Black Mesa

It seems, wherever you go in this part of the world, you find a Black Mesa. It shouldn’t be surprising, really, when you consider the Rio Grande crosses an oblique line of volcanoes.

There are two in this area. North of town, the ten-mile long finger of land between the Rios Grande and Chama has been called the Black Mesa by geologists since George Wheeler named it so in 1876. Down on the San Ildefonso grant near the road that people use to commute between the valley and Los Alamos there’s another, rising 500' from the surrounding flat lands that slope to the river.

When I first moved here, I was told or read the San Ildefonso mesa was the cap of the Valles Grande volcano that had landed there when it erupted. I’ve also been told it was the last retreat of the pueblo peoples fighting Diego de Vargas in the entrada and that there’s a pair of peregrine falcons nesting there.

Ted Galusha and John Blick resolved the ambiguous naming problem by calling the San Ildefonso mesa the Round Mountain. I prefer to find another name for the peninsula of land, perhaps Wheeler’s Black Mesa or the Chamita Black Mesa.

They also dispelled any romantic notions about its origins.

It’s an independent cinder cone built around a volcanic neck that was formed some 4.4 million years ago in the early Pliocene, possibly as part of the Cerros del Rio volcanic field southeast of the Otowi bridge. According to Daniel Koning, one of its lava flows has been dated to about the time the Rio Grande was becoming a perennial river, long before the Toledo and Valle Grande eruptions.

The base is dark gray to black basalt. The top is covered with river cobbles and pebbles laid down about 1.5 million years ago, long before the lakes described by Steven Reneau and David Dethier.

Cinder cones are the simplest type of volcanos, central vents surrounded by fans of erupted debris. Volcanic necks are formed when the magma hardens within the volcano. Red cinders found on the southwest side suggest an eruption was through that side.

When water washes away the softer materials that surrounds a volcano, the basaltic blocks drop into a dense mass around the base that eventually prevents further erosion. If indeed this volcano was standing in 500' of water in the early Pleistocene, there was a great deal of water available to consolidate the current formation into a fortress which has since survived those lakes and, perhaps, created the fans where juniper now grow.

Top: Black mesa behind cottonwoods along the Rio Grande taken from the west side along route 30.
Bottom: Mesa taken from northeast; the ranch road wanders towards it after leaving the far arroyo.

Fossils

Even when confronted with the rapid obsolescence of computers and cell phones and cameras, one can still lose sight of how much has changed in science since the men at Los Alamos set off their first test explosion.

Grade school is still the time we learn about the geologic past. Young boys are still infatuated with the Jurassic age of dinosaurs. For some reason, I got struck by the Pennsylvanian era of swamps and evergreens when coal was being formed.

Back in those days in the middle 1950's, the world began with the Precambrian. I never thought why, it was simply so. At that age, one didn’t consider the wonders of zero either or worry about negative numbers. One simply learned to count, one, two, three.

While I was reading Ted Galusha and John Blick’s article on Tertiary sediments in the Española basin, I suddenly realized why. When I was a child a principal way to date rocks was with fossils. There were no fossils before the Precambrian age. There was no life as we know it to produce fossils. The beginning of life was the beginning of rocks.

Oh, there was something called the Archaean to account for those things that were obviously below, but had no retrievable history. They simply existed after the big bang and solidification of the earth’s crust, but before time.

The problem with fossils is they often are dated by the strata in which they are found. In turn, they are used to date other strata in a closed, self-referencing system with few points of independent verification.

The whole time I was reading Galusha and Blick, all I really wanted to know was how old are the rocks Daniel Koning says lie under my house and how did they get there. Their answer was:

“The Tesuque Formation apparently was deposited through part of the Hemingfordian, Barstovian, and most, if not all, of Clarendonian (early Pliocene) time.”

To get anything more specific than late Miocene, I had to look up those fossil groups, which were filled with animals both strange (camels, rhinos, horses) and extinct (oreodonts), many of which migrated across the Bering land bridge.

At least, when you do go on-line for information, there are artists’ attempts to grapple with what those bones looked like when they were moving about. They don’t answer my questions about age, but they are diverting.

Dating techniques were beginning to change when I was a child. At Enrico Fermi’s University of Chicago, where so much preliminary research into the nature of matter and the predictable half lives of radioactive isotopes was done that lead to the bomb, Willard Libby was applying the same model to carbon to develop methods for using the carbon-14 isotope to date items that contained carbon.

By the time I was in college, his methods were being accepted, but they were only good for 62 million years. That’s the Tertiary Eocene. It could date a mastodon, but not a dinosaur. Still that was more than adequate for me. I was becoming an historian, not a zoologist or geologist.

