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Surtsey

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Author Topic: Surtsey  (Read 2420 times)
Adam Hawthorne
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« on: April 14, 2007, 05:17:30 pm »



Surtsey as seen from above

 permanent island
 
Surtsey as seen from aboveThe explosive phreatomagmatic eruptions caused by the easy access of water to the erupting vents threw rocks up to a kilometre away from the island, and sent ash clouds as high as 10 km up into the atmosphere. The loose pile of unconsolidated tephra would quickly have been washed away had the supply of fresh magma dwindled, and large clouds of dust were often seen blowing away from the island during this stage of the eruption.

By early 1964, though, the continuing eruptions had built the island to such a size that sea water could no longer easily reach the vents, and the volcanic activity became much less explosive. Instead, lava fountains and flows became the main form of activity. These resulted in a hard cap of extremely erosion-resistant rock being laid down on top of much of the loose volcanic pile, which prevented the island being washed away rapidly. Effusive eruptions continued until 1965, by which time the island had a surface area of 2.5 kmē.

28 December 1963 saw the onset of submarine activity 2.5 km to the north-east of Surtsey, which formed a ridge 100 m high on the sea floor. This seamount was named Surtla, but never reached sea level. Eruptions at Surtla ended on 6 January 1964, and it has since been eroded from its minimum depth of 23 m to 47 m below sea level.

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