416 MOUNTAINS, EARTHQUAKES, VOLCANOES, GEYSERS 



passed through warm regions and been heated. The Hot 

 Springs of Arkansas and the geysers of Yellowstone Park tell 

 us very plainly that the earth's interior is hot. Volcanoes 

 with their molten lava and burning cinders tell the same story, 

 The most wonderful hot springs of the United States are in 

 Yellowstone Park. In some of these springs the water is boiling 

 hot, and is so abundant that it forms large ponds. The 

 geysers of Yellowstone Park (Fig. 282) are simply spouting 

 springs ; Old Faithful Geyser, for example, throws out hundreds 

 of barrels of water every hour to a height of 150 feet. But few 

 geysers erupt as regularly as Old Faithful. 



Earthquakes, volcanoes, and geysers are evidence that the 

 earth's interior is not at rest, but is constantly changing. The 

 forces at work within the earth and those at work on the surface 

 alter the character of the land and keep it from becoming a flat 

 monotonous plain. 



