Dissertations, Theses, and Capstone Projects
Date of Degree
2-2025
Document Type
Dissertation
Degree Name
Ph.D.
Program
Earth & Environmental Sciences
Advisor
Marc-Antoine Longpré
Committee Members
Benjamin Black
Kennet Flores
Terry Plank
Subject Categories
Earth Sciences | Geology | Volcanology
Keywords
Volcano, Melt Inclusion, Stratigraphy, Nicaragua
Abstract
Life on Earth is inextricably intertwined with volcanic activity, and humans are no exception. The atmosphere we breathe, the oceans in which we swim, the rocks upon which we live, and the soils in which we tend crops for nourishment all contain components sourced from the materials that have been erupted over the 4.5-billion-year history of our planet. The relationship between volcanoes and civilization still persists. Everyday our planet’s volcanic terrains host tourists riding boards down scoria clad slopes, farmers tending to shade-grown chocolate and coffee beans on volcanic flanks, workers in hard hats servicing turbines that generate electricity from hydrothermal fluids, and much more. While volcanoes provide, they can also destroy. An explosive eruption can obliterate a landscape in minutes, erasing structures and lives. Much progress has been made in understanding and monitoring hazardous volcanoes since the fateful eruption of Vesuvius in 79 A.D. famously destroyed Pompeii, but there is still a great deal left to learn in order to properly forecast the timing and impact of explosive eruptions. This dissertation focuses on expanding our understanding of the eruptive history and triggering mechanisms of explosive volcanism in northwestern Nicaragua. A combination of field-based, analytical, and computational methods was employed investigate the Momotombo-Monte Galán volcanic system and Cosigüina volcano.
This work begins with a brief introductory chapter that presents background on eruption triggers and the history of volcanism in Nicaragua. Chapter 2 presents the results of a field campaign and subsequent geochemical investigation where the caldera-forming eruption of Monte Galán is identified and characterized. We then place this eruption into a regional stratigraphic context which allows the age of the eruption to be constrained to between 570 and 420 thousand years ago, making the tephra of this eruption some of the oldest assigned to a modern eruptive center of the Central American Volcanic Arc in northwestern Nicaragua. The similarity of chemistry between the eruptive products of this eruption and those of the neighboring Momotombo edifice, with which Monte Galán is structurally intertwined, raises a specter that the eruption hazards of Momotombo might be underestimated.
In chapters 3 and 4 the focus shifts north to a large compositionally zoned lapilli fall that was deposited 12 km to the west of the summit caldera of Cosigüina volcano. Early erupted dacite pumice and later erupted andesite scoria was sampled at fine scale and a combination of multiple geochemical approaches were applied to characterize matrix glass, plagioclase phenocrysts, and melt inclusions. The textures of the sampled clasts were also characterized using a combination of techniques at multiple scales. This work led to the discovery that prior to eruption the dacite and andesite were in close proximity in a shallow (~ 4 - 5 km), density stratified magma body. Geochemical evidence combined with the presence of equilibrated phenocrysts and phenobubbles suggest that pre-eruptive crystallization-driven volatile exsolution increased the overpressure in the magma reservoir, helping to trigger an eruption. Initially, the less dense dacite magma near the roof of the reservoir was exclusively samples but as the eruption continued the eruption sourced progressively deeper magma until only the underlying andesite was being sampled at the eruption’s culmination. The identification of these processes holds implications for monitoring Cosigüina and for the forecasting of future eruptions.
Recommended Citation
Zayac, John M. IV, "Stratigraphic and Geochemical Insights into Explosive Volcanism in Northwestern Nicaragua: Case Studies from the Momotombo-Monte Galán Volcanic System and Cosigüina Volcano" (2025). CUNY Academic Works.
https://academicworks.cuny.edu/gc_etds/6150
