214' G. M. Daivson — Geology of British Columbia. 



of an immense mass of the lava deposits in the crater, five miles in 

 circumference and of miknown thickness, which it is believed was 

 torn from its bed by an explosion which took place — presumablj'^ in 

 the volcanic vent beneath Aslcj'a — on the 4th January, 1875. This 

 explosion caused an earthquake which opened rifts forty miles in 

 length in the plains north of the Dyngjufjoll, and it was from fissures 

 in a tract twenty miles in length and about three in breadth which 

 sank to some depth between two of these rifts that the lava welled 

 forth ; pumice and ashes being alone ejected from Aslcja. 



The site of the subsidence in Aslcja is now the bed of a tepid lake 

 of considerable depth; the temperature of its water in 1878 was 

 97° Fahr. 



The presence of this immense body of water within the crater of 

 an active volcano is a most alarming feature ; a comparatively slight 

 eruption might be accomjjanied by an explosion that would further 

 disturb the lava floor of Aslcja, which appears to be but a roof to an 

 abyss in which molten matter, it is reasonable to believe, lies at no 

 great depth, the contents of the lake would find its way below when 

 a terribly violent eruption must inevitably ensue, one that will be 

 likely to cause an earthquake to which that in 1875 will be com- 

 paratively insignificant, and likewise to affect the volcanic repose of 

 Europe, by forcing back, by the violence of the concussion, the 

 molten tide lying in the channel or channels, connected with the 

 Earth's interior, underlying Europe; there being reason to believe 

 that such do exist connected with the Icelandic volcanic vents, 

 the great European earthquakes and volcanic disturbances having 

 been either followed or preceded by terrific eruptions in Iceland, 

 e.g. the earthquakes that destroyed Lisbon in 1755 were preceded 

 by the commencement of a series of terrible eruptions from the 

 Kotlugjd, which lasted a year ; while thirty-two years later the Upper 

 Calabrian earthquakes were followed by the outburst of prodigious 

 lava-floods in the vicinity of the SkaptdrjoJcull. 



There are two strangely contradictory statements in Herra 

 Thoroddsen's paper, with refei'ence to the STcaptdrjolcidl, " where," 

 he says, page 465, "an eruption has never yet occurred," but on 

 page 463 he credits the jolcull under its other name of SvSujolcull 

 with an eruption in the year 1389-90, and also with an eruption 

 in its vicinity in 1753. Upon all the maps of Iceland that I have 

 seen the jolcull is named " Skaptdr e^a (or) Si^ujolcull." 



VII. — Sketch of the Oeology op British Columbia. 



By George M. Dawson, D.S., A.R.S.M., F.G.S. 



(Concluded from page 162.) 



Cretaceous. — Lying everywhere quite unconformably below the 



Tertiary beds are the Cretaceous rocks, which constitute on the 



coast the true Coal-bearing horizon of British Columbia. These 



rocks probably at one time spread much more widely along the 



coast than they now do, but have since been folded and disturbed 



during the continuation of the process of mountain elevation, and 



