Exploring Arizona earth fissures: An anthropogenic geologic hazard
Published:September 04, 2019
Grace Carlson, Lorraine K. Carnes, Joseph P. Cook, 2019. "Exploring Arizona earth fissures: An anthropogenic geologic hazard", Geologic Excursions in Southwestern North America, Philip A. Pearthree
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Earth fissures are tensile surface cracks exposed at Earth’s surface. In Arizona, such fissures are predominantly found in the central and southeastern regions of the state, where they form in response to subsidence driven by groundwater pumping. Growth and erosion of these fissures often occurs during large monsoon storms, resulting in slumping and collapse of the fissure walls, propagation of the fissure head, as well as the development of gully networks out from the main fissure stem. Fissure initiation and propagation threaten existing infrastructure, can cause property damage, and increase the potential for groundwater contamination from surface pollutants. It is exceedingly important that these hazards be well understood, documented, and monitored.
The Arizona Geological Survey (AZGS) founded the earth fissure program in 2007 to systematically identify, map, and monitor earth fissures in Arizona. Data are released through an interactive viewer (https://uagis.maps.arcgis.com/apps/webappviewer/index.html?id = 98729f76e4644f1093d1c2cd6dabb584), which is regularly updated to show new fissures and growth of existing ones. Additionally, beginning in November 2018, repeated surveys of a series of large earth fissures in Apache Junction, Arizona, (50 km east of Phoenix) have been done using UAV-SfM (unmanned aerial vehicle–structure from motion) to better elucidate the processes controlling the short-term evolution of this geologic hazard.
This field trip will take us to two fissure locations in the greater Phoenix metropolitan area. The first will be the Apache Junction earth fissure area, where we will be able to observe the large, dramatic scale of these features, as well as highlight the important role large monsoon storms have on fissure propagation and geomorphological changes. Furthermore, we will show how high-resolution topographic surveys provide a means for significant improvements to current mapping and monitoring efforts for assessing hazards related to earth fissures. The second site will be a fissure location just to the southwest of Apache Junction in Chandler Heights, Arizona, which we refer to as the “Queen Creek” earth fissure area. At this field-trip stop, we will show how fissure initiation and growth threaten human development, as well as describe the role the AZGS earth fissure program plays in identifying and monitoring these hazards.
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Geologic Excursions in Southwestern North America
This volume, prepared as part of the Geological Society of America Annual Meeting in Phoenix, includes field guides covering aspects of the spectacular geology of southwestern North America. Field guides tackle the geology of the southern Colorado Plateau, from paleoenvironments of Petrified Forest National Park, to Jurassic sand dunes of southern Utah, to the San Francisco Volcanic Field, to awesome Grand Canyon. Appropriately for the 50th anniversary of the first lunar landing, one trip visits sites in northern Arizona that helped prepare astronauts for their missions. Several guides address aspects of the Proterozoic to Cenozoic tectonic development of the Transition Zone between the Colorado Plateau and the Basin and Range. Exploring the Basin and Range, guides feature Laramide tectonism and ore deposit development, features associated with large-magnitude Cenozoic extensional tectonism, large Miocene volcanic centers in northwestern Arizona, and tectonism and development of the lower Colorado River. Three field guides explore various aspects of northwestern Mexico, including tectonics and ore deposits of Sonora, fauna and paleoenvironments of Colorado River delta deposits, and volcanism in central Baja California. Finally, a guide analyzes anthropogenic earth fissures that have developed in the Phoenix metropolitan area.