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"This said week, and the two prior to it, more
poison fell from the sky than words can describe:
ash, volcanic hairs, rain full of sulfur and
salt peter, all of it mixed with sand. The snouts,
nostrils, and feet of livestock grazing or walking
on the grass turned bright yellow and raw. All
water went tepid and light blue in color and
gravel slides turned gray. All the earth's plants
burned, withered and turned gray, one after
another, as the fire increases and neared the
settlements."
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Rev. Jón Steingrímsson,
Fires of the Earth: The Laki Eruption, 1783-1784
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| Iceland
lies over a plume
of hot material upwelling from great depths
and the Mid-Atlantic Ridge, the boundary
between the North American and Eurasian
tectonic plates where new crust is being
created on the order of 45 cubic km per
1000 years. The island nation is one of
the few places on earth where you can see
an active spreading ridge above sea level
with the two plates moving apart about 1
to 2 cm per year. As a result, there is
volcanism from well-known volcanoes like
Hekla,
Krafla,
and Surtsey
and from enormous fissure eruptions like
Eldgjá
(Fire Chasm, ~934AD) and Laki
(Skaftar Fires, 1783-1784) as well as earthquake
activity. New crust is broken down into
smaller particles and into new minerals
by processes of physical (i.e., wave action,
glaciers, wind, rain, plants, thermal contraction)
and chemical weathering (i.e., alteration
of volcanic glass). Fresh- to saline-water
geothermal systems with temperatures ranging
from warm to super-critical are associated
with the volcanism. In 2005, geothermal energy provided
about 19.1% of Iceland's energy needs. Glaciers cover
about 11% of Iceland. They provide a glimpse into
the Pleistocene environment that existed
in Europe and North America 10,000 years
ago. Subglacial volcanic eruptions periodically
cause large meltwater floods known as jökulhlaups.
Iceland has also been the focus of studies
on climatic change produced by changes in
solar output and by large volcanic eruptions.
Iceland (874AD) and Greenland (985AD) were
colonized during a period of high solar
output known as the Medieval Warm Period
that reached a maximum around 1000AD.
By 1200AD,
the warming trend had culminated, climatic
extremes were the norm, and sea ice and
glaciers increased. The Little Ice Age from
1560
to 1890AD was a period of cold and severe
winters and short and wet summers. The cloud
of sulfuric acid aerosols from the ~934AD Eldgjá
and 1783-1784 Laki
volcanic eruptions most likely produced
the exceptionally cold
winters in Europe and elsewhere after
these eruptions. The 18th century marked
the most tragic era in Iceland's history
due to climatic change, crop failure, epidemics,
farm and fisheries mismanagement, livestock
loss, and volcanic eruptions. Around one-quarter
of the population died in the 1707-1709
smallpox epidemic (Lacy
1998). The 1780's were the coldest decade
in Iceland from 1501-1801 (Ogilvie
1995). Following the Laki eruption,
crop failure, the loss of most livestock,
and harsh weather contributed to a famine
that killed nearly one-quarter
of the population. For more information, visit Dynamic Geology of Iceland, GEO.Icelandic
Earth Science Resources, Geology
and Geodynamics of Iceland, Geology of Iceland, Geoscience of Iceland, Global
Volcanism Program, Iceland: Land of Fire and Ice,
Iceland
GeoSurvey, Iceland
Volcanoes and Volcanics, Icelandic
Meteorological Office, MantlePlumes.org,
National
Energy Authority, Natural
History of Iceland, Nordic
Volcanological Institute, Reykjanes Ridge Expedition, Tephrabase,
Tour
of Iceland Geology, Volcano
Live, Volcano
World, and Volcanoes of Iceland. |
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