Transcript Mauna Loa Kilauea Caldera

The Island of Hawai‘i is composed of five coalesced basaltic
volcanoes. Lava flows constitute the greatest volcanic hazard
from these volcanoes.
Hawaiian volcanoes erupt two morphologically distinct types
of lava, aa and pahoehoe. The surfaces of pahoehoe flows are
rather smooth and undulating. Pahoehoe flows are commonly
fed by lava tubes, which are well insulated, lava-filled
conduits contained within the flows. The surfaces of aa flows
are extremely rough and composed of lava fragments. Aa
flows usually form lava channels rather than lava tubes.
In Hawai‘i, lava flows are known to reach distances of 50 km
or more. The flows usually advance slowly enough that people
can escape from their paths. Anything overwhelmed by a flow
will be damaged or destroyed by burial, crushing, or ignition.
Mauna Loa makes up 51 percent of the surface area of the
Island of Hawai‘i. Geologic mapping shows that lava flows
Since written descriptions of its activity began in A.D. 1832,
Mauna Loa has erupted 33 times. Some eruptions begin with
only brief seismic unrest, whereas others start several months
to a year following increased seismic activity. Once underway,
the eruptions can produce lava flows that reach the sea in less
than 24 hours, severing roads and utilities. For example, the
1950 flows from the southwest rift zone reached the ocean in
approximately three hours. The two longest flows of Mauna
Loa are pahoehoe flows from the 50-kilometer-long 1859 and
the 48-kilometer-long 1880-81 eruptions.
Lava flow hazards on Mauna Loa, the largest of the island
shield volcanoes are of concern. Hilo lies 58 km from the
summit of Mauna Loa, the Kona coast 33 km, and the
southernmost point of the island 61 km. In 1984, lava reached
within 6 km (4 miles) of Hilo..
Computer image of the Island of Hawai‘i shows the lava flows emanating from Mauna Loa that
have been recorded since 1832. View is towards the west with the city of Hilo at bottom center,
the southwest tip of the island at upper left, and the Kona coast at the top
Mauna Loa will undoubtedly erupt again. When it does, the
first critical question that must be answered is: Which areas
are threatened with inundation?
The areas most likely to be affected by eruptions originating
on various parts of the volcano. This report contains such
estimates, based on the known source vents and areas affected
by past eruptions.
Mauna Loa Volcano
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Largest volcano on earth
has a caldera and two main rift zones
normal faulting, especially along southwest rift zone
giant submarine landslides off its southwestern flank
only has Subaerial Shield Stage rocks exposed
– all rocks are tholeiitic basalts
– Ninole Member, ~540 k.y.a.
• oldest exposed rocks on the island of Hawai‘i
• may represent an extinct earlier volcano or an early stage of Mauna Loa
• named for the Ninole Hills, former ridges between amphitheater-headed valleys
that have been overrun by later Mauna Loa eruptions
– Kahuku Member (unknown age)
• lavas that bury the Ninole Member
• separated from younger lavas by an erosional surface
– Ka‘u Member, 300 k.y.a. to present
• produced by current eruptive activity
• covers the surface of most of the volcano
– may be nearing the end of main shield-building activity since it has less
frequent eruptions than Kilauea
Mauna Loa overview Mauna Loa has a summit caldera and
two rift zones (fig. 1). The "summit" is defined as the area
above the 3,500-m (11,485-ft) elevation. A deep caldera,
Moku¯aweoweo, indents the summit and keeps lava erupted
within it from reaching the flanks of the volcano. The two rift
zones„elongate fracture systems„extend to the northeast and
southwest from the summit (fig. 1). Most of Mauna Loa's
eruptive fissures and vents are located at the summit and along
the rift zones.
Geologic mapping of the surface lava flows of Mauna Loa has
identified more than 500 flows originating from the summit
area, rift zones, or radial vents. These past flows help delineate
the approximate pathways of future flows that originate in the
same or similar locations.
Photograph showing night view (time exposure) of Halema‘uma‘u Crater, taken about 1967-68.
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Kilauea
Volcano
Most active volcano on earth
– has been continuously erupting since 1983 from vents on
the east rift zone
• has a caldera and two main rift zones
– caldera bounded by normal fault scarps
– faulting produces benches in the caldera walls
– rift zones have small lava shields, spatter cones, and
cinder cones
• slumping of southern (seaward) flank produces normal
faulting results from expansion of rift zones due to
dike injection seaward flank has dropped more than
600 meters
– can produce large earthquakes and tsunamis
•only has Subaerial Shield Stage rocks exposed
–all rocks are tholeiitic basalts
–Hilina Member, 100 to 31 k.y.a
–Pahala Ash, ~31 k.y.a.
