Early this morning, the USGS Hawaii Volcano Observatory reported that a new eruption started in the summit caldera at Kīlauea in Hawai'i. After a brief swarm of earthquakes, a series of fissures opened in the floor of the Halema'uma'u caldera, producing lava fountains and flows that have now crept along the caldera floor. This is only the third eruption at Kīlauea this year after the fall's small eruption in the East Rift zone near Napau Crater and June's brief eruption in the Southwest Rift Zone. It is also the first activity at the summit caldera since September 2023.
The New Eruption
Only 30 minutes elapsed between the increased seismicity at the summit caldera (called Kaluapele) and the start of the new fissure eruption. The earthquakes were mostly occur less than 5 kilometers down, likely from magma moving from the summit reservoir to the surface.
If you watch the live video of the eruption, you can see the lava slowly flowing from the vents that were more vigorous earlier in the eruption. The night time images are especially dramatic, showing the darker areas of cooled crust moving with the red hot lava underneath.
It is hard to see in that livestream, but the another really catches the most vigorous of the vents near the wall of the caldera. This is pretty typical for Hawaiian-style eruptions to start as a linear set of vents (a fissure) but then coalescing to a few or single vent that remains the most active.
Magma's Journey to the Surface
One way you can picture at eruption like this is a vertical sheet of magma (like a sheet of paper on its edge) rising and intersecting the Earth's surface. The lava is moving as sheet because it is following the path of least resistance caused by deforming the rocks above it to form linear cracks (and causing earthquakes). You can see the stress right before the December 23 eruption in the deformation measurements from the summit (above). So, when it hits the surface, it erupts as a line. However, once the eruption has started the ground is less stressed, so the path focusses on where the easiest place to erupt along that fissure is located.
As with eruptions at Kīlauea, this event might last anywhere from hours to months. It doesn't really pose a threat to life or property as it currently confirmed to the summit caldera. However, anytime there is a new eruption there is copious gas emissions and that sulfur dioxide can form volcanic fog (vog) that is a breathing hazard for people too close to the eruption. For now, the eruption is merely a spectacular showing of the constant production of magma underneath Hawai'i, manifesting as one of the this most active volcanoes on Earth.
