Fissure vent

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A fissure vent, also known as a volcanic fissure or simply fissure, is a linear volcanic vent through which lava erupts, usually without any explosive activity. The vent is usually a few meters wide and may be many kilometers long. Fissure vents can cause large flood basalts and lava channels. This type of volcano is usually hard to recognize from the ground and from outer space because it has no central caldera and the surface is mostly flat. The volcano can usually be seen as a crack in the ground or on the ocean floor. Narrow fissures can be filled in with lava that hardens. As erosion removes its surroundings, the lava mass could stand above the surface as a dyke. The dykes that feed fissures reach the suface from depths of a few kilometers. Fissures are usually found in or along rifts and rift zones, such as Iceland and the Great Rift Valley in Africa.

In Iceland, volcanic vents are often long fissures parallel to the rift zone where lithospheric plates are diverging. Renewed eruptions generally occur from new parallel fractures offset by a few hundred to thousands of metres from the earlier fissures. This distribution of vents and voluminous eruptions of fluid basaltic lava usually build up a thick lava plateau rather than a single volcanic edifice. The Laki fissure system produced the biggest eruption on earth in historical times, in the form of a flood basalt, during the Eldgjá eruption A.D. 934, which released 19.6 km³ (4.7 mi³) of lava.

The radial fissure vents of Hawaiian volcanoes produce “curtains of fire” as lava fountains erupt along a portion of a fissure. These vents produce low ramparts of basaltic spatter on both sides of the fissure. More isolated lava fountains along the fissure produce crater rows of small spatter and cinder cones. The fragments that form a spatter cone are hot and plastic enough to weld together, while the fragments that form a cinder cone remain separate because of their lower temperature.

[edit] List of fissure vents

Name	Elevation		Location	Last eruption
	metres	feet	Coordinates
Laki	1725	5659	64.42° N 17.33° W	1783
Lanzarote	670	2198	29.03° N 13.63° W	1824
Cordon Caulle	1798	5899	40.46° S 72.25° W	1960
São Jorge Island	1053	3455	38.65° N 28.08° W	1907
Vatnafjöll	1235	4052	63.92° N 19.67° W	1200 BP
Quetena	5730	18799	22.25° S 67.42° W	Unknown
Nejapa Miraflores	360	1181	12.12° N 86.32° W	Unknown
Manda-Inakir	600+	1968	12.38° N 42.20° E	1928
Hertali	900?	2953	9.78° N 40.33° E	Unknown
Gran Canaria	1950	6350	28.00° N 15.58° W	less than 1000 BP
Fuerteventura	529	1736	28.358° N 14.02° W	Unknown
Estelí	899	2949	13.17° N 86.40° W	Unknown
Butajiri Silti Field	2281	7484	8.05° N 83.85° E	Unknown
Bishoftu Volcanic Field	1850+	6069	8.78° N 38.98° E	Unknown
Alu	429	1407	13.82° N 40.55° E	Unknown
Singu Plateau	507	1663	22.70° N 95.98° E	Unknown
Ray Mountain	2050	-	52.23° N 120.12° W	Pleistocene

[edit] External links

• Detailed list and KML files for Fissure Vents
• Volcanolive.com Page on Fissure Vents