•contains Pele’s tears and Pele’s hair
–Puna Member, 30 k.y.a. to present
Mauna Loa
Kilauea
Caldera
Mauna Loa
active
Shield Volcanoes of Hawaii
Mauna Kea
Dormant?
Lava
entry
in the
sea
Vog
Laze
Kilauea
Halemaumau
Caldera
Puu Oo
Magma
Chamber
Kilauea Shield Volcano
Volcanic Activity 1983-2007
1 Mauna Loa : The largest volcano on Earth measures almost 11 miles from the ocean floor. From sea level, its peak is
13,679 feet high.
2 Mauna Kea: The 13,796-foot peak houses some of the largest telescopes in the world.
3 Hawaiian Volcano Observatory
Built in 1986, the HVO replaced the original observatory which was built in 1912.
4 Kilauea Caldera
The large summit basin contains the smaller Halemaumau Crater. The caldera is 2 to 3 miles across and several hundred
feet deep.
5 Kilauea Iki : The collapsed cone along Kilauea's southwest rift zone means "Little Kilauea." The floor of the crater is
350 feet below its rim.
6 Puu Oo: The main eruptive vent in 1983-86 and 1992 to the present. It means "Hill of the Oo bird."
7 Magma reservoir: Believed to be located 1 to 4 miles beneath the surface.
8 Active conduit: Provides a passage for lava to vents on the rift zone.
9 Dormant conduit: A lava passageway that was once active.
10 Kupaianaha pond: The lava pond was the focus of the eruption in 1986-1992. Often translated as "mysterious," it can
also mean "amazing."
11 Steam plume\: Where lava is currently entering the ocean
12 Lava tube: A hollow passageway on the earth's surface created by the topmost layer of a lava flow solidifying while
the flow below remains liquid.
Kilauea Volcano and its Active Rift Zones, moving 2 cm/year
Mauna Loa
Kilauea
Halemaumau Caldera
motion of
south flank
fault
scarps
Kilauea’s Southwest Rift Zone
moving 2-3 cm/year
June 28, 2007: There is considerably less fuming at Pu'u 'O'o.
Sometimes this vent would emit more than 2,000 tons of sulfur
dioxide a day. Now it's emitting 200 tons a day. The significant
danger of this cinder and spatter cone lies in the instability of its
crater walls. The walls crack, crumble and are continuing to
collapse.
LAVA LAKE GROWING IN PU'U 'O'O: Lava continued to
flow yesterday inside Kilauea's Pu'u 'O'o crater. The U.S.
Geological Survey's Hawaiian Volcano Observatory reports
that the lava pond is steadily rising, fed by two active vents in
the crater 07/07/2007
Creation’s caldron : Kilauea's immense, enduring display expands the horizons of science
Glossary
Lava Bench / Lava delta >> An area of new rock at the edge of the sea, often several acres in
size, which rests on loose sand and rubble. Cone >> A pile of erupted material surrounding a
vent. Called puu in Hawaiian, which means any hill but usually a volcanic cone.
Dike >> A narrow, upright, underground wall of magma.
Flank >> The land area on one side or the other of a rift zone. On the Mauna Loa side of Kilauea,
Mauna Loa holds the land in place. On the seaward side, nothing holds the flank in place and it is
slipping into the sea.
Hornitos >> Hollow tubes of spattered lava, from a few inches to several yards high, which form
over lava tubes.
Intrusion >> Movement of magma into underground spaces without it bursting to the surface.
Laze >> "Lava haze," gases from lava hitting sea water, including steam and hydrochloric acid.
Littoral cone >> A cone at the edge of the sea formed by steam blasting lava in a spray, creating
a hill.
Rift zone >> Underground lines of broken rocks, marked by present and former eruptions, in
Kilauea's case extending on land 33 miles east and 19 miles southwest.
Shatter rings >> Surface areas above a lava tube where lava pressure has pushed the roof of a
tube up and down, breaking the ground in circles or ellipses as big as a football field.
Shield >> A round-topped volcano, one that looks like an open umbrella rather than a pointed
cone.
Tumulus >> A small, dome-shaped mound of lava.
Vent >> The small hole, often in a crater, where lava and gasses come from.
Vog >> "Volcanic smog," gases from an eruption, including sulfur dioxide, which can turn into
sulfuric acid causing Acid Rain.
A’a Lava is rough, chunky cinders
form a lava flow takes when it loses
heat and gas takes place rapidly.
Pahoehoe lava is smooth, fluid
form a lava flow takes when it
retains its heat and gas.
Types of lava
Lava tube
Lava can flow long distance
rapidly and with less friction
in a Lava Tube.
A lava tube is a hollow passageway on the earth's surface created by the topmost layer of a lava
flow solidifying while thehot molten flow below remains fluid..