Hawai

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Hawaii (Big Island)                            
                                                  
                                                  
                                                  
                                                  
                                                  
                                                  
                       
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Long-lasting Eruption of Kilauea Volcano, Hawaii
Leads to Volcanic-Air Pollution
VolcanoTectonic StyleTemperature Kilauea SummitHot Spot1170C Erta AleDivergent Plate1130C MomotomboConvergent Plate820C
H20 37.1 77.2 97.1
C02 48.9 11.3 1.44
S02 11.8 8.34 0.50
H2 0.49 1.39 0.70
CO 1.51 0.44 0.01
H2S 0.04 0.68 0.23
HCl 0.08 0.42 2.89
HF --- --- 0.26
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Profile of Hawaiian shield volcanoes compared
with the profile of Mount Rainier, one of the
larger composite volcanoes of the Cascade Range,
drawn at the same scale.
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Aerial view of some of the prominent fissures
within the southwest rift zone of Kilauea
Volcano. The shiny dark lava was erupted from
these fissures in September 1971. (Photograph by
J.D. Griggs.)
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Growth profiles of Kilauea's newest volcanic
cone, built during the Pu'u 'O'o eruption.
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Map of the Big Island showing the volcanic
hazards from lava flows. Severity of the hazard
increases from zone 9 to zone 1. Shaded areas
show land covered by historic flows from three of
Hawaii's five volcanoes (Hualalai, Mauna Loa, and
Kilauea).
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Aa Lava on top of Pahoehoe Flows
Pahoehoe Flows Dominate
Pahoehoe Flows Dominate Extrusive Igneous Rock -
Lava (Hawaii)
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Shiny strands of volcanic glass, called Pele's
hair (above) are commonly found downwind from
active eruptive vents. Volcanic spatter commonly
becomes tightly welded to form mounds around
active vents (below). (Photographs by Donald W.
Peterson and Richard P. Moore, respectively.)
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Graph illustrating the difference in average
chemical compositions between lava erupted by
Hawaiian volcanoes and by Mount St. Helens in
1980. The number given for each chemical element
gives the amount (in weight percent) of that
element (expressed as oxide) contained in the
lava. Left Note the contrast in color and
texture between Hawaiian basalt (dark) and Mount
St. Helens dacite (light).
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The pyroclastic deposits exposed at Kilauea
indicate that about two dozen major explosive
eruptions have occurred during the past 70,000
years. Mauna Loa apparently has had less frequent
explosive eruptions during the same time
interval. Judging by their distribution and
thickness, Kilauea's prehistoric pyroclastic
deposits had to be produced by explosive
eruptions at least as powerful as the 1790
eruption and, in some cases, several times
stronger.
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Kilauea's explosions
Map showing areas covered by fallout from 4
explosions at Kilauea. This map is a work in
progress, and the question marks indicate areas
where more observations are needed
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Where can we see red lava? Currently, lava is
flowing in a remote area of the park, 3 miles
beyond the ranger station at the end of Chain of
Craters Road
Areas to the right (east) and seaward of the
dotted lines are closed due to the potential for
major land collapse.
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Methane Gas Explosions Underground explosions
occur in front of lava flowing over burning
vegetation. Plants burn in methane from soils
without oxygen as they are covered by lava,
creating methane gas explosions. The gas fills
underground lava tubes. When the methane ignites,
the ground explodes up to 100 yards/meters in
front of the advancing lava flow. Rocks and
debris blast in all directions. DO NOT APPROACH
LAVA FLOWING THROUGH VEGETATION!
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When Lava Enters the Sea Growth Collapse of
Lava Deltas
The new land where lava enters the ocean is
poised to collapse without warning.   The area
has been closed to the public. USGS 06/28/2005
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The island of Hawai'i, known as the Big Island,
is the largest in the Hawaiian Chain. Greater
than twice the area of the remaining main eight
Hawaiian Islands combined, Hawai'i encompasses
10,432 sq km (4028 sq mi). The island was formed
from five major volcanoes. The volcano of Mauna
Kea is the tallest mountain on Earth, reaching
nearly 9 km (5.5 mi) from the seafloor to the
summit. Although shorter, Mauna Loa's massive
size makes it the largest volcano in the world.
