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Volcanic Hazards: Lava Flows

Lava flows - Molten rock that has flowed out onto the Earth’s surface. When magma cools on surface it is called an extrusive igneous rock

Basaltic Lava Flows - These lava flows are very hot, low silica, and low viscosity. They can flow rapidly (up to 100 km/hr) & for long distances (up to several 100 km). There are two types: Pahoehoe lava (braids or ropes) and Aa lava (rough, jagged).

Andesitic Lava Flows - the higher SiO₂ content makes andesitic lavas viscous. Instead of flowing smoothly outwards, they mound around the vent and flow slowly, staying near the vent.

Rhyolitic Lava Flows - These magmas have the highest SiO₂ and therefore are the most viscous lava. Rhyolitic lava rarely flows, but instead plugs the vent as a lava dome.

Nyiragongo, Zaire

Last eruption: 2011
Elevation: 11,385' (3,470 m)
Type: Stratovolcano
Mountain range: Virunga Mountains
2002 Eruption: The lavas unusually low in SiO₂. The lavas flowed rapidly through the region from Goma to Lake Kivu. A total of 45 people were killed.

Iceland

Icelandic-type Eruptions are also known as fissure eruptions. These eruptions are usually peaceful due to the basaltic magma being erupted.

Eldfell Volcano, Iceland

Elevation: 656' (200 m)
Last eruption: 1973
Type: Stratovolcano
Volcanic arc/belt: Southern Volcanic Flank Zone
1973 Eruption: On 1/23/73 a fissure opened up near the town of Vestmannaeyjar (pop. 5,300). Lava flows and pyroclastic debris threatened to bury the town. The townspeople sprayed seawater on lava, diverted the flow away from the town, and the town was saved

Eyjafjallajökull, Iceland

Elevation: 5,466' (1,666 m)
Last Eruption: April 2010
Type: Stratovolcano
Volcanic arc/belt : East Volcanic Zone
2010 eruption - Minor eruption, but disrupted air traffic in N. Europe for weeks.

Bárðarbunga, Iceland

Elevation: 2,009 m (6,591 ft)
Last Eruption: ongoing, starting August 2014
Type: Subglacial volcano/Icelandic stratovolcano
2014 - August: 1,600 earthquakes preceded the under-ice eruption Currently still active.


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