For you who don’t know much about Iceland. Here is a small glance into its volcanic history and gives you an idea what we are dealing with. As you
see the Eyjafjallajökull eruption is like a small rowing boat compared to tankers like Katla, Bárðarbunga, Hekla, Öræfajökull, Laki and Eldgjá.
This will give another perspective on Iceland.
Öræfajökull – The largest and the most dangerous volcano in Iceland. Has very explosive eruptions. In 1362 AD the Öræfajökull super-erupted,
as powerfully as Krakatoa (1883 AD). This could have had some impact on the global climate cooling of the Little Ice Age.
The eruption which lasted for 2 days set of horrific pyroclastic flows which totally destroyed the nearby countryside. Before the eruption the country
side was Icelands most flourished area. After the eruption it was a bleak desert and has since then been called Öræfi (The Wasteland).
Recent evidence suggest the 1362 eruption was the biggest in Europe for the past 2000 years, bigger than the 79 AD Vesuvius episode which destroyed
Pompeii. Because of Icelands isolation and low number of inhabitants the scale of the 1362 eruption is only just being discovered.
Reknown volcanogist Thor Thordarson says: ,,This eruption was two or three orders of magnitude larger than Laki and the largest eruption in Europe in
the past 2000 years.”
ELDGJÁ AND LAKI.
Volcanoes erupt in one of two basic styles: lava outflows from fissures in the ground and ash explosions from vents on top of volcanic mountains.
During the past eleven centuries, the world has seen two enormous fissure eruptions: the Eldgjá (Fire Chasm) eruption in 934 and the Laki, or
Skaftareldar (Skaftar Fires), eruption in 1783, both in southern Iceland. As the photograph shows, their ancient lava flows appear intermingled and
Such older eruptions have been investigated by using various research techniques. Scientists measure the visible lava and ash exposures in the field.
Sulfuric acid fallout over polar areas can be detected in deeply drilled ice cores having clearly marked annual layers of ice. The anomalous cooling
appears in stunted annual growth rings of north temperate trees and, much more importantly, in contemporary reports compiled by competent witnesses.
For the oldest historic eruptions, however, these compilers may not be scientifically trained or even first-hand witnesses.
Using published historical documents, Richard Stothers at GISS has traced the climatic and demographic consequences of the great Eldgjá and Laki
eruptions. In both eruptions, the cloud of aerosols from the eruption traversed northern Europe on the prevailing westerly winds, and dimmed and
reddened the sun. This continued for months. King Henry of Saxony noted the ominous presence of the thick dry fog in 934, and Benjamin Franklin
observed it scientifically in France in 1783. Both eruptions were followed by a very cold winter, poor harvests the next summer, severe famine, and a
widespread disease epidemic. Conditions remained bad for 5 to 8 years after Eldgjá, but only for 2 to 3 years after Laki. The Eldgjá eruption,
though slightly smaller than Laki, injected far more aerosols into the middle stratosphere, where they persisted for a longer time than did Laki's
aerosols at lower layers of the atmosphere.
The climatic aftereffects of the largest historic eruptions are very important for verifying our knowledge of the aftereffects of the smaller, though
better documented, modern eruptions. While the older data may be poorer in quality and quantity, the old climatic signals were bigger, and therefore
more easily detectable, because the eruptions were larger. The eruption of Mount Pinatubo in 1991 may have looked impressive to us, but, by historic
standards, it was just a little puff. www.giss.nasa.gov...
For eight months during the years 1783-1784, lava erupted from dozens of vents along a 27-km-long (17-mile-long) fissure system in the highlands of
southern Iceland. Basaltic lava flows—just like the flows we see here in Hawai`i—poured south out of the mountains onto the coastal plains,
burying 599 square km ( 231 square miles) in the process. The total volume of lava erupted in eight months is estimated at 15.1 cubic km (3.6 cubic
miles). In comparison, Kīlauea's ongoing east rift zone eruption, approaching the end of its 26th year of activity, has produced only about 3.4
cubic km (0.8 cubic miles) of lava.
