Investigating Volcano-Tectonic Interactions in the Natron Rift, East Africa with Implications for Understanding Volcanic Eruptive Processes
| dc.contributor.author | Masungulwa, Ntambila Simon Daud | en |
| dc.contributor.committeechair | Stamps, D. Sarah | en |
| dc.contributor.committeemember | Battaglia, Maurizio | en |
| dc.contributor.committeemember | Zhou, Ying | en |
| dc.contributor.committeemember | Shirzaei, Manoochehr | en |
| dc.contributor.department | Geosciences | en |
| dc.date.accessioned | 2025-01-08T09:00:53Z | en |
| dc.date.available | 2025-01-08T09:00:53Z | en |
| dc.date.issued | 2025-01-07 | en |
| dc.description.abstract | An early phase continental rift is an emerging plate boundary where tectonic forces stretch and thin the continental lithosphere, shaping the Earth's surface. Continental breakup and its progression are typically driven by the interplay between repeated magmatic and tectonic activities, which have been explored through both tectonic and magma-assisted rifting models. Understanding volcano-tectonic interactions is key for evaluating the role of magmatic fluids in facilitating the initiation of continental breakup during early phase rifting. This study applies the magma-assisted rifting model to the Natron Rift and investigates volcano-tectonic interactions during early phases of continental breakup associated with observed changes in the volcanic plumbing system of the active volcano Ol Doinyo Lengai. The Natron Rift is a magma-rich rift in the southern segment of the Eastern Branch in northern Tanzania providing an ideal setting to explore the interactions between tectonic and magmatic processes in the early stages of rifting. To investigate tectonic and magmatic interactions, we began by characterizing the magmatic plumbing system of Ol Doinyo Lengai using Global Navigational Satellite System (GNSS) data from our TZVOLCANO network and Interferometric Synthetic Aperture Radar (InSAR) observations. We inverted the GNSS and InSAR data independently to identify potential deformation sources using the software dMODELS. We then conducted a joint inversion of both datasets and found results that were consistent with the independent inversions within 2-sigma uncertainty. Our findings suggest that Ol Doinyo Lengai is fed by an offset multi-tiered reservoir system, consisting of a shallow magma reservoir located east of the volcano connected to a deeper reservoir through a network of fractures. This magmatic system likely influences the nature, style, and magnitude of volcanic activity at the edifice. We also assessed temporal and spatial changes in surface motion observed with GNSS stations associated with magmatic activity to help mitigate risks to nearby communities, tourism, and air traffic. Detecting transient deformation is essential for forecasting eruptions since these signals often precede eruptive events. To detect transient signals using GNSS data from the TZVOLCANO network, we employed the Targeted Projection Operator (TPO) program which projects GNSS time-series data onto a target spatial pattern. We analyzed seven years of continuous GNSS data and divided the observations into three-year intervals. The TPO method detected rapid uplift between March 2022 and December 2022 followed by steady-state uplift through August 2023. The method also identified quiescent periods and non-eruptive inflation signals that enhance our understanding of the dynamic magma plumbing system of Ol Doinyo Lengai. When integrated with the TZVOLCANO network, which streams real-time GNSS data, this approach enables continuous monitoring and early detection of potential volcanic hazards. Ongoing monitoring is crucial for assessing volcanic risks and improving emergency response plans. Finally, we examined the role of interactions between tectonic and magmatic processes in the Natron Rift during the early stages of continental breakup, focusing on the evolution of the magma plumbing system beneath Ol Doinyo Lengai. Using the code PyLith, we developed a 3D model of the region. The modeling experiments test both homogeneous and heterogeneous medium, with and without topography to estimate surface deformation and stress changes on the Natron fault due to geodetically constrained magma source inflation and deflation. Our analysis focused on stress transfer from the magma sources to assess the likelihood of fault slip, considering the typical 0.1 MPa threshold for triggering slip in magmatic rift settings. Results indicate that during the inflation period from 2016 to 2023, slip on the Natron fault is inhibited adjacent to the volcano under all scenarios. During the magma source deflation phase that occurred from 2007 to 2008 due to explosive eruptions, slip on the Natron fault was promoted adjacent to the volcano under all scenarios. Shear stress change analyses reveal that during the magma deflation scenario, slip of the Natron fault is consistent with oblique normal fault movement that is dominated by normal faulting and has components of strike-slip motion. Finite numerical modeling results demonstrate that topography considerably influences stress changes caused by dynamic magma sources as compared to material heterogeneity highlighting the importance of incorporating topography in volcano-tectonic settings. This work suggests that the potential ongoing magmatic activity at Ol Doinyo Lengai and its proximity to the Natron Fault influence the development of the youthful Natron Rift during early phase rifting. However, this influence likely inhibits fault slip at present on the adjacent section of the Natron fault due to magma source inflation. | en |
