Friday, April 10, 2009

Exploring Canyonlands and Arches with the Museum of Northern Arizona

The Museum of Northern Arizona offers its members a travel and education program called "Ventures". Educational backpacks, house boat trips on the Powell Reservoir, and hotel-based excursions to Grand Staircase/Escalante and the Canyonlands are some of the itineraries offered. The latter near Moab, Utah is where I have been recently exploring some geologic wonders with some of our Museum members.


Here is the entrance sign at the new Visitor Center in Arches National Park. This modern facility was one of the first to use Ron Blakey's paleogeographic maps in their geology display. Their bookstore sells "Ancient Landscapes of the Colorado Plateau" (Blakey and Ranney, 2008) and visitors can now take these informative maps home with them to study at their leisure.


Wow - check out the faulting displayed across from the Visitor Center on Highway 191! The strata belong to the Pennsylvanian Elephant Canyon Fm. and were offset on a branch of the Moab Fault when the Spanish Valley salt dome deformed the rocks.


Our group hiked up to the iconic symbol of Arches National Park, Delicate Arch. It has been carved into the Entrada Sandstone and is unusual in that this small remnant of a fin is almost entirely opened as an arch. The chances that this could occur, let alone be preserved for even a short amount of time, are astronomically small. Which may prove to the non-curious that there must be a God, but to most others simply means that where there is erosion there is form, color, and beauty!


I like the "non-arch" sections of this park as well. The uplift of the salt domes has elevated the land such that the views are long and wide. The uplift raised rocks to elevations where they have been attacked by gravity, leaving many pinnacles and spires. The La Sal Mountains provide a truly stunning backdrop. I can think of no other combination - snowy mountains framed by red strata - that says "the American West."


We felt like getting close to the La Sals and so drove up on the La Sal Mountain Loop Road. This is a close-up view of the La Sals, a laccolith intrusion that is about 25 Ma (million years old). The sedimentary veneer that once capped these rocks is since eroded off.


As we drove off of the mountain's north flank, we were treated to a great view of the Castle Valley along the Colorado River.


For me, a visit to this part of the Plateau is incomplete without a stop at the Fisher Towers. The number of movies filmed here are testament to their great beauty but most people don't realize that a phenomenal geologic story is contained in the rocks here as well. It involves ancient mountains that no one ever saw, yet the debris washed out of those mountains remains.....


..... Look at the boulder on the left. Do you see the clasts of schist and gneiss in the sandstone? That is the evidence that a range of mountains, the Ancestral Rockies, once stood east of here about 285 Ma. As the ARM's eroded, material was shed to the west and became incorporated as the Culter Group. When you follow this formation to the east the clasts get bigger, and to the west they get smaller, giving the tell-tale signs of what direction the sediment was being shed.
























Ron Blakey's paleogeographic map for the Cutler Group, about 285 Ma. Notice the Ancestral Rockies in southwest Colorado. At the foot of the mountains just inside the Utah state line is where the Fisher Towers are located. Who says there are no time machines?


Just when I begin to feel like there might be too much "red rock fatigue", I turn the van into a small parking lot and we hike up into a watery wonderland called Negro Bill Canyon. You can imagine the older, less sensitive name (some Moab locals have taken political correctness to a new level and refer to this gem of a stream as "African-American William Canyon"). No matter what you call it, the canyon is beautiful and Bill or William had good taste in locating a home. There's nothing like water in the desert.


Two miles up at the head of a side canyon is a source of water coming out of a crack in the sandstone. The water emerges from near the contact of the Navajo Sandstone (the aquifer) and the Kayenta Fm. (the aquaclude or aquatard). Magic!


A hackberry tree against the cliff. Is there anything more special that being in places of such beauty?











Morning Glory Arch












The Island in the Sky District of Canyonlands is a place where you can get a sweeping view of everything. Here, Ron Hansen takes in the view.


Looking south towards the Abajo laccolith with the Needles District of Canyonlands in the middle distance. The Needles are part of the Cedar Mesa Sandstone which is the distal extension of the Cutler Group. This part of the region was far enough away from the Ancestral Rocky Mountains that only sand was preserved here. No cobbles of schist or gneiss made it this far out onto the ancient floodplain.


At the Green River Overlook we took in a view of the Turk's Head, a rocky eminence that resembled a turban to some old explorer. The Green River flows nearby. The Turk's head is capped with the White Rim Sandstone.


Looking west, we saw the Orange Cliffs and the Henry Mountain laccolith rising behind them. Why aren't the Orange Cliffs part of Canyonlands National Park?


We did a couple of short hikes around Upheaval Dome, an aptly named oddity in otherwise flat strata. I pulled out three different brochures from the park that reveal the changing interpretations made for this unusual feature. In the 1981 edition, a salt dome interpretation was presented. In a 1993 edition, the salt dome theory competed with an interpretation that this could be a meteorite impact structure. The newest edition of the trail guide lists meteorite impact structure first and salt dome second. An evolving view that highlights the scientific method. That is the beauty of science, it is self correcting and at times can be wrong. But always, science tends towards a more refined truth.


Look at the scalloped heads of these two canyons into the White Rim. There is no indication that the canyons were carved by water running from above. Rather, they seem to be formed from below, meaning that groundwater sapping has undercut the White Rim Sandstone, which causes headward dissection in the upstream direction. The canyons are created from the bottom up and not the top down. Come on a trip with the Museum of Northern Arizona and see for yourself!

6 comments:

Lockwood said...

That is spectacular. I've visited a number of the SW National Parks, but Arches isn't one of them. This makes it obvious there's a major hole that needs filled in my geo-expeditions log.

Alyn said...

A truly stunning post this week Wayne! Arches and Canyonlands have now joined Monument Valley at the top of my list of 'must sees' on my next visit to the USA!

Silver Fox said...

Wonderful views!

Roz said...

Wonderful pictures, Wayne. Can't wait to get out west again to experience this beauty!

Gail said...

Hi Wayne - This trip looks incredible! Everytime I think I've seen beauty in the SW, you manage to photograph something else that makes me go - wow! Hope you decide to repeat this trip next year - sign me up! gmj

Dan Burgess said...

I gotta come out there and hike with you sometime -- that is great stuff, and I have much to learn in the realm of geology. Thanks for blogging this, Wayne!