In addition to these enormous lava flows, eruptive episodes from the Laki fissure started with explosive eruptions that blanketed more than 8,000
square km (3,089 square miles) with volcanic ash and cinders. And if you think the vog here can be bad, Laki pumped out 122 million tons of sulfur
dioxide in eight months. Compare this to Kīlauea's 0.85 million tons from February to September, 2008—less than one percent of Laki's output over
the same length of time. Half of the livestock in Iceland died after eating grass contaminated with fluorine from the gas plume, and 20 percent of
Iceland's population starved during the famine that followed. The sulfur dioxide released led to crop failures throughout Europe and may have led to,
or exacerbated, other famines in the northern hemisphere that occurred at about the same time
Did Laki disrupt the Asian monsoon cycle, prompting famine in Egypt and cause the Mississippi river to freeze at New Orleans?
Just over 200 years ago an Icelandic volcano erupted with catastrophic consequences for weather, agriculture and transport across the northern
hemisphere – and helped trigger the French revolution.
The Laki volcanic fissure in southern Iceland erupted over an eight-month period from 8 June 1783 to February 1784, spewing lava and poisonous gases
that devastated the island's agriculture, killing much of the livestock. It is estimated that perhapsa quarter of Iceland's population died through
the ensuing famine.
Then, as now, there were more wide-ranging impacts. In Norway, the Netherlands, the British Isles, France, Germany, Italy, Spain, in North America and
even Egypt, the Laki eruption had its consequences, as the haze of dust and sulphur particles thrown up by the volcano was carried over much of the
Ships moored up in many ports, effectively fogbound. Crops were affected as the fall-out from the continuing eruption coincided with an abnormally hot
summer. A clergyman, the Rev Sir John Cullum, wrote to the Royal Society that barley crops "became brown and withered … as did the leaves of the
oats; the rye had the appearance of being mildewed".
The British naturalist Gilbert White described that summer in his classic Natural History of Selborne as "an amazing and portentous one … the
peculiar haze, or smokey fog, that prevailed for many weeks in this island, and in every part of Europe, and even beyond its limits, was a most
extraordinary appearance, unlike anything known within the memory of man.
"The sun, at noon, looked as blank as a clouded moon, and shed a rust-coloured ferruginous light on the ground, and floors of rooms; but was
particularly lurid and blood-coloured at rising and setting. At the same time the heat was so intense that butchers' meat could hardly be eaten on
the day after it was killed; and the flies swarmed so in the lanes and hedges that they rendered the horses half frantic … the country people began
to look with a superstitious awe, at the red, louring aspect of the sun."
Across the Atlantic, Benjamin Franklin wrote of "a constant fog over all Europe, and a great part of North America".
The disruption to weather patterns meant the ensuing winter was unusually harsh, with consequent spring flooding claiming more lives. In America the
Mississippi reportedly froze at New Orleans.
The eruption is now thought to have disrupted the Asian monsoon cycle, prompting famine in Egypt. Environmental historians have also pointed to the
disruption caused to the economies of northern Europe, where food poverty was a major factor in the build-up to the French revolution of 1789.
Volcanologists at the Open University's department of earth sciences say the impact of the Laki eruptions had profound consequences.
Dr John Murray said: "Volcanic eruptions can have significant effects on weather patterns for from two to four years, which in turn have social and
economic consequences. We shouldn't discount their possible political impacts."
Laki shrunk the mighty river Nile
Researchers found that Iceland's Laki event significantly changed atmospheric circulations across much of the Northern Hemisphere. This created
unusual temperature and precipitation patterns that peaked in the summer of 1783, including far below normal rainfall over much of the Nile River
watershed and record low river levels.
