I study overlapping problems in the fields of volcanism, magmatism, and tectonics to understand how volcanoes work and the origins and evolution of the continental crust. My work largely fits into two areas of focus. First, I investigate the spatiotemporal path of magma, particularly during eruption run-up, to improve knowledge of when, why, and how volcanoes erupt and the formation, location, and evolution of magma reservoirs. Second, I study magmatic volatiles and their role in magmatic systems. Central to my approach is the development of tools based on the chemical and textural analysis of macrocrysts, at both the individual and population scales. More specifically, I employ melt inclusion analysis, diffusion chronometry, experimental petrology, field investigation, and collaboration with other disciplines.

Melt inclusions provide invaluable insight into global volatile cycles, mantle melting, magma ascent and evolution, and volcanic plumbing systems. These bits of melt, captured by crystals during imperfect crystal growth, represent chemical snapshots of a magma chemically differentiating during storage and ascent. Importantly, melt inclusions provide a record of magmatic volatile contents. Volatile solubility is largely a function of pressure. Thus, magmas progressively degas volatiles as magmas decompress upon ascent (Fig. 1a). The pressure of melt inclusion entrapment is, largely, maintained by the host crystal, giving us our only direct view of pre-eruptive magmatic volatile contents and providing a powerful barometer.

The utility of melt inclusions depends on their ability to faithfully preserve the chemical character of the originally entrapped melt. Unfortunately, melt inclusions seldom make it to the surface without some physicochemical changes prior to quenching (Fig. 1b), which typically results in post-entrapment crystallization and diffusive Fe-Mg exchange, diffusive water loss, and vapor bubble formation. The first two processes are well known, and are commonly addressed with established methods. However, the final problem had been not properly addressed by the community, until a series of papers in the last few years have shown that vapor bubbles often contain a CO2-rich vapor (Hartley et al., 2014, Moore et al., 2015, Wallace et al., 2015) and that the vapor likely exsolved from the melt inclusion, forming the bubble, after entrapment (Bucholz et al., 2013; Maclennan, 2017). This process is extremely common, which is demonstrated by the ubiquity of vapor bubbles. Vapor bubble growth is driven by cooling and diffusive water loss and results in the exsolution of a CO2-rich vapor (Riker, 2005; Bucholz et al., 2013). Analysis of the glass yields low values of CO2, leading to underestimates of depth, erroneous degassing paths, and incorrect volatile budget determination. Several methods to reconstruct CO2 exist. No study has systematically compared these different approaches. Thus, there is no robust method for restoring original CO2.

Figure 1. Melt inclusion formation. (a) H2O and CO2 evolution in magma and melt inclusions. Heavyweight lines show H2O and CO2 degassing path of magma. Lightweight lines show the effect of bubble growth (solid lines) on the originally entrapped H2O and CO2 (dashed lines). Magma degassing path was modeling using Newman & Lowenstern (2002). (b) Magma plumbing system schematic showing stages of melt inclusion formation (I, II, III). (c) Description of stages I, II, III.

I am working on the vapor bubble growth problem. I have rehomogenized several olivine-hosted melt inclusions from Seguam and Fuego volcanoes. To do so, I have performed hydrous piston cylinder experiments and have developed a method that is relatively easy and has a high success rate (near 100%). This work indicates that the existing methods to reconstruct melt inclusion CO2 contents work in some cases but not in others. I have also performed bubble growth experiments on an experimental heating stage at University of Tasmania (Fig. 2). I am using this second set of experiments to develop a new computational approach for dealing with the vapor bubble.

Figure 2. Bubble growth experiment using a Vernadsky heating stage. (a) Photomicrograph. (b) The red outline indicates the starting morphology (at 1350 C), and the black line indicates the morphology after cooling the melt inclusion 125 C (to 1225 C). (c) Plot of experimental conditions (red line) and vapor bubble diameter (black line).

Unraveling the sequence and duration of magmatic events preceding volcanic eruption is central to understanding volcanoes and the hazards they pose. Geophysical observations of volcanic unrest give unparalleled insight into stirrings within a magmatic system. However, translation of the signals into magmatic processes is complex, and only a few volcanoes are monitored. Petrology offers powerful tools to study eruption run-up that benefit from direct response to magmatic forcings and applicability to most eruptions. Developing these tools, and tying them to geophysical observations, will help us identify eruption triggers and understand the significance of real-time signals during unrest.

