Program: RESESS Socorro
Major: Environmental Science
Academic Affiliation: University of California San Diego
Hassan is entering his senior year with a major in Environmental Science. He plans to earn his bachelor’s degree and further his education to earn a master’s in Volcanology. Hassan’s spark of interest in the field of Environmental Science began in his backyard where he vividly witnessed environmental injustices and thus grew his passion for the environment. As a RESESS intern, he will be testing samples of tephra deposits from various sites in New Mexico and Ecuador to connect the ashes to their volcanic organon.
Tephra, fragmented magma from explosive volcanic eruptions, is vital to understanding source volcanoes and their deposits. Tephrochronology is the study of the composition of tephra deposits which can be used to identify the sources and correlate time across landscapes. It is used to examine proximal deposits to assess tephra stratigraphy to understand eruption evolution and also used to examine distal deposits to deduce the source volcano, providing chronology to disparate sedimentary deposits. We used electron microprobe analysis to determine the major element chemical compositions of volcanic glass and minerals from tephra at Quilotoa volcano, Ecuador and from the Jemez Mountains, New Mexico, USA.
Analysis of five proximal tephra from Quilotoa are used to assess the geochemical evolution, and changes in eruption behavior, which will inform hazard assessment. Imaging of particles show that most tephra are highly inflated pumices with elongated vesicles that are indicative of highly explosive Plinian eruptions. Comparing previous glass chemistry of the eight known eruptions of Quilotoa to our five tephra samples allowed for two of the tephra to be correlated with a high certainty. On the other hand, the other two tephra samples were difficult to correlate because of limited data but can be correlated based on constrained stratigraphy. The final and oldest tephra appears to be from a previously undocumented and unknown eruption.
In New Mexico, chemical analysis of two distal tephra from sediments within the Rio Grande Rift was used to determine the age of the deposits via correlation with their source eruptions. Comparing the new tephra chemistry to published chemical data from local and regional sources, we concluded that the fine-grained tephra was from the Lava Creek eruption of the Yellowstone volcano. In contrast, the coarse-grained tephra was derived from the older La Cueva tuff sourced from the Jemez Mountains. The main distinguishing factor was the amount of FeO versus CaO, where the Lava Creek eruption has higher FeO and CaO than the Jemez Mountain volcanics. These findings suggest that the sedimentary sequence containing the fine-grained tephra was deposited ~ 630,000 ka (Lava Creek age), whereas the coarse-grained tephra is older, ~1.9 Ma (La Cueva age).