EAGER: Measuring 3-phase lava rheology at eruption conditions

Mauna Loa, on the Big Island of Hawai’i, is one of the largest and most active volcanoes on Earth. In the last few hundred years many flows emitted from either the summit or rift zones have reached the ocean. If that were to occur today, lava would cut the main highway around the island and cross the densely inhabited coastal strip.

Lava flows erupted from the SW rift zone in the last 200-years reached the coast in as little as 3 hours. Future eruptions could potentially travel even faster. Lava flow hazard assessment requires accurate data on the viscosity of lava, which controls how fast it flows.

These data must include the temperature range, crystallinity, and bubble content during eruptions. The UTSA HAMsTER lab recently developed a technique to measure the viscosity of erupting lava, including bubbles and crystals. However, the range of bubble and crystal contents that can be measured with this technique needs to be investigated.

Lava will be collected from 4 different eruptions of Mauna Loa, and then used as starting materials for the experiments. The data will lead to better modeling of volcanic processes and lava flow hazards. These improvements will also apply to other volcanoes in the US and elsewhere.

The project will support an Air Force veteran for the first two years of his PhD. Lab members will explain and demonstrate volcanoes to K-12 schools in San Antonio.

The goal of the project is to explore the capabilities of a new technique for measuring the rheology of three-phase basaltic lava (liquid + crystals + bubbles). This technique uses a high-temperature rotational concentric cylinder rheometer, with short heating and measurement times that enable retention of original crystal textures including olivine phenocrysts, and pyroxene and plagioclase microlites.

The mineralogy and CSD's of previous rheology techniques applied to basaltic lava have never adequately reproduced those found in field samples. Preliminary experiments using the new technique on lava from Kīlauea have crystal size and shape distributions that are indistinguishable from samples collected in the field. These samples had much lower viscosities (by up to an order of magnitude!) than would be predicted using current rheology models that are used in lava flow modeling.

Starting materials for new experiments will be lavas from Mauna Loa, including very high high crystal and bubble contents. This project will specifically (i) test what bubble contents can be retained during measurement and (ii) test current models for the rheology of three-phase suspensions. The expected contributions are (i) experimental measurements of direct relevance to future eruption hazard modeling at Mauna Loa and similar volcanoes, (ii) a unique rheological dataset for testing suspension rheology models, and (iii) validation of the range of conditions accessible to the new experimental method.

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.