Since I last paid attention, engineers have used all those technical skills that led to things like computers and satellites used by cell phones to develop other tools for probing the past. They send electromagnetic signals and interpret the resonances. They use the half-lives of other elements like potassium and argon. Their papers become tables of graphs and columns of numbers one has to take as true while looking for the scattered intelligible words in sentences like:

“Other east-west gravity profiles between latitudes 32^o and 38^o also show this asthenospheric diapir, which thus forms a ridge-like Moho unwarp approximately parallel to the surface trace of the rift.”

Thank God for Google and the ability to look up any word, to learn aesthenospheric refers to the mantle and Moho the boundary between the mantle and the crust, to learn something detectable exists deep in the earth below the rift valley that may account for all the geologic activity.

These tools which I have to take with the same faith I once took the word Precambrian are probing the time when the plates were colliding billions, not millions, of years ago. That really is astounding. The latest Geological Society of American time scale breaks the Archaean into four phases and has a created a new “dates unknown” period, the Hadean for older than 3.8 billion.

Santa Fe Group

Santa Fe Group is a term like sparrow or hummingbird. It allows you to describe things fairly accurately when, in fact, you don’t really know enough to be specific.

Ted Galusha and John Blick say that at one time or another it’s been used to describe almost anything along the Rio Grande. They narrow the term to middle Miocene and early Pliocene sediments found between the Sangre de Cristo and Jemez.

They identify two general areas, one they call Chamita, the other Tesuque. Within the second, which is the one found where I live, they identified five major strata: Nambé, Skull Ridge, Pojoaque, Chama-el Rito, and Ojo Caliente sandstone.

The laminated formations you see along 285 when you drive through Arroyo Seco between Santa Fé and Española are from the Skull Ridge and Pojoaque members. According to Daniel Koning, the first was deposited 16.2 to 14.6 million years ago; the second is dated between 14.6 to 11.6 million years ago.

Koning also indicates that rocks came from two sources in the late Miocene. Those towards the north and west are from the Peñasco embayment between the Picuris and Santa Fe Ranges of the Sangre de Cristo, while those to the south and east generally arrived from the Santa Fe Range.

The Los Barrancos fault zone runs to the west of the highway. Sediments to the east, the ones you see, are older than the ones to the west, which are the ones that come close to my house.

The rocks on the west side of the road in the top picture are from the Peñasco embayment with the Skull Ridge member exposed in Arroyo Seco. The rocks on the east side in the second picture have the same provenance, but are older.

The third picture was taken on Pojoaque pueblo land. Koning identifies them as Skull Ridge layers from the Santa Fe range. In the picture below rocks from the Pojoaque member of the Peñasco embayment rise behind the wall of the far arroyo.

Leisure Time

Time is the gift of retirement.

Only, I’m discovering it’s not the vista of another lifetime, another ten or fifteen years, that’s important. It’s the recovery of all the minutes lost to work in a day.

I have breathing problems which means some nights I’m a restless sleeper. I couldn’t get up to do something useful until I could sleep. I couldn’t afford to fully wake up. I had to lay there remembering the countries of Africa to force myself to sleep. Wasted time.

I’d wake later than usual. I had to economize to be on time. Instead of fully remaking the bed, I’d settle for pulling up the covers. It saved a few seconds.

After breakfast, I couldn’t afford the time for the water to run hot. I’d leave the pan to soak. I’d didn’t have time to run a cloth over the counter to clean any crumbs. I couldn’t be late.

There was no time to empty the dishwasher. It slowly became the cupboard for the most commonly used dishes.

I’d go back to the bedroom, look at what needed to go into the laundry basket. That was a walk to another room. It could wait.

Slowly, without really being noticed, things got a bit seedy. Christmas breaks became times to catch up on chores. Only, with my last job, I even had to work a couple days the week everyone else was off. Things got grimmer.

And now, while I wait for the hot water to run, I take a sponge and clean a counter. Another day, the freezer top.

I’ve made no great effort to clean the house, simply fallen back into old routines.

The oldest recovered routine may be the habit of walking. I always had to walk when I was a student - to grade school, junior high and high school. In college I often rode a bike because the Michigan State campus was so large. When I was a graduate student, I rarely took a bus because I didn’t have enough money and it was often faster to walk in Philadelphia.

Then I started to work. Jobs were never near where I lived. I had to drive. Somehow, I wouldn’t think about walking anywhere when I got home. There was always something that had to be done in the house. The yard became a substitute for being outdoors.

Now I can walk each day, though rarely even a mile. One cannot recover youth. The body has changed. Muscles need retraining.

But still, other habits are being recovered that had been submerged so long they’d become part of some past life. The willingness, nay the desire, to walk to the top of a mountain or the end of an arroyo, not settle for the familiar.

Leisure time is very real, and not at all what people tell you it will be.

Nasturtiums before and after last week’s freeze.

Mastodons

The first time I heard of a mastodon I was sitting in a lecture hall at Michigan State listening to Russel B. Nye, who often combined cultural history with American literature.

I don’t remember what he said beyond a nearly complete skeleton found in Ohio had caused quite a sensation in the early nineteenth century. Somehow, I got the idea the skeleton was lying, fully exposed, on top of the ground and was stumbled upon much like the mounds had been.

