Page 4 - gt1602

GSA TODAY | FEBRUARY 2016 Michael Poland, U.S. Geological Survey Cascades Volcano
Observatory, Vancouver, Washington 98683, USA; mpoland@usgs
.gov; Tim R. Orr, James P. Kauahikaua, Steven R. Brantley, Janet
L. Babb, Matthew R. Patrick, Christina A. Neal, Kyle R. Anderson*, the path it was following, it would have crossed a highway used
Loren Antolik, Matthew Burgess, Tamar Elias, Steven Fuke,
Pauline Fukunaga, Ingrid A. Johanson, Marian Kagimoto, Kevan
Kamibayashi, Lopaka Lee, Asta Miklius, William Million, Cyril
Moniz, Paul G. Okubo, A. Jeff Sutton, T. Jane Takahashi, Wes A.
Thelen**, William Tollett, and Frank A. Trusdell, U.S. Geological
Survey Hawaiian Volcano Observatory, Hawai‘i National Park,
Hawai‘i 96718, USA
ABSTRACT
Lava flow crises are nothing new on the Island of Hawai‘i,
where their destructive force has been demonstrated repeatedly
over the past several hundred years.The 2014–2015 Pāhoa lava
flow crisis, however, was unique in terms of its societal impact
and volcanological characteristics. Despite low effusion rates, a
long-lived lava flow whose extent reached 20 km (the longest at
Kīlauea Volcano in the past several hundred years) was poised
for months to impact thousands of people, although direct
impacts were ultimately minor (thus far). Careful observation
of the flow reaffirmed and expanded knowledge of the
processes associated with pāhoehoe emplacement, including
the direct correlation between summit pressurization and
flow advance, the influence of existing geologic structures on
flow pathways, and the possible relationship between effusion
rate and flow length. Communicating uncertainty associated
with lava flow hazards was a challenge throughout the crisis,
but online distribution of information and direct contact with
residents proved to be effective strategies for keeping the public
informed and educated about flow progress and how lava flows
work (including forecasting limitations).Volcanological and
sociological lessons will be important for inevitable future lava
flow crises in Hawai‘i and, potentially, elsewhere in the world.
INTRODUCTION
Basaltic lava flows were very much in the news in 2014. In
August of that year, Bárðarbunga erupted in Iceland, eventually
extruding more than a cubic kilometer during six months of
activity (Gíslason et al., 2015). Pico do Fogo in the Cape Verde
islands began erupting in November, sending out lava flows that
overran two villages and displaced ~1,000 people (González
et al., 2015).And in June 2014, an outbreak of lava at Kīlauea
Volcano sent flows toward communities in the Puna District on
the east side of the Island of Hawai‘i (Fig. 1).
GSA Today, v. 26, no. 2, doi: 10.1130/GSATG262A.1.
* Now at U.S. Geological Survey California Volcano Observatory, Menlo Park, California 94025, USA.
** Now at U.S. Geological Survey Cascades Volcano Observatory, Vancouver, Washington 98683, USA.
4
Kīlauea’s outbreak was noteworthy for its potential
(and uncertain) impact and long months of anticipation by
communities at risk. Had the flow extended far enough along
by thousands of vehicles each day; isolated a portion of the
island that is home to nearly 10,000 residents (Callis, 2014); cut
power, water, and other infrastructure on which those residents
depend; and overrun homes in multiple communities.The flow
stalled repeatedly within several hundred meters of the highway,
destroying only one house before breakouts ~15 km upslope
in March 2015 diverted lava away from the front.The activity
provided new information about the behavior of pāhoehoe lava
flows, as well as lessons about communicating information to
the public during a prolonged crisis.Although the 2014–2015
crisis has passed, the lava flow remains active and could threaten
communities in the future.
SETTING THE STAGE
Kīlauea, one of the most active volcanoes in the world, has
erupted almost continuously from East Rift Zone (ERZ) vents
since 1983 and from a vent at the summit (which hosts an active
lava lake) since 2008 (Orr et al., 2015a; Patrick et al., 2015a)
(Fig. 1).The current ERZ eruption has extruded more than 4 km3
of lava, covering more than 142 km2 of land (updated from Orr
et al., 2015a). Such a large amount of lava has had a significant
impact on island residents, destroying 215 primary structures as
of 2015, including nearly all of the village of Kalapana in 1990.
Roads and other infrastructure have also been covered, and vog
(volcanic smog) has impacted the health of people, animals, and
agricultural products across the island.
Pu‘u ‘Ō‘ō, a cinder cone and lava shield, is the dominant vent
for the ongoing ERZ eruption, although other vents within a few
kilometers uprift and downrift have also been active. Following
an uprift fissure eruption in March 2011, lava slowly filled the
crater of Pu‘u ‘Ō‘ō until September 2011, when a small fissure
eruption on the east flank of the cone fed the informally named
Peace Day lava flow. A lava tube system developed, and within
weeks, lava flowed southeast from the vent more than 10 km
to the Pacific Ocean (Orr et al., 2015a).While this behavior is
common for the current ERZ eruption, the lava discharge rate
for the Peace Day flow was low (1–2 m3/s), which is about half the
average rate measured since 1983 (Poland, 2014).
The eruption remained relatively stable until January 2013,
when lava overtopped the crater of Pu‘u ‘Ō‘ō and spread to
the northeast.The new flows, informally named the Kahauale‘a
flows (Patrick et al., 2015b), gradually became dominant, and the
Peace Day flow ceased activity by November 2013.The northeast
trajectory of the Kahauale‘a flows was significant because of the