The study provides new evidence that large volcanic eruptions north of the equator often have far different impacts on climate than those in the
tropics. "While considerable research has shown that eruptions in the tropics influence climate in the Northern Hemisphere winter, this study
indicates that eruptions in high-latitudes produce changes in atmospheric circulation in the Northern Hemisphere summer," said lead author Luke Oman,
Rutgers University, New Brunswick, N.J.
Using a sophisticated computer model developed by NASA's Goddard Institute for Space Studies, New York, the researchers linked the Laki eruptions to
a cascade of effects that rippled across much of the Northern Hemisphere, altering surface temperatures that ultimately resulted in much below normal
rainfall over the Sahel of Africa and record low water levels on the Nile River for up to a year. The Sahel is a stretch of land from the Atlantic
Ocean to the "Horn of Africa" that includes the Sahara Desert and savanna areas with sparse vegetation.
"These findings may help us improve our predictions of climate response following the next strong high-latitude eruption, specifically concerning
changes in temperature and precipitation," said Oman. "Many societies are very dependent on seasonal precipitation for their livelihood and these
predictions may ultimately allow communities time to plan for consequences, including impacts on regional food and water supplies."
The Laki event had such a significant impact on the climate because it released large amounts of sulfur dioxide into the atmosphere. When combined
with water vapor, the gas formed into tiny particles called aerosols that reduced incoming solar radiation, cooling the average temperature over
Northern Hemisphere land masses by as much as 3 degrees Celsius (5.4 degrees Fahrenheit) in the summer of 1783, as simulated with the computer model.
Tree ring data also showed significantly reduced tree growth in the summer of 1783, indicative of the coolest summer of the last 400 years in
northwestern Alaska, while tree growth in parts of Siberia was the least in 500-600 years.
These unusually cool temperatures reduced the temperature difference between the land masses of Eurasia and Africa and the Indian and Atlantic oceans,
weakening the African and Indian monsoon. A monsoon is a seasonal shift in wind direction and in this region marks the return of the rainy season.
Without a significant temperature contrast between land and ocean, onshore winds weaken, reducing the inland transport of moisture and rainfall in the
In contrast to the cooling over Northern Hemisphere land masses, computer simulations showed the weakening monsoon led to an area of significant
warming of 1 to 2 degrees Celsius (1.8 to 3.6 degrees Fahrenheit) over the Sahel of Africa, southern Arabian Peninsula, and India in the summer of
1783. The researchers believe the weaker-than-normal monsoon reduced the cloud cover in the region, allowing more of the sun's energy to reach the
surface, raising temperatures and further worsening drought conditions.
Computer model simulations also showed that this reduction in cloud cover was consistent with a decline in summer precipitation. "Some of the driest
weather occurred over the Nile and Niger River watersheds," said Oman. "The relative lack of cloud cover and increased temperature likely amplified
evaporation, further lessening water available for run-off."
To see what effect major high-latitude volcanic eruptions have on rainfall and river levels, the researchers used records on the height of the Nile
River that date back to 622 A.D. Record low Nile River water levels occurred in 1783-1784 following the Laki event. Similarly low levels were observed
after the Mount Katmai, Alaska, eruption in 1912, when the Niger River was also at a record low. And in 939 A.D. there was also low Nile River flow
following the Eldgjá eruption in Iceland. "Our analysis found there is less than a 3 percent chance that the Laki and Katmai low river flow events
could be attributed to natural climate variability," said Oman. www.nasa.gov...
This cloud was resident for 2-3 years after the eruption and led to, or accentuated the record-breaking cold winters of 1783-4 and 1784-5, and the
cool summer of 1784.
In fact, large Iceland fissure eruptions must have affected the whole of the northern hemisphere with the noxious gases and sulphuric acid aerosols
generated from the sulphur gases ejected into the atmosphere.
New studies by both French and US research groups have shown that the Laki aerosol cloud must have covered the whole of the northern hemisphere down
to the latitude of about North Africa. Historical documentation of the atmospheric effects due to these aerosols has been found from Japan to