28 



ELEMENTARY SCIENCE 



and heavy rains are frequent, and rock and soil are loose, 

 erosion is rapid. Where the land is level and well covered 

 with plants, erosion is very slow (see Fig. 4). But slow 

 or fast, the result is the same. The land is being worn 

 down to the sea. As long as there is a bit of soil or rock 

 that stands even one foot above sea-level, wind and water 



will attack it. They 

 will work at it till they 

 wear it down (see Figs. 

 5 and 6). 



The Rise of the Land. 

 -"But," you ask, "if 

 all this is true, why 

 have we any hills and 

 mountains left? Why 

 is not the whole surface 

 of the land worn down 

 nearly to sea-level?" 



If you have ever felt 

 an earthquake or seen a volcano you can probably guess 

 the answer. Earthquakes and volcanoes show us that in- 

 side the earth great forces exist. These forces are strong 

 enough to lift islands out of the sea, or gradually to raise 

 up whole ranges of mountains. They have done this in 

 the past, and in some places they are still doing it to-day. 

 Great though gentle movements of the land seem to be 

 going on all the time. 



Some hundreds of years ago an invading army landed on 

 the east coast of England. The town at which it landed 

 is now miles inland, so much has the land risen since that 

 time. There are many such places in the world. Also 



FIG. 5. Diagram showing how running water 

 cuts into the land and washes it away, until 

 it is finally lowered almost to sea-level. 



