DISCOVERY 



271 



hundred yards, then the gradient rapidly rose up the 

 face of a mountain. Deep ravines laid bare a succes- 

 sion of sedimentary strata i,ooo feet or more in thick- 

 ness, over which had been piled layer after layer of 

 lava-flows and beds of volcanic ash. The widely spread 

 sheets of basalt (in some places as many as thirty 

 superposed la%-ers), which give a terraced appearance 

 to the weathered face of the cliffs like that of the 

 rocks of Mull and other islands off the west coast of 

 Scotland, are proof of long-continued volcanic activity 

 on a stupendous scale. The photograph (Fig. 2). 

 taken near the Arctic Station on Disko Island after a 

 recent fall of snow, shows very clearly the layers of 

 lava and ash above the talus slopes.^ The darker rocks 

 in the foreground belong to the much more ancient 

 crystalline series which forms the greater part of 

 Greenland. Another expression of volcanic phenomena 

 is seen in the numerous dykes which frequently cut 

 across the beds of sandstone and shale. A dyke con- 

 sists of some igneous rock, often basalt, that has 

 been forced from below through cracks and fissures 

 in the overlying strata. The softer rocks fall an 

 easier prev to the action of the weather than the 

 harder and more compact dj-kes, which are left as 

 great ribs or dark-brown buttresses projecting on a 

 light-yellow background of less resistant material. 

 Part of a dyke of dark-brown basalt is seen at close 

 quarters in Fig. i ; it resembles a partially ruined 

 wall on a wind-worn denuded field of sand, the result 

 of disintegration of beds of soft sandstone. Here and 

 there adhering to the sides of the dyke are blocks of 

 sandstone which were hardened and rendered more 

 resistant to denuding agents by contact with the 

 molten rock which welled up against their fissured 

 sides. 



From the beds of shale exposed in the cliffs on the 

 south coast of Upernivik Island (lat. 71^ N.) above 

 the beach, littered with boulders, several impressions 

 of fossil plants were collected, including pieces of the 

 large fronds of a Cycad, a plant related to the so-called 

 Sago Palms, the majoritj- of which flourish in the 

 Tropics. An almost vertical dyke thrust through the 

 old sediments forms a prominent feature on the left 

 (Fig. 3). The two massive mountains in the distance 

 are portions of the highlands, bordering the western 

 edge of the Umanak fjord, composed of some of the 

 oldest rocks in Greenland. One of the most striking 

 mountains in Greenland, recalling in shape the Matter- 

 horn, rises almost sheer from the sea as a wall of igneous 

 rock nearly 4,000 feet in height on the small island of 

 Umanak off the north coast of the Nugssuaq peninsula. 

 The salmon-pink mass is cut across halfway up the 

 precipice by a thin black band bent on itself like an 



^ I.e. the sloping mass of fragmentarj' stones often found at 

 the foot of cliffs or rocky declivities. 



S lying on its side, an eloquent witness to the intensity 

 of the forces which folded and crumpled the rocks 

 of which the Umanak mountain remains as a detached 

 and magnificent bastion that in the course of ages has 

 been fashioned into its present form. Near the base 

 of the cliff is the settlement of Umanak with the 

 native huts and timber houses built on the small 

 level patches among the rounded hummocky rocks 

 which form a massive plinth to this pyramid that 

 dominates the island. 



One of the best localities in West Greenland for fossil 

 plants is Atanikerdluk, an uninhabited part of the 

 south coast of the Nugssuaq peninsula. The main 

 ravine is not only of special interest geologically ; 

 it also affords a most remarkable display of dykes, and 

 illustrates on a grand scale the relation between 

 scenery and rock structure. A stream flows among 

 jumbled heaps of boulders at the bottom of a steeply 

 inclined valley ; the valley slopes consist of natural 

 embankments of loose light-yellow sand mixed with 

 milk-white rounded pebbles of quartz detritus formed 

 by the erosion of the sandstones, which are here the 

 dominant rocks. In places the talus slopes are 

 replaced by exposures of the rocks themselves, thick 

 beds of sandstone with no division into layers, thinner 

 well-stratified beds, bands of shale, and an occasional 

 seam of coal. These sedimentary strata, having a 

 total thickness of many hundred feet, exhibit here and 

 there on an exposed plane of bedding a series of ripple- 

 marks and aftord other evidence of their origin as 

 sheets of sand and mud in shallow water and among 

 drifting currents. Many of the sandstones are made 



FIG. 3.— THE 1 : I'.IK ISLAND 



On the left an obliquely vertical a> ke ol bas.llt tbehiml the large bouUler 

 in the foreground) cuts across the sedimentary rocks ; the mountains on the 

 right are composed of older (Ardi.-ean) igneous rocks. 



up of thin layers, often rendered more conspicuous 

 by the presence of iron-stained bands, which exhibit 

 the well-known arrangement spoken of as current- 



