided with an ATV trail headed straight for the north end of the cliffs. The water ricocheted back. It was lower than the trail.

From there it ran parallel to the ATV track, preternaturally straight. Its depth varied with soil. When it found something soft, it was deep. One time it was deep, a wash was opening on the other side of the track. At another point the banks were caked with grey mud.

When a particular grass was resistant, it disappeared in the shadows.

When it encountered another channel coming from the southwest, it got lost in another flood plain, until the channel reformed next to the ATV track.

The pattern repeated itself: a straight run, a collision with another water stream, a confused path, rationalization along side the higher road.

Then, a competing channel came through at just a point in the descent where the ATV track was nearly level with my water path. The abutting channel swept across the track, pulling my stream in its wake.

An arroyo feeder formed in the softer soils, twisting and turning around small changes in the earth. Sometimes, one side was steep and the other a delta; it other places the sides were the same. It behaved again like one would expect water to behave.

Just before it reached the arroyo there was a small washout, perhaps formed when water was backup during a storm by stronger currents in the far arroyo.

The feeder entered the far arroyo downstream from where the ATV track began. The water dropped its final load of stones as it changed course when it met the passing waters. From there it flowed towards the Rio Grande.

Valley of the Arroyo

Yesterday I walked to the closest Tertiary formation in the Barracanos badlands. From the base I looked back towards the formations on the other side of the arroyo. A valley I’d never recognized spread out below. The arroyos and washes that dominated when I was in the valley had disappeared.

A few days before I’d walked downstream along the top of the left bank between the ranch road and the area widened by the irrigation ditch. In that small area I could see the level I called the second bottom existed on both sides and appeared to be the same height.

This isn’t a glimpse of the Tertiary past. Rather, this is what remains after waters filled, then retreated, waters that rose to different heights at different times.

Note: Picture 2 is looking down on the second bottom. In picture 3 the bottom continues on the opposite side in the space between the two bare banks.

Earthly Beginnings

The early history of the earth is more theory than fact, and those theories are taken more from astrophysics than other disciplines. Those with other interests tend to pick through the available information in hopes of arriving at some early history for their subject.

A great many look for the thread that explains the origin of life. Others want to know how the moon was made.

My focus has been the creation of the conditions that made possible the emergence of that part of the North American plate where New Mexico sits between 1710 and 1600 million years ago, with a certain inclination to pay some attention to the formation of Michigan, the state where I was raised.

For me, this means envisioning how a 4600 million year old cloud of gas and dust evolved into a stratified ball whose layers have been defined by the workings of heat and cold.

The most important element has been iron. According to Wikipedia, iron begins in stars hot enough to burn silicon and initiate a chain of reactions with helium that transform matter from silicon to calcium to titanium to chromium to an unstable iron. That iron fuses with a helium nucleus to create ⁵⁶nickel, after which the star collapses and the ⁵⁶nickle transforms into ⁵⁶iron via ⁵⁶cobalt.

During the earliest millennia of the planet, radioactive decay continued in particles of nickle in the cloud which created conditions warm enough to heat the iron dust whose melting point is 1535 degrees centigrade. Following one basic law of physics, liquids are heavier than gases, the molten iron would have begun to isolate itself from the heat generating gases.

As it moved away from the source of heat, the molten iron would have gone through several structural phases. When the temperature fell below 1540c degrees, it would have begun to solidify and at 770c degrees it became magnetic.

Following another simple rule of physics, heat rises and cold falls, the cooler materials would have drifted towards the center of the ball, and the gases remained on the surface. Once enough iron had fallen below 770c degrees, the magnetic core could form. This process took about 50 million years and was complete around 4535 million years ago.

Once the nickle and iron coalesced into a ball divided into two parts, the magnetic, solid inner core and the molten outer core where temperatures today range from 5000c to 2200c degrees, silicon, magnesium and similar elements were segregated into an outer layer. Steve Kershaw suggests the mantle emerged around 4000 million years ago, and that it took about 2000 million years for the separation to be completed sometime around 2000 million years ago.

While the interior was still evolving, the outermost layer cooled into a skin that became the precursor of the crust. The oldest rocks found so far on the North American plate are from the Nuvvuagittuq greenstone belt near Hudson Bay. They are estimated to be between 3800 and 4280 years old.

The skin created a barrier between the warmer interior and the lighter gases which allowed water to condense without turning into steam. Oceans existed more than 3900 years ago, according to Kershaw. Scientists argue whether all the water was native or was increased by collisions with meteors and comets which could still easily penetrate the surface gases.

