Alan V. Morgan
The following is the first part of a four-part series covering some of the volcanic activity which has taken place on the south coast of Iceland during the past 25 years. This section will cover some aspects of the eruption of Surtsey. Three later articles will cover the activity of the volcano Eldfell on Heimaey, during the early stages of the eruption, as it appeared a decade later, and finally as it is in 1998.
Introduction
Sometimes I get asked by students of various ages why I became interested in geology. My reply is that I became interested after finding a fossil snail with the impossibly long name (at least for an eight year old) of Pleurotomaria anglia Sowerby. My life adventure began ... June 1951... with me taking it home, and with my mother pointing out that it was not a snail made out of concrete (my interpretation), but a fossil snail. A visit to Emlyn Evans, the School Services Officer at the National Museum of Wales (Wales was enlightened towards teaching), confirmed that it was a fossil snail, "... a lower Jurassic gastropod, about 175 million years old." Perhaps at some other time I'll continue this early life geological experience. Suffice to say that with the interest of Emlyn Evans, and F.J. North of the National Museum, two grammar school teachers of geology and geography, Jack Edney and Jesse James (we really did have a "frontier" mentality in Wales), I knew that I was going to become "a geologist". Almost 50 years later I'm still not sure what kind of geologist, but I suppose that is why I teach "Earth sciences". I have the privilege to be able to roam from stratigraphy to paleontology to glaciology and volcanology almost at will, and when I consider this last topic I realise that my interests began while I was still in school, and with another "life event" which really made me believe that this was a great subject area to be in.
October 1959
Back in those days we had, in Britain, an organisation called "The British Schools Exploring Society". It was the creation of Murray-Levick, Scott of the Antarctic's Surgeon Commander. Murray-Levick's had founded the BSES to take "... schoolboys into wild and trackless country to teach them the qualities of initiative and leadership". My stretch of "wild and trackless country" was going to be, in the summer of 1960, central Iceland. We sailed from Leith in the MV Gullfoss, a small vessel which I was to encounter 13 years later off Heimaey, and which now rests at the bottom of the Red Sea.
Late in the afternoon of July 23, 1960, we passed through the Westman Islands off the south coast of Iceland. As the sun cast 10 p.m. shadows on the cliffs of Heimaklettur, I wrote in my diary that "The sun was sinking low in the sky as we passed by the Vestmannaeyjar Islands, bathing the dark cliffs in a pink glow, and showing the brilliant green of the grass and the small red and white houses to their fullest advantage." I can also remember noting that it seemed a silly place to build a town; - after all, those red and white houses were clustered along the flanks of a very youthful-looking volcanic cone! Little did I know that I would be on that same island almost exactly 10 years later en route for Surtsey, a volcano which was born in the early winter of 1963, and that I would return again, in 1973, to watch those same houses vanish beneath a wall of lava.
August 1970
The DC3 banked steeply in an azure blue sky as it turned over Heimaklettur and prepared to land on the small airstrip at Vestmannaeyjar. My wife, Anne, and I were arriving to join a small group of international scientists examining the biological colonisation of Surtsey. Surtsey was clearly visible some 20 kilometres south of Heimaey, a dark splotch in the glimmering silver of the North Atlantic. In the next few hours we met the researchers and prepared for the crossing to Surtsey. This was to be accomplished one at a time in a very small two-seater aircraft. Thoughts of danger were a long way from my mind as I flew across that intervening patch of water. We skimmed across the sea, just above the cliffs of some of the small islands; - all were remnants of some previous volcanic activity in the region. Most were just volcanic necks jutting from Atlantic inhabited only by guillimots, razor bills and puffins, and then, looming in front, as the nose went down was the foreshore of Surtsey. To this day, I'm still not sure exactly how the pilot managed to get the plane down in one piece, especially on that boulder-strewn foreshore, but I do know that it is the only time that I have been asked to get out of a moving aircraft! Over the rush of the slipstream I can still hear "Wait for the plane to slow, throw out your water and pack, jump out; - watch for the tail, catch hold of the tail and pull the plane around so I can take off immediately!" Well it worked, and one by one we arrived on the island of Surtur, the fire-giant! The next few days were spent exploring the island which covered an area of approximately 2.5 km2. But, first, let's review the origins of Surtsey.
