Volcano Watch — Lava flow continues in starts and stops

Last week we noted that, based on the activity in the pond inside Pu`u `O`o cone, the lull in activity at the episode 51 vent was probably just another pause in episode 51. Sure enough, the vent again began erupting Sunday morning about 9:30 a.m., or about the time you were reading about the eruption in last Sunday's paper.

The week has continued with several starts and stops at the episode 51 vent. By midnight on Monday, the vent was again inactive, but by Tuesday at 12:30 p.m., activity was slowly resuming. Since that time, the vent has been continuously active, although the erupted volume of lava has been only moderate. The level of the summit tilt throughout the week indicated that the volume of lava erupted is equal to the amount of new magma moving up into the summit magma reservoir from deep beneath Kīlauea. The flows have advanced toward the west, northwest, southwest, or in all these directions at different times during the week. On Friday around noon, the most active flow was moving west, and a smaller, less active flow was moving south.

Both flows were on top of flows emplaced earlier during episode 51. Much of the lava has formed a pond just uprift from the vent, and the flows are generally overflows or breakouts from that pond. The eruption has now built a spatter cone about 60 feet tall, and the pond and its overflows are constructing a low lava shield. When activity is low to moderate, the lava flows through the base of the spatter cone, but when activity is high, lava spills over the top of the cone.

The eruption site is extremely inaccessible. The Napau trail starting at the Mauna Ulu parking lot in Hawai`i Volcanoes National Park is the best approach, but the hike is a long and rough 19 miles round trip. On clear days, when the activity is high, the new spatter cone, lava shield, fume cloud, and sometimes, red lava can be seen with binoculars from the top of Pu`u Huluhulu, about one mile along the Napau trail mentioned above. The Pu`u `O`o cone and the glow from the episode 51 vent can be seen at night from Highway 11 in Glenwood near Glenwood Road.

When the vent is active there are two distinct sources of glow: the eastern one is from the lava pond inside the Pu`u `O`o cone and the western one is from the episode 51 vent and flows just uprift and outside the cone. The pond inside Pu`u `O`o is still about 125 feet below the lowest rim of the cone, but is fairly active.

At 4:51 p.m. Tuesday, an earthquake with a magnitude of 3.3 occurred two miles below the Devil's Throat area along Chain of Craters Road. This earthquake occurred in an area of recurrent seismicity near the location of the intense seismic swarm that occurred on March 3. That earlier swarm of earthquakes was caused by intrusion of magma into the upper East Rift Zone of Kīlauea Volcano.