Even though I finished my July 26 post last night at 1 am my time, HVO posted a few more photos after that. They show Fissure 8 pulsing, varying in lava output, not just due to summit collapses but simply as natural fluctuations.
July 26, 2018. Fissure 8 lava pulses. (Full-sized)
Caption: Pulses of lava from the fissure 8 vent sometimes occur every few minutes. These photographs, taken over a period of about 4 minutes, show the changes that occur during these pulses. Initially, lava within the channel is almost out of sight. A pulse in the system then creates a banked lava flow that throws spatter (fragments of molten lava) onto the channel margin. After the third photo was taken, the lava level again decreased to nearly out of sight.
(I often compare volcanic activity to weather— it’s essentially geological weather, with currents and flow and updrafts from deep within the Earth, only the medium is solid and molten rock rather than air and water. When people are asking for volcanic forecasts, they’re asking for weather forecasts, and should expect the same kinds of variability as rainstorms.)
And here’s a night view they posted in the wee hours of this morning (Jul 27):
July 26, 2018. USGS: “Nighttime view of fissure 8 lava as it exits the vent and feeds into the channel.” (Full-sized)
And while I’m at it, here’s the photos for the afternoon of July 27. HVO might post more later tonight.
USGS/HVO Deputy Scientist-in-Charge Steve Brantley has been giving weekly 10-minute slideshows at Tuesday evening Pahoa Community Meetings. Here’s last Tuesday’s.
Transcript:
Good evening. Thank you for coming out tonight. I have just a short presentation to provide for you this evening, and I invite you to come back to the back of the room at the end of the meeting. I have copies of the report that we put out on Thursday of last week, so you’re welcome to take a copy. Please, one per household. And I’ll draw attention to— the centerpiece of that report is a map. And I have a copy of the map back there that we can talk about if you’d like.
So the activity this past week has not changed significantly, either at Fissure 8 or along the lava channel or at the summit. The summit keeps dropping during these episodic earthquakes, where parts of the crater floor drop 2-2 ½ meters, 7-8 feet at a time, and also overall slow subsidence.
Three months ago today, shortly before 5 pm on May 3, lava began to erupt from one of several cracks that had opened in Leilani Estates in the Lower Puna district of the Big Island of Hawai’i. This followed several days of earthquakes indicating magma moving downrift from Puʻu ʻŌʻō, after its floor collapsed and its lava drained away overnight on April 30.
At first, the fissures spattered and sputtered, with most of the lava falling on both sides of the vents and building up ramparts (walls). Individual fissures erupted for several hours at a time, then died out. Some restarted, others simply steamed. A few sent out sluggish lava flows, claiming a few houses.
On May 19, the eruption began in earnest. Most of the old, stale lava stored in the rift zone since the 1955 and 1960 eruptions had been pushed out, and fresh, hot, runny lava from Puʻu ʻŌʻō began pouring out of vents, sending the first lava flows down to the sea (See the Honolulu CivilBeat livestream from that day, timestamp 6:03). Lava reached the ocean before dawn on May 20.
While Fissure 8 had originally opened on May 5, it was just one of many attempts for all that magma coming down the rift zone to find the most convenient exit. (Magma can reshape its own plumbing, just as we’ve seen lava do on the surface.) Fissure 8 reactivated again on May 28, and within a few days became the dominant vent for this eruption. Its lava flow reached Kapoho Bay the evening of June 3, and had covered the bay within 36 hours.
All that magma exiting the summit caused the lava lake at the summit to drain away, then Halemaʻumaʻu fell into it and started enlarging, and eventually much of the floor of Kīlauea caldera began to subside as well. The collapses were explosive at first, then, after the lava lake’s conduit had been thoroughly blocked by rubble, the collapses settled into a regular pattern.
So here we are. The LERZ eruption has added nearly 800 acres to the island, covering lower Puna with 34.0 square kilometers (13.1 square miles) of lava. We’ve almost come to take for granted this extraordinary eruption, which has dramatically reshaped the summit of Kīlauea and produced more lava in 3 months than Puʻu ʻŌʻō did in 35 years.
Today’s Eruption Summary
July 26, 2018. USGS: “Fissure 8 continues to erupt lava into the channel leading northeastward from the vent. This north-facing view of the cone, vent, and proximal channel was taken during HVO’s overflight this morning.” (Full-sized)
HVO’s volcanologists have told us that eruptions like this wax and wane— Puʻu ʻŌʻō certainly did, sometimes pausing for weeks— and that part of what makes Fissure 8 extraordinary is that it’s sustained such a high volume of lava effusion for so long. Today, it’s finally showed signs of weakening— maybe? The USGS reported that its lava flow seemed sluggish and that lava levels are down in the lower part of the channel. The flow margin remains stalled a mere tenth of a mile from Pohoiki’s boat ramp.
July 26, 2018. USGS: “At the coast, the lava flow in the Ahalanui area remains less than 0.1 miles from the Pohoiki boat ramp at Isaac Hale Park (left of center in this photo). The active ocean entry is a few hundred yards east (right) of this photograph.” (Full-sized)
USGS: “As of 2:00 p.m. HST, July 26, 2018, the lava flow margins had not expanded since the previous map, so no red areas (indicating expansion) appear on this map.” (Full-sized)