| dc.description.abstractgeneral | Continental rifts in their early phases mark the initial stage of plate boundary formation, characterized by the stretching and thinning of the Earth's outer, rigid shell under tectonic forces. Rifts are a significant agent in shaping the Earth's rigid, outer shell, ultimately leading to the formation of oceanic basins and volcanoes. Rifting occurs when tectonic plates break apart, creating faults and allowing magma that formed deep in the Earth to rise to shallower depths. This process not only contributes to the geological evolution of our planet, but it also poses significant hazards in the form of earthquakes and volcanic eruptions. Understanding the interaction between tectonic activity, like slip on faults, and magmatic processes, like volcanic deformation, is essential for assessing rift behavior, particularly in the early, immature stages of rifting when volcanic and tectonic activities are closely linked. This research focuses on the Natron Rift, a magma-rich segment of the southern part of the Eastern Branch of the East African Rift System located in Northern Tanzania. This region includes the active volcano Ol Doinyo Lengai, which is known for its unique magma composition and a history of explosive eruptions. The Natron Rift is an ideal setting to study the interactions between volcanic and faulting processes since it is still in the early stages of rifting. We examined the volcanic structure beneath the active volcano Ol Doinyo Lengai and its surroundings to assess the sources of magma supplying the volcano. We analyzed the geometry and location of a magma source using Global Navigational Satellite System (GNSS) data from our TZVOLCANO monitoring network and satellite images. We used the software dMODELS to independently model the surface displacements and identify potential magma sources. We also combined both datasets and jointly modeled them to test the independent results, which suggested a shallow, deflating magma source located to the east of Ol Doinyo Lengai. The magma source we found is likely connected to a deeper one through fractures that feed Ol Doinyo Lengai. The magmatic system determined from this study influences the nature and intensity of volcanic activity. We further assessed how the surface of Ol Doinyo Lengai volcano changes over time in response to magmatic activity to better understand and reduce the risks posed by eruptions. Volcanic eruptions at Ol Doinyo Lengai pose a risk to nearby communities, tourism, and air traffic, making it crucial to detect surface changes that could indicate an impending eruption. We developed computer models that identified potential non-eruptive volcanic signals due to magma source changes using seven years of continuous GNSS data from our monitoring network. The detected transient signals include a period of rapid uplift from March 2022 to December 2022 followed by steady uplift through August 2023. When the difference between the observed data and the expected pattern three times larger, this difference indicates transient surface motion that could signal an eruption in the near future. This information provides valuable context for eruption forecasting and serves as an early-warning system for the surrounding communities. Continuous monitoring using real-time data from the GNSS network is essential for the early detection of volcanic hazards and improving emergency response efforts. Finally, we investigate the roles played by the interactions between tectonic and magmatic processes in developing the Natron Rift during early stages of continental breakup. We use advanced modeling software called PyLith to create a 3D model of the region that incorporates known magma sources and the Natron fault. We estimate the surface motions and stress changes on the Natron fault due to changes in the known magma sources (inflation or deflation). Our stress transfer analysis indicates that during magma source inflation from 2016 to 2023 the Natron fault near the volcano section is clamped and prevents fault slip. For the deflating magma source associated with 2007-2008 explosive eruptions, stress changes on the Natron fault adjacent to the volcano section indicated fault slip likely occurred with dominantly normal faulting that includes a small component of strike-slip motion. The incorporation of topography significantly affects the amount of stress transferred on the fault under all scenarios. This study suggests that current magmatic activity at Ol Doinyo Lengai along with its closeness to the Natron Fault affects how the early stage Natron Rift develops. However, this influence likely prevents fault slip currently on the volcanic section of the Natron fault because of magma source inflation inhibiting slip the fault. | en |
| dc.description.degree | Doctor of Philosophy | en |
| dc.format.medium | ETD | en |
| dc.identifier.other | vt_gsexam:42160 | en |
| dc.identifier.uri | https://hdl.handle.net/10919/123920 | en |
| dc.language.iso | en | en |
| dc.publisher | Virginia Tech | en |
| dc.rights | In Copyright | en |
| dc.rights.uri | http://rightsstatements.org/vocab/InC/1.0/ | en |
| dc.subject | GNSS | en |
| dc.subject | Finite Element Models | en |
| dc.subject | magma plumbing system | en |
| dc.subject | transient | en |
| dc.subject | volcanoes | en |
| dc.subject | rifting | en |
| dc.subject | InSAR | en |
| dc.title | Investigating Volcano-Tectonic Interactions in the Natron Rift, East Africa with Implications for Understanding Volcanic Eruptive Processes | en |
| dc.type | Dissertation | en |
| thesis.degree.discipline | Geosciences | en |
| thesis.degree.grantor | Virginia Polytechnic Institute and State University | en |
| thesis.degree.level | doctoral | en |
| thesis.degree.name | Doctor of Philosophy | en |
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