The San Juan Mountains were clearly on fire. We could see and smell the forest fire 5o miles across the San Luis Valley. Ann and I abandoned our plan to camp at the headwaters of the Rio Grande. Instead, we turned east and spent the night in the Culebra range.
The setting sun illuminated the Spanish Peaks. The Ute tribe calls them “Wahatoya,” - “breasts of the world.” They are an impressive pair of mountains.
The sunset light filtered through forest fire smoke. The peaks are “stocks”, intrusions of magma that flowed and cooled underground. Large intrusions are called “batholiths.” Batholiths form the Pike’s Peak range and the Sierra Nevadas. Smaller intrusions or arms of a batholiths are called “stocks.” The Spanish Peaks stocks became prominent as they resisted the erosion that removed at least a vertical mile of surrounding rock.
The Spanish Peaks are known for their dikes. One dike is clearly visible here 20 miles away. Over 500 dikes radiate from the peaks and extend as far as 17 miles.
Some dikes are even named locally.
Next morning, we drove to a trail head for the western peak. There was no time to climb but a viewpoint was an easy mile up the trail. Walking that mile, I noticed 2 things that puzzled me:
1. The trail underfoot was river-rounded stones. Did the Forest Service surface the trail? No, the river pebbles were off the trail as well. The trail is on a ridge. Rivers avoid traveling on ridges. What’s going on?
2. The peak is a stock, an igneous body, so why does it have such obvious horizontal strata?
Horizontal structures are apparent.
Maybe I could find out.
A month later Russell, our oldest son, met me at Blue Lake Campground. The campsite is at 10,000’. Sleeping high is a popular method to make climbing easier. Your body acclimates as you sleep and boosts your red blood cells overnight. This can make a huge difference with your abilities the next day.
There was some daylight left. We took the pickup on a jeep road to the shoulder of Trinchera Peak. Past tree line, big marmots with bushy tails glared at us. Their alarm shrieks demonstrated why they are called “whistle pigs.”
We crossed the trinchera (trench) of Trinchera Peak. This valley under the peak is a cirque carved by a vanished glacier.
The ridge of Trinchera Peak is formed with layers of sandstone set on end.
The road ends on a shoulder, at 12,674’. The land falls away into the Rio Grande rift to the west.
To the east, the West Spanish Peak stood in the afternoon light.
The Taco truck did well although its longer-than-a-jeep wheelbase required some tight backing on some switchback turns.
The plan was to leave camp in the dark and be on the trail at first light. This would get us off the peaks before afternoon storms.
It rained. We remained in camp, in our beds, in the rain, even as daylight came.
Mid morning, the sky suddenly cleared. We left.
Being super strong and fit, Russell offered to carry most of the supplies.
It would have been rude to refuse.
Now I could examine the mysteries.
Here is what I found:
1. The round river pebbles are weathered from a conglomerate of river deposits.
The soft, sandy matrix easily releases the hard round stones.
2. When the stock fractured the country rock and filled radiating dikes with magma, it also separated horizontal beds of sandstone and filled those horizontal cracks with sheets called sills. There are many sills as well as dikes. North Spanish Peak is like a many-layered cake with magma frosting between layers of sandstone. The visible layer structure is made of both sedimentary and igneous rock but it’s horizontal structure is an artifact of the sandstone bedding.
At the peak, this same material has been heated between layers of magma and is harder, perhaps quartzite. (Sandstone can be changed by heat, pressure and time to become quartzite. The difference between the two rock types is that the harder quartzite will break through its quartz grains but sandstone breaks around them.)
We left a beautiful forest of Bristlecone Pines behind at tree line and proceeded up the slope of West Spanish Peak among wildflowers and broken rocks.
I stopped often to pick up rocks and poke about. Russell was commendably and obviously patient. He likes to run up 14ers. I like to look and examine things. Clouds were forming.
Broken off pieces of native rock carried in the flow of magma are called xenoliths (stranger rocks). The splitting and expanding into dikes and sills created many xenoliths. The dike and sill materials on the peak are rich with them.
Very pretty rocks.
Clouds accumulated, the clear blue sky was gone. There was still a thousand vertical feet to go.
We glanced up more often. The West Spanish Peak had a cloud cap.
The cloud grew to shadow us. No thunder yet.
We stopped. The cloud above tumbled and grew as we looked.
We agreed to turn back. I thought that we were wise and felt smug about maintaining a proper margin of safety, turning back with plenty of time.
I was wrong. There was no margin. Before getting to treeline, fireworks started. Lightning snapped and crashed above and below us. We hiked fast downhill and even ran across open meadows getting back to the car. It was scary but fun.
We’ll be back in September when the air is frosty dry and the aspens are yellow.