Pu`u `O`o lava overflows the cone repeatedly
This update current as of October 21, 1997[Eruption updates are posted approximately every two weeks. More frequent updates will accompany drastic changes in activity or increased threat to residential areas.]
[Previous eruption updates may be accessed through our archive index.]
For readers familiar with events of the past few months, recent changes include these:
The 55th episode of Kilauea's 14.5-year-long east rift zone eruption continues. This episode, which began February 24, 1997, was characterized in its early months by shifting vent locations on the west and southwest flanks of Pu`u `O`o cone and by rapid enlargement of the episode 50-55 lava shield. The flow field expanded slowly until, in July, lava reached the sea. The supply of lava to these flows became restricted to tubes, and surface flow activity diminished greatly.
During the last eleven weeks, eruptive activity has been concentrated at two main vents: a vent on the Pu`u `O`o crater floor and the "south shield," a new lava shield about 300 m south of the Pu`u `O`o cone. The most obvious of these has been the "crater vent," which began as a spatter cone on the Pu`u `O`o crater floor. In September, however, the spatter cone subsided into its own throat, leaving a pit. The pit is about 40 m in diameter, and from its cauldron lava froths and sloshes. This vent is the source of glow seen in the night sky from many vantage points on the east slope of Kilauea volcano.
Oblique aerial photo looking southwest at Pu`u `O`o and active vent on its floor. East-directed overflows from August visible in foreground; photo taken Oct. 2, 1997. The overflows from October 18-19 mantled the right side of the August flows in the foreground and also surged through the west-side gap to cover a small area on the volcano's west flank.
Lava issuing from the crater vent either forms a pond in the eastern half of the Pu`u `O`o crater or drains through holes in the crater floor, depending on the amount of opening and connectedness of passageways. In the past few days the pond has overflowed through low points in the crater rim. The overflowing lava never travels far but has been visible throughout much of east Hawaii.
View looking south across Pu`u `O`o crater at active vent on its floor. The inner cliff is about 20 m high. When overflowing, the cliff and throat of the vent are completely covered by active lava. Photo taken Oct. 2, 1997.
The other main vent is the south shield, source of the flows entering the ocean at the Waha`ula and Kamokuna sites near the eastern boundary of Hawai`i Volcanoes National Park. The flows are encased within lava tubes for most of their length and are visible only through skylights in the roof of the tube. Aside from the volumetrically small overflows from Pu`u `O`o, surface flows during the last two weeks have been limited to short-lived breakouts from the tubes on the coastal plain.
Skylight into lava tube. View north, with Pu`u `O`o cone in background. Skylights are locations where weakened roof of the lava tube collapses, opening the tube to view. The lava stream within the tube is moving toward the camera at a rate of about 3 meters per second. It travels down-tube 10 km across the flowfield, cooling only a few degrees in route to the shoreline. Photo taken Oct. 2, 1997.
The tubes discharge their lava at the shoreline. The hot lava, about 1150 degrees Celsius when it reaches the ocean, generates thick plumes of steam upon contact with seawater. The new lava builds low terraces or benches beyond the former seacliffs. Small explosions periodically disrupt the rapidly chilling lava and throw it onto the bench, building low nearshore (littoral) cones. A far greater threat exists, however: these benches can collapse into the sea without warning, triggering large steam explosions that hurl dense rock and molten spatter tens of meters inland. No one should venture onto the benches, no matter how stable the new land may appear.
Eruption-viewing opportunities are constantly changing, so those readers planning a visit to the volcano should contact Hawai`i Volcanoes National Park for the most current eruption information (808-985-6000).
This map current as of October 21, 1997
Updated: 31 March 1998