| Laki | |
|---|---|
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| Highest point | |
| Elevation | Varies: canyon to 1,725 m (5,659 ft) |
| Coordinates | 64°03′53″N18°13′34″W / 64.06472°N 18.22611°W /64.06472; -18.22611 |
| Geography | |
  Laki | |
 Geological features near the Grímsvötn fissure swarm. Legend
| |
| Geology | |
| Mountain type | Fissure vents |
| Last eruption | 1784 |
Laki (Icelandic pronunciation:[ˈlaːcɪ]ⓘ) orLakagígar ([ˈlaːkaˌciːɣar̥],Craters of Laki) is avolcanic fissure in the western part ofVatnajökull National Park,Iceland, not far from the volcanic fissure ofEldgjá and the small village ofKirkjubæjarklaustur. The fissure is properly referred to as Lakagígar, while Laki is a mountain that the fissure bisects. Lakagígar is part of a volcanic system centered on the volcanoGrímsvötn and including the volcanoÞórðarhyrna.[1][2][3] It lies between theglaciers ofMýrdalsjökull andVatnajökull, in an area of fissures that run in a southwest to northeast direction.
The system erupted violently over an eight-month period between June 1783 and February 1784 from the Laki fissure and the adjoining volcano Grímsvötn. It poured out an estimated 42 billion tonnes or 14 km3 (18×10^9 cu yd) ofbasalt lava as well as clouds of poisonoushydrofluoric acid andsulfur dioxide compounds that contaminated the soil, leading to the death of over 50% of Iceland's livestock population, and the destruction of the vast majority of all crops. This led to afamine which then killed at least a fifth[4] of the island's human population, although some have claimed a quarter.[5]
The Laki eruption and its aftermath caused a drop in global temperatures, as 120 million tonnes of sulfur dioxide was spewed into theNorthern Hemisphere. This caused crop failures inEurope and may have caused droughts inNorth Africa andIndia.
| 1783 eruption of Laki | |
|---|---|
| Start date | 8 June 1783 |
| End date | 7 February 1784 |
| Type | Phreatomagmatic,Strombolian,Hawaiian |
| VEI | 4 |
| Impact | 9500 human, 190,500 sheep, 11,500 cattle and 28,000 horse deaths.[6] |
| Maps | |
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On 8 June 1783, a 25 km-long (15.5 mi)fissure of at least 130vents opened withphreatomagmatic explosions because of the groundwater interacting with the risingbasaltmagma.[7] Over a few days the eruptions became less explosive,Strombolian, and laterHawaiian in character, with high rates of lavaeffusion. This event is rated as 4 on theVolcanic Explosivity Index,[8] but the eight-month emission of sulfuricaerosols resulted in one of the most important climatic and socially significant natural events of the last millennium.[7][9]
The eruption, also known as theSkaftáreldar[ˈskaftˌauːrˌɛltar̥] ("Skaftá fires") or Síðueldur[ˈsiːðʏˌɛltʏr̥] produced an estimated 14 km3 (18×10^9 cu yd) ofbasalt lava, and the total volume oftephra emitted was 0.91 km3 (1.2×10^9 cu yd).[10]Lava fountains were estimated to have reached heights of 800 to 1,400 m (2,600 to 4,600 ft). The gases were carried by the convective eruption column to altitudes of about 15 km (50,000 ft).[4]
The eruption continued until 7 February 1784, but most of the lava was ejected in the first five months. One study states that the event "occurred as ten pulses of activity, each starting with a short-lived explosive phase followed by a long-lived period of fire-fountaining".[11] Grímsvötn volcano, from which the Laki fissure extends, also erupted at the time, from 1783 until 1785. The outpouring of gases, including an estimated 8 million tonnes offluorine and an estimated 120 million tonnes ofsulfur dioxide, gave rise to what has since become known as the "Laki haze" across Europe.[4]
The consequences for Iceland, known as theMóðuharðindin[ˈmouːðʏˌharðɪntɪn] (mist hardships), were disastrous.[12] An estimated 20% of the population died in the famine after the fissure eruptions ensued with about 8,000 excess deaths.[13] Approximately 80% of sheep (190,500 head), 50% of cattle (11,500 head) and 50% of horses (28,000 head) died because ofdental fluorosis andskeletal fluorosis from the 8 million tons of fluorine that were released.[6][14][15] Milk yields halved.[13] The livestock deaths were primarily caused by eating contaminated grass, while humans deaths were from the subsequent famine not fluorine poisoning.[13]
The parish minister and provost ofVestur-Skaftafellssýsla, Jón Steingrímsson (1728–1791), grew famous for theeldmessa[ˈɛltˌmɛsːa] ("firemass") that he delivered on 20 July 1783. The church farm ofKirkjubæjarklaustur was endangered by a branch of the lava flow that halted not far from the farm while the Rev. Jón and his parishioners were worshipping in the church. The spot at which the lava diverted away from the church became known thereafter asEldmessutangi[ˈɛltˌmɛsːʏˌtʰauɲcɪ] ("Fire Mass Point").
