Sedona: Erosion on a Spectacular Scale
1/4/25 – In a Houston-area-flooding context, we usually consider erosion as a negative. It reduces the capacity of streams, channels and Lake Houston. It can also form sediment dams like mouth bars that back water up.
But elsewhere, many consider erosion a tourist attraction. And I’m not just talking about the Grand Canyon.
Welcome to Sedona
During the holidays, I took a break from blogging about flooding to join a family reunion near colorful Sedona, Arizona. We actually stayed in the Village of Oak Creek, an unincorporated area about five miles south of the main part of Sedona.
Always alert for photo ops, I launched my drone from the back porch of our rented home and captured some photos of red rock, blue sky and spectacular erosion.
The rocks around Sedona are famously red due to their high concentration of iron oxide. Millions of years ago, the Sedona region was covered by a vast shallow sea that deposited layers of sediments rich in iron minerals.
Over time, these iron-rich layers were uplifted due to tectonic activity. The iron in the rocks reacted with oxygen, resulting in oxidation – the same chemical reaction that gives rust its red color.
Then, erosion sculpted the landscape – over millions of years. It exposed these oxidized rock layers, which now dominate the area and give Sedona its iconic red hue. But why did the land erode in some areas and not others?
Caprock Protects Some Areas from Erosion
The spectacularly steep cliffs around Sedona can be attributed to the uneven distribution of what geologists call “caprock.” The term refers to the hard, erosion-resistant rock layers that sit atop mesas, buttes, and cliffs. These layers protect the softer rock below from erosion, helping to shape the striking red rock formations that make Sedona famous.
The caprock was formed from ancient sand dunes and marine deposits about 250–275 million years ago during the Permian period. Over time, these deposits solidified into dense rock layers responsible for Sedona’s intricate geological artistry.
The Value of Rust and Erosion
Sedona reportedly received approximately 4 million visitors last year, rivaling the Grand Canyon. That’s more people than live in Houston and almost as many as live in Harris County. Sedona’s stunning red rock formations and outdoor recreational opportunities make it a major attraction for both domestic and international travelers.
Rainfall and Flooding
Sedona receives an average of 19 inches of rainfall per year – less than 40% of Houston’s average rainfall. However, Sedona still experiences three types of flooding:
- Flash Flooding:
- Sudden, intense thunderstorms during the monsoon can cause flash floods. The steep terrain and rocky surfaces around Sedona lead to rapid runoff, overwhelming dry washes and creek beds.
- Flash floods are particularly hazardous in areas like Oak Creek Canyon, where narrow canyons can funnel water quickly.
- River Flooding:
- Sedona’s primary waterway, Oak Creek, can flood after prolonged rainfall or snowmelt from higher elevations. Heavy storms, particularly in winter, can cause the creek to rise significantly, affecting nearby properties and recreational areas.
- Urban Flooding:
- Heavy rain can overwhelm local drainage systems, leading to localized flooding in lower-lying areas.
Oak Creek flooded badly from severe winter storms in 2005. One of the most significant floods in recent memory, it damaged homes, businesses and bridges.
In 2023, heavy rains led to flash floods that temporarily closed hiking trails and roads.
Such floods sculpted the landscape you see in the photos above.
More About Sedona
Spanish explorers first passed through the area as early as the 1500s.
Homesteading began in the late 1800s.
Sedona became a popular filming location for Western movies due to its dramatic landscapes. Films like “Stagecoach” (1939) and “Broken Arrow” (1950) were shot in the area, bringing international attention to Sedona.
Improved roads and infrastructure led to a tourism boom beginning in the 1950s.
Today, Sedona is known for its outdoor activities (hiking, mountain biking, and jeep tours), yoga retreats, art galleries, and night skies. Re: the last point, Sedona is designated as an International Dark Sky Community. Star gazers enjoy freedom from “light pollution” – there were no streetlights where we stayed!
Posted by Bob Rehak on 1/4/2025
2685 Days since Hurricane Harvey
