Peru is prone to a series of natural disasters caused by both its young geological formation and its peculiar climate. On the western edge of South America, the Nasca Plate is slowly sliding beneath the continent, and the resulting friction causes periodic earthquakes and volcanic eruptions. The area most affected by this is southern Peru, especially Arequipa, which was destroyed by earthquakes in 1582, 1600, and 1604 (and also covered in ash during periodic explosions of the nearby Huaynaputina volcano). The city averages roughly one major earthquake per century, most recently in 2001, when one of the cathedral towers collapsed across the Plaza de Armas.

The hardest-hit region, however, has been the Callejón de Huaylas, a river valley situated between the Cordillera Negra and Cordillera Blanca ranges, where earthquakes cause glacial lakes to burst their dams and send huge mudslides (aluviones) to the valley below. In 1970, an earthquake measuring 7.8 on the Richter scale destroyed 90 percent of Huaraz and triggered a wall of mud and boulders that swept down the valley above the nearby town of Yungay. Within minutes, around 25,000 people were buried alive. The town has been rebuilt, and the only traces of old Yungay are the tops of a few palm trees poking out above the silt plain. These trees once graced the town’s square.

El Niño, the periodic fluctuation in the water temperature of the Pacific Ocean, wreaks havoc across Peru and appears to be having increasingly dramatic highs and lows; some scientists think this is a result of global dimatic change. In 1982 and 1998, El Niño events dumped torrential rains onto Peru’s northern desert, causing floods that washed out bridges and stranded highway motorists for weeks. These natural phenomena also caused droughts in the southern Andes and a collapse in Peru’s coastal fishery, as the plankton, anchovies, and larger fish moved deep into the ocean to follow the colder water.