The low-angle slopes of snow-capped Mauna Loa shield volcano give a deceptive perception of the size of the world's largest active volcano. Mauna Loa rises nearly 9 km from the sea floor to an altitude of 4170 m. Mauna Loa's elongated profile was created by repeated eruptions of thin lava flows, primarily from fissure vents along NE- and SW-trending rift zones. Almost 90% of the volcano's surface area consists of lava flows less than 4000 years old.

Photo by Richard Fiske (Smithsonian Institution).

Photos in the Types and Processes Gallery

Hawaiian Volcano Observatory scientists conduct an electronic-distance measurement (EDM) survey on the rim of Kilauea caldera in 1988, with snow-capped Mauna Loa in the background. The procedure uses a laser beam, which is reflected back to the EDM instrument from a distant cluster of reflectors. A precise determination of the horizontal distance between the two points is made by a small computer in the EDM instrument. These measurements allow scientists to detect inflation of the volcano as magma rises to the surface prior to an eruption.

Photo by J.D. Griggs, 1988 (U.S. Geological Survey).

The steep walls of Lua Poholo pit crater, immediately NE of Mokuaweoweo caldera, expose a small portion of the massive pile of thin, overlapping lava flows that have construced the Mauna Loa shield volcano. This view from the NE shows the rim of Mokuaweoweo caldera at the upper right. Lava flows from recent eruptions, including the last eruption of Mauna Loa, in 1984, fill the floor of the pit crater.

Photo by Paul Kimberly, 1994 (Smithsonian Institution).

Mauna Kea, Hawaii's highest volcano, is seen here from the south at the broad Humuulu Saddle between Mauna Kea and Mauna Loa. The fresh lava flow in the foreground was emplaced during an 1843 eruption that originated on the NE rift zone of Mauna Loa. The flow traveled directly north to the Mauna Kea saddle, where it was deflected to the west. The irregular profile of the unvegetated summit region of Mauna Kea shield volcano is produced by a cap of cinder cones and pyroclastic ejecta that is not present at Mauna Loa.

Photo by Paul Kimberly, 1994 (Smithsonian Institution).

Additional Photos

This spectacular aerial view from the south on March 5, 1984, shows lava fountains feeding a lava flow down the NE flank of Mauna Loa, with Mauna Kea volcano in the background silhouetted by the rising sun. The eruption originated at 0126 hrs from the summit and upper SW rift zone, but the eruptive fissure soon migrated across the summit caldera and down the NE rift zone. At the time of this photo a segment of the rift zone between 3700 and 3780 m altitude was active. Several hours later a new eruptive fissure opened 7 km farther to the east.

Copyrighted photo by Katia and Maurice Krafft.

A line of lava fountains cutting across the floor of Mokauweoweo caldera is seen from the west caldera rim on April 9, 1940, two days after the start an eruption from the summit and upper SW flank. The fissure originated from a point NE of the center of the caldera and propagated a total distance of 6 km across the caldera and down the SW rift zone. During the course of the eruption, which lasted until August, lava flows covered 2/3 of the caldera floor.

Photo by G.O. Fagerlund (U.S. Geological Survey).

A lava fountain rises from a cinder cone in the summit caldera of Mauna Loa on April 12, 1940. This view from the SW rim of Mokuaweoweo caldera shows the 1940 cone, which has remained the most prominent topographic feature within the caldera, and solidified lava flows in the foreground that originated from the cone. The eruption began within the caldera the night of April 7 from fissures which soon migrated down the SW rift zone. A 6-km-long fissure was active, and produced lava flows that covered 2/3 of the caldera floor. The eruption lasted until August 18.

Photo by G.O. Fagerlund (U.S. Geological Survey).

A billowing cloud of white steam rises from the west coast of island of Hawaii on June 2, 1950, at a point where a lava flow from Mauna Loa enters the sea. The incandescent flow at the right, the Kaapuna lava flow, was the last of three lobes that entered the sea on the second day of an eruption that originated high on the SW rift zone. The lava flow cut the road encircling the island near Heku Point and destroyed a new restaurant and several buildings. The eruption lasted until June 23.

Photo by Gordon Macdonald (U.S. Geological Survey).

