VOLCANOES AND IGNEOUS INTRUSIONS 



30S 



This island was indeed not known to be a volcano, until in August of the above- 

 mentioned year it became violently explosive (Fig. 296) and in two days blew away 

 about one half of its surface, so that now the sea is 1000 feet deep where the central 

 part of the mountain formerly stood. The amount of ash ejected was so great that 

 the neighboring seas and land were in total darkness during the eruption. The ash 

 was thrown to a height of 17 miles, and remained in the air many months, causing 

 brilliant sunrises and sunsets throughout the world (p. 54). Ships 1600 miles away 

 were covered with dust three days after the eruption; stretches of water with an aver- 

 age depth of 117 feet were so filled with the debris as to be no longer navigable. The 



\ j 



Fig. 298. — A roof collapsed by the weight of ash from Katmai, Alaska, one hun- 

 dred miles distant. The drift in front of the porch is volcanic ash. (National 

 Geographic Magazine.) 



noise of the explosions was heard 2000 miles away, and the shock produced waves 50 

 to 80 feet high, which swept the adjacent shores, deluging 1295 villages and drowning 

 about 35,000 people. The height and strength of the waves is well shown in the fact 

 that a large vessel was carried one and one half miles inland and left stranded on land 

 30 feet above sea level, and that blocks of rock weighing 30 to 50 tons were carried 

 inland two or three miles. 



(3) Katmai. — The eruption of Katmai, a volcano in the Alaskan peninsula, in June, 

 1912, was one of considerable violence, but one which did little damage because of its 

 situation in an almost uninhabited region. As will be seen from the map (Fig. 297), 

 the fall of ash was 50 inches deep 30 miles from the volcano, and 6 inches deep 160 

 miles to the east of the mountain. So great was the amount of dust in the air that 



