Research

Rheology of multiphase magma

Understanding the rheophysical properties of multiphase magma and its effect on magma chamber and ascent dynamics through laboratory experiments.

Figure shows the shear rate and maximum packing dependent rheology of crystalline magma from analog experiments. Moitra P and Gonnermann HM (2015), G-cubed, doi:10.1002/2014GC005554

Liquid-like to solid-like transition and fragmentation of crystal-bearing basaltic magma using analog extensional tests. The viscous liquid fractures in the presence of abundant solid particles analogous to microlites in magma. Moitra et al., 2018 EPSL (doi:10.1016/j.epsl.2018.08.003)

Modeling bubble growth, crystalization and conduit flow of magma during eruptions

Modeling bubble-crystal growth in a volcanic conduit (using finite difference) in order to understand the effects of multiphase rheology on magma ascent dynamics during volcanic eruptions. Figure shows the diffusive and decompressive growth of bubbles, crystallization, and subsequent fragmentation and gas-pyroclast flow during highly explosive Plinian eruption of basaltic magma. Moitra P, Gonnermann HM, Houghton BF and Tiwaty CS (2018), Earth Planet Sci Lett, doi:10.1016/j.epsl.2018.08.003

Conduit flow models of varying eruption styles and pyroclast microtextures

Using optical and scanning electron microscopy (SEM) along with imageJ or MATLAB to observe and analyze the microtextural characteristics of thin sections of natural pyroclasts in order to understand their implications for eruption dynamics. Figure shows the relationship between a dimensionless shape factor obtained from microtextural analyses of vesicles in pyroclasts and a dimensionless Capillary number obtained from numerical models of magma ascent. Moitra P, Gonnermann HM, Houghton BF and Giachetti T (2013), Bull Volc, doi:10.1007/s00445-013-0691-8

Magma chamber dynamics

Understanding the effect of volatiles, in the form of dissolved H2O or bubbles, and crystals on magma chamber dynamics. Figure shows the settling of mafic enclaves through a cooling magma chamber and formation of high silica magma. Lee Cin-Ty A, Douglas MM, Farner MJ, and Moitra P (2015), Am Mineral, doi:10.2138/am-2015-5121

(Moitra P and Gonnermann HM – Bubble rise through dense particulate suspensions with implications for magma chamber dynamics, in preparation)

Magma/lava/pyroclast cooling rates under subaerial  and subaqueous conditions: phreatomagmatic and submarine eruptions

Using high temperature laboratory experiments with natural rocks and heat trasnfer modeling, the interaction dynamics and heat transfer rates from magma/lava/pyroclasts to surrounding air and water is investigated. Quantification of magmatic heat flux estimates is key to understand the exploisve magma-water interactions during phreatomagmatic and submarine eruptions, and also the submarine lava flow morphologies.       

Experimental results show that the water boiling regimes transition from a stable water vapor film to a nucleate boiling regime with numerous bubbbles with derceasing magmatic temperature (doi:10.1016/j.epsl.2020.116194).     

Figure shows the explosive interactions of magma and water in cm verus meter scale set-up (doi:10.1029/2018JB015682).

Also shown are the cooling time scales of pyroclasts and solid crust formation under subaerial conditions (doi:10.1029/2018GC007510).

Dynamics of very recent explosive eruptions on Mars

Remote observation and numerical models exhibit the roles of magmatic and external (ground ice/water) volatiles on a very recent (<1 My) explosive eruption in Elysium Planitia, Mars. Figure shows the CTX imagery of the Cerberus Fossae mantling unit (CFmu) surrounding the fissure. The fissure is about 25 km long.

 ,Horvath et al.  Icarus (doi:10.1016/j.icarus.2021.114499)

Moitra et al. EPSL  (doi:10.1016/j.epsl.2021.116986)