Most of today’s news is about marauding lava flows in the Lower East Rift Zone, but the ESA just posted another satellite radar image of changes at Kilauea’s summit:
Radar from @ESA Sentinel-1 satellite, May 19 @ 6:30 PM HST (left) vs. May 25 @ 6:30 PM HST (right) shows expansion of summit vent. As of May 25, this included westward growth of the vent rim & a subsidiary pit N of Halemaʻumaʻu crater. Vent area now ~90 acres. #KilaueaEruptspic.twitter.com/z2gwcQ63HO
But Hawaii Civil Defense also confirms the now-quenched wells are “essentially safe.” The concern is that toxic hydrogen sulfide could be released if lava breaches a geothermal well. PGV worked to secure these wells last week, but they’re flying in 200,000 pounds of clay from California today to contain explosions, so…we’ll see.
UPDATE: Half hour Press Conference with Gov. David Ige and Tom Travis of Hawaii Emergency Management. The gist: the wells are secure, and they’re being monitored.
Lava covered one well this evening. So far, so good:
Eruption Update: Lava from Fissures 7 & 21 went on PGV property overnight & has now covered 1 successfully plugged well. Both it & a 2nd well 100 feet away are stable, secured, & being monitored. Neither well expected to release any hydrogen sulfide; none detected #MayorHarryKim
If you’ve followed this blog at all, you’ve come across the terms “pāhoehoe” and “a’a.” They’re Hawaiian words borrowed by volcanologists as technical terms for different types of lava. How can you tell which is which?
When I visited in 1986, the joke was that “a’a” is the noise you make when you walk on it, because it’s prickly, and “pāhoehoe” is the smooth stuff. But that’s oversimplified, and it confused me. Some of the old pāhoehoe flows we hiked on near Mauna Ulu seemed pretty bumpy to me.
Pāhoehoe lava is runny, faster-moving, and often described as “ropey.” It’s pretty obvious when it’s spilling into a crater or running swiftly in a river. Sometimes it has ripple marks. At other times, the leading edge slows down and turns blobby. Here’s an excellent USGS video of a pahoehoe front in night and day, May 24-25:
Pāhoehoe moves forward by inflating lobes of lava with fresh new lava from within.
Then there’s a’a lava: a crumbly, chunky mass of what looks like a heap of rocks and gravel and dirt, except it’s red-hot under the outer skin. It moves like a horizontal landslide in slow motion, bulldozing everything in its path:
It advances mostly by chunks tumbling forward off the front.
A’a is usually quite slow. You can outwalk it. In fact, you’d usually have time to pack a small suitcase if it showed up at the end of your street. Whereas when pāhoehoe flows downhill or becomes “channelized,” making itself a smooth chute, you can’t outrun it:
Both kind of lava make crinkly noises, but I think of a’a as “clinkity clankity” lava, whereas pāhoehoe tends to slither.
So now you’ll know how to explain it the next time someone asks, “What’s the difference between pāhoehoe and a’a?”
Puna residents watch with a sinking feeling of “I told you so” as a ponderous a’a flow crossed Pahoa Pohoiki Road slightly north of the geothermal plant, inching towards it. Officials think they’ve got the wells quenched (I notice they quietly dropped the idea of plugging them), and that they’re safe.
Meanwhile, Fissure 7 is causing trouble in all directions; its lava pond has sent another flow “cascading into Pawaii crater” (6:15pm). Looking at the map, I’m betting that crater is an old vent from a previous fissure eruption just like this one. In addition to fluid/runny pahoehoe flows, some of the longer flows are a’a.
The summit has also been busy today, with three ash explosions reaching the ~10,000 foot height between midnight and dawn, and some reaching “as high as 12-13K‘ [above sea level]” this morning. Reminder: Kilauea is 4009 feet above sea level (asl).
Moving on. I’ve gotten in the habit of checking the Lower East Rift Zone webcam last thing before I post:
USGS webcam of LERZ. Grabbed just before midnight, May 26. Is that a lava flow coming towards the camera?
I do believe it is. Has that lava pond broken loose?
Lava tally as of Saturday morning: 41 houses, 82 structures total. A further 37 homes isolated by lava crossing roads. Lava has covered 3.7 square miles/2372 acres so far.
Here’s the usual roundup of the day’s eruption news, astonishing views, and geeky info by geologists: