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 have covered more than 40 percent of the surface every 1,000 years.

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• 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.

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 Mauna Kea

Halemaumau Caldera

Lava entry in the seaVog Laze

Magma Chamber

Puu Oo

Kilauea

Shield Volcanoes of Hawaiiactive Dormant?

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 ObservatoryBuilt in 1986, the HVO replaced the original observatory which was built in 1912.

4 Kilauea CalderaThe 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.

fault scarps

motion of south flank

Kilauea Volcano and its Active Rift Zones, moving 2 cm/year

KilaueaHalemaumau Caldera

Mauna Loa

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 scienceGlossaryLava 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

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..

Lava tube

Lava can flow long distance rapidly and with less friction in a Lava Tube.