This past week, and the two prior to it, more poison fell from the sky than words can describe: ash,volcanic hairs, rain full of sulfur andsaltpeter, 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 grey. All the earth's plants burned, withered and turned grey, one after another, as the fire increased and neared the settlements.[16]
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There is evidence that the Laki eruption weakenedAfrican andIndianmonsoon circulations, leading to between 1 and 3 millimetres (0.04 and 0.12 in) less daily precipitation than normal over theSahel of Africa, resulting in, among other effects, low flow in the RiverNile.[17] The resultingfamine that afflictedEgypt in 1784 cost it roughly one-sixth of its population.[17][18] The eruption was also found to have affectedSouth Arabia and the already ongoingChalisa famine in India.[18][19]
TheGreat Tenmei famine of 1782–1788 inJapan may have been worsened by the Laki eruption. In the same year,Mount Asama erupted in Japan (Tenmei eruption).[20] The eruption may have affected a drought in eastern China.[21]
An estimated 120,000,000 tonnes ofsulfur dioxide was emitted, about three times the total annual European industrial output in 2006 (but delivered to higher altitudes, hence its persistence), and equivalent to six times the total1991 Mount Pinatubo eruption.[14][4] This outpouring of sulfur dioxide during unusual weather conditions caused a thick haze to spread across western Europe, resulting in many thousands of deaths throughout the remainder of 1783 and the winter of 1784.[citation needed]
The summer of 1783 was the hottest on record and a rare high-pressure zone over Iceland caused the winds to blow to the south-east.[14] The poisonous cloud drifted toBergen inDenmark–Norway, then spread toPrague in theKingdom of Bohemia (now the Czech Republic) by 17 June, Berlin by 18 June, Paris by 20 June,Le Havre by 22 June, and Great Britain by 23 June. The fog was so thick that ships stayed in port, unable to navigate, and the sun was described as "blood coloured".[14]
Inhaling sulfur dioxide gas causes victims to choke as their internal soft tissues swell – the gas reacts with the moisture in the lungs and producessulfurous acid.[22] The local death rate inChartres was up by 5% during August and September, with more than 40 dead. In Great Britain, the east of England was most affected. The records show that the additional deaths were among outdoor workers; the death rate inBedfordshire,Lincolnshire, and the east coast was perhaps two or three times the normal rate. It has been estimated that 23,000 British people died from the poisoning.[23]
The weather became very hot, causing severethunderstorms with largehailstones that were reported to have killedcattle,[24] until the haze dissipated in the autumn. The winter of 1783–1784 was very severe;[25] the naturalistGilbert White inSelborne,Hampshire, reported 28 days of continuous frost. The extreme winter is estimated to have caused 8,000 additional deaths in the UK. During the spring thaw, Germany andCentral Europe reported severe flood damage.[14] This is considered part of avolcanic winter.[26]
The meteorological impact of Laki continued, contributing significantly to several years ofextreme weather in Europe. In France, the sequence of extreme weather events included a failed harvest in 1785 that caused poverty for rural workers, as well as droughts, bad winters and summers. These events contributed significantly to an increase in poverty and famine that may have contributed to theFrench Revolution in 1789.[26] Laki was only one factor in a decade of climatic disruption, asGrímsvötn was erupting from 1783 to 1785, and there may have been an unusually strong El Niño effect from 1789 to 1793.[27][28]
In North America, the winter of 1784 was the longest and one of the coldest on record. It was the longest period of below-zero temperatures inNew England, with the largest accumulation of snow inNew Jersey, and the longest freezing over ofChesapeake Bay. At the time, the capital of the United States was situated on the Chesapeake atAnnapolis, Maryland; the weather delayed Congressmen who were traveling there to vote for theTreaty of Paris, which formally ended theAmerican Revolutionary War. A huge snowstorm hit theSouth; theMississippi River froze atNew Orleans and there were reports ofice floes in theGulf of Mexico.[26][29]