Volcano Surtsey
"Surtur
comes
from
the
South
...
the
hot
stars
down
from
Heaven
are
whirled.
Fierce
grows
the
steam
and
the
life-feeding
flame,
until
fire
leaps
high
about
Heaven
itself."
...From
the
Icelandic
poem
Voluspa
ca.
950
A.D.
Background
No-one is really sure exactly when Surtsey first broke through the sea floor of the Atlantic. The crew of the Westman Islands trawler Isleifur II were the first to notice the event at about 7:15 in the morning of November 14, 1963. Several crew members had smelled sulphurous odours and had experienced a strange motion in the vessel as they laid fishing lines some 7 km west of Geirfuglasker, a small island at the southern end of the Westman Archipelago. The sea floor in this area is at a depth of 130 m. At first they thought that signs of smoke and fire noted in the sea several kilometres away were probably from a ship in distress, but no emergency messages had been received by the Westman coastguard station. By 7:30 tephra was emerging from the sea, and there was little doubt that volcanic eruption was underway. It grew rapidly in size, possibly because of the undersea propagation of a fissure to the northeast, and by 8:00 a.m. two or three tephra columns were reaching heights of about 60 m. The eruption cloud grew very rapidly. By 10:30 a.m. it was about 3.5 km high and 30 minutes later, over 4 km. By mid afternoon the column was 6 km high. Like the eruption of Paricutin a decade earlier, and that at Eldfell a decade later, there was no obvious seismic activity associated with the initial rifting of the ground.
Surtsey grew in size from a shoal between the morning of November 14 and the 15th to a height of 145 m at year end. The tephra fountains had reached a height of close about 500 m. The question of whether the island was going to remain for any length of time was in doubt since the North Atlantic storms are so severe that it was felt by many that if there was any reduction in the tephra output, the island would soon vanish. However, landings made by three French adventurers in early December forced the Icelandic Place Names Committee to decide to name the new island Surtsey. Landings were also made on December 13th and 16th, and rock samples were collected. The ejecta turned out to be an olivine basalt with phenocrysts of olivine and anorthite plagioclase feldspar. Tuff fragments with shells intermixed were also found on the island. On December 28, 1963 a new vent was detected 2.5 km northeast of Surtsey, about halfway to Geirfuglasker. This volcano was informally named Surtla, but it never succeeded in breaking the surface of the sea. It was estimated as being 4-6 m below the surface, and measured on February 14, 1964 as being 23 m below the sea surface. The activity on this vent ceased on or about January 6, 1964. It should be noted that two other small volcanic islands emerged on either side of Surtsey during 1965. One, Syrtlingur (Little Surtur), poked out of the sea some 600 m northeast of Surtsey in October, and the second, Jolnir, arrived on December 26, approximately 900 m southwest of Surtsey. Both attained heights of about 70 m; neither produced lava, and both were rapidly eroded by winter storms, vanishing beneath the sea in 1966.
The only thing that ensured the survival of Surtsey, was the production of copious quantities of basalt lava extruded from the "Surtur II" crater. This activity started on April 4, 1964. A lava lake quickly developed. It was about 120 m in diameter with lava fountains rising some 50 m and from the lake small rivulets of lava made their way downslope to the sea. Many of these small streams vanished underneath a solid crust of lava of both aa and pahoehoe type, although the flows continued to move within small lava tubes in the flows eventually emptying at the sea cliffs on the southern end of the island. The first lava stage lasted until April 29th. This was followed by a period of quiescence until July 9 when a second lava outpouring stage commenced, continuing more or less unabated until May 7, 1965. Approximately 1.5 km2 of lava was extruded in this phase. The final phase of activity on Surtsey commenced on August 19, 1966 when a 200 m long fissure opened across the northern wall of the Surtur crater. Lava broke through on the north side of the tephra cone on January 1, 1967 and flowed for several days, threatening the research hut, but setting the stage for ideas and actions which helped on Heimaey six years later. On the south side lava continued to flow until June 5, 1967, and this represents the last recorded activity on Surtsey.
