occurred, it caused new slumping, starting about 1956. The increasingly violent weather of recent decades has exacerbated the problem. In 1984-5 there were several slumps, and the state government brought in surplus soil to make repairs to the major scar on the eastern side. A decade later, there was further slumping on the western side, so irregular that repair was impractical. Drains were installed to reduce the effects of heavy rain. It was during this process that workers discovered a mass of stone deep within the mound. The repairs of the 1980s and 1990s were only partly successful. In 2004-5 more serious slumping episodes occurred. These demonstrated that adding new earth to repair the major slump on the east side had been a mistake. Experts decided to take a new approach. In 2007, backhoes were used to dig out the entire mass of earth from this slump and another at the northwest corner, to a level beyond the internal slippage zone. Engineers created a series of anti-slip "steps" across the exposed face before the original earth (minus the imported repair material) was replaced at its original level. To avoid introducing water deep into the mound's interior, the work was carried out in high summer, and as quickly as possible. In parallel with the repair work, teams of archaeologists studied the evidence that was being revealed. The eastern sliding zone penetrated more deeply within the mound than originally estimated, and the excavation had to be very large- wide, to a height of above the mound base. This heightened concerns about a conflict between conservation and archaeology. See also List of Mississippian sites Mound 34 Mound 72 Southeastern Ceremonial Complex Sugarloaf Mound References Further reading Price, Douglas T. and Gary M. Feinman. Images of the Past, 5th ed. New York: McGraw-Hill (2008) . pp. 282–285. "The Trappists of Monk's Mound" — Illinois Catholic Historical Review, 8:106‑136 (1925) External links Monks Mound (Mound 38), Cahokia Mounds State Historic Site website. UNESCO – Cahokia Mounds State Historic Site Cahokia Mounds Photo Gallery 2016 discussion of new research indicating construction in as little as twenty years Buildings and structures completed in 1100 11th-century establishments in North America 1809 archaeological discoveries Middle Mississippian culture Archaeological sites in Illinois Protected areas of Madison County, Illinois Mounds in Illinois Pyramids in the United States Cahokia