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GEOLOGY DIAGRAM 20 



Lakes. When several springs unite, they form streams, which 

 in their turn unite to form a river, which flows to the sea where 

 the formation of the country permits it. But if this is not the 

 case, and the formation of the country opposes its course, the 

 waters accumulate, and form a lake or a pool. When the water 

 from rain or from a river is discharged into broad plains where 

 it can neither flow into the sea, nor accumulate to form a lake, 

 these plains become marshes and peat bogs. 



Banks and Cliffs. If rain water daily tends to remove pebbles 



from the mountains, 

 and to deposit gravel 

 in low lying plains, the 

 sea also plays a double 

 part on its banks. It 

 encroaches on the land 

 in some places, and is 



Cliffs. encroached upon by the 



land in others. This is especially noticeable at the mouths of 

 rivers. The earth and gravel carried down by the current after 

 rain gradually accumulates at the mouths of rivers and streams 

 and forms flats which advance further and further into the sea. 

 The sea in its turn throws up heaps of sand on some coasts, 

 while at other points it wears away its banks, and advances 

 into the land. When this is elevated a cliff is the result. 



Volcanoes. There are mountains in some countries with a 

 large hole in the summit called a crater, whence issue stones, 



Volcano in eruption, 

 dust, smoke, and flames. These mountains are called volcanoes. 



