338 ELEMENTARY GEOLOGY 
a depth of several hundred feet, or it may be only a 
tiny stream. Great lava flows occur in the Hawatian 
Islands, and in Iceland. In the former the course is 
frequently interrupted by the sea. 
In some parts of the world, there appear to have been great 
eruptions from fissures, without the accompanying formation of 
voleanic cones. In such places it seems as if the earth had 
cracked open, and lava had welled out from the fissure, overflow- 
Fie. 205. 
Mts. Shasta (on right) and Shastina, California. Two extinct volcanoes. 
ing the country with an immense flood of liquid rock. In the 
plateau of the Deccan in India, and in the Snake River valley of 
Idaho, this was apparently the case. In the former place, the 
area covered by lava is fully 200,000 miles, and its depth in some 
places 6000 feet. 
Nature of the Eruption. — The eruption of a volcano 
may take place from the crater, or it may begin from 
a fissure on the side of a cone, as is commonly the case 
