TY - JOUR
T1 - Water contents, temperatures and diversity of the magmas of the catastrophic eruption of Nevado del Ruiz, Colombia, November 13, 1985
AU - Melson, William G.
AU - Allan, James F.
AU - Jerez, Deborah Reid
AU - Nelen, Joseph
AU - Calvache, Marta Lucia
AU - Williams, Stanley N.
AU - Fournelle, John
AU - Perfit, Mike
N1 - Funding Information:
The Smithsonian field study was made possible by a grant from the Smithsonian Research Opportunities Fund. Acquisition of the INA data and support of J. Allan were funded by NSF grants OCE-8415270 and OCE-8508042 (R. Batiza), and ONR Grant 10-14-80-C-0856 (R. Batiza) and an NSERC Strategic Operating Grant 5-55847 (D. Chase). S.N. Williams acknowledges the NSF (INT-8608977, INT-8714954, EAR-8601458 and EAR-8721206) and NGS. Clifford A. Hopson made many useful comments on the petrography of the pumices. We wish to thank Eduardo Parra of IN-GEOMINAS, Manizales, Colombia, and his many colleagues for their assistance during the field studies. The manuscript was improved by the reviews of James Luhr, Gary Byerly, Amitava Roy, Richard Stoiber, and John Stix.
PY - 1990/7/15
Y1 - 1990/7/15
N2 - The petrology of the highly phyric two-pyroxene andesitic to dacitic pyroclastic rocks of the November 13, 1985 eruption of Nevado del Ruiz, Colombia, reveals evidence of: (1) increasingly fractionated bulk compositions with time; (2) tapping of a small magma chamber marginally zoned in regard to H2O contents (1 to 4%), temperature (960-1090°C), and amount of residual melt (35 to 65%); (3) partial melting and assimilation of degassed zones in the hotter less dense interior of the magma chamber; (4) probable heating, thermal disruption and mineralogic and compositional contamination of the magma body by basaltic magma "underplating"; and (5) crustal contamination of the magmas during ascent and within the magma chamber. Near-crater fall-back or "spill-over" emitted in the middle of the eruptive sequence produced a small pyroclastic flow that became welded in its central and basal portions because of ponding and thus heat conservation on the flat glaciated summit near the Arenas crater. The heterogeneity of Ruiz magmas may be related to the comparatively small volume (0.03 km3) of the eruption, nearly ten times less than the 0.2 km3 of the Plinian phase of Mount St. Helens, and probable steep thermal and PH2O gradients of a small source magma chamber, estimated at 300 m long and 100 m wide for an assumed ellipsoidal shape.
AB - The petrology of the highly phyric two-pyroxene andesitic to dacitic pyroclastic rocks of the November 13, 1985 eruption of Nevado del Ruiz, Colombia, reveals evidence of: (1) increasingly fractionated bulk compositions with time; (2) tapping of a small magma chamber marginally zoned in regard to H2O contents (1 to 4%), temperature (960-1090°C), and amount of residual melt (35 to 65%); (3) partial melting and assimilation of degassed zones in the hotter less dense interior of the magma chamber; (4) probable heating, thermal disruption and mineralogic and compositional contamination of the magma body by basaltic magma "underplating"; and (5) crustal contamination of the magmas during ascent and within the magma chamber. Near-crater fall-back or "spill-over" emitted in the middle of the eruptive sequence produced a small pyroclastic flow that became welded in its central and basal portions because of ponding and thus heat conservation on the flat glaciated summit near the Arenas crater. The heterogeneity of Ruiz magmas may be related to the comparatively small volume (0.03 km3) of the eruption, nearly ten times less than the 0.2 km3 of the Plinian phase of Mount St. Helens, and probable steep thermal and PH2O gradients of a small source magma chamber, estimated at 300 m long and 100 m wide for an assumed ellipsoidal shape.
UR - http://www.scopus.com/inward/record.url?scp=0025664175&partnerID=8YFLogxK
UR - http://www.scopus.com/inward/citedby.url?scp=0025664175&partnerID=8YFLogxK
U2 - 10.1016/0377-0273(90)90085-T
DO - 10.1016/0377-0273(90)90085-T
M3 - Article
AN - SCOPUS:0025664175
SN - 0377-0273
VL - 41
SP - 97
EP - 126
JO - Journal of Volcanology and Geothermal Research
JF - Journal of Volcanology and Geothermal Research
IS - 1-4
ER -