Friday, July 9, 2010

Bachelor Weekend Part 3: The Strangest Lake

I had one more stop I wanted to make on the way home, so Sunday I was up with Sun and soon rolling down off the Kaibab. Then North into Utah and through Kanab.

Side Note: I stopped in Kanab for gas, and stood outside for a moment checking email on my phone. As I did, I swatted away several Cedar Gnats, thereby disproving my “rule” about them not showing up in town, or else indicating the presence of Junipers within a few hundred feet of town…

Back at Long Valley Junction, I crossed back into the Great Basin, then immediately turned West, following Duck Creek- a tributary of the Sevier River- up onto the densely forested Markagunt Plateau.

IMG_5913 I’ve been referencing the Markagunt now and again for about the past year and a half on this blog. It’s the 3rd and last (for me anyway) of the great Southern plateaus, formed out of the same tilted/faulted ancient lakebed process* that formed its sister plateaus, the Paunsaugunt and Aquarius. On the East side it’s bounded by the Sevier Fault, which separates it from the Paunsaugunt, and on the West by our old friend, the Hurricane Fault, which separates it from the Basin and Range province, and which in fact marks the Western end of the Colorado Plateau. Though similar in many ways to its sisters (flora, hoodoos, spectacular orange cliffs) it’s different in others. For one thing it’s a good bit higher than the Paunsaugunt, and so supports large swathes of Engelmann Spruce and Subalpine Fir that you don’t see on the lower plateau.

*A process which I explained in this post.

Side Note: Another, related, difference is the huge expanses of Spruce-Fir forest which have been decimated by Bark Beetles over the last couple of decades. I’ve blogged about Bark Beetles (Mountain Pine Beetles, Dendroctonus ponderosae) before- over on the Paunsaugunt in fact- but their depredations are far more obvious on the Markagunt. Bark Beetles have caused large-scale Pine and PLT kills all over Western North America*, but the devastation on the Markagunt is the worst I’ve seen in Utah.

*I read a few years back (can’t recall the source) that they’ve taken out a chunk of Lodgepole forest up in BC about the size of Rhode Island.

IMG_5920 And geologically, it’s strewn with evidence of recent volcanic activity, much of it within the last 2,000 years, and you can actually see much of this evidence just driving along the highway, in the form of small lava fields, which look like broken up asphalt parking lots interspersed amongst the aspens and PLTs.

Extra Detail: The past volcanism on the Markagunt is actually more complex than meets the eye. On the higher reaches of the plateau- up around Sydney Peaks above Brian Head for example- the Claron formation is capped by volcanic rock layers dating back over 20 million years (Miocene). In other areas the plateau is capped by much more recent eruptions, only a couple of million years old (Quarternary). These older eruptions produced rock layers thousands of feet thick in places, and constitute a major structural component of the plateau.

But the lava you see on the plateau- the “busted-up parking lots”- is something altogether different. These flows are the result of much more recent eruptions, only within the last 2,000 years, and it is this series of eruptions that will play a starring role in this post.

I love mountain streams, and Duck Creek is a charmer. Here’s a clip from a roadside pullout at around 8,000 feet. (Remember this stream. It will turn out to be important later on in the post.)

I followed Highway 14 up alongside Duck Creek to the turn-off for Navajo Lake, IMG_5902then veered off and down to the Cascade Falls trailhead, along the top of the pink cliffs, marking the edge of the high Plateau. The Virgin River Rim Trail (VRRT) passes here, following the top of the Pink Cliffs (Claron Formation.) I parked here, and started pedaling West and up the VRRT.

The altitude is higher here than yesterday’s ride, about 8,800 feet at the trailhead, and over a couple of miles the trail climbs up to just under 10,000 feet. The forest along the rim is fairly-open Engelmann Spruce and Subalpine Fir mixed with stands of Aspen. Here’s what a typical stretch looks like:

My ride plan was to follow the VRRT West and up along the rim, then down around Navajo Lake and back, which would given me great forest singletrack, some wonderful views to the South, and a close-up view of the lake.

