The guts of the Moab Fault...

exposed near the entrance to Arches National Park, just above the Visitors Center. A chunk of the Moenkopi Formation is trapped in the gouge zone in between a pair of extensional faults (yellow lines). More than a half-mile of vertical displacement has occurred across this zone, that is, the Entrada Sandstone lies considerably higher in the stratigraphic section than the Honaker Trail Formation, so UP on the left and DOWN on the right across the fault zone in the view seen below.

View is towards the northwest. Note the tour bus on the park road on the right side of image. Yellow lines are normal faults.

Like a liquid buzz saw...

the Gunnison River has deeply incised the Black Canyon, exposing the ~1.7 billion year-old Precambrian metamorphic rock that comprises the enormous Painted Wall, caught at sunrise and the moment of first light.

Wide pre-dawn view of the 2,250 foot (686 meter) high Painted Wall, showing pegmatite dikes intruding the foliated gneiss and schist creating a natural abstract mural nearly a half-mile high.

Bighorn sheep (Ovis canadensis) enjoying sunset near Cedar Point the evening before.

An early aerial sunrise...

is captured over central Idaho as my trajectory boomerangs back to canyon country.

Mount Timpanogos looms more than 7,000 feet (2,130 meters) above greater downtown Provo, Utah and Utah Lake.

Dissected pediments extend below the Book Cliffs near Sunnyside, Utah.

An early morning departure...

from GJT to SLC and onward to GEG yielded several interesting views when the weather allowed. Remember, geologists always get window seats.

View northwestward across Grand Junction, Colorado shortly after departure. The sinuous dark area is the confluence of the Gunnison and Colorado Rivers.

View northward, turning into the Salt Lake Valley over Utah Lake with the snow-covered Wasatch Mountain front.

The historic earthen causeway for the Lucin Cutoff railroad line separates the Great Salt Lake into two waterbodies with differing aquatic ecologies.

A peculiar roller cloud, about 40 miles (64 km) in length along its north-south axis, sits atop and defines Hells Canyon in Idaho.

An interesting groundwater seep...

at the stratigraphic contact between the Cutler and Moenkopi Formations below Adobe Mesa bears some further examination, but it’s a difficult scramble to its location on steep and unstable slopes. Light-colored mineral deposits, likely either calcium carbonate (calcite) or calcium sulfate (gypsum), occur at the margins of the seep.

Peering into the abyss...

of Sevenmile Canyon north of Moab on a spectacular mid-winter day.

An immense pour-off defines the upstream end of Sevenmile Canyon, west of Arches National Park.

The Slick Rock Member of the Entrada Sandstone comprises the vertical walls of Sevenmile Canyon, capped by the Moab Member of the Curtis Formation (Middle Jurassic (174.1-163.5 Ma)). The Windows Section in Arches National Park on the horizon is eight miles (~13 km) distant.

Sediment aggradation will almost certainly occur...

in the ephemeral stream channel upstream of the newly installed concrete ford in Placer Creek, rather than being continuously transported across the structure when the stream is flowing. Engineers should have matched the elevation of the stream bed rather than maintain the road grade at the crossing. While this structure isn’t going anywhere in future floods, it will require maintenance after each event in clearing accumulated sediment, in perpetuity. It could have been self-maintaining, so let’s see how it performs over the next decade.

The brand-spanking-new $188,889 mega-concrete stream crossing structure on Placer Creek at the entrance of Round Mountain State Park.

Expansive views with endless vistas...

can be found at the apex of the Maverick singletrack at the Moab Brands mountain bike trail system. It’s nice to get out of the canyons occasionally and enjoy a seemingly infinite horizon.

View to south: Arches National Park on the east (left), La Sal Mountains to the south (center) and Gold Bar Rim and the Moab Fault to the west (right).

View into unnamed tributary canyon to Courthouse Wash in Arches National Park as seen from the Rockin’ A singletrack. Note the horizontal contact across the center of the image that is weeping groundwater, separating the Moab Member of the Curtis Formation from the underlying Slick Rock Member of the Entrada Sandstone (Middle Jurassic (174.1-163.5 Ma)).

