VOLCANOES 413 



of the poisonous ones carry death to the regions over which they 

 pass. 



Volcanoes are dangerous and destructive. Mt. Vesuvius, 

 Italy, in one eruption threw out enough cinders and ashes to 

 bury the city of Pompeii completely. So great was the dis- 

 charge of the volcano that the city was covered by a 2O-foot blan- 

 ket of cinders and ashes, and was completely lost to view. 

 Not until centuries later was the volcanic mass dug away, and 

 the ruined city brought to light. Volcanoes are not con- 

 stantly active; sometimes they are quiet for years, or throw 



Detroit Photographic Co. 



FIG. 280. Mt. Shasta. These mountains were once active volcanoes. 



out so little matter that they cause no real damage. Mt. Vesu- 

 vius has periods of rest and quiet eruption followed by periods 

 of violent action. One of the worst eruptions of Mt. Vesuvius 

 was in April, 1906, when thousands of people were destroyed by 

 the hot matter which was thrown out over the country. 



Until 1914 the United States was thought to be free of active 

 volcanoes because, since the white man had known America, no 

 volcanic outbursts had taken place. But in 1914, Mt. Lassen 

 in California began erupting, and since that time has continued 

 to erupt at frequent intervals (Fig. 279). The eruption which 

 took place on March 21, 1915, was the eighty-third eruption 



