THE EARTH AS IT IS. 85 



Thus the Rocky Mountains are higher than the range of 

 mountains which run down from Maine to Georgia, 

 called by the general name of the Appalachian range. 

 So also, as the Pacific Ocean is broader opposite to 

 South America than opposite North America, the Andes 

 are much higher than the Rocky Mountains. The same 

 plan, essentially, is carried out in Africa, Australia, and 

 also in Europe and Asia, though not in so clear and sim- 

 ple a manner. 



There is much variation in the arrangement of differ- 

 ent ranges of mountains. They are more commonly 

 curved than straight, and the manner in which the indi- 

 vidual mountains stand toward each other is very differ- 

 ent in different cases. 



There are certain prevalent directions of the chains of 

 mountains, and the same is true of groups of islands, 

 which are often really the summits of submerged mount- 

 ain ranges. In the Pacific Ocean they have usually a 

 northwesterly direction, or trend, as it is termed. 



163. Volcanoes. Some mountains throw out occasion- 

 ally from their summits large quantities of liquid lava 

 and matter in gaseous form ; often also solid rocks, ash- 

 es, mud, etc. The exhibitions made in these eruptions 

 are among the most magnificent in nature. About two 

 thirds of the volcanoes are on islands, and the greater 

 part of the other third are near the ocean on the conti- 

 nents. This nearness to water is supposed to show that 

 steam must have much to do with the eruptions, which 

 also seems to be proved by the fact that in these erup- 

 tions great quantities of steam escape. In Fig. 32 (p. 86), 

 in which the shaded parts indicate the localities of vol- 

 canoes, not only is their vicinity to the ocean shown, but 

 the fact that, like ordinary mountains, they are very often 

 arranged in ranges. 



164. Plateaus and Lowlands. Any extended region, 

 whether it be flat or diversified, if it be much elevated 

 above the level of the sea, is called a plateau, while the 