At this point, the history of the earth diverges into four separate narratives - the mantle and its skin, the oceans, the gases, and the crust and its plates - which rejoin sometime before New Mexico makes its appearance on the stage.

Notes:
Chandler, Harry. Metallurgy for the Non-Metallurgist, 1998, on properties of iron.

Kershaw, Steve. “Precambrian Ocean Change” in Oceanography: an Earth Science Perspective, 2000, with contributions from Andy Cundy.

Wikipedia entries on Earth’s history and iron.

A Green Rock

The trouble with rocks is they have a tendency to follow you home. If you’re not careful, your living room becomes encrusted with quartz, the kitchen counter lined with granite. I keep telling myself, look but don’t touch.

Of course I don't listen to myself.

Yesterday I found a handsome green rock in the bottom of the near arroyo. I suppose it’s some form of granite, with red iron splotches.

I don’t know what the white streak is.

I probably won’t ask at that rock store. The last time I went, the young salesperson looked down at my rock from Dixon, and declared that’s just a rock. Now a mineral, he wanted me to understand, has specific characteristics.

Characteristics I repeated to myself, not character.

At least, before he dematerialized, he did deign to tell me the rock from the Dixon area wasn’t shale. Maybe granite. He couldn’t say. But definitely not shale. Just a rock.

Rocks are impervious to the wisdom of the young.

Ranch Animals

Last week I returned to the washes that lay to the right when I was following the road south of my fence. The thing that originally struck me was that the wash stopped at the fence that marked the boundary with pueblo land.

I couldn’t see how nature would respect mere strings of barbed wire and sapling posts. I supposed it was possible, given the way the land varies, that whoever claimed land out of the pueblo grant followed some natural indicator, say the variety of grass which reflected something about the underlying soil structure, but I really couldn’t credit the idea much.

I turned to follow the fence towards the arroyo and found something strange. Maybe ten feet to the side of the barbed wire boundary was a line of farm fence topped by several lines of barbed wire creating a sort of no-man’s land between. The gully began at the farm fence post.

The lane ended abruptly with a line of barbed wire cutting between the two fences and a wash that made it nearly impossible to walk by. The boundary fence continued to the arroyo; the farm fence stopped. It could have been some kind of animal enclosure, but I couldn’t really see what or why.

Yesterday, I went back to the near arroyo to follow the right bank back to the cactus field. The arroyo maintained its lake like appearance on this side of a barbed wire fence marking the pueblo boundary.

I followed the bank back to its farthest corner where I found the remains of wooden chutes used in some way to corral animals. If the current width is any indication, it was probably sheep rather than cattle.

There had been similar remains on my uphill neighbor’s land and in the barbarian’s wash near the road, but they’ve since been cleared away.

As I looked out over the land, the eroded gullies were, for the most part, limited to the private side of the fence like they were further south.

I now wondered exactly what animals could have done to precipitate the natural forces that were uncovering the older landscape. If the contours existed then, I suppose they would have followed the valleys were grass might be lusher and eaten the ground bare, leaving it open to wind and water.

I suppose it’s also possible that the softer spots in the land caved under their weight, and those low spots became the targets of the weather. Between the gullies, the land remains grassy knolls that hide the open trenches. The steppe scrub that returns with overgrazing appears in limited patches in the washes and nearest the road and ATV trails.

On Learning

My plunge into reading New Mexico geology has taken me back to my first weeks as an undergraduate at Michigan State when I realized there were a great many people in my classes who had attended much better public schools than I.

I recognized I either had to work harder to stay even or fall below my personal standard, which wasn’t particularly high, given that mediocre school system, but still high enough to refuse to accept failure.

I remember making the decision some Saturday when my room mates went off to the football game and I stayed behind to study. That day alone, when I first forsook the life of parties, I began developing an ability to teach myself.

It’s a helpful skill now when I read books or articles that claim to be aimed at both the beginning graduate student and the professional. They assume a level of knowledge, mainly about plate tectonics, but also volcanism, that I simply don’t have. It means constant on-line connections to find the definitions of words and concepts.

Fortunately, no one I’ve read so far expects a greater knowledge of chemistry or physics than I have. My high school science teachers were among my worst. Unlike botany, which has been so revolutionized by biochemistry that after some five years of reading about plants I still have difficulty with articles about photosynthesis that assume an understanding of concepts like feedback mechanisms and communication pathways, most of the geology I’ve read so far expects no more than a recognition of the symbols for elements, a minimal understanding of how compounds change, and the understanding of the technical definitions of words like reduction that have broader, general meanings.

This is probably because many senior geologists, those of my general generation, don’t know much more than they learned in high school. Once they specialized, they didn’t need to know more.

