Award Abstract # 1358886
Degassing Dynamics that Lead to Repeated Lava Dome Growth and Collapse at Persistently Active Stratovolcanoes

NSF Org: EAR
Division Of Earth Sciences
Recipient: UNIVERSITY OF ALABAMA
Initial Amendment Date: September 11, 2013
Latest Amendment Date: September 11, 2013
Award Number: 1358886
Award Instrument: Continuing Grant
Program Manager: Jennifer Wade
jwade@nsf.gov
 (703)292-4739
EAR
 Division Of Earth Sciences
GEO
 Directorate for Geosciences
Start Date: August 1, 2013
End Date: December 31, 2015 (Estimated)
Total Intended Award Amount: $116,504.00
Total Awarded Amount to Date: $116,504.00
Funds Obligated to Date: FY 2013 = $116,504.00
History of Investigator:
  • Kimberly Genareau (Principal Investigator)
    kdgenareau@as.ua.edu
Recipient Sponsored Research Office: University of Alabama Tuscaloosa
801 UNIVERSITY BLVD
TUSCALOOSA
AL  US  35401-2029
(205)348-5152
Sponsor Congressional District: 07
Primary Place of Performance: University of Alabama Tuscaloosa
AL  US  35487-0104
Primary Place of Performance
Congressional District:
07
Unique Entity Identifier (UEI): RCNJEHZ83EV6
Parent UEI: TWJWHYEM8T63
NSF Program(s): Petrology and Geochemistry
Primary Program Source: 01001314DB NSF RESEARCH & RELATED ACTIVIT
Program Reference Code(s):
Program Element Code(s): 157300
Award Agency Code: 4900
Fund Agency Code: 4900
Assistance Listing Number(s): 47.050

ABSTRACT

The October 2010 eruption of Mt. Merapi, one of Indonesia?s most active volcanoes, demonstrates the devastation and sudden loss of human life that can result from even moderate to small eruptions of active stratovolcanic systems throughout the world. The ability to observe current activity on Merapi, and the existence of preserved erupted sequences resulting from long-lived activity, allow for a detailed examination of volatile degassing dynamics during lava dome growth and major dome collapse events. It also provides an opportunity to formulate a general model of how such systems evolve over time. Because lava dome growth and collapse is a dominant mechanism for the production of dangerous and unpredictable volcanic phenomena (e.g., pyroclastic density currents, ash fall) that have devastating effects on both local and regional populations, understanding the physical parameters that trigger dome collapse events and influence the generation of pyroclastic hazards is paramount to improving the hazard mitigation strategies at this persistently active stratovolcano.

In exploring the causes of major dome collapse events at andesitic stratovolcanoes, this project seeks evidence for geochemical and textural signals for these impending events in erupted products, with the objective of determining how the dynamics of volatile degassing during lava effusion contributes to particular characteristics of resulting pyroclastic density currents and ash fall hazards. Existing samples collected from Merapi will be targeted by a focused range of analyses in order to constrain similarities or differences in particular characteristics between single eruptive events and temporal variations over the long-term course of eruptive activity, including:
1. Grain size distributions of fall and flow units and ash grain morphologies within the most efficiently fragmented portion of the tephra.
2. Microlite number density and microlite morphology within lava samples, plagioclase phenocryst rim compositions, rim textures, and amphibole reaction rim thicknesses.
3) Lava vesicularity, vesicle morphology, bubble size distributions, and development of permeable networks for gas escape during dome growth.
4) Behavior of volatile elements (H2O, CO2, Li) in minerals and melts during magma ascent and dome effusion.

By comparing several dome-producing events over time within a single stratovolcanic system, this study seeks to quantify the rheological parameters leading up to major dome collapse events, attempting to explain why these collapse events occur, why they occur on variable time scales, and how the behavior of volatile elements and the degassing of these elements will influence the resulting characteristics of pyroclastic hazards. Quantifying the physical parameters within volcanic conduits and understanding how these parameters vary over time to cause major dome collapse events will allow researchers to more accurately model (and ultimately, forecast) volcanic behavior. This will lead to improved hazard assessment strategies for not only Merapi, which represents a significant volcanic hazard for the nation of Indonesia, but for the other >100 active stratovolcanic centers throughout the world that display similar behavior.

