Large igneous provinces (LIPs) represent the most intense manifestation of volcanism on Earth. They occur both on land and in the oceans and cover areas of hundreds of thousands of square kilometers under thick stacks of basaltic lava flows hundreds of kilometers in length. Similar phenomena constitute the bulk of volcanism on other terrestrial planets in the solar system, and on Earth they are known to disrupt climate as well as the chemical balance of the oceans. Though these events are rare in our planet's history, many are linked with mass extinctions of animal and plant species. Despite their importance in our planet's evolution, the physical eruption processes of LIPs are poorly understood. This project aims to understand the changes in eruptive style during the course of LIP emplacement, focusing on the transition from complex lava flows fed from large central volcanoes to extensive sheet flows sourced from elongate volcanic cracks. The project will use a combination of fieldwork in the Deccan Traps of India (a LIP emplaced during the Cretaceous-Paleogene mass extinction, 65 Myr ago) and laboratory experiments using analog materials that effectively mimic the behavior of lava flows. This transition in eruptive style appears to be a fundamental feature of continental LIPs and partly controls the release of gases from these eruptions, and therefore also controls their potential climatic and environmental impact.
The Deccan Traps, formed 64-67 Myr ago, are a continental LIP presently covering ~500,000 km2 of the central and western Indian subcontinent, and likely were two to three times larger at the time of emplacement. Recent work has shown the prevalence of compound lava flows in the lower part of the Deccan stratigraphy, whereas simple flows dominate the upper lava formations. Similar transitions have been documented in other LIPs (e.g., Etendeka, North Atlantic Igneous Province, Ethiopian Traps), suggesting a common evolution of architecture for many LIPs. Historically, compound flows have been interpreted to be sourced from large central shield-like volcanoes at relatively low effusion rates, whereas simple sheet flows are thought to originate from individual, scattered fissure and point vents sustaining high effusion rates for prolonged periods of time. These historical interpretations inform our starting hypotheses: (1) A shift in edifice architecture occurs at the compound-to-simple flow transition (2) Lava flow morphology is dependent on effusion rate episodicity Establishing the manner in which magma is delivered from the volcanic feeder system to the distal parts of the longest lava flows documented on Earth is essential to understanding the thermal budget of lava flows, the architecture of LIPs, and the release of volatile species into the atmosphere during such eruptions. Fieldwork will aim to quantify the prevalence of compound and simple flows in different formations, determine the timescale of the transition in flow style, and document lateral changes in flow morphology. This work will be complemented by analog laboratory experiments that simulate lava flows and have been designed to isolate the factors that control the compound-simple flow transition and flow morphology, such as effusion rate, spatial distribution of vents, and episodic flow patterns. Two novel approaches will be used to measure thermal conditions and cooling during the experiments: temperature-dependent planar laser-induced fluorescence will measure the temperature distribution within the flows, and an infrared camera will measure changes in surface temperatures.
