Mount Ellsworth, 8,235', Little Rockies, Henry Mountains

Essence: Mount Ellsworth is the tallest peak in the Little Rockies sector of the Henry Mountains. Don't underestimate this short climb--it is steep and rugged, the navigation complicated. Scale a series of inclined porphyry slabs. Summit views of the surrounding region are exceptional. The concept of a laccolith was developed in the Henry Mountains by G.K. Gilbert in 1877. A summary of regional geology is included at the end of this post.
Travel: From the intersection of UT 95 and UT 276, drive 19.4 miles south. Turn left onto a dirt track that crosses the highway (signed BLM 13940 on the west side of UT 276). In a high clearance vehicle with 4WD low and a locking differential, drive up the steep and rocky road until it ends in 1.7 miles. (See photos and description below.)
Camping: Starr Springs Campground is five miles up a good dirt road. From the junction with UT 95, drive 16.7 miles south on UT 276 and turn right. Water (2024), cottonwood shade, stellar views of the Little Rockies, fire pits, tables, pit toilets, fee, carry out your trash.  
Distance and Elevation Gain: 3.5 miles; 2,250 feet of climbing
Total Time: 3:30 to 4:30
Difficulty: Off-trail; navigation difficult; Class 2+; mild exposure on pitched slabs; carry all the water you will need. Thank you, John Bregar, for scouting this route.
Maps: Mount Holmes; Ticaboo Mesa, UT 7.5' USGS Quads
Date Hiked: April 27, 2018
Quote: You don’t climb mountains without a team, you don’t climb mountains without being fit, you don’t climb mountains without being prepared and you don’t climb mountains without balancing the risks and rewards. And you never climb a mountain on accident – it has to be intentional. Mark Udall, U.S Senator, Colorado, 2009 - 2015

Mount Holmes and Mount Ellsworth are the two primary peaks in the Little Rockies. This image was taken from the Starr Springs Campground in afternoon light. (THW, photo)

Route: In general, ascend the northwest-running ridge to Point 8,045'. The route does not hold true to the ridge but wavers due to significant obstacles. Pivot onto the northeast ridge of Mt. Ellsworth.

This Google Earth capture shows the route from the end of the road to the summit. Broken terrain and gendarme dodging makes navigation difficult. Note the confusing nature of ridge transitions.    

The drive to the end of the access road is a journey in itself. This image was shot where the track leaves the highway. To begin, the road runs parallel to the blacktop heading north.

It hooks east, gets considerably steeper and cluttered with large rocks. One of our vehicles couldn't make the climb, backed down to the corner, shown, and parked. Walking up the road adds about 1,000 feet of vertical and 3.4 miles roundtrip. (THW, photo)

These hikers are standing at the end of the road, elevation 6,338'. The initial climbing ridge is left of image-center. The route transitions from the gendarme crested spine to a north-northwest face before regaining the principle ridge. Mt. Ellsworth is the softly rounded and treed summit, image-center-right.

A wildcat trail leaves from the east side of the road and descends a red slope. On the ascent we flanked the initial gray knob just a tad too low. Footing was precarious on exposed scree. We dialed it on the return. Stay on the ridge and contour just below the knoll.

This image was shot south of the knob on our return. It looks back at the proper contour location. Once back on the ridge, climb over the red outcrop, shown.

Climb the west side of an inclined porphyry sill. This is the first of many slabs. I found the bare rock climbing to be a pleasure but it is steep. The rock has plenty of features and small ledges to wedge feet. This photo was taken on the descent and shows the initial slab relative to the red outcrop.

This photo was taken at the top of that first stone pitch. This is where we began to transition east on the north-northwest-facing slope. The obstacle-covered ridge at skyline was too imposing. Notice the rock outcrop image-center.  

Hug the wall of the outcrop on the west side, shown here shooting back.

Continue ascending on a pitched slab. If it feels too exposed, walk up the east side of it on dirt. This image looks down the solid rock. To thread things together, notice the outcrop we just hugged at the base of the stone slant.

At 7,360 feet you will have completed the transfer from the face to the principle ridge. This is a compelling location. Lake Powell is visible to the east. Mount Hillers stands stately across open desert in the northwest. (THW, photo)

From here, angle slightly right/west on the rock and then work back to the ridge.