This shows most in their attempts to continue to use the basic concepts of Newtonian mechanics relating to the behavior of heat to explain the, to them, new phenomenon of plate tectonics. I don’t know if this was a valid assumption or not, but it was an understandable one given the conservative nature of both science and the human mind.

This brings me to the second thing I realized my first term in school, that I was more interested in interdisciplinary studies than specialized ones. MSU then had a required freshman course called American Thought and Language, which sought to meet the history, English and composition requirements in a single class that placed important writers in their cultural context.

I think I may have spent that long ago Saturday reading Roy Horton and Herbert Edwards’ Backgrounds of American Literary Thought, the first unassigned book I ever bought, trying to understand what my professor was saying about Puritanism. By chance it was the one he was using to prepare his lectures.

I found I wasn’t interested in knowing more and more about Emerson or the XYZ Affair, which is where a major in English or history inevitably leads. I wanted to know about the houses where readers of Emerson lived and the influence of the French more than I did transcendentalism or diplomatic history.

Such a pursuit, if it’s to be more than gadfly dilettantism, requires some discipline, as my graduate school professors never tired of telling us. More important it demanded that ability to plunge into reading something beyond one’s existing level of knowledge.

This brings me to the third thing I realized that first term in college, that no matter how much one learns, there’s always something beyond that’s unknown. Some are so taunted by that edge it drives them to push the frontiers of knowledge. It sends others with a strong desire for explanations into deep theological inquiries.

I realized one is either driven or tormented or one sets limits. I learned to recognize the point where the answers to my questions were pulling me into areas I wasn’t interested in pursuing, and simply accepted that such was the case and I could exist without knowing.

Deciding what to pursue and what to ignore is something we all do to get through the day. Someone once asked Penelope Lively, a novelist who delineated the undercurrents in human relations, how, once she was aware of such things, she could ever get through the mechanics of a family meal when a person simply must ask another to pass the butter.

Geologists must make those decisions when they write an article. They define the purpose, then exclude things that are extraneous. When Steven Whitman and Karl Karlstrom wrote about the formation of the North American continent, they realized their contribution was a series of drawings showing the progression through time. Indeed, one can learn a great deal by only looking at the pictures.

Their supporting evidence was drawn from the rocks themselves. They assumed you knew the rocks. I’m less interested in specific rocks than geologists or rock hounds, and so took their facts as facts not to be bothered with yet. I wanted to know why, not how to properly identify or date a specimen.

They took the Precambrian world as a given. They assumed you knew what that was or that it didn’t matter to understanding the phenomenon they were describing. As an historian, I was lost. If this part of New Mexico began as an island arc, I needed to know more about the ocean at that time, something they barely mention.

I went on line and innocently keyed in the search words Precambrian and ocean. I discovered some German heavy metal group called The Ocean had recorded an album called Precambrian. Interesting, but not what I wanted to know.

With some refinements in my Google search, I eventually found a chapter by Steve Kershaw on Precambrian oceans in his book, Oceanography. He was interested in why the earth didn’t freeze in its early years when the young sun wasn’t as hot as it would become, and so devoted a great deal of space to the Young Sun Paradox.

That’s indeed an interesting question, but not what I immediately needed to know. However, to cover his material for that hypothetical new graduate student, he did mention things I did want to know: when the oceans came into being, how deep they were, how much space they covered.

In the process he also suggested something I hadn’t thought about, how changes in the chemistry of sea water, as recorded by rocks, affected the development of islands like those that would become New Mexico.

The final thing I learned, not my freshman year, but when I actually became that hypothetical graduate student in American studies, is that no one ever tells you exactly what you want to know.

Whitmeyer, Karlstrom and Kershaw have all told me things I need to know, but they are writing for a general audience. It’s going to be up to me to figure out what it means for understanding the geological history of the place I live in the Rio Grande rift valley.

Light

My greatest photography problem seems to be light - too much outdoors, not enough inside. With my digital cameras, when the light’s wrong, the focus doesn’t always work correctly.

My travel camera allows you to alter the light exposure, so the problem of too much light can be mitigated. Of course, you have to get the settings right. As my pictures taken on my trip west of Albuquerque show, a certain amount of experience is required to develop an instinct for those settings.

However, experience is one of those things one can get. It just requires patience and time.

The problem with not enough light requires non-human resources, especially since my close-up camera has no light control. As I looked at my failed pictures of sample rocks taken in the house, I recalled those images of fashion photographers at work with banks of lights in a room and what look like umbrellas in front of the lights to diffuse their effects.

