Surtsey is a small island off the southern coast of Iceland that emerged through explosive volcanic eruptions and lava flows between 1963 and 1967. A UNESCO World Heritage Site since 2008, it has been protected since birth as a pristine natural laboratory for studies of biological and geological evolution. In a recent study of drill cores from Surtsey, researchers used the Advanced Light Source (ALS) to gain unique insights into the transformation of volcanic glass to form mineral cements in the basaltic rock of underwater volcanoes.
“It’s not often that we have geologic processes that we can watch change at the human scale. So Surtsey is very important in that regard. It’s also a window into the oceanic crust,” said Marie Jackson, a research professor of geology and geophysics at the University of Utah who led the study.
Jackson and her colleagues explored mineralogical changes that occurred beneath the island over 54 years by comparing the composition and microstructure of drill cores from 1979 and 2017. Various techniques were applied to the core samples, including x-ray microdiffraction and microfluorescence at ALS Beamline 12.3.2.
A key question was how tephra (glass, crystal, and rock fragments ejected by explosive eruptions) begins to consolidate to form tuff (the rock created by the compaction and cementing of tephra). The beamline’s small spot size enabled the micron-scale mapping and correlation of the microstructures and compositions of a dynamic mineralogical system. The results showed that pores in the samples are filling up with new mineral cements, most intriguingly, aluminous tobermorite (Al-tobermorite).
“The only other places with that much aluminous tobermorite are ancient Roman harbor structures where Romans synthesized this mineral in concrete,” said Jackson. “Surtsey basalt is providing a geologic analogue for Roman seawater concretes. No human input was needed to create these very robust materials.”
If we could mimic those kinds of processes today, Jackson said, it could open up a whole new foundation for longer-lasting marine concrete, with manufacturing techniques that have less environmental impact than modern processes that contribute significantly to industrial carbon dioxide emissions.
M.D. Jackson, M.J. Heap, G. Vola, M. Ardit, J.M. Rhodes, J.G. Peterson, N. Tamura, and M.T. Gudmundsson, “Material and mechanical properties of young basalt in drill cores from the oceanic island of Surtsey, Iceland,” Geol. Soc. Am. Bull., early publication (2024), doi:10.1130/B37037.1.