PUBLICATIONS PRODUCED AS A RESULT OF THIS RESEARCH

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Genareau, K., Cronin, S.J., and Lube, G. "Effects of Volatile Behavior on Dome Collapse and Resultant Pyroclastic Surge Dynamics: Gunung Merapi 2010 eruption." Geological Society of London: The Role of Volatiles in the Genesis, Evolution and Eruption of Arc Magmas , v.410 , 2014 , p.199
KIMBERLY GENAREAU, SHANE J. CRONIN, & GERT LUBE "Effects of Volatile Behavior on Dome Collapse and Resultant Pyroclastic Surge Dynamics: Gunung Merapi 2010 eruption" Geological Society of London: The Role of Volatiles in the Genesis, Evolution and Eruption of Arc Magmas. , 2014

PROJECT OUTCOMES REPORT

Disclaimer

This Project Outcomes Report for the General Public is displayed verbatim as submitted by the Principal Investigator (PI) for this award. Any opinions, findings, and conclusions or recommendations expressed in this Report are those of the PI and do not necessarily reflect the views of the National Science Foundation; NSF has not approved or endorsed its content.

Chemical and textural analyses were conducted on deposits from the 2010 eruption of Merapi volcano (Java, Indonesia) to determine the role of volatiles (CO2, H2O) in influencing eruptive dynamics. Grain size distribution and componentry analyses of the ash were coupled with selection of feldspar crystals for further geochemical and textural study.  Helium pycnometer measurements of the lava were used to determine the density and porosity of the samples. Following density analysis, several of these samples were sent for sectioning. Scanning electron microscope (SEM) examination of lava from several stages of the eruption was performed in order to assess the degassing efficiency of the lava and to quantify the number density of minerals within the groundmass glass. Electron microprobe analyses of crystals were used to determine the geochemical evolution of the magma during different stages of the 2010 eruption. Secondary ion mass spectrometry (SIMS) analyses of the groundmass glass provided measurement of CO2 and H2O within the magma at the point of eruption and revealed the presence of carbonate. SIMS chemical profiling of crystals showed variations in the behavior of volatile elements (H, F, Li) between different stages of the 2010 eruption. SEM examination of the chemically profiled crystals provided bubble number densities preserved in glass on crystal surfaces, allowing calculation of the decompression rate experienced by the magma during the initial explosion of the 2010 eruption. Inductively coupled plasma-optical emission spectroscopy (ICP-OES) analyses were performed on leachates derived from the deposits to measure the dissolved cation concentrations in waters exposed to the volcanic deposits.  The numerous analyses revealed that carbonates present in the underlying stratigraphy are incorporated into the Merapi magma, which will affect the eruptive dynamics and influence the degassing behavior.  The lava dome emplaced during the previous eruption in 2006 sealed the vent of the volcano prior to the 2010 eruption, allowing development of significant overpressure in the shallow plumbing system. Failure of the cap rock due to excess overpressure resulted in a decompression rate comparable to much larger volcanic eruptions, contributing to the explosivity that created the deadly pyroclastic density currents.  Results of this project indicate that the inability of gases to escape the system led to the uncharacteristic explosion that initiated the 2010 eruption, providing data necessary to accurately model explosive dynamics.  Additionally, volcanic deposits may pose hazards well after eruptive activity has ceased, due to potential effects on water quality and local ecology. Results of this project were presented at six international scientific conferences.  One undergraduate research assistant was funded under the project and a graduate student has utilized the project to complete her M.S. degree, gaining significant expertise in operating the scanning electron microscope, which she uses to instruct other students on the analysis of volcanic samples.  

 


Last Modified: 01/13/2016
Modified by: Kimberly D Genareau

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