The eruptive fissure, 25 km long, with its craters.
Painted by J.C. Leclerc.
Painted by Michel Gibault and Ingrid.
One of the craters from Laki.
The 934AD Eldgjá eruption was the largest (19.6 cubic
km lava), the 1783-1784 Lakagígar (Laki) eruption was the second largest fissure
eruption (12 to 13 cubic km lava) in recorded history. Laki is named after a 818
m high mountain split by a fissure. Lakagígar is the vent (i.e.,
fissure) for the eruption. The Laki eruption is also called Skaftáreldar ("Skaftá
river fires") or Sîđueldur. It is generally believed that the
Laki eruption was derived from magma injected laterally along dikes from a shallow
chamber beneath the Grimsvötn caldera, located 40 to 70 km to the northeast beneath
the Vatnajökull ice cap. The vent complex is made up of ten parallel fissures
that extend for 25 km. A continuous row of scoria, spatter, and tuff cones 40
to 70 m high lie over these fissures. The Laki eruption, which began on June 8,
1783, lasted until February 1784. As the amount of groundwater decreased, the
eruption style along newly opened fissures changed from explosive activity to
lava fountains 800 to 1400 m high. Reverend Jón Steingrímsson (1728-1791) wrote
a vivid description of the eruption known as the Eldritiđ or the Fire Treatise.
On July 20, 1783, the advancing lava stopped miraculously a little over a mile
from the church at Kirkjubćjarklaustur where Rev. Steingrímsson was delivering
his famous eldmessa ("Fire Sermon"). In the Eldgjá and Laki eruptions,
a cloud of sulfuric acid aerosols traversed northern Europe dimming and reddening
the sun. King Henry of Saxony observed this thick dry fog in 934AD and Benjamin
Franklin described the fog when he was Ambassador to France in 1783. Franklin's
observations laid the cornerstone for subsequent studies on the relationship between
volcanic eruptions and climate. Both eruptions were followed by cold winters,
livestock loss fromfluorine-contaminated grass, crop failure from acid rain, famine,
and epidemics. Conditions were bad for the next 5-7 years after Eldgjá and next
2 years after Laki (Wood 1992). Seventy-five percent of the livestock and over
9,000 people, one-quarter of the population, died following the Laki eruption
during a period known as the Móđuharđindin ("The Misty Plague")after
the ash mist. The Eldgjá eruption injected more aerosols into the middle stratosphere,
where they would absorb heat for a longer period of time, whereas aerosols from
Laki only reached the lower atmosphere (Wood 1992). In eastern North America,
the winter of 1783-1784 was the longest and one of the coldest in American history.
It was the longest period of below zero temperature in New England, the largest
accumulation of snow in New Jersey, and the longest freezing over of the Chesapeake
Bay. There was ice skating in Charleston Harbor, a huge snowstorm hit the south,
the Mississippi River at New Orleans froze over, and there were even ice floes
in the Gulf of Mexico (Wood 1992).
Steve Lonker* Informations
and images about Laki's eruption (by Volcanism Global Program).