HOT SPRINGS AND GEYSERS 



415 



In time all volcanoes cease to be active. Lava ceases to flow. 

 The crater fills up and the destructive volcano becomes a harm- 

 less mountain. Many extinct or inactive volcanoes exist in 

 the United States; Mt. Hood, Mt. Shasta (Fig. 280), and Mt. 

 Rainier were at one time active volcanoes. To-day they are 

 among the most beautiful of our mountains. So high are these 

 one-time volcanoes that the snow and ice never disappear 

 from their summits. On their lower slopes rich forests thrive 

 and beautiful flowers grow in abundance. 



The lava and rock fragments thrown out from an active vol- 

 cano may spread many miles from the vent and build up land. 

 Very often a volcano has more 

 than one crater, and lava fre- 

 quently streams forth (Fig. 281) 

 through weak places along the 

 sides of the volcano as well as 

 from the crater. Volcanoes, 

 because of the matter which 

 they erupt, have an important 

 effect on a region. They build 

 up mountain slopes, or they 

 raise the general level of the 

 land on which their erupted 

 matter falls. As a result of 

 volcanoes in the Pacific Ocean, 

 several new islands have been 

 formed in recent years. 



Hot springs and geysers. 

 The surface of the earth is cold, 

 but its interior is hot. Men 

 cannot work in the deep mines 

 unless cold air is pumped down to lessen the heat. Hot water 

 bubbles out of the ground in various places, showing that it has 



FIG. 



282. A geyser in Yellowstone 

 Park. 