A window into the Honaker Trail Formation...

can be found below Deadman’s Curve on the old highway grade west of Arches National Park. This Upper Pennsylvanian-age (~300 Ma) carbonate unit crops out as a cliff former in very few places in the Moab area, seen in the image below as the grayer strata beneath the paved bike trail across the canyon, captured from a high vantage point on the Rusty Spur mountain bike trail.

Fifty-two years ago today...

man last walked on the Moon in Taurus-Littrow valley. Here’s tonight’s waxing gibbous Moon, three days from full, with the Apollo 17 landing site indicated by the orange x where astronauts Gene Cernan and Harrison Schmitt (a geologist) performed three days of exploration in 1972.

Taurus–Littrow valley is located on the southeastern edge of Mare Serenitatis, the landing site of Apollo 17, indicated by the tiny orange x.

The Culebra Cut of Castle Valley...

is being excavated at the Placer Creek dry stream crossing. Methinks this is a grossly overengineered and expensive solution to an erosion problem that no longer exists, but that’s just 40+ years of experience as a fluvial geomorphologist talking.

Meanwhile, elsewhere in the community, the drainage ditches that are choked with sediment from summer flooding go largely unattended. Pure negligence.

One hundred million years of Earth history...

is exposed in the strike valley below Castleton Tower, seen below in this geologically annotated image that includes the formation names and ages (Ma = mega annum = millions of years). The tilted beds of the Cutler Formation (right) comprise the northeastern limb of the Castle Valley salt anticline.

View toward the southeast with Adobe Mesa in the distance. (Click on image to expandify.)

Yes, it was another terrific afternoon for a bike ride in Castle Valley National Park.

These enormous imbricated boulders...

were certainly moving as bedload in this ephemeral wash below Adobe Mesa during the flash flooding events this summer. Here they now sit, shingled on top of one another, likely stranded for a decade or more until mobilized in the next extreme hydrologic event in this drainage.

As artificial as the sky and cloudscape appears in this image, it was that lovely of a day in Castle Valley.

The footprint of flood impacted areas...

throughout Castle Valley is clearly seen in the recently updated satellite imagery available in Google Earth and Google Maps. Light-colored sedimentary deposits paint the areas affected by overland sheet-flooding and where floodwaters escaped ditches and natural channels. Compare and contrast.

Imagery date: 7 August 2024.

Imagery date: 14 October 2022.

Hint: Learn to use the time slider tool in Google Earth to time travel into the past and examine earlier satellite imagery.

Three well-preserved Miocene-age tree molds...

occur in the Wanapum Basalt Formation (Columbia River Basalt Group) along the Fish Lake Trail, exposed in a railroad cut through the volcanic formation within 100 yards (meters) of one another. One can easily imagine a landscape with a stand of large trees being invaded and enveloped by an advancing lava flow around 15 million years ago. I’m certain that 99% of the trail users aren’t aware of these interesting features and the story they tell.

Note the silicified wood that is preserved near the base of this large tree mold.

This tree mold is about 20 inches (0.5 meters) in diameter.

The underlying paleosol (ancient soil horizon) in which the tree were rooted is clearly seen here beneath the overlying basalt formation. This tree mold is about 15 inches (0.4 meters) in diameter and penetrates the interior of the volcanic unit.

Following a historic railroad grade...

southwest of Spokane, Washington, the Columbia Plateau State Park Trail extends for 130 miles (209 km) across the semi-arid Channeled Scablands. Some portion of this trail system is part of my daily ride, usually a section between Spokane and Amber Lake, at its very northeastern end.

Open ponderosa pine forests and seasonal wetland ponds dominate the flat-lying terrain that traverses the 1908 path of the Spokane, Portland and Seattle Railroad.

A typical crowded day on the trail.

Two aging geologists slowly undergoing fossilization...

met for lunch at our favorite Mexican restaurant last week. Emeritus Professor Ernest Gilmour (below left) was the chair of the department when I was hired as a fledgling assistant professor in the summer of 1984, a full 40 years ago, and he remains a good friend and valued colleague. We’re both retired from the university today, but he’s still doing active research in paleontology and publishing on bryozoans. It’s a scientific fact that fossilization is delayed if one stays active, both mentally and physically!