The course of events of the volcanic activity in Surtsey and the adjacent area can be divided into seven main phases:
Submarine phase I
This phase probably started about 6 November 1963, in a fissure, 130 m deep, running N 35° E to S 35° W, in lat 63° 18′ 22″ N, long 20° 36′ 5″ W, 3 nautical miles west-south-west of Geirfuglasker, the southernmost of the Vestmannaeyjar (Fig. 1) The seismograph at Kirkjubæjarklaustur registered weak earthquakes in this area from 6 to 8 November. During the following week submarine action built up a narrow ridge, presumably mainly consisting of pillow lava, near the bottom of the sea floor, and an increasing amount of hyaloclastites as the ridge came nearer the surface.