River Rock

River rock is one of those terms used everywhere in the country that everyone knows what means and no one defines. Generally, it’s rock that has a relatively smooth surface. I say relatively, because its not as smooth as a polished tombstone, but it’s not jagged.

If you ask for something more specific, people take the adjective smooth and turn it into a verb. There the trouble begins, because they start to say things like “the erosive action of the moving water from a river smooths and shapes the stones. Other times, they say something slightly romantic like “smooth surfaces created by tumbling around in rivers for years.”

Maybe, elsewhere in the country. Here, even when the Rio Grande is running high, like it was in the above picture take last October under the Griego Bridge in Española, the water only creates rapids. You don’t see rocks being tossed about. More likely you see them laying outside the action where silt can filter through them.

Smoothing and polishing are not the same thing. The second is done by removing material, often by breaking large pieces into smaller ones. In a rock tumbler, the polishing is done by some kind of abrasive grit, something like silicon carbide, with water used as a facilitating lubricant, not as the active agent . The winds here move sand at high enough velocities to blast surfaces.

The above is a piece of granite I found in the area of the far arroyo this weekend. Part of it has striations that left a relatively smooth surface. The darker corner at the top in the picture below was untouched. There the smoothed section has a lighter color because the abrasion removed the tops of the softer, darker mica, but harder flecks of quarts remained.

The smoothing of river rocks is done by filling in rough surfaces with finer sand that drops when the river currents slow. It often is the same general material loosened by wind and deposited in the water. Eventually the sand becomes welded to the surface, like a rind.

I first noticed this with a bit of granite I picked up somewhere along route 554 north of Ojo Caliente last fall. You can see the brown outer skin is very different than the quartz and mica inner stone. If you look carefully, you can see the outer layer isn’t uniform in thickness, but penetrates in low edges to fill the rough places. That’s what creates the coarse textured, smooth feeling exterior surface.

If the river rocks were polished by removal, they’d look more like tombstones or the stone above. Instead, they look like amorphous potatoes. Round, formless, grey lumps.

Someone broke the above rock outside a near neighbor’s drive. Since he works for Cook’s Transit Mix, I assume the rock came from somewhere just north of Española. You can just see the lighter colored outer layer that built up around the granite, especially on the lower curve in the upper left had corner.

Last weekend my immediate neighbor had loads of sand brought into our shared drive by a friend of his who said it came from his yard in Velarde. A broken piece of granite filled with quartz and mica landed near my gate.

Again, you can see the boundary between pock marked grey shell and the uneven texture of the broken face. It may looked like it’s been smoothed by removal, but if you look closely you can see the uneven fill that protects the bright interior with a dull overcoat. In places it has even started to colonize the surface.

White Sand

There are things you always say you’re going to do, and something always intervenes.

Every time I drive north towards Taos from Velarde I tell myself I really must pull over on the way back and look. Fallen lava boulders litter the right shoulder as you rise. By necessity, the turn offs are all on the other side. The road has too many blind spots to simply cross over.

But then, when you’re coming home, you’re, well, coming home. It’s a different mental state. There’s never time to pull over.

Well, I finally did it. When I was coming back from the Dixon area a few weeks ago, I pulled over in some of the places between Embudo and Velarde where the rift is narrow, the Rio Grande close to the road.

The look up towards Taos isn’t quite as dramatic as it was when I was driving north - but then it’s like the drive down La Bajada Hill - there are no turn offs when the rocks are the most menacing. The turn offs are only where there’s room, which, by definition, is not where it’s most exciting. Perspective is different from fifty feet across the road.

The river turns out to look like a river there, like any river anywhere in the country where water actually flows and doesn’t simply ripple around sand islands as it does in Española. Nice, unusual actually for New Mexico, but conventional still the same.

Then there’s the unexpected, the thing you didn’t know was there because you never stopped.

In this case, there was a patch of white sand near the river with Russian thistles and purple asters. You think, wait a minute, white sand? New Mexico?

The White Sands in the Tularosa Valley are gypsum dunes. This glittered in the sun. It had to be ground quartz, which of course is as much silica as sand. In fact ground pure quartz provided the material for Venetian glass makers.

Quartz has the greatest weather resistence of any of the rocks in the area. It’s often the last remaining eroded rock from the Sangre de Cristo. This “dune” looks suspiciously like how that sedimentary grey rock I saw earlier in the day beyond Dixon would look if everything soft disappeared and left only the quartz and shining mica. And it photographs the same way, too brown and out of focus, or all glare.

Between Dixon and Picuris

Now that I have a new camera I have to test it.

My usual method for day tripping has been to look at the map, find something that looks interesting, load the ice chest, and start driving.

There is nothing that can repeat the absolute surprise you feel when you come upon something like the Abiquiu Dam when you’re not expecting it and nothing you want to do to deaden that heart-stopping awe, that sense of unity with all the explorers from the stone age to the present who’ve been there before.

When I get home, I start to read about the place I’ve just been. Then when I go back, I have some better ideas what to look for and some idea about where it’s safe to pull off the road.

Saturday, I took the new camera back to that road beyond Dixon where I had problems with my tires earlier this summer.

After NM 75 leaves Dixon, it feels very much like a typical mountain road with the Rio Embudo on the right side, an occasional gorge coming down from the left, and continually opening V’s as the road climbs towards the Sangre de Cristo south of the Picuris mountains. The trees are all still juniper, but closer together than they were below.

Then I came to a section where raw rock was exposed, standing on edge. It looked like shale at the Rio Grande end, then layers of sandstone. However, they seemed so weathered they had no distinct colors, and I’m not sure I even know what shale looks like, other than it’s gray.

My first thought was, why on earth did anyone go to the expense of blasting a road through here. This is New Mexico, where they didn’t widen the road to Los Alamos until after I moved here. Route 75 was described as “a graded dirt road” in the 1930's WPA Guide when the road that came up from Chimayó through Truches and Las Trampas could get you to Picurus pueblo and Peñasco.

I spent yesterday learning absolutely nothing.

The Española Basin, which tilts west down to the Rio Grande, ends at Velarde. The San Luis Basin, which tilts east, begins farther north. Between the two lies a diagonal belt of disruption that goes from the Picuris mountains to the northeast through the Embudo Fault across the peninsula between the Chama and Rio Grande rivers toward the opening into Santa Clara Canyon.

I presume I was somewhere on the edge of that fault, but can get no confirmation. Is this what a fault looks like?