August 1970
After we had arrived, one by one from Heimaey, we settled in to the research hut on the north side of Surtsey. Each day we moved out to examine the lava fields and surrounding tephra slopes to see if we could find new life colonising the island. My interests were in examining the physiographic and geological features of this very young volcano. The island could be divided into three geomorphic zones. The southern half which formed the low-angled lava fields of this small shield volcano; the high tephra mounds of the craters in the north-central part of the island and, finally, the northernmost wave-cut platform (the landing strip area) where a small lagoon had been formed.
It was very obvious that nature worked rapidly on this exposed island. The total material extruded during the eruption was about 1.1 km3. Of this, less than 10 percent projected above the Atlantic and the ocean was certainly trying hard to take this all back. The dark grey to black basalt flows in the southern part of the island ended abruptly in vertical cliffs, 20 to 30 m in height. Anne and I had the opportunity of entering a number of small lava tubes, and, after crawling through one for some distance, we emerged (much to the concern of a number of sea birds) on a ledge with a precipitous drop into the sea. The surface of the lava flows was largely aa, with a few pahoehoe flows in restricted areas where lava had coursed through small levees, or had spilled over the sides of the lava tubes.
The wave-cut platform in the north, and the beaches along the east and west sides of the island showed the immense erosive power of the sea. Huge, rounded basalt boulders armoured the shorelines and illustrated the considerable carrying capacity of the longshore drift moving around the island.
The high tephra cliffs in the centre of Surtsey were a buff-yellowish colour, composed of sideromelane (a basaltic glass) which had been created by the rapid quenching of the tephra which was mixed with seawater. Most of this debris was stratified, sorted by the height and force of the explosion and winnowed by the prevailing winds as it fell from the sky. The size fraction of about 85 to 90 percent of the tephra was between .05 and 5.0 mm. Large areas of the tephra were covered in a white precipitate of calcium sulphate (gypsum). Other areas closer to the still-hot geothermal regions were becoming devitrified, gradually changing to a dense brown tuff known as Palagonite. This is commonly found in many parts of Iceland in the formations termed "Moberg" and these regions were created by sub-glacial volcanic eruptions under the Quaternary ice sheets which mantled most of the country in the recent past.
One thing which we found fascinating was that a number of the ejected pyroclastic blocks scattered around the Surtur vents had marine shells fragmented within them, illustrating the problems that clams have living in this portion of the North Atlantic!
That very last lava flow which moved down the northern flank of the volcano in one of the last stages of the eruption is also worthy of mention. The flow had moved to within 100 m of the research station when someone suggested that it might be possible to cool the lava front with seawater and stop the movement of the lava to the hut. I don't know whether it really worked, but it was tried, the lava flow did stop and the stage was set for a far larger experiment on Heimaey three years later.
Anne and I left Surtsey on a stormy August day, taken off in a rubber raft and sailing by trawler to Heimaey. We stayed for several days in a small guest house on the island, little suspecting that the house, the street, and that section of the town would be consumed by fire within the next 900 days as the next eruption struck the "Isles of the Western Men".
References:
- Fridriksson, S. 1975. Surtsey. John Wiley and Sons, N.Y. and Toronto. 198 pp.
- Thorarinsson, S. 1964. Surtsey: The new island in the North Atlantic. Almenna bookpublishing. Reykjavik. 63 pp (and photo plates).