Earth fissure undermines Houston Avenue in Apache Junction, Arizona
The 2018 monsoon season has produced some fresh earth fissure activity near Apache Junction east of Phoenix.
On 9 Aug. 2018, ~ 2 inches of rain fell on Apache Junction in northern Pinal County. An existing earth fissure in the southwest corner of Apache Junction reopened and undermined a section of Houston Avenue that had previously collapsed in the July 2017 (Figure 1). The recent collapse was triggered as a van rolled across the undermined section of road (Figure 2). Fortunately, the driver was not injured; a tow truck hauled the van to safety.
On the following Monday morning, 13 Aug., AZGS’s Joe Cook (Earth Fissure program manager) and Brian Gootee (drone pilot) examined the fissure and captured video illustrating the impact on Houston Avenue along with diagnostic features of the earth fissure north of the road (https://tinyurl.com/EF-HoustonAve-2018). The drone portion of the video, about 45 seconds long, begins north of the junction of E Baseline Ave. and S. Meridian Road and follows the fissure for about 2,500 feet to its intersection with Houston Ave.
The Houston Ave. earth fissure was first reported in the 1980s. It’s active today and continues to disrupt roads and damage private property.
With further monsoon rains, we can expect new or re-activated earth fissure activity in basins in Cochise, La Paz, Maricopa and Pinal Counties where fissures have broken out in the past. The Natural Hazards in Arizona viewer displays the locations of all earth fissures mapped in southern Arizona. The viewer includes strategies for minimizing the impact of fissures on roads, infrastructure, and property.
How you can help. We continue to monitor earth fissure activity and update our earth fissure study area maps as needed. But we need your help. Please report any new or reactivated fissures to either Joe Cook (AZGS Earth Fissure Program manager; joecook@email.arizona.edu") or Mike Conway (fmconway@email.arizona.edu). Thanks!
Background. Earth fissures are an anthropogenic hazard in some basin in southern and southeastern Arizona. The first fissures were reported in the late 1920s from near Eloy in the Picacho Basin. Fissures result from withdrawing groundwater from subterranean aquifers. As the groundwater is withdrawn, sediment grains are compacted, and the basin floor subsides. Subsidence drives tensional forces that result in fissure formation along the basin perimeter or above and adjacent to bedrock highs in the subsurface.
Mike Conway (Arizona Geological Survey at The University of Arizona)
fmconway@email.arizona.edu
