GEOLOGY AND SCENERY OF NORTHEAST COAST 99 
of feet. It is, indeed, possible that their fissures reached 
quite to the surface and built volcanic cones and lava 
plains long since destroyed. That inference is supported 
by the discovery on the Labrador of just such volcanic 
accumulations, although these have not yet been suffi- 
ciently studied to show actual connection between the 
lavas and the dikes of trap. That the latter were thrust 
into the fissures of the mountain-core with enough energy 
to force the molten rock to the surface is implied in the 
conditions of Figure 14. 
Striped Island gets its name from a remarkable group of 
thin, nearly horizontal sheets of black trap cutting common 
gray gneiss. The causes of the intrusion here may have 
differed from what they were in the case of the vertical 
dikes, which, as we have seen, entered the base of the moun- 
tain-range by a kind of permission; great mountain blocks 
moved apart and permitted the plastic trap to enter the 
opening fissure. But the sheets of Striped Island, as they 
forced their way into place, had apparently to lift a rock- 
cover weighing countless millions of tons. Their intrusion 
began along so-called “‘joints’’; that is, microscopic though 
continuous cracks previously developed in the gneiss. 
The imagination may well be staggered in the attempt 
to grasp the magnitude of a force which could so thrust 
fluid rock into almost infinitesimal cracks, wedging up a 
whole mountain in the process as if a Titan had worked 
with an omnipotent jack-screw; yet there seems to be no 
escape from the conclusion that such a wonderful display 
of power in the molten under-earth has taken place. 
In summary, then, the different formations composing 
the Basement Complex of Labrador, though understood 