I have worked on eruption run-up at Shishaldin volcano, which is published here. I have current projects underway at Westdahl, Cleveland, and Pavlof volcanoes.

I am working to understand the controls on magma storage depth. I will be presenting my findings at CoV 10 in September 2018.

As a Ph.D. candidate at Columbia, my research is based in the Aleutian arc. Working in collaboration with Terry Plank, Diana Roman, and Erik Hauri, the central goal of our combined geochemical and geophysical study is to determine the influence subduction dynamics might have on the crustal transport and storage of magma, which bridges the gap between two normally desperate research areas: tectonics and crustal magmatism. There is ample evidence that characteristics of the slab and overlying mantle control the composition, and importantly water content, of primary arc magmas (e.g., Sadofsky et al., 2008), and some have argued that the composition of magma (again, importantly water) exerts a control on the depth of magma storage (e.g., Annen et al., 2005). My objectives are to (1) compare the composition of melt entering the lower crust with subduction parameters and (2) determine the location of crustal reservoirs. Our study area is an ideal location for such work (Fig. 1), as there is a systematic variation in the depth to the slab below the arc (and arc-trench distance), while other characteristics of the subduction zone are relatively invariant (e.g., thickness of the overring crust and slab dip, velocity, age).

Map of my study area in the Aleutian arc. My efforts have focused on the labeled volcanoes, which have all been historically active (i.e., had eruptions or been in a state of unrest). Dashed yellow, orange, and red lines are slab depth contours (Syracuse and Abers, 2006). The plate boundary is from Bird (2003). Plate motion from Kreemer et al. (2014).

Toward objective (1), I study evaluate large melt inclusion and bulk rock datasets. Because this study requires specific samples (primitive side cones and historical summit samples) and high precision complete chemical datasets for bulk rock and melt inclusions, we have collected most of the data ourselves. One of the interesting findings we have made is that there is a systematic variation in slab surface temperature (indicated by H2O/K2O ratio) and slab depth (Fig. 2). We also have found a systematic relationship between slab depth and both the flux of fluids from the slab (e.g., Ba/La) and the primary SiO2 contents (an indicator of equilibration temperature). Therefore, it appears that slab dynamics are important in controlling primary magma compositions. I am currently writing up this work to publish as an invited review paper at JVGR.

Depth to slab and H2O/K2O contents of melt inclusions. Each color indicates a volcano in the central Aleutians. Open symbols are for samples erupted from the main vent. Closed symbols are for side cones. The symbols indicate the average of the top 3 H2O/K2O values (the error bars show the range of the top 3 values).

Toward objective (2), I use volatile, major, and trace element abundances in melt inclusions to study magma ascent, storage, and differentiation. I have also compiled geophysical indicators of magma storage depth. There is a strong correlation between the primary water content of magma (indicated by the maximum observed water content in large melt inclusion suites) and the depth of magma storage inferred by geophysical means (Fig. 3), indicating magma composition is an important control on magma storage depth. I will be presenting this work at Cities on Volcanoes 10, and I am currently preparing the work for submission to a peer review journal.

Relationship between magma storage depth and water content. The black symbols are volcanoes in the Aleutian arc, and the gray symbols show volcanoes at other arcs. Water contents are the maximum observed water in large melt inclusion suites. Magma storage depths are compiled from geophyiscal and multidisciplinary studies.

I am interested in degassing and transport of CO2-rich alkalic magmas at Ross Island, Antarctica. Melt inclusions from the four volcanic centers on the island record extremely CO2-rich (up to 1.8 wt.%) magmatism and span a full range of compositions from primitive basanite to phonolite. Thus, they record ascent from near-Moho depths and differentiation from near-primary compositions. As a masters student, I worked to understand variations in H2O and CO2 concentrations recorded in melt inclusions, and to use the variations to investigate ascent timescales and depths of crystallization and mixing. The results have been published and can be found here.

