Peru is a country rich in extreme geographical features, and its mountainous terrain is home to a significant number of volcanoes, concentrated primarily in the southern third of the country. While many of the approximately 400 structures are ancient and extinct, a specific cluster remains active and is closely monitored for potential hazards. This active volcanic landscape is a direct result of immense forces deep within the Earth, shaping the region’s geography and influencing population centers.
The Peruvian Volcanic Arc
The presence of active volcanoes in Peru is a direct consequence of plate tectonics, specifically the convergence of two massive crustal plates. The oceanic Nazca Plate is actively sliding, or subducting, beneath the continental South American Plate along the western coast. This geological process is a major component of the larger Andean Volcanic Belt.
The friction and heat generated by this subduction cause water and other volatile compounds to be released from the descending slab, lowering the melting point of the mantle rock above it. This molten rock, or magma, rises toward the surface, feeding the volcanoes of the Central Volcanic Zone (CVZ).
Volcanic activity does not extend across the entire country because the subduction angle changes further north, creating a volcanically inactive region known as the Peruvian flat-slab segment. In this northern gap, the Nazca Plate plunges at a very shallow angle, preventing the slab from reaching the necessary depth to generate magma. Consequently, all of Peru’s monitored active volcanoes are situated in the south, in departments like Arequipa, Moquegua, and Tacna.
Key Active and Dormant Volcanoes
The most prominent and potentially hazardous volcanoes in Peru are found in this southern volcanic arc, exhibiting varying levels of activity. An active volcano is defined as one that has erupted in historical times or shows current signs of unrest. A dormant volcano has not erupted recently but still retains the potential to erupt. The most active structure is Ubinas, located in the Moquegua Region.
Ubinas has a record of more than two dozen explosive eruptions since the 16th century, making it the country’s most consistently active volcano. Its activity is characterized by moderate explosive events and the persistent emission of gases and ash. Recent periods of unrest, including an eruption in 2023, have frequently prompted the evacuation of nearby communities that rely on the valley for agriculture and dwelling.
Another significant volcano is El Misti, which towers over the city of Arequipa, less than 20 kilometers from its densely populated center. Although currently classified as dormant, El Misti is considered one of the world’s most dangerous volcanoes due to its proximity to a city of over a million people. Its last major explosive eruptions occurred between 1440 and 1470 AD, though it has experienced periods of increased fumarolic activity more recently.
Sabancaya, situated northwest of Arequipa, is considered the second most active volcano and has been in an almost continuous eruptive phase since 2016. This continuous activity involves frequent explosions and the emission of gas and ash columns that can reach several kilometers in height. The ongoing eruptions demonstrate the region’s geological volatility.
Monitoring and Hazard Assessment
The task of monitoring Peru’s active volcanoes falls to the Instituto Geofísico del Perú (IGP), through its specialized Centro Vulcanológico Nacional (CENVUL). This government body is responsible for keeping a constant watch over approximately 12 of the most active and potentially active volcanic systems in the southern region. Their work is a multidisciplinary effort designed to provide the earliest possible warning of an impending eruption.
Monitoring methods include the installation of extensive seismic networks, which detect the small earthquakes and tremors caused by magma movement beneath the surface. Scientists also use high-precision Global Positioning System (GPS) instruments to measure ground deformation, looking for subtle swelling or subsidence that indicates pressure changes within the magma chamber. Furthermore, gas geochemistry analysis is conducted to track the composition and flux of volcanic gases, which can signal a change in the magmatic system.
The data collected from these techniques are used to prepare volcanic hazard maps, which outline the zones at risk from ash fall, pyroclastic flows, and lahars, or volcanic mudflows. CENVUL regularly issues scientific bulletins and alerts to local civil defense authorities and the public, communicating current risk levels and warnings. These warnings are crucial for coordinating emergency responses and the timely evacuation of populations in the valleys surrounding volcanoes like Ubinas and Sabancaya.