| NSF Org: |
EAR Division Of Earth Sciences |
| Recipient: |
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| Initial Amendment Date: | June 2, 2014 |
| Latest Amendment Date: | June 2, 2014 |
| Award Number: | 1445634 |
| Award Instrument: | Standard Grant |
| Program Manager: |
Jennifer Wade
jwade@nsf.gov (703)292-4739 EAR Division Of Earth Sciences GEO Directorate for Geosciences |
| Start Date: | June 1, 2014 |
| End Date: | May 31, 2016 (Estimated) |
| Total Intended Award Amount: | $49,961.00 |
| Total Awarded Amount to Date: | $49,961.00 |
| Funds Obligated to Date: |
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| History of Investigator: |
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| Recipient Sponsored Research Office: |
1500 SW JEFFERSON AVE CORVALLIS OR US 97331-8655 (541)737-4933 |
| Sponsor Congressional District: |
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| Primary Place of Performance: |
104 Wilkinson Hall Corvallis OR US 97331-8507 |
| Primary Place of
Performance Congressional District: |
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| Unique Entity Identifier (UEI): |
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| Parent UEI: |
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| NSF Program(s): |
Petrology and Geochemistry, International Research Collab |
| Primary Program Source: |
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| Program Reference Code(s): |
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| Program Element Code(s): |
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| Award Agency Code: | 4900 |
| Fund Agency Code: | 4900 |
| Assistance Listing Number(s): | 47.050 |
ABSTRACT
Sinabung Volcano, located less than 25 miles from the northern edge of the Toba caldera, Sumatra, has been erupting dangerously since November, 2013 with significant potential hazard to the more the 100,000 people living in the surrounding Brestagi-Kabanjahe districts. 25 miles to the NE lies Medan, the capital of the North Sumatra province with over 2million people. Most concerning is that there is evidence that the erupted magma compositions of Sinabung and Sibayak (its neighbour) share more in common with the Toba magma system, than with other arc volcanoes in Suantra. Without trying to be alarmist, this affinity to Toba has obvious consequences for the way we should think about hazards from Sinabung and Sibayak as Toba-like compositions tend to result in more explosive eruptions that normal arc volcanoes. Moreover, if these two volcanoes are somehow linked to the Toba magma system, then we must factor that into predicting the potential hazard.
To test the hypothesis of a link between Sinabung-Sabayak and Toba magma systems, these researchers propose to look for a Toba ?signal? in Sinabung and Sibayak. The signal will be in two parts. First, they will focus on microscopic zircon crystals and obtain age dates that will help them identify any Toba-aged components. They will do this by obtaining in-situ U-Th age determinations in zircons and then combining these data with He-in-zircon. This will allow them to track the Toba signature back through the history of activity at Sinabung and Sibayak through time. In addition, detailed analysis of zonation of zircons would allow them to differentiate between two alternative explanations for the Toba signal; a) re-melting solidified remnants of Toba and b) rejuvenating an old Toba magma. Both these scenarios will influence the eruptive style of Sinabung and Sibayak, but the latter would connote that the Toba signal is recent and beneath Sinabung and Sibayak. Second, the chemical fingerprint of Toba will be searched for using whole rock major and trace elements, and isotopic ratios The work needs to be done in a timely fashion under the auspices of RAPID, while the iron is hot so to speak, because the opportunity to sample the most recent eruption must be taken before the explosive deposits, which are small, are removed by monsoon rains and their context lost. This work will be done in collaboration with Indonesian colleagues and other international groups addressing volcanic hazards from Sinabung.
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.
Sinabung volcano (Sumatra, Indonesia, 3.17°N / 98.39°E) has been erupting with significant effect since August, 2013. Activity continued even last week with significant impact on the communities of Brestagi and Cabangahe. Sinabung and Sibayak (its neighbour) are located just 22 miles north of Toba caldera, the famous supervolcano that erupted 74ka. Sinabung and Sibayak have long been thought to be arc volcanoes with no relation to Toba and its history. However, available Sr-isotopic data showed that Sinabung is unique in its chemical and isotopic composition compared to other arc volcanoes, including Sibayak, in Sumatra. In fact magmas erupted at Sinabung is isotopically more like Toba caldera compositions than the arc volcanoes of Sumatra. Given their location, we hypothesized that Sinabung might be tapping the northern edge of the Toba magmatic system. As such the current activity there could represent the most recent activity from the Toba magmatic system. Without trying to be alarmist, we suggested that this has obvious consequences for the way we should think about hazards from Sinabung. We proposed to test our hypothesis by looking at zircons from Sinabung. Zircon is a very versatile recorder of magmatic processes beneath volcanoes and can be used to track the development of the magmatic system in a volcano. We hypothesized that the presence of zircon of Toba age (1.4 million to <74 ka) and zircon trace element compositions in Sinabung magmas would confirm the geochemical link with Toba. This would be a critical piece of information to inform the hazard assessment for the region. The work needed to be done in a timely fashion. The opportunity to sample the most recent eruption was to be taken before the explosive deposits, which are small, would quickly be removed with monsoon rains or buried by lahars and collapses and their context lost.
Results obtained during this project confirms that Sinabung magmas share characteristics with the Toba system. First, new Sr-isotope data from samples collected in 2014 all confirm the previous published data showing overlap between Sinabung and Toba. New 87Sr/86Sr data extend from 0.710 to 0.712. There are no arc volcanoes with 87Sr/86Sr close to 0.710, so even the least radiogenic Sinabung samples are outliers from the arc. Some Toba post-caldera domes extend down to 0.710. So in isotope and trace element space Sinabung and Toba overlap. Second, analyses of U and Th on the surfaces and exteriors of zircons from the recent eruptions of Sinabung and 11 Toba samples show that Sinabung zircons overlaps Toba zircon ages dating back to ~350 ka, but the Sinabung population extends to younger crystallization ages. These data indicate that zircon crystallization under Sinabung overlaps in time with the climactic magma system at Toba, but has continued well after any known post-caldera eruptions at Toba. These data strongly suggest that Toba and Sinabung share magmatic plumbing that taps the same magmatic source. What is unknown is at what depth the two systems might be connected. Nevertheless, this has important implications for how we should think about hazards associated with the current Sinabung eruption.
This project has been fantastic training for a graduate student from Oregon State University working with the PI, and collaborators including local scientists to continue to unravel this mystery to help expand our understanding of the potential hazards of this system.
Last Modified: 09/15/2016
Modified by: Shanaka L De Silva
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