422 Prof. NordensJcioId — Ex2)edUion to Greenland. 



rocks, and accordingly newer than these latter. Also the fossils in 

 these beds belong to the Tertiary Period. It follows then, that the 

 eruptions, which have given rise to these vast beds of hasalt, have taken 

 place subsequently to the commencement of the Cretaceous, and have 

 censed before the termination of the Tertiary Period. 



In the preceding pages I have intentionally spoken of basalt strata 

 and schists. In almost every place where I have had the oppor- 

 tunity of examining it, the Greenland basalt is so stratified that one 

 is forced to admit, that it is only exceptionally that we have to do 

 with consolidated masses of lava, but for the most part with eruptive 

 sedimentary beds of volcanic ashes and volcanic sand, which in the 

 course of thousands of years have become hard again and assumed a 

 crystalline structure. 



Any clearly decided lava- streams I have scarce had occasion to 

 observe, even larger or smaller dykes are not so common as one 

 might expect, and where they are found the mass of lava ejected has 

 scarcely produced any effect upon the loose beds of sand, clay, or 

 basalt that it has pierced. 



No volcanoes, either extinct or active, are met with in these parts, 

 although circular depressions in the basalt plateau, caused by glaciers 

 or brooks, may, when carelessly observed, easily be mistaken for 

 true craters. It is, of course, quite natural that great cavities in the 

 interior of the earth must arise in the places whence the great 

 eruptions have issued, which have produced the basalt region of 

 Greenland, and that these in their turn must, within a short period, 

 be followed by the destruction of the superjacent volcanic cone. 

 The place or places where these old volcanoes once rose high over 

 the surrounding plains will therefore now most probably correspond 

 to the greatest depths in the neighbouring sea. 



At Godhavn the lowest strata resting immediately upon the gneiss 

 formation {e.g. outside Blasedalen) consist of a basalt tuff or breccia 

 containing various species of zeolites (according to Giesecke, only 

 apophyllite) , next comes columnar basalt, free from zeolites, then 

 again basalt tuff with zeolites, alternating with true basalt. A coarse 

 crystalline dolerite, very similar to the Spitzbergen hyperite, forms 

 at Atanekerdluk, near the shore, a hill several thousand feet high. 



The basalt beds are 50 to 100 feet thick, and may be traced for 

 miles along the shores, often separated from' each other by thin 

 layers of red basaltic clay. Sometimes the layers are crossed by 

 dykes of a hard, fine-grained basalt. 



Not only dykes, but also basalt beds have, on the cooling of the 

 melted mass, or during the drying and crystallizing process which 

 the volcanic ashes have undergone in their transformation to basalt, 

 been broken into regular columns, mostly hexagonal. Brannvin- 

 shamn, Skarffjall, Kudliset, and other places on Disko and the 

 peninsula of Noursoak, afford examples of this kind of basaltic 

 structure, comparable in magnificence with Staffa and other geo- 

 logically famous European localities. 



Volcanic eruptions, as has been above remarked, no longer occur 

 in this region. Yet, in consequence of the rapidity with which 



