Volcano Watch — Eruption makes spectacular entry into sea

The eruption on Kīlauea's East Rift Zone continues with lava flowing into the sea at Kamoamoa. Lava is fed to the ocean in underground tubes from two erupting vents on the south and west sides of the Pu`u `O`o cone. The lava pond inside Pu`u `O`o remains at about the same level, roughly 265 feet below the lowest point on the rim of the cone. The pond was sluggish, with slow surface circulation from west to east and low-level spattering against the east wall.

A large new crack that forms a notch in the rim of the cone and extends downslope towards the collapse pits, which are up-slope from the episode 51 vent area, has appeared on the west slope of Pu`u `O`o. Both the episode 51 and 53 vents are actively feeding lava into the tube system that carries lava to the sea, but both vents are crusted over, and no lava is visible. The crater in Pu`u `O`o, each of the episode 51 and 53 vent areas, and the two collapse pits on the flank of Pu`u `O`o emit large amounts of volcanic fume, consisting mainly of water vapor and sulfur dioxide gas. In addition, large columns of fume are also emitted from several skylights in the tube system near the vents.

Starting August 21 and continuing through much of the week, the lava entries into the ocean were quite spectacular, although also quite dangerous. Several large lava benches slid into the ocean during the week. The largest occurred on August 21 and measured about 200 feet long and 30 feet wide. After the lava bench slid away, the activity at the coast increased, with small steam explosions that threw angular blocks of incandescent lava onto the lava delta. Lava fountains reached to 150 feet high, and many lava bubbles were formed above a skylight just inland from the ocean entry point. The lava bubbles expanded to about 30 feet in diameter before exploding into thin sheets of transparent brown-colored glass. This activity settled down by Wednesday, and the eruption has been much less spectacular since then.

Starting the evening of August 22 and continuing through August 26, we recorded a series of small, deep earthquakes beneath the summit of Kīlauea. On the 24th, about 280 events occurred in a 24-hour period. This type of earthquake is caused by movement of magma rather than by the breaking of rock; we think they are caused by replenishment of magma from below into the summit magma chamber. However, the summit region has not yet shown any inflation due to the addition of this new magma from depth. Previous swarms of these small, deep earthquakes have been followed, within a few weeks, by increases in eruptive activity.

On Thursday evening at 5:38 p.m., a magnitude 3.0 earthquake shook the summit region of Kīlauea. The epicenter was located a few miles southeast of Halema`uma`u. This earthquake may be indirectly related to the swarm of deep earthquakes beneath Kīlauea that took place this past week.