VOLCANOES. 



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1. Lnva-cones. — Lavas, when quite liquid, flow off naturally at a 

 small angle — usually between three and eight degrees. The great 

 volcanoes of Hawaii, Mount Loa and Mount Kea, shown in the map 

 (Fig. 1111), and sections of which are given in Figure 1110, are 



Fig. 1111. 



a\rale 



Map of part of Hawaii. 



mainly lava -cones ; and the general slope is six to eight degrees. 

 ./Etna has a similar low inclination. A horizontal section of Mount 

 Loa, 1,800 feet below its top, would be nearly twenty miles broad. 



In true lava-cones, like Mount Loa, the crater is generally a pit- 

 crater, — a great depressed area in the surface of the mountain, like a 



Fig. 1112. 



Crater of Kilauea, in 1840 : a, large boiling lake of lava ; at o and near e, sulphur-banks ; r, an 

 adjoining small crater : p, neck between Kilauea and the crater r. 



pit or quarry-hole in a plain, as in the summit-crater of Mount Loa 

 and in Kilauea, the latter 4,000 feet above the sea. A larger bird's-eye 