As an undergraduate, I studied magma generation in the Lassen region of the Cascade arc. Owing to the young age of the subducting slab, this arc is a near endmember in hot subduction. Questions have been raised about the amount of water retained in the slab by the time subarc depths are reached. I gathered volatile and major element data on melt inclusions in supposed wet and dry endmember magmas (calc-alkaline basalt and low-K tholeiitic basalt, respectively) to investigate the role of water in generating magmas. The results have been published and can be found here.

You can find my Google Scholar profile here.

Phillips, E.H., K. W. W. Sims, J. Blichert-Toft, R. C. Aster, G. A. Gaetani, P. R. Kyle, P. J. Wallace, D. J. Rasmussen (2018). The nature and evolution of mantle upwelling at Ross Island, Antarctica. Earth and Planetary Science Letters, 498, 38-53. Link

Rasmussen, D. J., T. A. Plank, D. C. Roman, J. A. Power, R. J. Bodnar, E. H. Hauri (2018). When does eruption run-up begin? Multidisciplinary insight from the 1999 eruption of Shishaldin. Earth and Planetary Science Letters, 486, 1-14. Link

Rasmussen, D. J., P. R. Kyle, P. J. Wallace, K. W. W. Sims, G. A. Gaetani, E. H. Phillips (2017). Understanding degassing and transport of CO2-rich alkali magmas at Ross Island, Antarctica using olivine-hosted melt inclusions. Journal of Petrology, 58(5), 841-861. Link

Walowski, K. J., P.J. Wallace, M. A. Clynne, D. J. Rasmussen, D. Weis (2016). Slab melting and magma formation beneath the southern Cascade arc. Earth and Planetary Science Letters, 446, 100-112. Link

Rasmussen, D. J., T. Plank, D. Roman, M. Zimmer (2018). The link between magmatic water content and geophysically determined magma storage depth. Cities on Volcanoes 10 Abstracts, Naples, Italy. pdf

Delph, J., K. Shimizu, D. J. Rasmussen, B. Ratschbacher, X. Pu (2018). A geochemical and seismic search for deep, active MASH zones. Goldschmidt 2018 Abstracts, Boston, MA.

Lopez, T., T. Fischer, T. Plank, A. Rizzo, D. J. Rasmussen, E. Cottrell, C. Werner, C. Kern, T. Ilanko, L. Buff, J. Andrys, K. Kelley (2017). New constraints on subduction inputs and volatile outputs along the Aleutian arc. AGU 2017 Fall Meeting Abstracts, New Orleans, LA.

Pu, X., J. Delph, K. Shimizu, D. J. Rasmussen, B. Ratschbacher (2017). Where do arc magmas differentiate? A seismic and geochemical search for active, deep crustal MASH zones. AGU 2017 Fall Meeting Abstracts, New Orleans, LA.

Rasmussen, D. J., T. Plank, D. Roman (2017). The run-up to volcanic eruption unveiled by forensic petrology and geophysical observations (invited). AGU Fall Meeting Abstracts, New Orleans LA. pdf

Rasmussen, D. J., T. Plank (2017). Double, double toil and trouble: The melt inclusion bubble. AGU 2017 Fall Meeting Abstracts, New Orleans, LA. pdf

Rasmussen, D. J., T. A. Plank, D. C. Roman, J. A. Power, R. J. Bodnar, E. H. Hauri (2017). When does eruption run-up begin? Multidisciplinary insight from the 1999 eruption of Shishaldin volcano. VolcaNYC 2017 abstracts, New York, NY. pdf

Phillips, E.H., K. W. W. Sims, J. Blichert-Toft, R. C. Aster, P. R. Kyle, G. A. Gaetani, P. J. Wallace, D. J. Rasmussen (2017). The nature and evolution of mantle upwelling at Ross Island, Antarctica. GSA 2017 Fall Meeting Abstracts, Seattle, WA.

Plank, T. A., D. J. Rasmussen, L. Buff, E. Lev, D. Roman, E. Hauri, K. Nicolaysen, P. Izbekov (2017). The role of slab depth in the magma input to volcanic arcs. IAVCEI 2017 General Assembly Abstracts, Portland, OR.