Kiluea, long thought to be part of Mauna Loa, is
the only currently active subaerial volcano in
the Hawaiian Island chain and is home to Pele,
the Hawaiian volcano goddess.
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Kilauea is a shield volcano that rises
approximately 6100 m from the ocean floor and
1239 m above sea level. Its summit area consists
of a caldera that is 4 km long and 3.2 km wide.
This caldera formed by subsidence when magma was
withdrawn from beneath the summit (Stone 1926).
The main vent of Kilauea is a collapsed crater in
the floor of the summit caldera, called
Halemaumau. Until the 1959 eruption, the volcano
had erupted about once every 4 years.
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Once considered a curiosity, explosions at
Kilauea are now recognized as an important type
of eruption with significant hazard to people on
the ground and in the air. How did this
revolution in thinking come about? Deposits of
tephra (anything solid exploded by a volcano)
known as the Keanakakoi Ash are a familiar sight
at Kilauea's summit, particularly southwest of
the caldera, where the trade winds often blew ash
during eruptions. Geologists thought that the ash
formed during eruptions in, or within a few years
before, 1790, when 80-800 people were killed.
Some older explosion deposits, such as the
Uwekahuna Ash, were known but had not been
studied carefully. In the late 1980s, Jocelyn
McPhie, an Australian on a Fulbright fellowship
at UH-Manoa, studied the Keanakakoi Ash and
found two ash beds distributed southeastward,
though most of the ash, slave to the trade wind,
went southwestward. She had no time to continue
her work, but her important discovery set the
scene for what was to follow.
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Kilauea is capable of exploding debris into the
westerly jet stream, which then transports the
fallout into areas where people live. Small
explosions, more numerous than the larger ones,
may be driven by groundwater. They may happen
when the floor of Halemaumau or of the caldera
drops down to about the level of the water table,
more than 500 m (1,600 feet) deep. Such a drop
would serve as a warning that explosions,
dangerous to people in the summit but less so in
outlying areas, could occur.
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What drives such powerful explosions? Around
1,000-1,200 years ago, the largest explosion
brought up rocks several kilometers (miles) from
the volcano's depths. This explosion was likely
caused by rapid expansion of carbon dioxide
bubbles within Kilauea's deep plumbing system.
Were the Keanakakoi explosions also driven by
CO2? What is the interplay between gas from the
magma and steam from groundwater? These and other
questions will take time to answer.
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Glowing lava flows erupt from vents on the south
flank of the Puu Oo cone. Ongoing collapse of
the southwest (left) side of the cone has formed
a scallop-shaped scar, revealing red layers of
welded spatter (deposited as clots of molten
lava) that underlie loose tan-colored cinders
(bubble-filled, glassy lava pieces that
solidified while still airborne). (USGS photo by
Richard Hoblitt, January 2004.)
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During the first 3½ years of the eruption,
fallout from lava fountains at Puu Oo built a
cinder-and-spatter cone 835 feet (255 m) high,
more than twice as high as any other cone on
Kilaueas east rift zone. Cone growth ceased
after the activity shifted to Kupaianaha in
mid-1986. When the eruption returned to Puu Oo
in 1992, lava flows from flank vents built a
shield against the west flank of the cone
(top). In 1993, collapse pits appeared on the
west flank of Puu Oo as subsidence over the
flank vents undermined the cone. When the crater
floor dropped in January 1997, the weakened flank
also failed, leaving the prominent west gap.
Note growth of the shield (bottom). (USGS photos
by Tari Mattox and Christina Heliker.)
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Kilauea's south flank is moving seaward at up to
three inches per year. This area experienced a
magnitude 7.2 earthquake in 1975 it is also
where the most spectacular palis (the Hawaiian
word for cliffs) are found. The southeast flank
of Mauna Loa is also moving seaward, but at a
slower rate. This region of Mauna Loa experienced
a magnitude 6.7 earthquake in 1983. Although
these motions are a small fraction of those that
occurred during the earthquakes, they indicate
that the forces that produced the earthquakes and
created the palis are still active.
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ERUPTION STATISTICS 1983 TO 2004 Lava flows
Area covered 45.1 square miles (116.9 km2)
New land 560 acres (225 ha) Volume 0.6 cubic
miles (2.6 km2) Thickness along coast 33 to
115 feet (10-35 m) Coastal highway covered
8.9 miles (14.3 km) Structures destroyed 189
Puu Oo Maximum height, 1987 835 feet (255
m) Height, February 2004 595 feet (181 m)
Crater size 820 x 1,312 feet (250 x 400 m)