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Types and Processes Gallery - Lava Flows

Lava Flows
Lava flows are one of the most visually dramatic manifestations of volcanoes. Their incandescent trace across the landscape has inspired countless paintings and photographs. Two common lava flow types are often produced during the same eruption. Aa and pahoehoe are Hawaiian terms referring respectively to clinkery, rough-textured, higher-velocity flows, and less viscous, smooth-textured, lower-velocity flows. More silica-rich magmas produce block-lava flows, whose surfaces consist of dense solidified blocks the size of televisions to small houses, and obsidian flows, which contain large masses of glassy, crystal-poor rocks. Lava flows vary widely in viscosity and volume, and are distinguished from lava domes by their elongated extent downslope. Most lava flows travel less than 10 km, but fluid pahoehoe flows can reach lengths of 50 km or more. Overlapping lava flow lobes in low-relief terrain can form broad lava fields. Flow velocities are typically low enough that lava flows most often do not pose a direct hazard to human observers, but long-term, long-duration flows such of those currently occurring at Kilauea volcano can cause extensive damage to houses and other structures. In 2002, fluid lavas from Nyiragongo volcano in the Democratic Republic of Congo flowed through the business district of the city of Goma.

Ol Doinyo Lengai
The chemically exotic lavas of Tanzania's Ol Doinyo Lengai volcano have unusually low temperatures and viscosities; it is the only volcano actively erupting carbonatitic (sodium carbonate) lava flows. Its lava flows are only incandescent during nighttime. The flows are usually only a few centimeters thick and travel only a few tens of meters from their source. This 1966 photo shows a small lava flow, only a meter wide, with miniature channels and levees (note the person at the top for scale).

Photo by Gordon Davies, 1966 (courtesy of Celia Nyamweru, Kenyatta University).

Lava fountains from the new cone of Mikombe on the lower NE flank of Nyamuragira volcano feed the lava flow in the foreground. This photo was taken from the SE on 29 September, nine days after the start of the eruption. During the first week the new cone grew to a height of 60-70 m. Lava flows had traveled 6-7 km NE by the time of this photo. The eruption continued until February 1993, by which time lava flows had traveled 19 km NE.

Photo by Minoru Kasahara, 1991 (Hokkaido University).

Bagana volcano, on Papua New Guinea's Bougainville Island, is characterized by the extrusion of thick, viscous andesitic lava flows. This photo shows a large lava flow with prominent lateral levees descending from the summit and ponding against forested hills at the base of the volcano. Bagana is constructed almost entirely of overlapping lava-flow lobes. Slow lava extrusion, occasionally accompanied by explosive activity, has been common since the mid-1800s.

Photo by Wally Johnson, 1988 (Australia Bureau of Mineral Resources).

A nighttime view from Legaspi City on 14 September 1984 shows incandescent lava flows descending the SW flank of Mayon volcano in the Philippines. The flows traveled about 4 km to the lower flanks of the volcano, adjacent to previous flows from eruptions in 1968 and 1978.

Photo by Norm Banks, 1984 (U.S. Geological Survey).

A black lava flow descends from the snow-mantled summit lava dome of Bezymianny volcano in Kamchatka in September 1990. The lava dome formed during the past forty years both by expansion when new magma was intruded into the dome and by the extrusion of lava flows down its flanks. The dome has grown within a large crater, whose southern rim is visible behind the lava flow.

Photo by Dan Miller, 1990 (U.S. Geological Survey).

The Big Obsidian Flow erupted from Newberry caldera in central Oregon is composed of glassy rhyolite, formed when lava rapidly cools. The flow covers 20 km2 of the caldera floor. Obsidian flows are never entirely glassy, but also contain large amounts of frothy pumiceous material and devitrified (crystallized) spherulites, which commonly form bands alternating with layers of glass.

Photo by Lee Siebert, 1981 (Smithsonian Institution).

Submarine extrusion of lava produces a characteristic "pillow lava" morphology, as seen here on Loihi seamount SE of the island of Hawaii. Thin streams of molten lava are extruded in a form that resembles toothpaste squeezed out of a tube. The outer surface of the lava is quickly chilled by the water and solidifies, while the interior remains molten and continues to flow, lengthening the tubes.

Photo by the Hawaii Undersea Research Laboratory (University of Hawaii).

Lava flows are commonly fed through tubes beneath the crusted-over surface of the flow. The ceilings of lava tubes frequently collapse, producing skylights, through which the flowing lava is visible. This 21 October 1970 photo of a lava flow from Mauna Ulu at Hawaii's Kilauea volcano shows several ledges within the lava tube that mark previous levels of flow. The walls and roofs of lava tubes are efficient thermal insulators that allow the lava to travel long distances without solidifying. Some tubes formed during the Mauna Ulu eruption were 11 km long.

Photo by Jeffrey Judd, 1970 (U.S. Geological Survey).

Two types of lava flows, pahoehoe (left) and `a`a (right), are different textural forms of otherwise identical lava. The different textures relate to different flow dynamics and both can form in the same lava flow. Because of differential weathering rates, the overlying pahoehoe flows look younger than the associated aa flows, and the two flows are easily mistaken for flows of greatly differing age.

Photo by Lee Siebert, 1987 (Smithsonian Institution).

