In retrospect, maybe locating your city on a tectonic plate boundary isn’t such a good idea. I’m looking at you, Oakland.
First South American Civilisation Wiped Out by Earthquake
The downfall of this powerful civilization was its location. The Supe valley is where the Nazca Plate and the South American Plate crash. When the big one hit, this earthquake-prone region was also hit by mudslides, which clogged the rivers. This coincided with heavy rainfall brought on by a strong El Niño, thus forming a 60-mile-long ocean ridge, which sealed off coastal bays. These filled with sand and therefore eliminated the Supe society’s source of food.
Tough luck? Says archeologist Daniel H. Sandweiss of the University of Maine: “By not being able to look decades ahead, they [the inhabitants of Supe valley] were not able to cope with it.” With the technology of the time, it was near impossible. Sometimes, when it rains it just pours.