Hike Distance: 5.5 miles
Although we had hiked this trail last year we decided to revisit it since it's close by and the Indio Hills is an interesting area.
The Geology of Straight Lines in the Coachella Valley
When you look at the valley floor one things stands out. The San Andreas fault (SAF) follows a uniformly straight course through valley - from the Indio Hills to the Salton Sea. Despite the fact the fault is associated with catastrophic movement of the tectonic plates, it is defined in the valley by | straight lines |.
The line of Willis Palms along the fault network is a case in point. In this aerial view of the NW Indio Hills, the palms line up along the Banning Fault which has dammed groundwater in the fault zone to nourish the tree. Geologists refer to this scenario as 'localized groundwater flow and associated plant growth in a narrow fault-bound lineament'. Groundwater flows more easily along fault zones, where the rock mass is broken and more permeable.
But it's not just the palms that form a straight line. The San Andreas fault zone is marked by discrete elongated zones of fault-bound uplift along the SAF network of faults. The Indio Hills have been cut and uplifted along the Mission Creek and Banning branches of the San Andreas Fault; while the Mecca Hills were uplifted by action along the SAF and the parallel faults in the hills. Two distinct and separate regions of uplift but when viewed from above it's evident that just like the palms, these Coachella Valley hills form a straight line along the SAF. In the pictorial below IH = Indio Hills; MH = Meccas Hills and DH = Durmid Hills.
(CITATION: Bergh, S.G., Sylvester, A.G., Damte, A., and Indrevær, K., 2019, Polyphase kinematic history of transpression along the Mecca Hills segment of the San Andreas fault, southern California: Geo‑ sphere, v. 15, no. 3, p. 901–934, https://doi.org/10.1130 /GES02027.1.)
The parking lot at the trailhead was almost full, not a great sign when you're hiking in the early stages of a global pandemic. Fortunately, most of the people were following the trail leading to the lake and not following it to the Badlands trail. We crossed the flats past the power lines and entered the the Indio Hills.
So what constitutes 'badlands'? Badlands are a type of dry terrain where softer sedimentary rocks have been extensively eroded by wind and water. They are characterized by steep slopes, minimal vegetation, shallow or nonexistent rock covering, high drainage density and rapid erosion rate. All of these factors contribute to the unusual topography of the Indio Hills.
The trail weaved through what looked like drainage gullies. I can only imagine what this place looks like during a heavy rainstorm.
Although the conglomerate surface was rough on contact with the skin, the surfaces were smooth as a result of water runoff and wind erosion.
The hills are covered in these circular shaped cavities.
The cavities are caused by a combination of rain and wind erosion. Rain splash from strong rainstorms seeps into surface cracks of the sedimentary stone that swell when rain strikes the rock surface. Over time the rain water dissolves away material and enlarges the surface openings. Wind-blown sand blasts away more material, carving out these smooth cavities in the rock face. This cycle continues until the surface looks like swiss cheese surface we see today.
The trail climbed above the heavily eroded lower hills. Badlands erosion is the initial interesting element of the trail but climbing to the higher elevations highlighted the second interesting element - tortured rock formations.
The Indio Hills were uplifted by movement along the Mission Creek, Banning and San Andreas faults. These plate movements caused incredible pressure to be exerted on the weak sedimentary rock beds. These beds were compressed and uplifted so that they buckled and faulted into tightly compressed near vertical folds stacked on top of each other.
Here's an aerial view of the near vertical folds of the Indio Hills. They resemble a stack of dominos. Courtesy of the USGS.
This is how the folds appeared on along the trail. When the pressure is applied too quickly, rocks in the shallow crust behave as brittle solids and break like these folds.
Even in the shallow crust where rocks are relatively brittle, folding can occur if the stress is slow and steady and gives the rock enough time to gradually bend like some of the folds below.
(iPhone pictures came out so much darker than the 35-mm camera pics)
A 12-inch long Western Whiptail lizard ran across the sandy path. When being attacked by a predator, the western whiptail will drop its tail. The muscles in the tail will continue contracting causing the tail to flop around. This is used to distract the predator from the lizard. However, this is a last ditch effort. It is very stressful for the lizard. It takes a lot of energy to regrow the tail, and the lizard loses a lot of stored food. This is a tactic often used when the lizard is threatened by a domestic or feral cat.
There were several wildflower patch in the sandy soil including these lupines.
Once the trail reached the top of the badlands, it followed a ridgeline before descending back into a narrow wash at the base of the hills.
Along the way we had some amazing views across the hills to the San Jacinto and Santa Rosa mountains.
These lizards can grow to 24 inches in length. They can withstand high temperatures and are out and about after other lizards have retreated into their burrows.
There was lots of odd erosion patterns in the wash and side gullies.
As the trail exited the hills and returned to the desert flats, we saw a few more desert iguanas among the creosote bushes. We had seen more lizards on this hike than any previous hike this or last year.
It's always a great time hiking in the Indio Hills.