Another Road, Another Wash

[I originally wrote this in November 2011, but never posted this series on the local geology. The pictures are still worth seeing.]

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 signed 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 sand 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 island.

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.

Ranch Road

[I originally wrote this in November 2011, but never posted this series on the local geology. The pictures are still worth seeing.]

Yesterday I walked out the ranch road towards the Black Mesa. I went as far as the pueblo boundary where it branches, with one prong going through a gate to the ranch and the other through an arroyo and on toward the mesa.

The road looks and feels like the arroyo bottom, but the neighboring soil is the usual erodible mix of clay and sand. When you get to the Y, the road on pueblo land becomes two tracks of uncovered dirt that would be difficult for a car to negotiate in wet weather.

As I walked back on compacted soil veneered with fine gravel, I wondered if the ranch owners had dredged the bottom of the far arroyo to protect their road, and if others had also done that in the past here and in the other arroyos.

If that were true, I wondered if the arroyo bottom had once been filled with gravel, had been bare like it is now, or had once supported vegetation like the arroyo on pueblo land. I also wondered if their mining had widened or flattened the bottom, or if the general shape had been carved by nature and only slightly been modified by them.

Bottom photograph shows the land to the side of the road, taken when I stopped to take the middle picture of the road.

Wind

[I originally wrote this in November 2011, but never posted this series on the local geology. The pictures are still worth seeing.]

Wind and water together sculpt the land. The effects of water are to be seen everywhere land appears more level than normal. Wind preys on the spaces between bunch grasses and shrubs where soils can dry.

Saturday the Rock Queen and I went driving west from Albuquerque in search of agate, oblivious to the winds that had developed in the city after the rain had moved through there in the morning. Let it not be said that a rock hound can be deterred by mere weather.

We first noticed a completely bare hill on the south side of I-40 where the dust was rolling a few inches above the surface like water running over a flat stone. We dismissed it as the work of man, for that hill had not a sprig of vegetation.

As we continued west, the winds grew stronger. The land alternated between fields of bunch grass, exposed layers of sediment, mesas and fragments of dark lava. The sky was only occasionally blue. Even in places where vegetation exists, a fog of dust crept a few feet above the surface, moving in, out and around high points.

We stopped to look for rocks near some odd formation that was near valleys that fed a lowland in a pattern of receding herringbones. On the leeward side where no wind could reach us, the surface of sand was frozen in inch-high waves from some previous wind. Whatever vegetation that had existed there had not survived the drought.

I’ve lived through sand storms in Abilene, Texas, where the dirt was so dense, you had to close your eyes to protect them. Grains got into you teeth. The paint on the car was blasted.

But those storms didn’t have the animate form the winds did yesterday outside Albuquerque. They were simply sheets of dirt moving through, often dense enough to turn the sun silvery at noon. They had none of the sinuous form of tunnels and layers that glided around the mesas and outcrops.

The desolation the universe can create was on full display, but jasper littered the ground.

Note: Pictures are dark because I didn’t set light openings correctly on the camera, not because the sand blocked out the sun like it would have in Abilene.

Black Mesa

[I originally wrote this in November 2011, but never posted this series on the local geology. The pictures are still worth seeing.]

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.

Photographs
Top: Black mesa behind cottonwoods along the Rio Grande taken from the west side along route 30.

Bottom taken from northeast; the ranch road wanders towards it after leaving the far arroyo.

Notes:
Galusha, Ted and John C. Blick. Stratigraphy of the Santa Fe Group, New Mexico, 1971.

Koning, Daniel J. Preliminary Geologic Map of the Española Quadrangle, Rio Arriba and Santa Fe Counties, New Mexico, 2002, map and report.

Fossils

[I originally wrote this in November 2011, but never posted this series on the local geology. The pictures are still worth seeing.]

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 that 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 Rio Grande 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.