Rasmussen, D. J., T. Plank, D. Roman, P. Izbekov (2017). Multidisciplinary insight into petrological indicators of eruption run-up. IAVCEI 2017 General Assembly Abstracts, Portland, OR. pdf

Werner, C., C. Kern, D. Coppola, D. J. Rasmussen, P. Kelly, J. Lyons, K. Wallace, D. Schneider, R. Wessels, T. Lopez (2017). Linking gas emissions, lava extrusion, and melt S contents for a better understanding of shallow magmatic processes at Mount Cleveland volcano, Alaska. IAVCEI 2017 General Assembly Abstracts, Portland, OR.

Rasmussen, D. J., T. Plank, D. Roman, A. Lough, P. Stelling, R. Bodnar, E. Hauri (2016). Run-up to the 1999 sub-Plinian eruption of Shishaldin volcano unveiled using petrologic and seismic approaches. AGU 2016 Fall Meeting Abstracts, San Francisco, CA. pdf

Roman, D. C., T. Plank, E. Hauri, D. J. Rasmussen, J. Power, J. Lyons, M. Haney, C. Werner, C. Kern, T. Lopez, P. Izbekov, P. Stelling (2016). From slab to surface: Origin, storage, ascent, and eruption of volatile-bearing magmas in the Aleutian arc. AGU 2016 Fall Meeting Abstracts, San Francisco, CA.

Werner, C., C. Kern, D. Coppola, P. Kelly, D. J. Rasmussen, D. Schneider, K. Wallace, R. Wessels (2016). Linking surface and subsurface: Gas emission, lava extrusion, and inferred melt S contents from Mount Cleveland, Alaska. AGU 2016 Fall Meeting Abstracts, San Francisco, CA.

Rasmussen, D. J., T. Plank, A. Lough, P. Stelling, D. Roman (2016). Petrologic chronology of the 1999 sub-Plinian eruption of Shishaldin Volcano. JKASP 2016 Abstracts, Fairbanks, AK. pdf

Phillips, E. H., K. W. W. Sims, J. Blichert-Toft, P. R. Kyle, G. A. Gaetani, P. W. Wallace, D. J. Rasmussen (2015). Sr-Nd-Hf isotopes reveal the nature and evolution of mantle upwelling at Ross Island, Antarctica. Goldschmidt 2015 Abstracts, Prague, CZ.

Rasmussen, D. J., P. R. Kyle, P. J. Wallace, K. W. W. Sims, G. A. Gaetani, E. H. Phillips (2015). Volatile variations in olivine-hosted melt inclusions: Insight into the assembly, transport, and degassing of CO2-rich magmas. SOTA 2015 Abstracts, Montserrat. pdf

Rasmussen, D. J., P. R. Kyle, P. J. Wallace, K. W. W. Sims, E. H. Phillips, G. A. Gaetani (2014). Magmatic plumbing of Ross Island, Antarctica uncovered by melt inclusions from alkalic CO2-rich magmas. Goldschmidt 2014 Abstracts, Sacramento, CA.

Rasmussen, D. J., P. R. Kyle, P. J. Wallace (2013). Using melt inclusions to trace the evolution of primitive alkalic magmas from Ross Island, Antarctica. AGU 2013 Fall Meeting Abstracts, San Francisco, CA. pdf

Walowski, K.J., P. J. Wallace, E. H. Hauri, M. A. Clynne, J. Rea, D. J. Rasmussen (2013). Magma formation in hot-slab subduction zones: Insights from hydrogen isotopes in Cascade Arc melt inclusions. AGU 2013 Fall Meeting Abstracts, San Francisco, CA.

Walowski, K., P. Wallace, M. Clynne , I. Wada, D. J. Rasmussen (2013). Magma Formation in Hot-Slab Subduction Zones: Insights from Volatile Contents of Melt Inclusions from the Southern Cascade Arc. Mineralogical Magazine, 77(5) 2441.

Walowski, K. J., D. J. Rasmussen, P. J. Wallace, M. Clynne (2012). Understanding magma formation and mantle conditions in the Lassen segment of the Cascade Arc: Insights from volatile contents of olivine-hosted melt inclusions. AGU 2012 Fall Meeting Abstracts, San Francisco, CA.