I decided my problem with photographing rocks is that I lacked enough diffused light at table level. I went to the hardware store with some vague idea of a 25-watt lightbulb on a cord somehow set on a low stand, maybe one of those clips they sell for mounting work lights.

As I walking though the lighting department I noticed those gooseneck lamps magazines are always marketing to people of a certain age whose eyes now tire. They claim their array of low-wattage lamps produce something like daylight and imply a panacea for aging.

The store happened to have a desk top model with a light that sits about 11" above the surface. For $15, it was worth a test.

It’s not quite voila yet, but the problem has been changed from helplessness in the face of changing conditions, to learning how to use a tool. Depending on the rock, I have to move it nearer or father from the light. Sometimes, I’ve tried draping a white plastic bag over the top to adjust it a little.

To illustrate my problem I took a stone I picked up in a neighbor’s yard that was the right size to throw at a threatening dog. I quickly realized it was a keeper.

I first got a decent picture of it with my travel camera (picture 3). I then turned off the lamp, but left the altered light settings (picture 2). I next let the settings revert to the default problem (picture 1).

I then took out the indoor closeup camera. The lamp was too bright to show the detail of the rock, and so I used different sheets of colored typing paper as shields (pictures 4 and 5). As you can see, the biggest problem after focus is color reproduction. This is a grey and clear rock, with only a hint of a golden hue to the naked eye.

Another Road, Another Wash

A road branches to the west from the ranch road just below my fence. It was always there in some form, but some years ago some trucks came through and made it more obvious.

At the time someone told me the Indians did it to get back to some clay deposits they needed for their pottery. The person who told me was simply passing on something he’d heard. However, it sounded like one of those things you’re told by people who are aware others exist in the universe who live differently than they, but don’t actually know any of them and so attribute everything to them in an almost conspiratorial fashion to establish they really do know what’s going on.

Another possibility was that some utility had to get back.

The one thing it wasn’t was an enlightened county project to build a recreation trail. However, that’s how it’s been used since by those who walk their dogs or their hearts. The trucks haven’t been back, but it’s been kept open by ATV’s.

It never seemed particularly interesting to me, because I’d already learned few wild flowers grew with the prairie grasses. The far arroyo was more rewarding.

Yesterday was the first time I walked farther than the junipers.

A wash opened on the right that wasn’t connected to the one that had backed up from the acequia drop. The ranch road goes between the two with no sign it’s been filled. Still this wash looked like it might be part of the same weak area.

The banks were steep and maybe 8' high with isolated tongues of soil in the center. It went back as far as a fence and stopped, for no apparent reason.

I didn’t go in to explore. That was the adventure for another day. Today I wanted to know where the road went.

The fence wire had been removed between three posts for the road, which continued to climb toward a row of utility poles. It got to them, and continued to the left, which would be north. So much for that theory.

It rose to a crest, then dropped into a wash, this one the upstream section of the one by the cone I call the barbarian’s wash for reasons best left to the imagination. It had the same characteristics as the one to the south, steep banks and chiseled islands.

There were no signs anyone had mined the area, only that ATV’s had been through on their way north along the front of the tertiary uplands. So much for the theory it led to a special deposit of clay. It was simply a trail.

Tertiary Hill

On the way back from the barbarian’s wash I noticed a hill that had grass growing at it’s base, but was bare at the top. Oddly it supported several junipers.

The slope wasn’t steep. Up I went.

The grass gave way to what looked like caked mud.

Only it wasn’t. I picked up a piece. It was thin rock of no particular distinction.

I continued to the top where the fragments began to take on the shape of some kind of flow over what must have once been soft mud.

If the washes were slowly revealing some previous landscape, this hill top represented how deep those sediments must have been. Presumably, the land was all at this height at some time, but the rock kept this from being eroded as completely.

The junipers had found their water beneath the slabs.

When I got home I discovered the nondescript rock wasn’t some piece of rough-textured sediment, but a slice of conglomerate, I assume from the Tertiary age. How it got atop the sediments is another mystery, if indeed the sediments are younger.

Gravel Heap

As I got nearer home, a line of bare dirt caught my eye. It appeared to be a berm outlining a square filled with piles of gravel.

The imagination can come up with explanations besides a geometrically obsessed gopher.

It looked a bit like an archaeological site that had had a layer removed and sifted. However, I doubt any archaeologist would do the sifting within the confines of an excavation.

Another possibility was that it had once been a much taller pile of gravel, perhaps like the cone, and someone had sieved it to take away the finer stones for a road or drive. They may have built the berm to keep the rock from sliding away. However, I can’t imagine why they would have bothered to create a square, rather than an encircling ring.

It remains one of those inexplicable marks humans leave on the land that the weather hasn’t yet erased.