Thursday, September 12, 2013

Into the Great Unknown: "Disaster" in National Canyon and the Volcanoes of Grand Canyon

Yeah, I was not feeling all that comfortable. It was day 13 on our journey into the Great Unknown, the Colorado River through the Grand Canyon. Day 13, and Lava Falls Rapid, the worst rated rapid on the river was...13 miles downstream. And I didn't know it yet, but we would arrive there at 13:00 hours. I'm not at all superstitious, but it was nice when the message written in the sands of time on the river shore appeared. Okay, I put it there myself, but I was apprehensive just the same!
We were camped at the mouth of National Canyon, which for many years was one of the larger and more popular campsites on the river. And then in the summer of 2012 it was hit by an apocalyptic flash flood that just about wiped the camp out of existence.
It's hard to imagine the scale of the flood. Estimates put the flow at 15,000 cubic feet per second. To put that into perspective, the flow of the entire Colorado River for most of our journey was around 8,000 to 12,000 cfs. And the flood was witnessed. A Western Rivers Expedition boat was passing by, and captured the flood entering the Colorado. Check out the video below by Joe Clark, one of the river guides:

Our campsite was rocky, but we found places to sleep. The rocky plain was barren of plant life. There is hope that a few artificial floods may ultimately deposit more sand on top of the bouldery deposits, but I wonder if the Bureau of Reclamation will be doing any artificial floods in light of the ongoing drought.
In any case, the experienced members of our crew were curious about how much the canyon above the river had been changed by the flooding. To me, the canyon was a beautiful place, regardless of how it might have once looked. How could I know any difference?
I could see that eroded ledges of Muav Limestone had indeed been buried in debris, and barely a single plant was visible along the course of the creek, despite the presence of a clear babbling stream. The going was tough in a few places. Boulders choked the channel.
The barren nature of the canyon was almost disturbing. It felt like there should be plants growing along the water. It drove home the point that no matter what ever else may happen, the rocks remain. Battered, broken, or polished smooth, they will last as everything else passes. But the rocks were also very beautiful, though, and the narrows spectacular. It occurred to me that this canyon, were it to be anywhere else in the country would be a national park or monument in its own right. Here, it was simply a tributary to the larger river, one of many.
The sun was high, and it was getting hot. We got onto the river and rowed downstream. We had reached a fairly long stretch with no major rapids, and lots of quiet passages through vertical canyon walls of Paleozoic sediments. In places we could see all the way to the canyon rim four or five thousand feet above us. The rim, and the world beyond, seemed remote and very far away.
I did a double take at Mile 176. Thousands of years ago massive landslide had broken away from the Supai cliffs out of sight above, and had come thundering over the Redwall Limestone, coming to rest near the river. It is called the Red Slide.
Over time erosion began to tear away at the debris-covered slopes, but here and there a large boulder protected the underlying soft material. The boulders were left standing on spires called hoodoos. It was yet another strange sight along the river.

I was on the lookout, because for the first time we would be seeing a new rock unit (the last "new" rock unit had been 100 miles upstream). It is not a familiar rock to the vast majority of visitors to the Grand Canyon, and in fact, most people are surprised to find out that such rocks are present in the national park: there are volcanoes and lava flows!
I looked high on the walls, and there was the first one, a fragment of black basalt clinging to the cliff. It was an exciting moment for me, because I've never seen these rocks before. I will deal with the profound effects of the lava flows in one of the next posts.
There were more signs of volcanism along the river where a sill had intruded into the Muav Limestone. It was one of the finer examples I've ever been able to photograph.
Soon we could see the source of some of the lava flows, a cinder cone on the high canyon rim called Vulcan's Throne.
We could also see the long tongue of lava from Vulcan's Throne that had reached the river. John Wesley Powell's description remains one of his most poetic writings:

Just over the fall a cinder cone, or extinct volcano, stands on the very brink of the canyon. What a conflict of water and fire there must have been here! Just imagine a river of molten rock running down into a river of melted snow. What seething and boiling of the waters; what clouds of steam rolled into the heavens!
And then, one of the strangest sights of all. A huge mass of congealed lava stuck right in the middle of the river. It was a plug of lava that filled the vent of one of the cinder cones. Called Vulcan's Anvil, it seemed like a message or a warning to river travelers, which indeed it is.
When we passed the anvil, we know we had less than a mile to one of the biggest challenges on the river: Lava Falls Rapid. The moment of truth had arrived...
The Anvil receded into the distance, and we prepared to scout the wildest rapid on a wild river.


Celia Lewis said...

I watched the video of last year's muddy muddy muddy flood waters pouring into the river - amazing experience! Very interesting to see the lava evidence of volcanoes. Great photos and journal once again, Garry. I'm holding my breath to hear how you do on THE rapids! Cheers.

Garry Hayes said...

It ain't gonna be pretty!

Lyle said...

As you approached lava falls which was a dam for the river where there any signs of sediment left from the lakes behind the lava flows. Given how much sediment there is in Lake Powell and Lake Mead, such lakes must have left a lot of sediment.
This partly gives some idea of how long it will take nature to remove the sediments in Mead and Powell once the dams are gone.

Garry Hayes said...

The sources I've found (mainly Hamblin in Beus and Morales, Grand Canyon Geology, 2003) mention that the sediments do exist, but most of them have been washed away, as they were unconsolidated silt and mud. I didn't see or recognize any of them while I was on the river.

Lyle said...

Thanks for the information. In a way it suggests that the sediments deposited behind the dams are transitory in terms of the life of the canyons as well, since I doubt the dams will last as long as the lava dams did.

Gaelyn said...

I loved to see the lava flows. And while on the river kept craning my neck to see where Toroweap is way above.