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Most recent eruption of the Mono Craters, eastern central California

Sieh, Kerry and Bursik, Marcus (1986) Most recent eruption of the Mono Craters, eastern central California. Journal of Geophysical Research. Solid Earth, 91 (B12). pp. 12539-12571. ISSN 2169-9313. doi:10.1029/JB091iB12p12539.

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The most recent eruption at the Mono Craters occurred in the fourteenth century A.D. Evidence for this event includes 0.2 km^3 of pyroclastic fall, flow, and surge deposits and 0.4 km^3 of lava domes and flows. These rhyolitic deposits emanated from aligned vents at the northern end of the volcanic chain. Hence we have named this volcanic episode the North Mono eruption. Initial explosions were Plinian to sub‐Plinian events whose products form overlapping blankets of air fall tephra. Pyroclastic flow and surge deposits lie upon these undisturbed fall beds within several kilometers of the source vents. Extrusion of five domes and coulees, including Northern Coulee and Panum Dome, completed the North Mono eruption. Radiocarbon dates and dendrochronological considerations constrain the eruption to a period between A.D. 1325 and 1365. The lack of lacustrine laminae or aeolian and fluvial beds between individual pyroclastic beds suggests that the explosive phases of the eruption took place over a period of not more than several months. Within the resolution of the available radiocarbon and dendrochronologic dates, the North Mono eruption is contemporaneous with the latest eruption of the Inyo volcanic chain, about 20 km to the south. However, the Inyo tephra blanket clearly overlies, and thus postdates, all North Mono tephra. Minor disturbance of the North Mono tephra prior to deposition of the Inyo tephra indicates that the period of time between the North Mono and Inyo eruptions was probably no more than a year or two. This near contemporaneity of the two eruptions suggests a genetic relationship. Liquefaction of North Mono sands on the floor of Mono Lake occurred twice during the waning stages of the North Mono eruption and 3 times immediately before and after pulses of the Inyo eruption. This is evidence that five earthquakes of M_L ≳ 5.5 occurred during the North Mono and Inyo eruptions. The chemical and textural similarity of the erupted products and their nearly simultaneous evacuation from aligned vents indicates that the North Mono eruption resulted from intrusion of a dike beneath the northern 6 km of the volcanic chain. Several observations suggest that dike intrusion beneath the Mono Craters has replaced normal faulting as the mechanism for elastic rebound and permanent extension of the crust at this latitude. However, dike widths compatible with relief of purely tectonic strains (≲3 m) are probably too narrow to have allowed the North Mono magma to erupt. Overpressurization of the Mono Craters magma reservoir by another mechanism, perhaps magma mixing, appears necessary as well. The gradually diminishing explosiveness of the North Mono eruption probably resulted from a decrease of water content downward in the dike. The pulsating nature of the early, explosive phase of the eruption may represent the repeated rapid drawdown of slowly rising vesiculated magma to about the saturation depth of the water within it.

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Sieh, Kerry0000-0002-7311-2447
Additional Information:© 1986 American Geophysical Union. Paper number 6B5929. Received January 14, 1986; revised June 4, 1986; accepted June 23, 1986. Spencer Wood first encouraged us to continue his unfinished work at the Mono Craters as a mapping project for an undergraduate summer field geology class in 1981. Scott Stine has been a wonderful source of information and enthusiasm during many conversations and field excursions. We were fortunate to be working in this area while he was discovering the Holocene stratigraphy of Mono Lake. Dan Miller's and Dan Sampson's recent discoveries to the south, in the Inyo volcanic chain and Pat Kelleher's study of the Mono Craters have also added to our enthusiasm for this work. Dave Stevenson tutored us in our attempt to understand the mechanism of the eruption. Conversations with Ari Fuad, Ed Stolper, and Sally Newman about their water content data also have helped us in attempting to understand the eruption. We are grateful for the assistance of Jim Drake, Pat Williams, Norm Brown, and Paul Haase in the field and to Paul Hawley and Jan Mayne for typing this manuscript and drafting most of the figures. Roy Balley and Ken Cameron provided very helpful reviews of the manuscript. Field work during the summers of 1982-1985 and radiocarbon dating were supported by generous donations from the Allan V.C. Davis Foundation. Part of M.B.'s field work in 1984 was supported by a Penrose grant (#3265-84) from the Geological Society of America. Caltech Division of Geological and Planetary Sciences Contribution number 4379.
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Geological Society of America3265-84
Allan V. C. Davis FoundationUNSPECIFIED
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Caltech Division of Geological and Planetary Sciences4379
Issue or Number:B12
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Official Citation:Sieh, K., and Bursik, M. (1986), Most recent eruption of the Mono Craters, eastern central California, J. Geophys. Res., 91(B12), 12539–12571, doi:10.1029/JB091iB12p12539
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:98574
Deposited By: Tony Diaz
Deposited On:11 Sep 2019 17:36
Last Modified:16 Nov 2021 17:40

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