A cinder cone formed during an eruption of Mauna Loa in 1940 is seen in the center of Mokuaweoweo caldera in this 1966 view from the south rim of the caldera with the west caldera wall in the background. The eruption began along a 6-km-long fissure that cut across the caldera and down the SW rift zone. Activity soon became focused within the caldera, where fissure-fed lava flows covered 2/3 of the caldera floor. The 1940 cinder cone has remained the most prominent feature of the caldera floor.

Photo by Richard Fiske, 1966 (Smithsonian Institution).

This 1966 view from the SW, on the east rim of South Pit, a pit crater that cuts the south rim of Mokuaweoweo caldera, shows lava flows from the 1949 eruption of Mauna Loa. The 1949 eruption produced lava flows that covered the southern half of the caldera floor, poured through the breach into South Pit, covering its entire floor (foreground), and then spilled an additional 9 km down the south flank. The small cinder cone on the left skyline was constructed along the main eruptive fissure, which fed a lava flow that traveled 11 km down the west flank early during the eruption.

Photo by Richard Fiske, 1966 (Smithsonian Institution).

A lava flow from the NE rift zone of Mauna Loa travels down the east flank on March 30, 1984. The flow developed a braided morphology as it detoured around topographically higher areas. These flows originated from the easternmost vents of the 1984 fissure, which opened during the afternoon of March 5 at 2900 m altitude, just below Puu Ulaula, and remained the only active vent of the eruption until it ended on April 15.

Photo by J.D. Griggs, 1984 (U.S. Geological Survey).

This nighttime view from the city of Hilo shows lava flows from Mauna Loa descending its NE flank. The flows traveled 42 km from vents on the upper NE rift zone of Mauna Loa, finally stopping only 5 km from the Hilo city limits. The 1984 lava flows were among the longest during historical time from Mauna Loa, matching the length of the 1942 flows. Only the 1855 and 1881 lava flows traveled significantly longer; the latter reached within 2 km of Hilo Bay.

Photo by David Little, 1984 (U.S. Geological Survey).

A campsite on the eastern rim of Mauna Loa's summit caldera looks across the floor of Mokuaweoweo caldera to the volcano's slightly higher west rim. The west caldera wall rises about 180 m above the caldera floor. Dark-colored lava flows, most recently from the 1984 eruption, cover the caldera floor. Lava flows from the 1975 eruption also covered almost the entire floor. Incremental filling of the caldera has almost halved the maximum caldera depth of 320 m recorded during historical time.

Photo by Lee Siebert, 1987 (Smithsonian Institution).

The steep walls of Lua Poholo pit crater in the foreground, immediately NE of Mokuaweoweo caldera, expose a small portion of the massive pile of thin, overlapping lava flows that have constructed the Mauna Loa shield volcano. This 1987 view from the NE shows the west rim of Mokuaweoweo caldera, which forms Mauna Loa's summit. The vast field of fresh lava flows covering the floor of the caldera was erupted in 1984.

Photo by Richard Fiske, 1987 (Smithsonian Institution).

Lava stalactites are abundant on the ceiling of a 1984 eruptive vent along a fissure that cut across the Mokuaweoweo caldera of Mauna Loa. The 1984 fissure at this location on the SW rim of the caldera cut through the cinder cone of the 1949 eruption. Intense heat partially melted the vent walls; the dripping lava then solidified, forming the stalactites.

Photo by Paul Kimberly, 1994 (Smithsonian Institution).

Kilauea Iki crater in the foreground was the site of a major eruption in 1959. The 800 x 1500 m wide crater, seen here from the east with snow-capped Mauna Loa in the background, is located at the head of Kilauea's east rift zone. Steam rises from the floor of Kilauea caldera at the left.

Photo by Richard Fiske, 1967 (Smithsonian Institution).

This 1975 photo of the snow-covered summit of 4170-m Mauna Loa volcano from the SW shows the 2.4 x 4.8 km wide Mokuaweoweo caldera in the center, with three circular pit craters in the foreground. South Pit (partially truncating the SW caldera rim), Lua Hohonu, and Hua Hou (foreground), formed by collapse along the upper SW rift zone. Mauna Kea shield volcano rises to a height of 4206 m in the distance.

Photo by Don Peterson (U.S. Geological Survey).