Plate beneath the South American Plate in the Peru–Chile Trench, at a pace of . The Southern Volcanic Zone is one among several volcanic belts in the Andean Volcanic Belt. Areas without volcanic activity separate it from the Central Volcanic Zone in the north and the Austral Volcanic Zone in the south. These gaps appear to coincide where the Juan Fernández Ridge and the Chile Rise, respectively, subduct in the Peru–Chile Trench. In the volcanic gaps, the subducting slab seems to be attached to the overriding plate without an asthenosphere in between, suppressing the production of magma. There is a strong northsouth gradient among volcanoes of the Southern Volcanic Zone. The northernmost volcanoes are the highest and lie on thicker crust which causes their magmas to have a stronger crustal contribution. The output of the northernmost volcanoes is dominated by andesitic and more evolved magmas and they have the highest quantity of incompatible elements in their magmas. Southern volcanoes are lower, tend to erupt mafic magmas and are located west of the continental divide. Volcanism in areas of subduction is caused by the release of slab fluids from the subducting slab into the abovelying asthenospheric mantle. The injection of such fluids triggers fluxing and the formation of magmas. Conversely, the descending slab itself is usually not considered a major contributor to magma genesis. Such exceptional magmas are often referred to as adakites, but magmas with such a chemistry can also originate by other processes. Local Nevado de Longaví lies within a small mountain chain. It was formerly considered or high; the accepted elevation is . The volcano has a summit crater and many adventive craters on its slopes. The summit crater is heavily degraded by erosion. Lava flows extend radially away from the summit crater and form the bulk of the volcano. The adventive craters are also associated with lava flows. These lava flows are accompanied by breccia and reach thicknesses of . Lahar deposits are found on the eastern slopes. Scarps on the eastsoutheast flanks resulted from sector collapses of the volcano. This collapse is known as Lomas Limpias and its scar has a surface area of . The collapse scar was later filled with products from explosive eruptions. Another collapse occurred on the southsouthwestern flank, forming the Los Bueyes collapse and terrace deposits. Nevado de Longaví is a relatively small volcano. With a diameter of , a basal