ARIZONA GEOLOGICAL SURVEY EARTH FISSURE MAPPING PROGRAM

In 2006, Arizona legislature passed a statute directing the Arizona Geological Survey (AZGS) to map earth fissures in the state. The statute requires that this map information be included in the disclosure documentation for real estate transactions in the state. The fissure map is hosted by the Arizona State Land Department (ASLD) on their Internet Mapping Server (IMS) giving the public easy access to the maps. Separate study areas were delineated in central and southern Arizona based on the known distribution of earth fissures. When mapping is completed in each study area, we deliver the data to the ASLD to speed up the transfer of the information to the public.

Several issues have deterred earth fissure mapping efforts in the past: (1) fear of liability associated with map accuracy and completeness; (2) the dynamic nature of earth fissures; and (3) logistical issues associated with making the maps readily available to the public. Our mapping program addresses each of these issues. We identified earth fissures through a review of publications and reports, air photo analysis, and field reconnaissance. Relatively high-precision waypoints were collected along the length of earth fissure surface exposure. Fissures were categorized as “continuous”, “discontinuous”, and “unconfirmed” if we were not able to find and map previously reported fissures. Dynamic aspects of earth fissures require remapping of an area after a period of time to document new and growing earth fissures. Map change requires archiving of the information and date stamping of the data to qualify the mapped information. For example, an earth fissure that was revisited after two strong rain events grew 100 meters within four months of initial measurements. Accessibility and readability are fundamentals in delivering the information to the public. Using IMS we are able to define the layers of the geographic information displayed with the earth fissure maps. Access to the map and general information about our mapping program via the web has enabled the AZGS to deliver an accurate mapping program. Stakeholders have been consulted in the development of the mapping process and local geological consultants have reviewed the maps. Although these maps are imperfect due to multiple factors, they are the first step in responsible development in earth fissure prone areas.