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NASA » Ol Doinyo Lengai Volcano eruption
Ol Doinyo Lengai Volcano - Eruption Effects
A NASA satellite image pair and description published by Earth Observatory in September, 2009.
| NASA satellite image of Ol Doinyo Lengai volcano acquired July 16, 2004 while the landscape still showed the effects of effusive eruptions. Dark areas on the crater floor are recent lava flows (days to weeks old), while the beige and white regions are older lava that have reacted with rain and moisture in the atmosphere. Lava flows are visible as beige fingers radiating down the sides of the mountain. Dark green vegetation covers the upper slopes of the volcano. Image credit NASA / Earth Observatory |
| NASA satellite image of Ol Doinyo Lengai volcano acquired September 12, 2009 after explosive eruptions have modified the landscape. Explosive eruptions in 2008 built a cone over 100 meters (330 feet) high with a steep-walled crater. The new cone and crater are clearly visible in the center of the image. The dark spot in the crater may be fresh lava erupted from a new volcanic vent. Gray ash covers the volcano and much of the surrounding landscape. Image credit NASA / Earth Observatory |
Carbonatite Lavas of Ol Doinyo Langai
Ol Doinyo Langai in Tanzania
is the only volcano in the world that erupts natrocarbonatite lava.
Natrocarbonatites are rich in calcium, sodium, and potasium, but low in
silica (silicon dioxide).
Because of their lack of silica the lava of Ol Doinyo Lengai is extremely
cool (500–600° C, compared
to 1,160° C for typical basaltic lava) and relatively fluid. Ol Doinyo
Lengai alternates between eruptions
of liquid lava that form lava lakes and fountains (called effusive
eruptions) and explosive eruptions that
build large cinder and ash cones. (For more details and photos of the
unique lava flows of Ol Doinyo Lengai
visit our article on carbonatite
lavas.)
Effusive Eruptions
The natural color images images above show the changes on Ol Doinyo Lengai’s
summit caused by
the switch from a long period of effusive eruptions to a series of violent
explosions. The top image,
acquired on July 16, 2004, by the Advanced Land Imager (ALI) aboard the
Earth Observing-1 satellite
shows the summit after a long period of effusive eruptions. Beginning in
1983 lava began to fill the crater
of an ash cone formed during explosive eruptions in 1966 and 1967. Over time
the lava filled the crater
and created a large flat platform. Dark areas on the crater floor are recent
lava flows (days to weeks old),
while the beige and white regions are older lava that have reacted with rain
and moisture in the atmosphere.
In 1998 lava began to spill over the rim of the crater to the north and
east. These lava flows are visible as
beige fingers radiating down the sides of the mountain. Dark green
vegetation covers the upper slopes of the volcano.
Explosive Eruptions
In September of 2007 explosive eruptions began on Ol Doinyo Lengai, spewing
ash thousand of meters into the air.
Ash also covered the surrounding landscape, forcing local
residents—primarily herders—to flee with their livestock.
Explosive eruptions continued into 2008, building a cone over 100 meters
(330 feet)high with a steep-walled crater.
The new cone and crater are clearly visible in the center of the ALI image
acquired on September 12, 2009. The dark
spot in the crater may be fresh lava erupted from a new volcanic vent. Gray
ash covers the volcano and much of the
surrounding landscape.
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