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There’s a pumice mine in the Coso Range that I’ve not been able to get into since Hurricane Hilary washed out the road a year ago. Finally decided a folding electric bike would do the trick, since I could walk it through washouts. And so, with eBike assembled, gave it a try.

Access is via a powerline road, which bypasses the major washout and intersects the mine road at washout number two. As I approached that intersection, I noticed a fairly overgrown BLM road I had missed before. Pretty good shrubs in the middle, but the wheel paths were clear, so I tried it. 

As it turned out, it intersected the mine road past washout number two, so I was able to drive almost to the mine. Only a geologist would call the current mine road a “road,” with the horrible shape it’s in. Since the last few hundred feet were not anything close to a road, unfolded the bike, since I wanted to see what it would do, and rode on up.

The attraction? Pyroclastic tuff balls, which form more or less like snowballs rolling down hill. The pumice deposit was formed as a part of a sideways blast of pumice and ash from a volcanic vent, glowing hot. Pieces of rock, hot enough to be sticky, tumbled along in the glowing ash cloud, picking up red hot ash and rock fragments. I’ve looked at a lot of ash flows and pumice deposits, and this is the only spot I’ve seen these. Tuff is a rock formed of welded volcanic ash.

The mine had suffered significant erosion. Took photos and found what I was looking for. That evening, wanting to send photos to someone, discovered none of the pix had gotten into the icloud, so reached for my phone. What?! Not in my pocket? Find my phone showed me roughly where it was, in the mine!! Aagh!

Next day went up there and found the phone. Cooled off with a giant iced tea in Ridgecrest, fed the van with cheap (relatively) gas, and though it was 110 degrees, drove up an aqueduct road to collect some teaching examples of true granite, nothing at all like countertop granite, 99% of which isn’t granite at all. The outcrop was in the shade by the time I got there.

Granite is not so common, but “granitic” rocks are, in the family with granite but differing in mineral percentages.

Crazy couple of days, but overall pretty good. The phone was cooked, but after a cooldown, it still works!

Here's T Cat watching a hole. He at least, had the good sense of not trying to go in. This is in a ridge of fault gouge along the San Andreas Fault, all clay and fairly easy for some critter to dig a burrow. The approach has been excavated by rain, forming that gully, and it wasn't easy to tell if someone was home.

A few years ago I was here with Cucumber as field assistant. She's T Cat's little sister, and she fit in that hole perfectly. Back then, there wasn't any gully, just the hole and a pile of fresh excavations out front.

I found her with just her tail sticking out, and grabbed it. It seemed likely that whatever did the tunneling, which was fresh, had a nifty cavern where it could turn around and attack any intruder. Cucumber, however, would have to back up, and I wasn't taking any chances. She backed out as I pulled. Here she is, on a different trip, when a motorcycle went by. "I think I'll jump in right now!"

These two field assistants come along, one at a time, on collecting trips. They both jump in the van when I'm ready to leave and I ring a bell, or when a motorcycle approaches.

In 2023, parts of California and the southwest got a lot of rain. In August, the remnants of Hurricane Hilary arrived. The result? Many mine roads were so badly damaged that they are totally impassible, except possibly by a motorcycle. This has had a big effect on collecting, since inactive mines where we regularly have collected are impossible to reach. At one mine road, north of Las Vegas, I cruised up the paved road at night, intending to camp at the mine and collect in the morning. 

At one point, the mine road passes through a gap in a ridge that had been carved by water. Instead of grading the rocky stream channel, usually dry, the miners simply covered the rocky bottom with dirt. That had lasted for years, but the dirt is all gone now, thanks to the power of flowing water. In the dark I thought I could thread through the mess, got stuck, jacked up the van, piled in rocks and backed out. In the morning got a better look, walking, found the burned out remains of a jeep, and decided there was no way through with anything that has four wheels.

The road that's covered with rocks was easily drivable to the mine in an ordinary sedan - until 2023! The miners whose grader was buried were lucky. One side of their road became a canyon, with the edge coming within a few feet of parked mining equipment. Don't underestimate the power of running water, that's for sure.

In October 2022, a collecting trip that crossed the Basin and Range province required driving over a lot of caterpillars. It was caterpillar, then a valley, then another caterpillar and another valley. In the Basin and Range Province, there are over 500 of them. Caterpillars, that is.

In an 1886 report from the Secretary of the Interior to Congress, geologist Clarence E. Dutton wrote, "The great belt of Cordilleras coming up through Mexico and crossing into United States territory is depicted as being composed of many short, abrupt ranges or ridges, looking upon the map like an army of caterpillars crawling northward. At length, about 150 miles north of the Mexican boundary, this army divides into two columns, one marching northwest, the other north-northeast."

The northwest marching caterpillars are the ranges of the Basin and Range. If you are driving in an east-west direction, it's up, down, up, down, over these ranges. This geomorphic province has interior drainage, with no through-flowing rivers to take sediments and dissolved minerals to the sea. As a result, many of the basins, the valleys between the ranges, have salt flats in their bottoms. These are seasonally wet or dry and are called playas, the loosely applied Spanish word for "beach." The Bonneville Salt Flats in Utah and the salt flats at Badwater in Death Valley are classic examples. 

On the first part of the route we took US Highway 6. At Ely, Nevada, we detoured onto US 93 and then US 93 Alternate, heading for the Great Salt Lake. It was caterpillars and valleys all the way. Just west of Wendover, Utah we coasted down the last caterpillar into the last valley, where I-80 crosses the Bonneville Salt Flats and skirts the south edge of the Great Salt Lake.

The easternmost edge of the Basin and Range is the Wasatch Front, behind Salt Lake City, Utah, where eastbound, you climb onto the Colorado Plateau. We zigzagged around on this trip, with the ultimate aim the K-T boundary exposures in Montana and North Dakota. We had found the boundary clay in 2021, but it was snowing. That clay formed when the meteorite that finished off the dinosaurs blasted tons of pulverized crust into the atmosphere. This fell back to earth and in some places, where it wasn't washed away by rain, it has formed a roughly two-inch layer of clay. K stands for Cretaceous, from the German spelling, the last time period with dinosaur fossils. T stands for Tertiary, where sediments lack dinosaur fossils entirely. The two inches of clay mark the extinction.

It was an interesting collecting trip, and most of the boxes are still waiting to be unpacked. Wondering why there is a long gap between these posts? Well, we're busy. We still have 20 boxes of lava types from Hawaii to unpack, but that's another story. And keep an eye out for the K-T clay.