All About Navajo Lake

IMG_5918 Large, natural freshwater lakes are fairly uncommon in the Southwest, and so always worth checking out. But Navajo Lake is particularly interesting. First off, to be clear, it is not entirely natural, but is- like Fish Lake (which Bird Whisperer and I visited last Fall) a natural lake which has been subsequently “enhanced” so as to increase and stabilize the water level. But there was a nice lake there before people messed with it as well.

The lake, which at just over 9,000 feet lies just North of and below the high plateau rim is only 900 years old, and was formed as a result of the most recent series of eruptions, one of which released a lava flow that blocked the downstream/Eastern end of the stream that formerly ran through the valley, backing it up and creating the lake.

Navajo Lake Ride Map Here’s a video that shows everything. Now I know that I show a lot of helmet-cam video and that some of it gets repetitive, and a number of readers, er, blow it off. But this one you need to watch, because in one 3 minute clip, it shows all the geography- and most of the geology I’m describing in this post. What happens is this:

The video starts with me riding open forest alongside the rim at ~10,000 feet. Then, at about 0:30, I dismount, and walk out onto the point. I pan right and left, taking in the sweep of the Pink Cliffs, as well as straight down, giving you a feel for the height and exposure of the point.

VR Zoom Below me, the forested green terrace rolling off into the foreground is the Kolob terrace, which is composed of Cretaceous (65M – 125M years old) rock. In the distance, at about 1:04 (as I raise my camera to snap a photo) you can see Zion Canyon, composed of Jurassic Navajo (~175M years old) sandstone. So get this: we standing on tertiary rock (Claron formation), looking across Cretaceous rock (Kolob Terrace) to Jurassic rock (Zion Canyon). We are looking across about 120 million years of rock!

But wait- the best is yet to come! I return to the bike, remount, and start descending Northward. At 2:31, dead ahead through the trees, you see it- Navajo Lake, 1,000 feet below me.

Side Note: Yes, I know I post a lot of helmet-cam footage. But seriously, do you know anybody who gets more great science out of a helmet-cam clip?

OK, so down, down I went, to and around the upper end of the lake. Here’s what the ride looked like along the North shore of the lake, moving East.

Eventually the trail reaches the Eastern end of the lake and passes over the (now enhanced) lava dam. In this clip I’m riding the Navajo Lake Loop Trail through the lava, and in doing so, riding over rocks less than 1,000 years old.

Botanical Side Note: The white blooms you see in the video are Elderberry (the big bushes) and Columbine. Up close, IMG_5925these Columbines- which seem to be getting along in the middle of a lava field just fine thank you very much- have light pink sepals. I’m always interested to notice how the color of Columbine sepals varies by locale. Not Red Columbine or Yellow Columbine- those are different species, and have totally different color schemes. I’m talking about Colorado Columbine, Aquilegia coerulea.

IMG_5926 When I lived in the Colorado Front Range, Columbines seemed to almost always have light blue sepals. Here in the Wasatch of Northern Utah, they’re almost always white. But the Navajo Lake Columbines all had light pink sepals. The only other place I remember seeing so many pink Columbines is in the Medicine Bow Range of Southern Wyoming.

I rounded the Eastern End of the lake, re-entered the forest, crossed the road, climbed back up to the Rim, and retraced my path back to the trailhead. But here’s what I didn’t do: I never crossed an outlet stream.

Navajo Lake has no obvious visible outlet. And yet it’s not stagnant or brackish; the water’s fresh. How and where does it drain?

Cascade Falls captionBack at the trailhead, another trail leads a short way to Cascade Falls. The Falls, which lie ~1,000 feet below and just South of the Virgin River Rim, burst forth from a hole in the cliff, and are fed by underground lava tubes and fissures that drain Navajo Lake. The Falls are the source of the North Fork of the Virgin River, which subsequently joins with the Virgin, then the Colorado, and eventually the Sea of Cortez and the Pacific Ocean.

