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LAVA CONTINUES TO ENTER SEA
This update current as of October 2, 1997[Eruption updates are posted approximately every two weeks. More frequent updates will accompany drastic changes in activity or increased threat to residential areas.]
For readers familiar with events of the past few months, recent changes include these:
- the eruption has taken on a regularity of vent location, lava supply, and occurrence of flows on the flow field. Molten lava flows through tubes from the vent to the ocean. Eruption rate has been about 500,000 cubic meters per day during the past few weeks.
- At the coast the lava continues to build a bench seaward from the land's edge, with small cones constructed whenever the hot lava interacts explosively with seawater.
- At the Pu`u `O`o vent, the "crater cone" within Pu`u `O`o has collapsed, leaving a pit to mark the throat of the active vent there.
- Sulfur dioxide gas is emitted at a rate of 1,000-1,500 tons per day from the vents in the Pu`u `O`o area.
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 nine 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 "crater cone," which began as a spatter cone on the Pu`u `O`o crater floor. Recently, however, crater cone subsided into its own throat, leaving a pit ("crater crater"). The pit is about 30 m in diameter, and from its cauldron lava froths and sloshes. This vent is the source of incandescent 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; episode-54 lava from January 30, 1997, forms the small black areas visible at top right of photo, in area of Napau Crater. Photo taken Oct. 2, 1997.
Lava issuing from this "crater 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. Several times between mid-June and early August, the pond rose until it overtopped the crater rim to either the west or east. The most voluminous pond overflow occurred August 6 and produced pahoehoe flows that extended 1.2 km to the northeast. On September 28 a minor overflow crept a few meters west of the rim and a few tens of meters to the east.
View looking south across Pu`u `O`o crater at active vent on its floor. A cone about 30 m high stood recently in the area now marked by the pit and its incandescent 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 only visible 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. Tube-bound lava is moving toward the camera at a rate of about 3 meters per second. It passes downtube 10 km along the flowfield, cooling only a few degrees in route to the shoreline. Photo taken Oct. 2, 1997.
Both ocean entries have formed lava benches, where new land is building out beyond the former seacliffs. These benches can collapse into the sea without warning, triggering 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 2, 1997
Eruption-viewing opportunities change constantly, refer to the HVO home page for current information. Those readers planning a visit to Kilauea or Mauna Loa volcanoes can get much useful information from Hawai`i Volcanoes National Park.
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