Lava chemistry reveals details of eruption
Every year about this time, we write about the chemistry of lava erupting from Kilauea volcano.
In previous articles, we have discussed the significance of monitoring subtle changes in the chemical composition of new lava. With specialized equipment, we can monitor the composition of crystals grown within the lava, the uncrystalized glass that quenched around them at sampling time, and the tiny remnants of the parent magma frozen within the crystals, or melt inclusion, to assess conditions of magma storage and transport within Kilauea volcano.
The crystals and glass can tell us the amount of time that was spent and the depth through which this magma traversed before being erupted at the earth’s surface. Analyzing the melt inclusions can tell us about the source of the magma batch before it started its upward journey. This information, along with volcano seismicity, deformation, gas emissions and eruptive behavior, is the core of our multifaceted approach to understanding and forecasting the behavior of ongoing summit and east rift zone eruptions of Kilauea.
For the last decade, near-vent lava samples collected by HVO geologists were shipped to the Cascade Volcano Observatory in Vancouver, Wash., where they were carefully examined and processed. This has worked pretty well, because most of the analytical work is accomplished using specialized lab facilities on the mainland. However, it was usually weeks to months before lab results were available.
When there are sudden and significant changes in eruptive activity, quick results are needed to determine whether the lava composition has changed. For this reason, HVO started a cooperative program with the geology department at the University of Hawaii at Hilo 18 months ago. The program promotes sharing of some routine responsibilities related to petrologic monitoring of Kilauea, while training and educating prospective scientists at the same time.
Under the direction of Cheryl Gansecki, students and staff at University of Hawaii at Hilo have been trained in HVO’s protocol for the processing and preparation of lava samples. The school group has also added its own methods and instrumentation to the effort. The project is funded by the U.S. Geological Survey through a cooperative agreement between the Hawaiian Volcano Observatory and UH-Hilo, administered by the Center for the Study of Active Volcanoes.
Now, when lava is sampled in and around Puu Oo, or Pele’s hair is collected at Halemaumau, the samples are sent directly to the University of Hawaii at Hilo’s geology department. There, a geologist provides a brief summary of character and appearance of samples, along with assessments of the abundance of any crystals observed in the raw samples. Any apparent changes in the eruption samples, or the lack of changes, are immediately communicated to HVO scientists.
Portions of larger samples are carefully separated for more specialized analysis in mainland laboratories, and then rapid trace-element analyses are performed using an X-ray fluorescence instrument to detect possible changes in the magma source. After that, finely polished grain-mounts of carefully selected crystals and lava fragments are prepared for detailed analysis on the mainland, using very narrow X-ray beams capable of resolving chemical changes finer than 0.002 inches. Finally, a scanning electron microscope is used to image crystal textures and to obtain qualitative analyses for mineral identification compositions and glasses in Kilauea grain mounts and melt inclusions. This work by UH-Hilo provides an eloquent array of targets for quick quantitative analysis of Kilauea eruption samples while enabling efficient use of more specialized instruments available only on the mainland.
Results so far indicate that the program is working well, confirming that no significant changes have occurred in the magma source. The partnership provides a local collaborator for routine hazard-related HVO petrology tasks while providing new opportunities and experience for staff and students at the university. This addition to our eruption-monitoring routine has added advantages of rapid turnaround of lava-chemistry information for immediate use in monitoring and forecasting eruptive activity in Hawaii.
Kilauea activity update
A lava lake within Halemaumau produced nighttime glow that was visible via HVO’s webcam during the past week. As of Thursday, the lava level for the week had been relatively steady, generally staying around 151 to 157 feet below the rim of the overlook crater.
On Kilauea’s east rift zone, the Kahaualea 2 flow continued to be active northeast of Puu Oo. The active flow front was 5.1 miles northeast of the vent on Puu Oo when last measured March 21, and no significant advancement has occurred since. Webcam images indicate that small, lava-sparked forest fires continue to burn.
There were no earthquakes felt in the past week on Hawaii Island.
Visit hvo.wr.usgs.gov for past Volcano Awareness Month articles and current Kilauea, Mauna Loa and Hualalai activity updates, recent volcano photos and recent earthquakes. Call 967-8862 for a Kilauea summary. Email questions to askHVO@usgs.gov.
Volcano Watch is a weekly article and activity update written by scientists at U.S. Geological Survey’s Hawaiian Volcano Observatory.