CHAPTER VIII 

 CRUSTAL MOVEMENTS 



Though the crust of the earth seems to be firm and stable, it 

 is in reality subject to frequent movements. Earthquakes are 

 of rather common occurrence, and there is abundant evidence that 

 other movements, too slow to be seen or felt, are going on all the 

 time. Some of the proofs that such changes have taken place in 

 recent times are the following: 



Relative rise of coast lands. 1. Along some coasts, old docks 

 near sea-level when they were built, are found many feet above it 

 on dry land. This is the case, for example, at the west end of the 

 island of Crete, in the Mediterranean Sea. Clearly the sea has 

 sunk, or the land has risen, since the docks were built. 



2. In the Baltic Sea there are rocks now above the water which 

 within historic time were beneath the sea, though so near its surface 

 as to be dangerous to navigation. The bottom of the shallow sea 

 has risen, or the surface of the water has become lower. 



3. Some animals in the sea attach themselves to the cliffs at 

 sea-level or below it. Their shells or other hard parts sometimes 

 remain long after the animals are dead. Among the animals which 

 have this habit are barnacles, and their shells are sometimes found 

 many feet above the surface of the water, attached to the rocks 

 where they grew. They show that the land has risen relative to 

 the sea since the animals lived. 



The shells of marine animals are also sometimes found above 

 sea-level, in sand, gravel, etc. Where such shells are in sediment 

 which was deposited beneath the sea-water, they show that the 

 sea bottom has become land since the animals lived. 



Beds of sediment containing sea shells, certainly deposited be- 

 neath the sea in recent times, are now found above the water in 

 many places, as in North Greenland, on the Pacific coast of the 



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