Environmental Geology

Dr. Phil Pearthree presents Geologic Hazards in (Central) Arizona before the American Society of Civil Engineers. Phoenix Branch Luncheon Noon, May 9, 2018 Calvin C. Goode Municipal Building East Conference Room 10th Floor, 251 W. Washington Street, Phoenix, AZ

Sampling & classifying clasts from a high standing river cobble deposit near the Gila Box east of Safford, AZ. The clasts are separated into felsic, intermediate, and mafic volcanics, granites, and quartzites.
The research objective is to identify which of the Gila River's tributaries contributed rocks to the deposits.
Step 1. Harvest cobbles from the deposit
Step 2. Classify the cobble - e.g., volcanic, granite, quartz ...
Step 3. Count classified clasts to ascertain clast ratio.
B. Gootee pictured, photos by J. Cook

Quaternary mapping along Schultz Pass Rd, San Francisco Mtn, AZ

Mid-Pleistocene fan composed of debris flows (bouldery units) and alluvial deposits. Here, the alluvial beds are mostly sands, fine gravel, reworked lapilli and some silt and clay (finely laminated unit). Pebble/cobble debris flow deposits above and below. Pewe and Updike called this the Espil member of the Sinagua Formation. These debris flows dominated fans are all around the mountain.

The environmental geology team is mapping the San Jose 7.5 minute quadrangle near Solomon, AZ (upstream on the Gila River from Safford). This is a view across the Gila River Valley from the south looking north while standing on a late Pleistocene Gila River cobble-capped terrace; the flat-topped, tall bluffs in the distance are matching elevation river terraces. A thin strip of cottonwood along the channel are just leafing out with the springtime weather. Most of the river valley bottom in this area is utilized for agriculture irrigated with Gila River water.

Posted by J.P. Cook

Blog post by Ann Youberg, 'Deadly debris flows in the SW U.S. fueled by drought, wildfire, and rain'

On January 24, the LA Times reported that residents in the Montecito, California, area received conflicting information regarding evacuation zones prior to the worst post-fire floods and debris flows (often called mudflows) in recent California history.  Arizona is subject to similar post-fire hazards. To read the blog, visit http://blog.azgs.arizona.edu .

AZGS is preparing to release the Arizona Statewide Landslide Inventory Database (AzSLID). Debris flow deposits are underrepresented but the database provides a baseline of sorts of recent debris flows in Arizona. We continue to document debris flows where they occur.

A team of geomorphologists including AZGS' Ann Youberg just published research on post-wildfire landscape change and erosional processes in the Chiricahua Mountains, Arizona. The research team applied repeat terrestrial lidar to observe and document change in a headwater catchment.

DeLong, S.B., Youberg, A.M., DeLong, W.M., Murphy, B.P., 2017. Post-wildfire landscape change and erosional processes from repeat terrestrial lidar in a steep headwater catchment, Chiricahua Mountains, Arizona, USA. Geomorphology. https://doi.org/10.1016/j.geomorph.2017.09.028