490 C. H. HITCHCOCK MOHOKEA CALDERA 



Thirdly, all the segments of the crust fall into the reservoir beneath; 

 vertical walls encircle a pit. This is the stage of Kilauea and Mokua- 

 weoweo. 



Fourthly, the caldera with encircling walls is formed, but the lower 

 walls give way. Great rivers of lava now to the sea. As the fires die 

 down several small craters are developed on the principal floor. This is 

 Haleakala. 



Fifthly, the eruptions of the smaller craters like Halemaumau multiply 

 and the whole pit is filled. The caldera is smothered, the smaller craters 

 continue to be developed until the internal reservoir is exhausted. This 

 is the Mauna Kea stage. 



I could count twenty-four craters of small size visible from its summit, 

 and the government map delineates between 75 and 80 of these cinder 

 cones above the contour of 6,500 feet. Most of them represent the latest 

 stages of the volcanic life of Mauna Kea and not improbably the filling 

 of a now concealed caldera. 



Volcanic Ash of Hawaii and its Source 



The district of Kau between Puna and Kona is proverbially dusty. 

 The floor is of modern lava, covered over an area of 300 square miles with 

 a light yellowish dust. Mountain torrents have washed away some of it, 

 revealing basalts just beginning to disintegrate; that which remains is 

 very loose, easily moved by- wind or water. In the older days the natives 

 enjoyed jumping from a high bank into the dust, just as they might leap 

 from a bluff into the water. Of course this material is badly cut down 

 by teams along the roads. It is utilized for the growth of sugarcane 

 everywhere that plantations exist on the west side of Kilauea. These 

 soils are free from rocks and are very deep, so that a crowbar or cane 

 may be readily thrust down its whole length, just as would be true of 

 large piles of wood ashes in a dry country. Neither is there anything 

 adhesive in this dust when wet. No part of it adheres to one's shoes 

 when walking over it in time of rain. 



These soils suffer badly from drought. Extensive fields will be 

 parched and clouds of dust will be very annoying, even imparting a red- 

 dish yellow tint to the sky. When the rain comes in torrents much dam- 

 age will be done to the land by the cutting of trenches and the trans- 

 portation of earth. The dry and wet periods are registered in the varied 

 and irregular length and diameter of the joints of the sugarcane stalks. 

 In the season of drought much pains are taken to prevent the starting 

 of fire in the grass, as it spreads long distances beneath the surface, be- 



