This May, 19 alumni from the Northern Arizona University Geology program came to Flagstaff for our 4th annual Grand Canyon Reunion Rafting Trip. We had a wonderful time traveling with old and new friends. Many of the participants this time were from my time at NAU, including a few from the 2000s and three from the 1970s. Geology at NAU is awesome!
NAU’s Dr. Jim Gauherty was on the faculty with his wife, Dr. Donna Shillington. Here Jim is near Sunset Crater and the San Francisco Peaks talking about shifting volcanic activity in the region.
Ralph Hopkins (center) and Mike Durr (right), two close friends from their days as NAU geology students in the 1980s, are at the Desert View Watchtower on a site visit before our river trip.
Preparing for departure at Leith Ferry.
Reptile footprints in the Coconino Sandstone. Avalanche features are also visible on this surface.
Vashi’s Paradise is back after last winter’s abundant snowfall on the Kaibab Plateau, a bountiful spring that has been mostly dry in recent years due to a lack of precipitation.
The limestone “hump” seen in the center of the photo is a mound of mud within the Redwall Limestone. Algae likely grew on this ocean floor about 340 million years ago, trapping silt and clay-sized particles.
Raft past Grey Castle, carved into Marble Canyon’s Bright Angel Shale.
The garnets found in the Vishnu Schist show us the temperatures and pressures at which the schist was metamorphosed from shale or sandstone. This type of garnet forms at temperatures and pressures that are now found about 10-15 miles below the Earth’s surface. It’s incredible to think that these rocks, now back at the surface, were once buried in so much of the Earth’s crust. Where did they go? Not into space, but eroded away somewhere in the ancient landscape. But it’s been so long that no one knows where they are now.
A typical camping scene – this is the view from downstream Garnet Camp near mile marker 114 on the river: Powell Plateau is on the skyline at the upper left.
The oldest rocks in the canyon are the Elf Chasm Gneiss, which is 1.84 billion years old, making it 90 million years older than the Vishnu Schist.
I’m fascinated by cavitation pits that form in limestone near river banks. When fast-flowing river water hits small protrusions on the surface of smooth rock, the water pressure pushes the water away from the rock surface, creating a vacuum between the water and the rock. When the vacuum is broken, the force of the impact causes part of the rock to pop off, creating the wave-shaped pits.
Again, no one has photographed this site and the landslide, which is made entirely of limestone debris. Fellow river rafting buddy John Hirsch was the first to notice and describe the landslide.
Our group had a truly amazing trip, with lots of good memories and new ones made on the Grand Canyon River!