Lava flows are produced when magma reaches the surface and is erupted non-explosively. Basaltic lava flows, such as this September 1979 flow from the East Rift Zone of Kilauea volcano, are Earth's most common volcanic product. Basaltic lava flows typically have initial temperatures of 1,000-1,250°C with a range of flow velocities.

Photo by Richard Moore, 1977 (U.S. Geological Survey).

An `a`a lava flow, with a characteristic surface containing abundant angular chunks as it cools, advancing across a smooth-textured pahoehoe lava flow. The hot, incandescent flow interior is visible. The front of this 3 June 1994 flow at Laeapuki, near the Puna coast of Kilauea volcano, is about 1 m thick.

Photo by Paul Kimberly, 1994 (Smithsonian Institution).

The black, newly solidified glassy surface of pahoehoe lava flows commonly has a silvery or iridescent color. Pahoehoe lavas form during eruptions that are characterized by the upwelling of hot, low-viscosity magma. This smooth-textured pahoehoe flow at Kilauea volcano was photographed in August 1994.

Photo by Paul Kimberly, 1994 (Smithsonian Institution).

A steaming lava flow issuing from a fissure on the SE flank of Bárcena volcano, in the Revillagigedo Islands west of México, forms a peninsula about 300 m wide that extends about 230 m out to sea. This photo from the SE on 11 December 1952 was taken three days after the beginning of lava extrusion. By the time the eruption ended in February 1953 the lava delta had extended the shoreline by 700 m.

Photo by Adrian Richards, 1952 (U.S. Navy Hydrographic Office).

The El Norte lava flows cover most of the N flank of Ceboruco volcano in western México. The south wall of the inner caldera forms the far summit ridge. The andesitic El Norte flows cover a broad area 3.5 km in length and forms a 3.5-km-wide lava flow field at the base of the volcano. Their youthful morphology and unvegetated surfaces suggest a young age, possibly during one of the two 16th century eruptions.

Photo by Jim Luhr, 1980 (Smithsonian Institution).

The lava flow in the foreground, which was emplaced during the 1975-76 eruption of Mexico's Colima volcano, can be seen descending through the vegetation at the center. The flow originated from the summit and traveled 3.5 km down the SE flank. The flow bifurcated on the upper slopes to form another lobe that traveled E, forming the darker area that descends into the vegetation at the upper right.

Photo by Jim Luhr, 1983 (Smithsonian Institution).

Santa Maria
A dacitic lava flow that traveled to the SW from El Brujo vent of Santiaguito is seen in April 1963, a month after it ceased flowing. The slow-moving lava flow is approximately 50 m thick and extended about 1.5 km from the vent. El Brujo, near the western end of the Santiaguito dome complex of Guatemala's Santa María volcano, is the youngest at Santiaguito and was the focus of increased effusive activity from 1959 to 1963.

Copyrighted photo by Dick Stoiber, 1963 (Dartmouth College).

Spatter cones form when blobs of molten lava that are ejected from a vent solidify to form a steep-sided cone. This small spatter cone formed in MacKenney crater of Pacaya volcano in Guatemala on 10 February 1985, during an ongoing eruption that began in 1965. At the time of this photo, the spatter cone was 6-m high, ejecting incandescent volcanic bombs from its vent and extruding lava from its eastern (left) side.

Photo by Alfredo MacKenney, 1985.

Successive lobes of the 1905 lava flow from Momotombo volcano in Nicaragua spread out on the flat slopes below the volcano, forming a broad terminus. This photo shows how lava flow direction is controlled by the topography, with individual lobes diverted around slightly higher areas of the pre-eruption surface, surrounding these prominent forested "islands" of older rock, known as kipukas.

Photo by Jaime Incer, 1982.

Lava fountains from Fernandina volcano in the Galápagos Islands feed multiple lobes of lava in 1978 that travel across a down-dropped block of the NW caldera bench, about 380 m below the caldera rim. The 1978 eruption began on 8 August when a 6-km-high eruption plume rose to be visible from distant locations in the archipelago. During the course of the eruption lava flows traveled 2 km into the caldera lake, more than 400 m below. Activity ended on 26 August.

Photo by Marc Orbach, 1978 (courtesy of Tom Simkin, Smithsonian Institution).

The ropy texture of pahoehoe lava flows is produced when the thin solidifying surface of the flow is pushed by the advancing, still-molten interior. This pleated pahoehoe lobe, on a lava flow at Santiago shield volcano in the Galápagos Islands, advanced slowly from the bottom left to the top right. Pahoehoe lavas are the least viscous of common lava types, and thus form diverse surface structures.

Photo by Lee Siebert, 1978 (Smithsonian Institution).

A steaming lava flow, 30-35 m thick and 1-km-wide, originating from Navidad cinder cone on the NE flank of Chile's Lonquimay volcano advances down the Río Lolco valley. By the time of this 25 March 1989 photograph, the flow had traveled about 7 km. Lava effusion began on 27 December 1988, two days after the beginning of an eruption that lasted until January 1990. The velocity of the slow-moving flow front decreased exponentially with distance from the vent. By the end of the eruption the lava flow reached 10 km from the vent and had a volume of 0.23 km3.

Photo by Hugo Moreno, 1989 (University of Chile).