488 C. H. HITCHCOCK MOHOKEA CALDERA 



which the first is Makawao, estimated to exceed 3,500 feet in height. It 

 is hardly separated from Pakua, which is not represented on figure , a 

 map of this district copied from the government map of Hawaii, 1901. 

 A broader notch separates Pakua from Kaiholena, 3,824 feet high. 

 There are five blocks in this row, into the last of which a tunnel has been 

 driven two hundred feet in quest of water for irrigation. The east side 

 of this line of blocks is quite precipitous, representing the place of a 

 fault. Both the lines of blocks have been elevated, as indicated on the 

 map, their altitudes being greater than that of the adjacent territory. 

 The lowland between the elevated blocks and the east side rises gradually 

 to the steep wall behind, toward Puu iki. The land is not cultivated for 

 most of the distance, and is covered by the original forest of tree-ferns, 

 ohias, and other hardwood trees, similar to those seen on the volcano 

 road in Olaa. On the west side of Pakua may be seen the bed of a moun- 

 tain torrent, usually dry, but often too full of water to be safely forded. 

 This skirts the eastern border of another lowland area like those already 

 mentioned, save that it is cultivated and used for pasturage. It is over 

 a mile wide and has a floor of fresh looking pahoehoe, sloping gradually 

 to the edge of the frontal escarpment, about 1,200 feet high. Eruptions 

 of aa have proceeded from this edge along the whole width of the caldera. 

 The Enuke and Kaiholena ridges are higher than the slopes of the 

 Mauna Loa basalt opposite them,, of which it is supposed they once formed 

 a part. Hence the lowland depressions can not be regarded as the results 

 of canyon erosion; they probably were depressed, while the blocks were 

 elevated. Following the definition of the caldera, it may be said that 

 portions of the mountain crust were dropped, while other sections were 

 elevated. Its development was arrested. The making of the caldera 

 was incomplete. Possibly the great size of Mohokea, comprising 30 

 square miles, while Haleakala is only 19, may have militated against the 

 thorough fusing of the entire bulk. 



Mohokea compared with Haleakala 



For a further understanding of a caldera, reference should be made to 

 Haleakala on Maui. This pit has an area of 19 square miles and the 

 shape of an elbow. It is 4 miles across from the outer to the inner angle. 

 The greatest length, toward (east) Kaupo, is 7.48 miles. Toward 

 Koolau (north) the distance is 6 miles. The greatest width is 2.37 

 miles. The depression is 2,000 feet deep, with many small craters in- 

 side — up to 760 feet in altitude — so it is a true caldera. The north arm 

 is called Koolau gap ; the east arm is called Kaupo gap. There is a grad- 



