In this Aug. 12, 2016 photo, the Pastoruri glacier is reflected in a lagoon in the Huascaran National Park in Huaraz, Peru. Glacial lakes are often pretty fragile structures, created when rocks and rubble carried by a glacier form a moraine that dams up its water outflow. The dam can also be created by chunks of a glacier’s own ice. These inherently unstable structures can collapse quickly, especially in places like Peru that are prone to frequent, violent earthquakes. (AP Photo/Martin Mejia)
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