So there’s something really interesting here. Despite lying North- and on the Great Basin “side” of the Virgin River Rim, the lake is actually part of the Pacific Watershed. Isn’t that freaky?

Not so fast- it’s even freakier. The thing is, not all of the lake’s water drains out through Cascade Falls. Only about 40% of it does. So where does the remaining 60% go?

IMG_5898 It drains into that pretty little stream we drove alongside to get here- Duck Creek*. When we were looking at the creek earlier, we were looking at water that had worked its way over a mile underground through lava tubes before surfacing in the creek. So Navajo Lake is part of the Pacific Watershed, but it’s also part of the Great Basin. It’s both and neither, a hydrological never-never-land.

*How do scientists figure this kind of stuff out? With dyes, apparently.

Navajo Drainage If you drop a cup of water into almost any lake, pond or stream in the world, you know where it will end up. That portion which doesn’t evaporate, get siphoned off, or seep down into an aquifer will eventually end up somewhere- an ocean or an inland playa/saline lake, and you can follow a map and see where that somewhere is. But Navajo Lake is different. The path of every drop of its water is uncertain, and depending on chance, timing, currents and weather, it could wind up in the Pacific Ocean or in the weird desert shallows of Sevier Lake. When you look at Navajo Lake, you’re looking at uncertainty and possibility, something radically different from the relative hydrological determinism of the ordinary world.

After 2 ½ days of riding and exploring, tired but content, I felt I’d gotten my money’s worth out of my Bachelor Weekend. I loaded up the Watchermobile and continued on the highway West, up and over, then down off the Colorado Plateau and into the Great Basin. Down below, as I approached Cedar City through the jumbled canyon marking the Hurricane Fault, it was hot, and I briefly pulled out alongside Coal Creek. In the late afternoon sun I splashed my face and head in the softly flowing water before the long drive home.

Note About Sources: Most of the hydrological info in this post regarding Navajo Lake came from This Land: A Guide to Western National Forests, by Robert Mohlenbrock.

Note About Me: The Watcher Family will be on vacation* up North for a bit, and I’ll be taking a break from posting for about a week and a half.

*Yes, Ray is staying at the house, and I swear he’s getting just meaner and angrier than ever. Don’t even think about it.


Anonymous said...

That is pretty cool about lake. I am fascinated how watersheds to different but this lake takes the cake for its non-conformity. How were the lava tubes for the waterflow discovered?

mtnb w

Kikkerts said...

I had to write much of the hydrology sections for an environmental impact statement on the Dixie National Forest, and I have to say, your description is more complete. We should talk some time about the lava fields, they have some interesting hydrological features as well.

Dave (we have a mutual friend in J. Manos).

Watcher said...

mtb w- They supposedly figured it out with dyes, though I don’t know the details. Given the position of Cascade Falls relative to the lake, and the obvious pile of porous lava at the downstream end, it was probably an obvious suspect outlet, but I bet the Duck Creek outlet was more surprising.

Dave- Small world. I’ll look forward to learning more about the lava-hydrology from you, maybe while we’re out skiing sometime with Fast Jimmy.

Lucy said...

Nice helmet cam. I rode those trails during Stage 3 of the Brian Head Epic a couple of years ago, but at that time, I think it was around mile 40, all I could do was muster a "cool" when climbing the lava dam. I knew the hydrology of Navajo Lake was interesting and unusual, but you make it sound phenomenal!
"When you look at Navajo Lake, you’re looking at uncertainty and possibility, something radically different from the relative hydrological determinism of the ordinary world."
Kids will read that and want to become hydrogeologists. Then they will get to play with dyes and say "Vishnu Schist". :-)

I suspect the split hydrological paths in Navajo Lake are only temporary until the drainage becomes more mature, i.e. one of the outlets clogs up or a direct surface outlet makes the "need" for water to travel through lava tubes unnecessary. If so, then we are in one of those short periods in geologic time where streams get captured - similar to the unknown length of time it took the ancestral Colorado River to capture east flowing stream(s) like you talked about in a previous post.