Náttúrufræðingurinn - 1969, Síða 31

NÁTTÚ RUFRÆÐINGURINN
135
3). On Jan. 1 1967 the fissure opened up on the N side of the tephra wall of
Surtur I (Pl. IV a) and lava flowed down into the lagoon, nearly filling it and
seriously threatening the research hut Pálsbær (named after professor PaulBauer,
the bcnefactor of the Surtsey Research Society). This flow stopped on Jan.
4 at a distance of 120 m frorn the hut (Pl. IV b).
The total amount of tephra and lava (pillow lava and hyaloclastites included)
of the entire Surtsey eruption is 1.1 to 1.2 km3, whereof tephra comprises about
two thirds.
Fig. 9 shows sections ol' Surtsey and the submarine ridges of Surtla, Syrtlingur
and Jólnir, according to the hydrographic survey carried out July 12 to 25,
1967 by a British survey party from H.M. Surveying Ship Hecla, in close
cooperation with the Icelandic Hydrographic Service.
Summing up we find that the Surtsey eruption 1963—1967 can be divided
into the following main phases:
I. Submarine. About Nov. 8, 1963, to Nov. 14, 1963. A submarine ridge
was built up on a fissure beneath the present Surtsey.
II. Phreatic explosive. Nov. 14, 1963, to April 4, 1964. The island Surtsey
was built up to a height of 173 m above sea level and an area of 1.15 km2.
At the end of Jan. 1964 the activity shifted from the crater Surttir I to
Surtur II.
III. Effusive (Hawaiian). April 4, 1964, to May 17, 1965. A lava shield was
built up by Surtur II, increasing the area of Surtsey to 2.45 km2.
IV. Submarine. About the middle of May 1964 to May 22, 1964. The socle
of tlie island Syrtlingur, 0.6 knt NF of Surtsey, was built up.
V. Phreatic explosive. May 22, 1965 to Oct. 17, 1965. The island Syrtlingur
was built up to a height of 70 m ancl an area of about 0.15 km2. Before
Oct. 24, 1965 Syrtlingur had been completely washed away.
VI. Submarine. May have begun towards the end of Oct. 1965, ended Dec.
26, 1965. The ridge beneath the later island Jólnir was built up half a
mile SW of Surtsey.
VII. Phreatic explosive. Dec. 26, 1965 to Aug. 10, 1966. The island Jólnir was
built up to a heiglit of nearly 70 m and an area of about 0,3 km2. By
Sept. 20, 1966 the island had been nearly completely washed away.
VIII. Effusive (Hawaiian) phase. Aug. 19, 1966 to June 5, 1967. Fissure
eruption starting in Surtur I, extending Jan. 1, 1967 to the north side
of its tephra wall. This eruption built up a second lava shield, covered
1 km2 with lava and increased the area of Surtsey to 2.8 km2.
Beside these phases there was a submarine activity 2.5 km ENE of Surlsey
between late Dec. 1963 and early Jan. 1964 and probably sonte lava was ex-
truded a short distance SW of Surtsey in May and June 1964. In addition sub-
marine lava veins opened up on the flanks of Surtsey now and then during
1964.