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Types and Processes Gallery - Fissure Vents

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 10 May 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 rose from vents along the N end of the fissure. Minor lava fountaining can be seen here at the lower-center, near the N coast. White steam marks the entry of the lava flow into the sea after overrunning two villages.

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


Pinatubo
The 1991 eruption of Pinatubo began on 2 April with a small phreatic eruption on the upper NW flank. The eruptions formed several craters along a 1.5-km-long, E-W-trending alignment. Steam rises from a vent at the SW end of the fissure. Activity continued at two of these vents through April-May and increased prior to extrusion of a small lava dome at a NW-flank vent on 7 June.

Photo by Chris Newhall,1991 (U.S. Geological Survey).


Kuchinoerabujima
Gas-and-steam plumes emanate from a newly opened, 800-m-long arcuate fissure on Shindake, the summit crater of Japan's Kuchinoerabujima volcano, on 29 September 1980. A brief eruption at the fissure the previous day ejected blocks and ash up to 2 km above the crater. All historical eruptions have occurred from the Shindake crater; ejecta from frequent explosive eruptions since 1840 have sometimes damaged villages near the crater.

Photo courtesy of Japan Meteorological Agency, 1980.


Pagan
A fissure that formed during an eruption of North Pagan volcano in the Mariana Islands in 1981 cuts across the summit of the volcano. Three principal vents were active along the fissure. A scoria cone (foreground) was constructed at the northernmost vent, and vents on the north and south rims of the summit crater fed lava flows that traveled down the flanks. Blocks as large as 1 m in diameter were ejected to distances of 2 km from the vent. This 16 June 1981 photo shows South Pagan volcano at the upper right.

Photo by U.S. Navy, 1981.


Hokkaido-Komagatake
Gas-and-steam plumes emanate from a new eruptive fissure cutting the summit of Japan's Komagatake volcano on 7 March 1996. A phreatic eruption began the evening of the 5th and deposited ash onto snow. The eruption took place from the 1929 crater and from a 200-m-long N-S fissure on the S flank. Eruptive activity, producing steam-rich ash plumes, was strong until 7 March and declined after 12 March.

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


Tolbachik
On 6 July 1975 a new fissure opened along the south rift zone of Tolbachik volcano during the "Great Tolbachik Fissure Eruption" of 1975-76, ending on 10 December 1976. Scoria cones grew to nearly 300 m high at the northern end of the 30-km-long eruption zone, with lava sheets covering more than 40 km2.

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


Krafla
Lava fountains erupting along a fissure at Iceland's Krafla volcano early in the morning on 5 September 1984. A gas plume is visible along the length of the fissure. 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.

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


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

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