264 Mciiwirs Bcniicc P. Bisliof^ i\[usciini 



The habitable islands are of volcanic origin. /Vt present there are no signs 

 of volcanic activity and earthijuakes are nnknown, but on some islands old sea 

 caves now several meters above high water level suggest that ele\-ation still con- 

 tinues. The to})ography of all the large islands is similar, each having a high 

 central mountain chain from which sharp ridges, often ending in sheer cliffs, ex- 

 tend to the sea. With a few exceptions, the valleys are short and narrow. There 

 is no coastal shelf and many of the valleys are accessible only from the sea. Nuku 

 Hiva and tli\a Oa, the largest islands of the group, have so-called plateaus at 

 altitudes of from one to two thousand feet. These plateaus include some areas 

 of comparatively level ground, but are for the most part eroded into innumerable 

 small, steep side valleys, which render traverse difficult, even for a man on foot. 



The climate of the Marquesas is without extremes of heat or cold, the 

 mean annual temperature being between y^ and 80 degrees Fahrenheit. Hurri- 

 canes, the scourge of the Tuamotus, are rare, but ]}-ing north of the belt of sea- 

 sonal rains, the islands are visited by destructive droughts which have been 

 known to last three years. Even in favorable years the climate throughout most 

 of the group is dry rather than humid. There is a progressi^-e decrease in rainfall 

 from south to north ; Fatu Hiva, the southernmost island, is well watered but Ei 

 Ao, the northermost, is arid, 'i'he prevailing winds are easterly and the westerly 

 sides of the most of the islands are semi-arid, with few running streams. 



The marked differences in the vegetation on diff'erent islands and on dif- 

 ferent parts of the same island correspond to variations in rainfall. On Fatu 

 Hiva a dense growth of vegetation mantles the almost vertical sides of the moun- 

 tains and fills the valleys with thickets. East of the high mountain ridge on Hiva 

 Oa the valleys are choked with thick bush and the higher slopes are covered with 

 forests containing mrmv tree ferns. West of the ridge the tree ferns disappear com- 

 pletely, giA'ing ])lace to stunted guava scrul) and upland reed, and large areas are 

 covered with matted fern scarcely a foot high. Wherever a depression serves to 

 collect the moisture there are open groves of ])andanus or fan (tree hibiscus) 

 while the higher ridges are crowned with straggling clumps of casuarina. The 

 slopes of the deeper valleys are covered with a growth of large trees beneath 

 which is little or no undergrowth and only along the water courses, where the 

 fau grows in tangled masses, is there any a])proach to jungle. Were it not for 

 the occasional clumps of palms in the valleys the visitor might imagine himself in 

 the hills behind San Francisco rather than on an island within ten degrees of the 

 equator. Ei Ao, the northernmost island, has the least rain, and its bowl-like top 

 is covered with short grass and scattered groves of trees so open that a man on 

 horselxick could i^ass anywhere with ease. 



[4] 



