MOUNTAIN FORMATION 



Moreover, if we suppose that after a time the water again 

 penetrates, and again comes into contact with rocks that 

 have again become heated up, there will be another 

 explosion, and yet others. Each of these explosions will 

 push along the ejected streams of lava, step by step, 

 till they reach the land, and even till they reach the 

 mountains bordering the sea. The forces thus arising 

 would cause upheavals, even if they did not cause earth- 

 quakes. Such forces might bend strata, contort the 

 rocks, and cause " faults." 



But why, the reader may ask, do you suppose that all 

 these explosions of lava are directed to the land ? We do 

 not suppose that they are. The lava may be forced away 

 from the land. Then if that occurs a ridge may be 

 upheaved, or possibly a submarine volcano. 



"At the Hawaii Islands on 25th February, 1877," 

 writes Sir Archibald Geikie, " masses of pumice during a 

 submarine volcanic explosion were ejected to the surface, 

 one of which struck the bottom of the boat with con- 

 siderable violence and then floated. At the same time, 

 when we reflect to what a considerable extent the bottom 

 of the great ocean basin is dotted over with volcanic 

 cones, rising often solitary from profound depths, we can 

 understand how large a proportion of the actual eruptions 

 may take place under the sea. The foundations of these 

 volcanic islands doubtless consist of submarine lavas and 

 fragmentary materials, which in each case continue to 

 accumulate to a height of two or three miles, till the pile 

 reaches the surface of the water and appears above it. 

 The immense abundance and wide diffusion of volcanic 



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