Mass-waste events from volcanic edifice collapse constitute one of the world's most catastrophic natural hazards. To date, hazards associated with collapse have generally been considered evenly dispersed about a volcano. However, these events are often referred to as sector collapses because only part of a volcano's summit and flank collapse. This is because volcanoes do not have uniform geology or geotechnical characteristics and, thus, their hazard distributions are also non-uniform. To assess the non-uniform distribution of geologic controls on volcano stability, we have developed a method that combines field-based geologic mapping and sampling with mineralogic, petrologic, stable-isotope geochemical, and geotechnical laboratory studies. Our results provide methods that help quantify the non-uniform stability of stratovolcanoes and significantly improve volcanic hazard and risk assessments.