Enjoy a momentary reprieve on a small dirt platform and then climb another pitch, shown heading down.

Climb a beautiful grassy slope interspersed with with sage, ephedra, buffaloberry, piñon, and an elder juniper, shown. We found bighorn scat on this hillside. A member of our group startled a ram on Mt. Holmes so they are out there. (THW, photo)

Four ridges join at Point 8,045', image-left.We skirted this pleasant knob on the ascent but walked right over it coming downhill. Walk southwest toward the summit, image-right.

Flank Point 8,095' on the right.

The summit slope is open with good footing.

Crest the highpoint of the Little Rockies at 1.7 miles. There is a solar powered weather station and a peak register on the roomy summit. (THW, photo)

The views are gorgeous. Looking east, the La Sal Mountains and Abajo Mountains are on the horizon. Image-center, White Canyon flows into the Colorado River arm of Lake Powell from the east. Fourmile Canyon is a slash from the west cutting into a massive meander that's barely holding onto its land bridge. (THW, photo)

Looking south, from the left is Navajo Mountain, Point 8,100', the Straight Cliffs and the village of Ticaboo.

In the west, Waterpocket Fold and Boulder Mountain halt the march of the desert. (THW, photo)

Mount Ellsworth Geology
The geologic discovery of a laccolith occurred in the Henry Mountains. Here's what I learned about laccoliths from John Bregar, geologist. Magma works its way up a vertical conduit into a relatively undisturbed sedimentary section and injects itself between layers that are weakly bonded, initially forming sills, but eventually building up into a giant blister. (A sill is created when magma injects itself parallel to bedding planes and spreads out.) Sedimentary rocks below the blister can remain relatively undisturbed, but sediments above the blister bow up into a dome. Subsequent erosion can remove the sedimentary cover from the dome, exposing the igneous core.

That's the simple textbook description.

Apparent on Mt. Holmes and Mt. Ellsworth (and elsewhere in the Henry Mountains) is a more complex story. Magma intruded in between several weak rock layers, creating multiple sills that can sometimes extend a mile or more away from the main intrusion. We also observe places where the magma between two sedimentary layers suddenly cuts across bedding to higher or lower strata. Adjacent to the main magma blister as it continues to build, these sills, along with the sediments enclosing them, get tilted up, sometimes to almost vertical. Erosion has exposed this complexity on the flanks of the Henry Mountains, and since the sills are generally more resistant to erosion than the adjacent sediments, they often form the tops of mesas, cuestas, hogbacks, and flatirons surrounding the main igneous intrusions. This is readily apparent on the lower part of the Mt. Ellsworth climbing route, where several igneous hogbacks (held up by sills) and intervening soft sedimentary saddles must be negotiated. Sediments involved in this deformation are at least as old as the Chinle or Moenkopi Formations in the Little Rockies.

Of note, nearby Navajo Mountain may look like a volcano but it is also a laccolith. It is exceptional because the sedimentary layers draping the igneous core have not yet been eroded off.

This image shot from roughly 7,900 feet, looks upon the southern slopes of Mt. Holmes. Beneath the laccolith core is the Morrison Formation (a fertile source for dinosaur fossils); arch forming Entrada Sandstone; Carmel Formation deposited in a shallow-sea environment; Navajo Sandstone, the predominant formation on the Colorado Plateau; and ledge-forming Kayenta Formation. Quartzite, baked metamorphic sandstone, is exposed on the slopes of Mt. Ellsworth.

As you ascend into the igneous rock you will notice the gray stone is peppered with white feldspar crystals. These large crystals began to solidify while most of the magma remained liquid, slowly growing in size until the magma was emplaced at a shallow enough depth that the remaining liquid crystallized more quickly, forming the finer-grained ground mass.  Large crystals formed within a fine-grained igneous matrix are called phenocrysts. Igneous rock containing phenocrysts is called porphyry. This water-smoothed boulder tumbled off Mt. Holmes and rolled into Swett Creek.

Here's another angle on Mount Ellsworth, seen from UT 276 and the access road.