Dynamics of crystal mush: Insight from 2D and 3D analysis of drill cores from Kilauea Iki lava lake, Hawaii

Drilling hot lava sounds like science fiction, but it is not only a suggested source of clean energy but was actually done multiple times between 1960 and 1988. Then scientists at the Hawaiian Volcano Observatory probed a lava lake that formed during an eruption in 1959. The goal was to ‘watch’ the lake cool and solidify by collecting drill core samples.

Early drill cores sampled only the upper crust of the lake, which comprised both fully crystalline rock and crystal ‘mush’ comprising crystals with up to 45% melt (quenched to glass by water during coring). Later cores were drilled through the entire lake, sampling both upper and lower solid crust as well as interior mush. Chemical analysis of the resulting drill cores showed that during solidification, melt, bubbles and crystals were moving around within the lava lake.

Knowing what processes control those movements could improve our understanding of how, when and why melt, bubbles and crystals are rearranged in magmatic systems under volcanoes. It may also reveal how the movement of bubbles and crystals prepare for and trigger volcanic eruptions. The team will use x-ray scanning technology to get 3D images of the cores that will show the spatial distribution of glass plus crystals plus bubbles as a function of position in the lake and time since 1959.

Individual core images can be used to model properties - such as melt percentage, connectivity and permeability - that control melt movement. Tracking these processes through space and time will not only provide an unprecedented look into a volcano but also aid future drilling efforts.

For a century, conceptual models of (1) melt evolution in magmatic systems and (2) formation of eruptible (melt-rich) magma bodies were framed around the concept of large, long-lived, melt-dominated magma chambers. However, both geophysical imaging and petrologic analysis of magmatic systems suggest that they dominated by crystal ʻmushʻ that contains lenses of melt.

Reconciliation of these two perspectives is key to improving our understanding of the magma systems that feed volcanic eruptions and requires improved understanding of the physical processes that control, and the chemical consequences of, redistribution of melt, crystals and volatiles within mush-dominated systems. This project will address this problem using µCT scans of a suite of cores obtained by drilling into the solidifying Kilauea Iki lava lake, Hawaii. 18 cores collected between 1960 and 1988 include samples with up to 45% melt (now glass), track the initial growth of a cooling crust and later transected both the upper and lower crust as well as intervening crystal mush.

Petrologic studies of the cores have documented complex and diverse movements of melt, crystals and bubbles within the lake. New 3D data will be used to map the physical properties of crystal mush in space and time. Additional 2D analysis will examine the chemical consequences of melt and crystal distribution and, specifically, look for evidence of reactive flow associated with different types of melt channels.

Accompanying 2D analog experiments and modeling will track particle-particle interactions when gas is fluxed through suspensions of viscous liquid + photoelastic solid particles. The results of the combined work will improve understanding of lava lake (and sill) solidification and aid interpretation of geophysical signals from partially molten systems.

The idea of drilling into volcanoes also captures the public imagination and has practical applications to the development of “clean” hydrothermal energy. The researchers will develop these themes in a virtual exhibit for the Smithsonian Institution on the topic of Drilling Hot Lava.

This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.