19-14. Frequency and sources of the largest explosive eruptions in Alaska from ocean core archives: Subduction zone science team project
Closing Date: January 4, 2021
This Research Opportunity will be filled depending on the availability of funds. All application materials must be submitted through USAJobs by 11:59 pm, US Eastern Standard Time, on the closing date.
How to Apply
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The Alaska-Aleutian arc includes over 50 historically active volcanoes including Novarupta-Katmai, the source of the largest eruption of the 20th century in 1912 that erupted 13.5 km3 of magma (Hildreth and Fierstein 2012). Large eruptions like the Katmai event evacuate an immense volume of magma that results in large collapse calderas and are referred to as caldera-forming eruptions (CFEs). Eight other Holocene-aged CFEs in Alaska were identified by Miller and Smith (1987), including six with over 50 km3 eruption volumes. Since this assessment, additional large tephra-producing eruptions, including CFEs, have been identified. These largest eruptions cause devastating local impacts, with potentially serious regional and global consequences.
Like earthquakes that have occurrence frequency inversely proportional to their magnitude, CFE-style events are also relatively infrequent compared to smaller eruptions (Mason et al. 2004). Therefore, an older record of volcanic activity is needed to develop a statistically relevant model of occurrence. Extensive Pleistocene glaciations in Alaska have largely removed proximal terrestrial records of tephra deposits. This erosion leaves only a Holocene record of explosive volcanism, which limits knowledge of the long-term eruptive behavior of Alaska volcanism.
For this project, we seek proposals that will interrogate the on- and offshore record of Alaska CFEs and other large tephra-producing eruptions via robust geochemical and statistical analysis. This effort will better catalog and characterize these important deposits, link them to probable sources, and will lead to a better understanding of Alaska’s most destructive volcanic eruptions.
To achieve these goals, this research will synthesize data and samples from two ongoing research efforts: (1) >250 samples from drill core sites in the Gulf of Alaska (Jaeger et al., 2014); and (2) a collection of source-proximal samples from known CFEs and other large tephra-producing eruption deposits in Alaska, updating the work of Miller and Smith (1987) and available to the Fellow at the Alaska Volcano Observatory, with at least 65 major Holocene eruptions at 26 source volcanoes.
A key component of this project will be application of sophisticated analytical methods to characterize tephras (Kuehn et al. 2011), as well as statistical tools to correlate deposits of the same tephra across the region and to their probable source volcanoes (e.g., Lowe et al. 2017). Analytical methods can include, but are not limited to, major oxide, trace element, isotopic ratio, and geochronologic analysis of glass and/or minerals in tephra. Applicants may identify other methodologies to achieve their goals.
The tephrochronology community lags behind many other disciplines in application of robust statistical methods for correlating tephra deposits. Tephras can be heterogeneous in composition, can overlap in composition, age, and stratigraphic position with other eruptions; thus, using statistics to link multiple deposits of the same tephra over a broad region is a multivariate problem. We thus encourage applicants to develop and apply new statistical tools to aid in tephra characterization and correlation, leveraging ongoing projects within the USGS and within the broader tephrochronology community.
While research is the focus of this project, the Fellow would be part of a Subduction Zone Science (SZS) Mendenhall Fellow Team with the goals of developing skills needed to do collaborative and integrative science, and of facilitating communications about SZS within the USGS and broader SZS community. This Team would participate in SZ4D Working Groups (www.sz4d.org) and develop and implement mechanisms to facilitate exchange of information among USGS SZS scientists.
Interested applicants are strongly encouraged to contact the Research Advisor(s) early in the application process to discuss project ideas.
References:
Hildreth, W, Fierstein, J, 2012, The Novarupta-Katmai eruption of 1912: Largest eruption of the twentieth century: Centennial perspectives: USGS Prof Paper 1791, 259 p.
Kuehn, SC, Froese, DG, Shane, PAR, 2011, The INTAV intercomparison of electron-beam microanalysis of glass by tephrochronology laboratories: Results and recommendations: Quat Int, v. 246, p. 19–47.
Jaeger, J.M., Gulick, S.P.S., LeVay, L.J., Expedition 341 Scientists, 2014. Proc. IODP, 341: College Station, TX (Integrated Ocean Drilling Program).
Lowe, DJ, Pearce, NJG, Jorgensen, MA, Kuehn, SC, et al., 2017, Correlating tephras and cryptotephras using glass compositional analyses and numerical and statistical methods: Review and evaluation: Quat Sci Rev, v. 175, p. 1–44.
Mason, BG, Pyle, DM, and Oppenheimer, C, 2004, The size and frequency of the largest explosive eruptions on Earth: Bull Volcanol, v. 66, p. 735-748.
Miller, TP, Smith, RL, 1987, Late Quaternary caldera-forming eruptions in the eastern Aleutian arc, Alaska: Geol, v. 15, p. 434–438.
Proposed Duty Station: Anchorage, AK
Areas of PhD: Geology or related fields (candidates holding a Ph.D. in other disciplines, but with extensive knowledge and skills relevant to the Research Opportunity may be considered).
Qualifications: Applicants must meet the qualifications for: Research Geologist
(This type of research is performed by those who have backgrounds for the occupations stated above. However, other titles may be applicable depending on the applicant's background, education, and research proposal. The final classification of the position will be made by the Human Resources specialist.)
Human Resources Office Contact: Beverly Ledbetter, 916-278-9396, bledbetter@usgs.gov