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Grimsvotn Volcano - John Seach
Iceland
64.42 N, 17.33 W
summit elevation 1725 m
caldera
Grimsvötn volcano is located under Vatnajökull ice cap in central Iceland. Two major volcanic centers lie beneath the ice, the Bardarbunga volcanic centre and the Grimsvötn volcanic centre. Grimsvötn centre is the more active of the two.
About every 5-10 years glacial melting causes large floods (jökulhlaup) on the sandur plain. Eruptions at Grimsvotn Volcano are phreatomagmatic.
2004 Subglacial Eruption
A 5-day long eruption began at Grimsvotn Volcano on 1st November 2004. An intense swarm of volcanic earthquakes began 3 hours before the eruption. The eruption began under 150-200 m of ice and melted its way to the surface in 1 hour. On 2-3 November an eruption plume reached an altitude of 13 km, accompanied by volcanic lightning. The ash plume reached Norway, Finland, and Sweden.The total volume of the jökulhlaup was 0.5 cubic km.
1998 Eruption
A 10-day eruption began on 18th December 1998 within the caldera of Grímsvötn volcano, at a location 10 km S of the 1996 eruption. Within 10 minutes a plume rose 10 km above the Vatnajökull glacier. The plume was visible from Reykjavik, 200 km W. Eruption vents were located along a 1.3 km long fissure orientated E-W on the S caldera fault.
1996 Eruption
A 2-week long subglacial eruption began on 30th September 1996, along part of the East Rift Zone that traverses beneath the NW side of Vatnajökull, Europe's largest continental glacier. The eruption
was preceded by earthquakes on 29th September at Bardarbunga volcano. The high-frequency tremor resulted from lateral magma
injection from a shallow magma chamber beneath Bardarbunga toward the 1996 eruption site at Gjalp.
Within a day, the earthquake hypocenters migrated 20 km south, where a subglacial eruption started during the evening of 30th September. The eruption caused glacial ice to subside by 50 m in 4 hours, forming a bowl-like depression. On 2nd October the eruption broke through the ice, creating an ash plume 500 m high. By 3rd October the glacier had subsided over an area 8-9 km long and 2-3 km wide. On 4th October, water in the caldera lake reached this highest levels of the 20th century. The eruption occurred within 70 km of the great Laki fissure eruption of 1783-85.
1983 Eruption
An eruption began at Grimsvotn Volcano on 28 or 29 May 1983. The eruption broke through ice on 29th May and deposited a 5-km long thin layer of ash on the ice cap, south of the vent. Explosions occurred in the lake, and a steam plume rose to a height of 8000 m.
1982 Eruption
On 28th January 1982 a glacier burst (jökulhlaup) occurred at Grímsvötn caldera in Vatnajökull glacier. The eruption volume was 1.3 cubic km and lowered the ice level in the caldera by 50 m.
1972 Eruption
A glacial outburst flood occurred at Grimsvotn Volcano in March 1972.
Laki (Skaftar Fires) and Grimsvotn eruptions 1783-1785
The
eruption at Laki began on 8th June 1783 with a brief explosive
event on a short fissure, and lava rapidly began to flow
into the Skaftfi river gorge. Lava reached the lowlands, 35 km away, four days later.
Laki eruption created a 25 km long fracture and basalt lava flows extended 70 km. The lava flow covered 565 square km (14.7 cubic km). Large amounts of gas were produced in the eruption which covered most of Europe in a blue haze.
Fluorine was released by the eruption and cattle died from eating the contaminated grass. Over 200 000 livestock were killed in Iceland and the resulting famine resulted in 10 000 deaths.
Grimsvötn Volcano Eruptions
2004, 1998, 1996, 1984?, 1983, 1972, 1954, 1948?, 1945, 1941?, 1939?, 1938, 1934, 1934, 1933,1922, 1902-04, 1897, 1891-91, 1887-89, 1883, 1873, 1867, 1861?, 1854, 1838, 1823, 1816, 1794?, 1783-85, 1774, 1768, 1753, 1725, 1716, 1706, 1684-85, 1681, 1659, 1638, 1629, 1619, 1603, 1598, 1500?, 1354?, 1341, 1332, 1060?, 905?