Types and Processes Gallery

Fissure Vents
The intrusion of magma into an edifice can produced large fractures, or fissures, that locally become the focus of explosive activity or lava effusion. Fissures often extend radially away from the summit and can reach from the upper part of the volcano to its base. Fissures can also reflect regional tectonic trends independent of the volcanoes themselves, such as in Iceland, where the mid-Atlantic Ridge rises above sea level, or along continental rift zones such as those in eastern Africa. Volcanoes in the Galápagos Islands are notable for circumferential fissures that parallel the rims of large summit calderas. Although explosive eruptions and lava effusion can occur simultaneously over long portions of a fissure, activity often migrates along a fissure and is subsequently localized at a few specific points, where cones or craters can form. Much larger scale fissures of Tertiary or older age fed voluminous eruptions of lavas known as flood basalts. These massive eruptions have produced extensive lava fields covering tens of thousands of square kilometers in both continental areas, such as the Columbia River Plateau in the Pacific Northwest of the U.S. and the Deccan Traps of India, and oceanic areas such as the Ontong-Java Plateau in the SW Pacific. The Deccan Traps and Siberian Traps flood basalt provinces have been linked temporally to major Cretaceous/Tertiary and end-Permian faunal extinctions, respectively.

Banda Api
An eruption of Indonesia's Banda Api volcano, seen here on May 10, 1988, took place from a N-SSW-trending fissure that cut across the island. Both explosive activity and lava effusion occurred along the fissure. Billowing, ash-rich eruption plumes rise from vents along the north-side fissure. Minor orange-colored lava fountaining can be seen here at the lower-center, near the north coast. White steam marks the entry of the Batu Angus lava flow into the sea after overrunning two villages.

Photo by Willem Rohi, 1988 (Volcanological Survey of Indonesia).


Hokkaido-Komagatake
Clouds of steam pour from a new eruptive fissure cutting the summit of Japan's Komaga-take volcano on March 7, 1996. A phreatic eruption began the evening of the 5th and deposited ash on snow. The eruption originated from vents in the 1929 crater and from a 200-m-long N-S fissure. Eruptive activity, producing steam-rich ash clouds, was strong until March 7, and declined after after March 12. Komaga-take is one of the most active volcanoes on Japan's northernmost island, Hokkaido.

Photo by the Shin Engineering Consultant Company, 1996 (courtesy of Mitsuhiro Yoshimoto, Hokkaido University).


Krafla
Lava fountains play along an eruptive fissure at Iceland's Krafla volcano early in the morning on September 5, 1984. During the first hours of the eruption, which began just before midnight on the 4th, two eruptive fissures joined to become active along a total length of 8.5 km. As is often the case with fissure eruptions, activity was later concentrated along a localized part of the fissure.

Photo by Michael Ryan, 1984 (U.S. Geological Survey).


Krafla
Incandescent lava fountains play above an eruptive fissure at Krafla volcano in NE Iceland on September 6, 1984. After a quiet interval of 33 months, an eruption began on September 4 along a fissure extending from Leirhnjúkur 8.5 km to the north. Initially, the fissure was active along its entire length, but later lava production was highest at the northern end of the fissure.

Photo by Michael Ryan, 1984 (U.S. Geological Survey).


Kuchinoerabujima
Steam plumes pour from a newly opened arcuate fissure on Shin-dake, the summit crater of Japan's Kuchinoerabu volcano, on September 29, 1980. A brief eruption from the new 800-m-long fissure the day before ejected blocks and ash up to 2 km above the crater. A group of young stratovolcanoes forms the eastern end of the island of Kuchinoerabu-jima in the Ryukyu Islands. All historical eruptions have occurred from Shin-dake, which has had frequent explosive eruptions since 1840 that have sometimes damaged villages located near the crater.

Photo courtesy of Japan Meteorological Agency, 1980.


Pagan
A fissure that formed during an eruption of Pagan volcano in the Mariana Islands in 1981 cuts across the summit of the volcano. Three principal vents were active along the fissure. A cinder cone (foreground) was constructed on the north flank, and vents on the north and south rims of the summit crater fed lava flows that traveled down the flanks of North Pagan volcano. This June 16, 1981 photo shows South Pagan volcano at the upper right.

Photo by U.S. Navy, 1981.


Tolbachik
On August 16, 1975, a new fissure opened along the south rift zone of Tolbachik volcano during the "Great Tolbachik Fissure Eruption" of 1975-76. The following day formation of the third of a group of new cinder cones at the northern end of the rift zone began. Formation of the first cone began on July 6 and ended on August 9, the day that the second cone began erupting. The eruption occurred along a fissure system that extends 70 km SSW of Plosky Tolbachik volcano

Photo by Yuri Doubik, 1975 (Institute of Volcanology, Petropavlovsk).