Tremors & Landslides
Records of aluviones, a deadly mix of avalanche, waterfall and landslide, date back almost 300 years in the Cordillera region, but three recent ones have caused particular devastation.
The first occurred in 1941, when an avalanche in the Cojup Valley, west of Huaraz, caused the Laguna Palcacocha to break its banks and flow down onto Huaraz, killing about 5000 inhabitants and flattening the city. Then, in 1962, a huge avalanche from Huascarán roared down its western slopes and destroyed the town of Ranrahirca, killing about 4000 people.
The worst disaster occurred on May 31, 1970, when a massive earthquake, measuring nearly 8.0 on the Richter scale, devastated much of central Peru, killing an estimated 70,000 people. About half of the 30,000 inhabitants of Huaraz died, and only 10% of the city was left standing. The town of Yungay was completely buried by the aluvión caused by the quake and almost its entire population of 25,000 was buried with the city.
Since these disasters, a government agency (Hidrandina) has been formed to control the lake levels by building dams and tunnels, thus minimizing the chance of similar catastrophes. However, a combination of climate change and a marked rise in glacial meltwater has raised Palcacocha's danger level in recent years. Adding to the problem, Huaraz's population has increased 10-fold since 1941, meaning far more people now live in the lake's floodplain.
To allay these worries, a new more sophisticated early-warning system is currently being developed and was due to be installed near Laguna Palcacocha in late 2018.