Volcano Watch — Episode 51 continuing

The eruption from the episode 51 vents, located on the west flank of the Pu`u `O`o cone on the East Rift Zone of Kīlauea Volcano, continues with little change. Lava is being fed to the coastline near Kamoamoa through a well-established underground tube system with only a few skylights, through which the flowing lavacan be seen from the air. The episode 51 vents had several small collapses that have created small craters where the spatter cones used to be. At the coastline, the entire flux of lava is pouring into the ocean most of the time. Occasionally, small surface-fed flows break out of skylights in the tube system or flow onto the new lava bench adjacent to the ocean. 

As the lava enters the ocean, numerous small steam explosions continue to occur. These explosions generate new black sand, some of which is carried by currents along the coast towards the west. Most of the newly created sand slides downslope and blankets the steep slope offshore. Offshore sampling and photographic surveying was conducted in 1991 by the marine geology group of the U.S. Geological Survey and by scientists from the University of Hawai`i at Manoa. Their work took place offshore from Kalapana where the flows erupted from Kupaianaha entered the sea and demonstrates that the newly formed sand extends far down the slope to depths as great as 8,000 feet. It probably continues even farther downslope and accumulates on a gently-sloping bench that occurs between depths of 8,000 and 10,000 feet. 

On rare nights, when the weather has been clear enough to see the Pu`u `O`o cone, we have observed a greatly diminished glow since month ago due to a deeper and smaller lava pond inside the cone. After the earthquake that occurred near the cone on October 2, 1992, the level of lava in the pond has been deeper than the elevation of the 51 vent, whereas before the earthquake, the level was always higher than that of the eruptive vents. The plumbing system beneath the Pu`u `O`o cone was changed by the earthquake or by the occurrence of the episode 52 eruption. The lava pond continues to get smaller and deeper and may completely solidify soon. 

During the past two weeks, four earthquakes occurred that had magnitudes greater than 3.0. The first, with a magnitude of 3.0 occurred on January 8 at 7:04 p.m. and was located west of the island at a depth of about 21 miles. The second, which took place on January 13 at 2:07 p.m., had a magnitude of 3.1 and was located offshore, south of Cape Kumukahi, at a depth of 27 miles. The third, with a magnitude of 3.1, occurred on January 17 at 6:01 a.m. and was located west-southwest of the summit of Kīlauea at a depth of 8 miles. The final earthquake, which took place on January 19 at 5:17 a.m., had a magnitude of 3.0 and was located beneath Volcano Village at a depth of 15 miles. The first two earthquakes are caused by the enormous weight of the islands, which causes the lithosphere beneath the islands to bend. The earthquake west-southwest of the summit of Kīlauea is probably caused by slippage along the boundary between Mauna Loa Volcano and the underlying ocean crust. The final earthquake beneath Volcano Village is probably related to movement of magma beneath Kīlauea Volcano. Neither offshore earthquake was felt, but early risers in Pahala and Volcano, respectively, felt the last two.