This article was published in Scientific American’s former blog network and reflects the views of the author, not necessarily those of Scientific American
Kilauea's been quiet since August, but here's the thing about volcanic eruptions: the science doesn't end when the lava stops flowing. While it's going on, events are happening too fast to process on more than a superficial level. The amounts of data being generated are staggering. Volcanologists are scrambling to merely collect it, and as far as interpreting it, most of the in-depth stuff has to wait until the volcano goes sleepy-bye. The eruption generally doesn't give anyone a chance to do more than the most superficial analysis when it's sudden and constantly evolving.
Just to put things in perspective: we are still interpreting and re-interpreting data from the 1980s eruptive sequence of Mount St. Helens. And it's been, what, 38 years? Eruptions can be freakishly complicated, is what I'm saying.
We'll be sorting through what Kilauea had to teach us this go-round for years, probably decades. It's early days yet! What have we learned so far? Let's have a look:
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This Was a Rather Unusual Eruption
It can be rather hard to remember that our knowledge of volcanoes is relatively new and still growing by leaps and bounds. Eruptions like this most recent one show us that, while we've been studying Hawaiian volcanoes for over a century now, they can still take us by suprise:
First, summit collapses like the one that so profoundly reshaped Kīlauea Caldera and Halema‘uma‘u earlier this year are relatively rare. At Kīlauea, this was the largest summit collapse since at least the year 1800, and it included the strongest summit explosions since 1924. Only three comparable events have occurred at basalticvolcanoes worldwide in the past 50 years. Much larger explosive events have occurred in Kīlauea's past but not since 1790, more than 200 years ago.
Other aspects of the 2018 activity were also unusual. The magnitude-6.9 earthquake that struck Kīlauea's south flank on May 4 was the largest in Hawaii since 1975. The emission rate of sulfur dioxide gas during the main phase of the lower East Rift Zone eruption, at least 50,000 tons per day, was the highest ever measured at Kīlauea. The lava production rate from fissure 8 also was unusually high for Kīlauea, about three times higher than during the 1955 and 1960 lower East Rift Zone eruptions.
Such extraordinary events give scientists an opportunity to study aspects of Kīlauea's behavior first-hand, to challenge old ideas, and to test new ones. For example, based on visual observations of the 1924 explosive activity at Halema‘uma‘u, scientists thought such events were caused by the interaction of groundwater with hot rock or magma. The 2018 collapse was the most thoroughly monitored event of its kind in history, but preliminary analyses of the data haven't turned up any evidence for groundwater involvement in the explosions.
Scientists love surprises like that, because they challenge conventional wisdom and lead to better understanding. Stay tuned.
Are you excited? I'm excited! Even if Kilauea decides it's done with opulent displays of magma for now, we'll still have plenty to keep us enthralled.
There's More to Kilauea Than Meets the Eye
Sometimes, when we're so distracted by what's going on at the surface, we forget that volcanoes have deep roots. And when it comes to Kilauea, we're talking about a volcanic island. Most of it exists underwater. And there's a lot of action going on beneath the waves!
Although Kīlauea’s submarine south flank is a major part of the volcano, its motion is much harder to monitor than is the part above sea level. While we can record earthquakes occurring beneath the flank, only the largest, and those closest to shore, are well-captured by the USGS Hawaiian Volcano Observatory (HVO) seismic network. In general, only a few offshore earthquakes are recorded. However, following the M6.9 earthquake and Kīlauea’s LERZ eruption, a significant number of earthquakes took place beneath the south flank, some of which were in regions that have not typically been very seismically active.
To better understand what’s going on within Kīlauea’s south flank and help determine how it has been affected by the eruption, a group of scientists from Western Washington University, Rice University, and the University of Rhode Island deployed 12 ocean bottom seismometers (OBSs) on the submarine Kīlauea south flank in July.
The data they've collected will help us understand a realm we can't easily access. What we learn here will help us understand volcanoes all over the world. Science is awesome.
It doesn't matter how extensively-researched a volcano is and how generally predictable its behavior is – it can still surprise the heck out of volcanologists! Case in point: the magma from Kilauea's most recent eruption:
When the first lower East Rift Zone (LERZ) lava sample was collected on May 3, 2018, the University of Hawaiʻi-Hilo geochemistry lab swung into action, working with the USGS Hawaiian Volcano Observatory to determine, within hours, that the erupted lava was from stored magma. The LERZ lava was much cooler (about 1090 degrees Celsius, or 2000 degrees Fahrenheit) and more “evolved” than any Puʻu ʻŌʻō lava (typically 1140 degrees C, or 2080 degrees F) erupted over the past 35-plus years. While this finding was not a surprise, it was the first time it had been documented during an eruption.
But there was one surprise: Fissure 17—the only vent not in line with the others—erupted the coolest and most chemically evolved lava ever found on Kīlauea. Its temperatures were as low as 1030 degrees C (1890 degrees F).
And that's only the beginning of what the evolving magma of the Lower East Rift Zone told us about the eruption, and how it would unfold. You may have to sign up for Facebook to see this article, but it's worth it!
Yes, indeed, I did just date myself.
But look. That's not important. What we're learning from the volcanic ash emitted during the eruption is. And folks, that ash got salty!
During an eruption, chemical reactions that occur between volcanic ash and the SO2-rich plume form salt coatings on the surfaces of ash particles. These coatings contain a wide range of components that are soluble (easily dissolved).
Upon contact with water, either through ash falling into water catchments or by rain falling on ash, the soluble components are washed from the ash. This can impact human and agricultural activities, both positively (if ash supplies nutrient elements, such as sulfur, to soil) and negatively (if ash can release potentially toxic species, such as fluoride).
The composition of the ash coating can be measured in the laboratory through ash leaching experiments. This is performed by mixing samples of freshly erupted volcanic ash with ultrapure water and measuring the change in the water chemistry.
These "leachate" results from the laboratory can then be scaled with the amount of ashfall to evaluate the potential impact on water resources, agriculture, and human health. If the ash coating poses a hazard, then appropriate protective actions can be communicated.
We haven't heard the end of Kilauea, folks. There is more. So very much more.