caa a22 4500 475826132 CHVBK 20180406123829.0 cr unu---uuuuu 170329e20000501xx s 000 0 eng 10.1007/s004450050288 doi (NATIONALLICENCE)springer-10.1007/s004450050288 The caldera-forming eruption of Volcán Ceboruco, Mexico [Elektronische Daten] [James E. Gardner, Steve Tait] 3: of magma erupted, ∼95% of which was deposited as fall layers. During most of the deposition of P1, eruptive intensity (mass flux) was almost constant at 4-8×107 kg s−1, producing a Plinian column 25-30 km in height. Size grading at the top of P1 indicates, however, that mass flux waned dramatically, and possibly that there was a brief pause in the eruption. During the post-P1 phase of the eruption, a much smaller volume of magma erupted, although mass flux varied by more than an order of magnitude. We suggest that caldera collapse began at the end of the P1 phase of the eruption, because along with the large differences in mass flux behavior between P1 and post-P1 layers, there were also dramatic changes in lithic content (P1 contains ∼8% lithics; post-P1 layers contain 30-60%) and magma composition (P1 is 98% rhyodacite; post-P1 layers are 60-90% rhyodacite). However, the total volume of magma erupted during the Jala pumice event is close to that estimated for the caldera. These observations appear to conflict with models which envision that, after an eruption is initiated by overpressure in the magma chamber, caldera collapse begins when the reservoir becomes underpressurized as a result of the removal of magma. The conflict arises because firstly, the P1 layer makes up too large a proportion (∼75%) of the total volume erupted to correspond to an overpressurized phase, and secondly, the caldera volume exceeds the post-P1 volume of magma by at least a factor of three. The mismatches between model and observations could be reconciled if collapse began near the beginning of the eruption, but no record of such early collapse is evident in the tephra sequence. The apparent inability to place the Jala pumice eruptive sequence into existing models of caldera collapse, which were constructed to explain the formation of calderas much greater in volume than that at Ceboruco, may indicate that differences in caldera mechanics exist that depend on size or that a more general model for caldera formation is needed. Springer-Verlag Berlin Heidelberg, 2000 Caldera eruptions nationallicence Tephrostratigraphy nationallicence Caldera collapse nationallicence Volcán Ceboruco nationallicence Marquesado pyroclastic flow nationallicence Gardner James E. Department of Geological Sciences, Brown University, Providence, RI, USA e-mail: gardner@gi.alaska.edu Fax: +1-907-4745163, US aut Tait Steve Laboratoire de Dynamic des Systèmes Géologiques, Institut de Physique du Globe, 4 place Jussieu, F-75252 Paris cédex 05, France, FR aut https://doi.org/10.1007/s004450050288 text/html Onlinezugriff via DOI 1 research-article jats NATIONALLICENCE 856 40 https://doi.org/10.1007/s004450050288 text/html Onlinezugriff via DOI NATIONALLICENCE 700 1- Gardner James E. Department of Geological Sciences, Brown University, Providence, RI, USA e-mail: gardner@gi.alaska.edu Fax: +1-907-4745163, US aut NATIONALLICENCE 700 1- Tait Steve Laboratoire de Dynamic des Systèmes Géologiques, Institut de Physique du Globe, 4 place Jussieu, F-75252 Paris cédex 05, France, FR aut Metadata rights reserved Springer special CC-BY-NC licence nationallicence BK010053 XK010053 XK010000 NATIONALLICENCE NATIONALLICENCE NL-springer