Figure 7.

Conceptual model of Turrialba Volcano showing the plumbing system as envisioned from gas compositions and modeling. Pulses of new magma arrive at midcrustal depths (8–10 km) during phases 2 and 5, producing CO₂‐rich gas pulses and destabilizing a lower magma reservoir. Shortly thereafter, magma, volatiles, and heat are injected to the shallow magmatic system, triggering phreatic and phreatomagmatic eruptions. An extensive hydrothermal system contributes volatiles and modifies magmatic gas compositions mostly during phases 1, 4, and 5 and to lesser extent during phases 2 and 3. Phase 3 eruptions (particularly the 29 October 2014 event) ruptured hydrothermally sealed breccia (green triangles) previously sealed at chemical and thermal interfaces between magmatic vapor and hydrothermal liquid zones, allowing massive degassing of hydrothermally stored volatiles during stage 4.