LYONS ON LIFE HISTORY OF A VOLCANIC ISLAND. 93 



Loa, the lat(M- la\a lldws having coiisisicd of less tliiid maii'iial. Tlio 

 picvailiiiji color of the lava is icd i-atlici' llian black. I'aiioclioci is 

 rarely if cvim- iiicl with, lis uialcrial. Jiidjicd by what apjtcars at the 

 surface consists of loose fra^^iiieiil s. ( )f course the tlec-jicr strnctiire is 

 tlie same as in .Manna Loa — made np of snccessive siieets of lava live 

 to twenty feel or more in thickness, intercalated w'itli the fra^meutary 

 material from cxphtsive ernptions, and traversed b,\' dykes i-e])resent- 

 inji tissnres thronuh which the lava has reached the snrface. 



Manna Kea, like .Manna Loa, has its rain belt, the mass of the moun- 

 tain s(M'vinji' as a condenser for the moisture of tlie trade winds, but 

 in this case we find the windward slopes of the cone scored deeply in 

 Iheir lower reaches with ravines, carryinji' to the sea after every rain 

 roariiiii torrents. The mountain is so higli that heavy i)r(M-i]»itation 

 extends only about half way to the summit. Aecordinjily the upper 

 part of the mounlain shows as yet only shallow water courses, these 

 beiny- dry c^xcepl immediately after rain or during- a thaw at the 

 mountain summit in winter. 



The slope of Manna J>oa is continued in most ]>laces quite to the sea 

 h^vel. Where this is not the case, it is not because the sea has en- 

 croached on tlie base of the mountain. This, however, is on the leeward 

 side of the island, where the coast is not subject to violent attack 

 by the waves of the ocean. Manna Kea, on the other hand, is w^ashed 

 at its base by a sea whose majestic swells roll in with an impetus 

 j^ained under the incessant lashing of the norflieast trade winds over a 

 course of a thousand miles or more. That such an expenditure of 

 energy should produce striking;- effects might be. easily enough pre- 

 dicted, and yet wdien one sees the base of this new^ mountain eaten 

 into ajtparently fully half a mile, the blue ocean dashing against the 

 base of cliffs three or four hundred feet high, one is apt to be a little 

 staggered in the belief that even such a force could be adequate to 

 bring about such a result in so brief a time. We must remember, how- 

 ever, that this action must have begun while the mountain was still 

 an active volcano — must have been in ])rogress, indeed, from the day 

 there was a mountain or an island at all, that it must have been over 

 precipices like these that in ages past the lava Hoods poured themselves 

 while the mountain was growing most rapidly. It is therefore not 

 true that these escar])ments re|)resent the actual removal of a corre- 

 sponding portion of the mountain's base. 



So too the scoring of ravines in the sides of the mountain probably be- 

 gan long before volcanic activity w'holly ceased. In one case, indeed, we 

 find the bed of one of the deepest of the ravines occu])ied with the lava 

 of a recent How. One would say that this particular lava flow prob- 

 ablv occurred less than a thousand vears ago, and mav be considerablv 

 more recent even than that, but it would be safe also to venture the 

 opinion that there have been few if any great lava flows from Manna 

 Kea within the last ten thousand years. 



Hawaii has yet another volcanic cone, so ancient that the precipices 

 on its windward exposure are 1,000 to 1,500 feet high, and yet a "young" 

 mountain, its features still tracealde more to the volcanic agencies 

 which formed it than to the shaping of weather and storm. Molokai and 

 West Maui show us volcanoes so changed by erosive agencies that one 



