The question of the week… Is it over?
Eruptive activity began to wane at the end of last week,with the lava fountains diminishing, then disappearing over the weekend. Views in the webcams showed a steady decrease in activity at fissure 3 over the course of several days.
At this point no lava appears to be emerging onto the surface, with only a few dribbles left in the lava flow to be seen as minor glows across the flank of the mauna.
Oddly Kilauea, after erupting continuously for over a year seems also to have paused. There is no longer any visible lava or even a glow within the Halemauʻmauʻu crater.
So is it really over? Quite possibly. But maybe not… I have seen a few eruptions suddenly resume at this point, often enough not to call this one over just yet. Even the USGS waits 60 days with no visible activity to declare an eruption pau.
The one sign that may indicate that this eruption is over is the disappearance of the low level tremor indicating magma moving in the rift. This low level constant tremor detectable with nearby seismometers has been a steady indicator of magma motion through the mauna all through the eruption. This tremor was undetectable Monday.
It has been a spectacular couple weeks. With dramatic photos and spectacular views of lava flows pushing down the northeast flank of Mauna Loa. Tens of thousands of local residents and tourists flocked to see this spectacle, often creating traffic jams on Saddle Road.
I mounted three trips into the night to view the eruption, the advantage of living close by. A fourth was planned for this last weekend, but scrubbed when the eruption waned. Those who delayed going are now lamenting that decision, tourists who arrived a few days too late are mourning the lava.
What now?
I have spent a bit of time looking through the eruptive history of the mauna. Perhaps a guess can be made through looking at the patterns of the past. This eruption was pretty short, with typical eruptions usually lasting longer than this. Decades of inflation hint at much larger stores of magma within the edifice of the volcano.
While the typical Mauna Loa pause between eruptions is a few years to a decade my eye is drawn to the 1870’s. During the period of 1868 to 1881 a series of often short eruptions occured, often just a few days or a week or two in duration. This series of eruptions saw the volcano erupt nearly every year, sometimes twice a year, usually in the Mokuʻāweoweo caldera.
While guessing the next eruption date is folly, I have a feeling that it will not be four decades this time, it may not even be a full year.
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