Gilbert White recorded his perceptions of the event atSelborne,Hampshire, England:
The summer of the year 1783 was an amazing and portentous one, and full of horrible phaenomena; for besides the alarming meteors and tremendous thunder-storms that affrighted and distressed the different counties of this kingdom, 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. By my journal I find that I had noticed this strange occurrence from June 23 to July 20 inclusive, during which period the wind varied to every quarter without making any alteration in the air. 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. All the 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, and riding irksome. The country people began to look, with a superstitious awe, at the red, louring aspect of the sun; ...[30]
Benjamin Franklin recorded his observations in America in a 1784 lecture:
During several of the summer months of the year 1783, when the effect of the sun's rays to heat the earth in these northern regions should have been greater, there existed a constant fog over all Europe, and a great part of North America. This fog was of a permanent nature; it was dry, and the rays of the sun seemed to have little effect towards dissipating it, as they easily do a moist fog, arising from water. They were indeed rendered so faint in passing through it, that when collected in the focus of a burning glass they would scarce kindle brown paper. Of course, their summer effect in heating the Earth was exceedingly diminished. Hence the surface was early frozen. Hence the first snows remained on it unmelted, and received continual additions. Hence the air was more chilled, and the winds more severely cold. Hence perhaps the winter of 1783–84 was more severe than any that had happened for many years.
The cause of this universal fog is not yet ascertained ... or whether it was the vast quantity of smoke, long continuing, to issue during the summer fromHekla in Iceland, and that other volcano which arose out of the sea near that island, which smoke might be spread by various winds, over the northern part of the world, is yet uncertain.[31]
According to contemporary records, Hekla did not erupt in 1783; its previous eruption was in 1766. The Laki fissure eruption was 70 km (45 mi) east and the Grímsvötn volcano was erupting about 120 km (75 mi) northeast.Katla, only 50 km (31 mi) southeast, was still renowned after its spectacular eruption 28 years earlier in 1755.
Sir John Cullum ofBury St Edmunds,Suffolk, England, recorded his observations on 23 June 1783 (the same date on which Gilbert White noted the onset of the unusual atmospheric phenomena), in a letter toSir Joseph Banks, then President of theRoyal Society:
... about six o'clock, that morning, I observed the air very much condensed in my chamber-window; and, upon getting up, was informed by a tenant that finding himself cold in bed, about three o'clock in the morning, he looked out at his window, and to his great surprise saw the ground covered with a white frost: and I was assured that two men at Barton, about three miles (five kilometres) off, saw in some shallow tubs, ice of the thickness of acrown-piece.[32]
Sir John goes on to describe the effect of this "frost" on trees and crops:
Thearistae of thebarley, which was coming into ear, became brown and withered at their extremities, as did the leaves of the oats; the rye had the appearance of being mildewed; so that the farmers were alarmed for those crops. The wheat was not much affected. Thelarch,Weymouth pine, and hardyScotch fir, had the tips of their leaves withered.[32]
This article incorporates text from a publication now in thepublic domain: Thoroddsen, Thorvaldur; Powell, Frederick Y.; Blöndal, Sigfús (1911). "Iceland". InChisholm, Hugh (ed.).Encyclopædia Britannica. Vol. 14 (11th ed.). Cambridge University Press. p. 229.
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