I’ve since heard the animal was a glacier age mammal hunted by people using Clovis points. For some reason, that led me to think of them as great grass eaters.

When one’s interest in a subject is superficial, one’s knowledge tends to become a brew of facts, romantic legends and false conjectures.

I was, understandably, quite startled to find someone I think was Francis Klett say:

“In these beds, near Ildefonso, I made some excavations in 1873, while on the way to Fort Defiance under your expedition, (division 2,) and brought to light fossil bones of a mastodon, only one of them perfect, however; others were broken and yielded but fragments.”

The quotation is from the 1873 Annual Report of George’s Wheeler’s Geographical Surveys West of the 100th Meridian, and the location must be somewhere just north of route 502. That’s almost as close as the Otowi Bridge.

I suddenly needed to know more about mastodons. As I read, accretions of secretly hoarded facts dissolved.

It was true mastodons were glacial creatures and had been found in association with Clovis points.

However, they were associated with cold spruce woodlands, not grassland refuges.

Spruce growing where grass has been having a hard time surviving this year's drought.

Spruce near the Otowi bridge when those boulders blocked the Rio Grande creating lakes.

Spruce along those arroyos with the Qayi late-glacial sediments identified by Daniel Koning.

Spruce in my backyard. Who cares about a mastodon eating the foliage. Cold climate spruce right here where I’m writing.

Spruce.

Lakes

The morning of the day the Las Conchas fire started, the air was so hot, the soil so dry I went looking to see if any prickly pear were blooming anywhere this season.

One place I walked was an open field just beyond the near arroyo. Nothing. Not a flower, hardly a healthy plant in a place they bloom year after year.

The Pacheco fire was still burning towards Tesuque and was sometimes visible from the road in the area. I looked that way from somewhere in the center of the field and, besides smoke, saw something I’d never noticed before. The field looked like a great bay that water had washed over from a break in the badlands.

Saturday, when I was in the near arroyo, I wondered how it connected to that open space which it had to border somehow. The bed narrows between five or six foot walls a little beyond the point where water begins channeling itself for the culverts. As I went up stream from there, it turned to the left and suddenly opened into a great, wide expanse with almost no banks.

I remembered something similar in the far arroyo. Yesterday I walked back to refresh my memory. Again, the tall walls make a turn, this time to the right, and a great expanse opens.

I came home to pour over Daniel Koning’s map of the Española quadrangle and I noticed something I’d missed before, that some of the places I’d read as Qay1 were really Qayi.

Qay1 is his code for alliuvial soils laid down in the first phase of the post-glacier Holocene period. The river bottom is Qay2, a younger layer.

Qayi turns out to be some intermediate phase of sand and gravel bands, the very strata I’d noticed along some of the taller walls in the far arroyo. The same pattern appeared in the shallow walls of the great expanses of both arroyos. This is precisely where he’d marked Qayi on the map.

Some passing reference in Ted Galusha and John Blick’s article on Española sedimentation that I’ve slowly been reading sent me to look up the Otowi lava flows they said had dammed the Rio Grande in recent times.

I discovered Steven Reneau and David Dethier’s work on area lakes created when landslides dammed the Rio Grande around the Otowi bridge. One occurred around 43 thousand years ago and created a lake some 15.5 miles long that lasted anywhere from a hundred to a thousand years.

Another landslide created a pool 13 miles long about 17.5 thousand years ago which broke suddenly. The most recent, formed about 12.4 thousand years ago, was also about 15.5 miles long and filled completely with layers of sediment.

During much of this time, the very end of the Pleistocene, there was greater rainfall than now, so the river levels would have been higher. The most recent lake was 100' deep.

This area is well within 10 miles of the Otowi bridge, probably much closer if you’re a crow or a drop of water.

One small mystery has been solved, the origin of those gravel bands. What still is unknown is why the channels that are being opened now in the arroyos and washes were there to be filled by Qay1 and Qayi in the first place.

The Cone

This afternoon I went back to the cone, determined not to be fooled again by its wiles. This time I took the simple path, the one from the near wash. As I walked up the easy grade, I realized the cone might just be the tip of the hill I live on, the one that had caused so many water problems in the past.

As soon as I got close I saw that it wasn’t bare because of erosion caused by the ATV rider. It was actually stone and not some soft soil. Daniel Koning had said it was tertiary, not the more recent quaternary. The two were there to see on the slope where the grass couldn’t hold its own.

I started climbing the cone. The more I climbed, the more the top receded into a face of gravel.

I felt no overwhelming urge to make it to the top and yodel. My knees were chanting "Jack and Jill went up the hill." The view of the black mesa was quite spectacular where I stood.

On the way back down I picked up some pieces of the grey, rough textured stone for the Rock Queen.

Hopefully she can tell me what it really is, something more useful than tertiary side of the geological change.