360 ME. HELGI PJKTURSSON ON A SHELLY [Aug. I903, 



as indicative of cold (Glacial) conditions. In fact, the above-named 

 six species of molluscs are among those found in the Scandinavian 

 deposits of the Yoldia-ae&; and it can hardly be doubted that here 

 too they lived in an icy sea before they got into the ground- 

 moraine of an advancing glacier — which took place before the 

 eruption of the ' pre-Glacial dolerites ' of Prof. Thoroddsen and 

 others. On Prof. Thoroddsen's new geological map of Iceland, 

 published in 1901, the doleritic lavas are shown as pre-Glacial and 

 Glacial ; while on his special maps published before 1900 they are 

 shown only as pre-Glacial. As a matter of fact, they are largely 

 inter-Glacial, or at any rate inter- morainic. 



A discussion of the facts alluded to above, and many others con- 

 nected with them, must be deferred until I am able to give a fuller 

 account of the investigations which I carried out in 1901 and 1902 ; 

 only a few points may be here briefly mentioned. 



I take it to be an unquestionable fact that the basement-layer of 

 the ' breccia-formation ' of Sngefellsnes is a ground-moraine ; and in 

 other parts of the country beds of indurated ground-moraine are 

 found very deep in this formation, buried under hundreds of feet of 

 rock — not to say more. Now, I do not mean to contend that the 

 shelly Boulder-Clay of Bulandshofdi is necessarily of the same age 

 as the lower moraine of other sections of the Mavahlid-plateau 

 (fig. 1 ), but we learn from this section (fig. 2) that at least some of 

 the older moraines (' palagonite-moraines ') are of Pleistocene age. 



I do not believe that the tuff- and breccia-formation ever had an 

 average thickness of 3000 or 4000 feet, but rather that the frag- 

 mental materials have been piled up to this great thickness around 

 centres of eruption only. Indeed, I imagine that, on further 

 examination, it would not be difficult to point out a considerable 

 number of the wrecks of the volcanic cones of the breccia-formation ; 

 although I must confess that I did not recognize any of them until 

 the summer of 1902, after I had had occasion to see the quite 

 unmistakable remnant of such a volcano near Kerlingarskard, 

 tSncefellsnes. 1 



It is highly probable that further research will tend to confirm 

 the hypothesis, not only that volcanic activity continued uninter- 

 ruptedly in Iceland during the Glacial Period, but that it was of 

 great intensity, especially perhaps towards the beginning and the 

 close of a glaciation, and that the eruptions, unlike the fissure- 

 eruptions of pre-Glacial and in part also of recent times, 2 resulted 

 to a great extent in the building-up of bulky hills of scoriae and 

 ashes, some of which have survived the Glacial Period as volcanoes 

 (and are still covered with snow and ice, and belching forth, not lava, 

 but scorise and ashes); while others have become extinct and 



1 It ought perhaps to be mentioned here that Prof. Thoroddsen wrote in 

 1898 in regard to Siidur (Dansk. Geograf. Tidsskr. vol. xv, p. 11) : ' Perhaps 

 we have here the wreck of a volcano dating from the close of the Tertiary Era.' 



2 See Sir Archibald Geikie's ' Ancient Volcanoes of Great Britain ' vol. ii 

 (1897) chap. 3d. 



