Kilauea's Volcanic Phenomena: What Exactly Is a "Gas Piston"?
Kilauea volcano, one of Hawaii's most active volcanoes, has been experiencing episodic gas pistoning within its summit caldera since December 23, 2024. The latest episode (27) occurred on June 29.
Gas pistoning is a unique volcanic phenomenon, characterised by the sudden ascent of lava due to the accumulation of gas beneath the lava lake. This process is akin to a gas-driven piston effect, where gas accumulates in the magma chamber or conduit, increasing pressure until it forces the lava upward in a "piston" motion.
At Kilauea, this mechanism has been observed to cause fluctuations in the lava lake level, pauses with strong degassing, and bursts of lava fountains and flows. Small gas-piston events have been documented preceding larger eruptive phases. The lava is very fluid, and the gas-rich nature of the magma facilitates gas accumulation and release cycles.
If the lava reaches the top of the conduit, it can spill out, causing the top lava layer to thin out and the gas layer beneath to be released, often accompanied by spattering and bubble bursts. Conversely, any lava that does not spill out can drain back down deeper into the conduit, where it may or may not become part of another gas piston cycle.
Gas pistons during the current Kilauea eruption can result in lava overflows or drain back without visible overflow. They may destabilise on their own or require an external force to destabilise, such as a rockfall puncturing the top layer of viscous lava.
Volcanic tremor and sulfur dioxide emission rates drop to low levels when the lava is rising or at a static high level, with most of the gas trapped in the foam layer. Sulfur dioxide emission rates are elevated in the summit region during active eruption episodes.
The phenomenon of gas pistoning has been observed in the eruption of Kilauea for over a hundred years and is expected to continue during the ongoing eruption and future eruptions. It has been noted in various locations within Kilauea, including the 2008-2018 lava lake, vents at Pu'u'o'o between 1983 and 2018, and earlier eruptions such as at Maunaulu in the 1960s and in Halema'uma'u in the early part of the 1900s.
While scientists are still working to understand why gas pistons are a precursor to high-fountaining episodes and why they behave differently from episode to episode, this intriguing volcanic behaviour adds to the complex interplay between gas pressure and magma ascent in Kilauea’s eruptive dynamics.
It is worth noting that Mauna Loa, another active volcano in Hawaii, is not currently erupting, and its USGS Volcano Alert Level is at NORMAL. No earthquakes were reported felt in the Hawaiian Islands during the past week.
As the current Kilauea eruption continues, the Hawaiian Volcano Observatory (HVO) will continue to monitor the volcano closely, providing updates on any significant changes in activity.
- Understanding the complex interplay between gas pressure and magma ascent in Kilauea's eruptive dynamics involves studying phenomena such as gas pistoning, which has implications for medical-conditions like respiratory issues due to sulfur dioxide emissions and space-and-astronomy research that explores volcanic gas compositions and their effects on Earth's atmosphere.
- As technology advances, scientists can utilize seismic and gas emission data to predict potential changes in Kilauea's volcanic activity, including gas pistoning events that might affect medical-conditions and the surrounding environment, as well as contribute to our knowledge of science, space-and-astronomy, and the interplay between volcanic dynamics and technology.
