The magmatic and eruptive evolution of the 1883 caldera-forming eruption of Krakatau: Integrating field- to crystal-scale observations

Explosive, caldera-forming eruptions are exceptional and hazardous volcanic phenomena. The 1883 eruption of Krakatau is the largest such event for which there detailed contemporary written accounts, allowing information on eruptive progression to be integrated with stratigraphy geochemistry its products. Freshly exposed sequences deposits Krakatau, stripped vegetation by a tsunami generated flank collapse Anak in 2018, shed new light sequence. Matrix glass from base chemically distinct more evolved than overlying sequence indicating presence shallow, silicic, melt-rich region that was evacuated during early activity May onwards. Disruption silicic magma may have led coalescence mixing similar melts representative range magmatic conditions, as evidenced complex varied plagioclase phenocryst zoning profiles. This mixing, over period two three months, culminated onset climactic phase 26th August 1883. Pyroclastic density currents (PDCs) emplaced this show change transport direction north east south west, coinciding deposition lithic lag breccia unit. attributed partial an elevated portion island, resulting removal topographic barrier. Edifice destruction potentially further reduced overburden underlying system, leading most explosive energetic morning 27th final caldera collapse, recorded second breccia. massive PDC contain glassy blocks up 8 m size, observed first time 2019, pyroclastic These interpreted representing stagnant, shallow portions reservoir disrupted stages formation. study provides evidence role precursory amalgamation crustal bodies play months eruptions.