Pause in Eruption Leads to
New Surface Flows
This update is current as of February 10, 1999.
Eruption updates are posted every 4 to 6 weeks; more frequent updates will be
made when there are drastic changes in activity or when residential areas are
threatened by lava flows.
Photograph by H. McGiffert on February 7, 1999
Pahoehoe flow on coastal plain, Kilauea Volcano
The eruption of Pu`u `O`o continues to deliver lava to the sea
through the lava-tube system that developed on the coastal plain in
August 1998. Between November and early February 1999, there were
very few surface flows on the volcano, except for many small pahoehoe
flows on the active lava delta. This changed abruptly on February 7
following a brief pause in the supply of magma to Pu`u `O`o. When
lava reoccupied the tube system leading from Pu`u `O`o, lava
spilled from several skylights and fed both `a`a and pahoehoe flows
above and below the pali. Some flows were still moving slowly on
February 8. In mid January, intermittent bubble fountains played from
the delta as water temporarily gained access to the tube within the delta. A
new littoral cone was built by the bubble fountains.
Summary of pause #22
On Friday evening, February 5, Kilauea's summit region went through an
abrupt deflationary event (see tiltmeter plot below). The deflation
was followed by a decreased supply of magma from the summit
to Pu`u `O`o, the active vent on the volcano's east rift zone.
Whether this reduction resulted from constriction along the
subterranean path or from changes at the summit magma chamber is
uncertain. Regardless, supply of lava to the tube system
dwindled, and by early afternoon on Saturday, Feb. 6, the steam plume at
the coast ceased. These conditions persisted until after midnight.
Early on Sunday morning, Feb. 7, the summit underwent about 7 microradians
of inflationary tilt along an axis N50W-S50E, measured in our borehole
tiltmeter near Uwekahuna vault. The inflation lasted little more than one hour
and was followed by summit deflation. About two hours later a substantial supply of
magma must have reached the vent area, because GOES satellite imagery shows
a thermal spike between about 3:15 and 3:30 a.m. By dawn, lava flows were
visible from the end of the Chain of Craters road, a popular viewpoint place
for park visitors.
Record showing tilt along azimuth N50W from summit borehole
tiltmeter at Uwekahuna vault. Tilt is recorded in microradians; one radian
equals 57.3 degrees. (For those unfamiliar with tilt units, one
microradian is roughly the tilt created by inserting a dime beneath the end
of one-kilometer-long beam.) The tilt record shows an episode of deflation
on February 5, which led to a cutoff of magma supply from the
summit to the east rift zone eruption. Early Sunday morning, an abrupt
7-microradian inflation of Kilauea's summit area was followed by abrupt
deflation. This latter event coincided with resupply of magma from the summit
to the east rift zone, and about two hours later (3:30 a.m.) new lava flows were
spreading across the flow field.
Photograph by C. Seaman on February 8, 1999
When the eruption resumed at Pu`u `O`o early on February 7, lava poured from several
skylights to feed surface flows above and below Pulama pali. In the photo above, the
white line marks the edge of an `a`a flow that spilled down the pali.
Lava delta explosive activity in mid-January
Photograph by C. Seaman
on February 8, 1999
Aerial view east toward the active lava delta (light-toned surface), which is
about 150 m wide. White fume clouds rise from areas where lava is entering the
sea. The littoral cone near the southeast edge of the delta was built by spectacular explosive
activity in mid-January, caused when water temporarily gained access to the lava
tube within the lava delta. Blue-colored fume in upper left escapes from a
Map showing area covered by lava flows emplaced during the Pu`u `O`o - Kupaianaha
eruption between 1983 and February 8, 1999. Flows emplaced between February 7 and
February 8, 1999, are shown in pink. The lava tube delivers lava to the ocean a few hundred
meters west of a prominent littoral cone (star) at Kamokuna (click map for a larger
view of the map).
Eruption-viewing opportunities change constantly, so those readers planning
a visit to the volcano should contact Hawai`i
Volcanoes National Park for the most current eruption information (ph.
Additional photographs and descriptions of the Pu`u `O`o - Kupaianaha eruption
may be found at:
The URL of this page is:
11 February 1999