Soil Sequences in Hawaii — Sherman and Ikawa 
459 
hand, there is a wide range of annual rainfall — 
from 5 to over 500 inches per year, the heaviest 
occurring at the higher elevations of 2,000 to 
4,500 feet. The distribution of rainfall varies 
from strongly seasonal in some areas to rather 
uniform distribution in others. The variable rain- 
fall results in widely different types of vegeta- 
tion — shrub, open forest, and rain forest. These 
vegetation types range from a high base circulat- 
ing system in low rainfall areas to a very acidic 
system of the fern forests of the tropical rain 
forest areas. 
The islands have developed as peaks of a 
mountain built up by volcanic action on the 
ocean floor. Progressive lava flows of basalt, 
andesite, and trachyte and their pyroclastic 
deposition of volcanic ash and cinders have built 
up a series of islands ranging in geological age 
from several million years to current depositions 
of lava. The oldest island is Kauai at the north- 
western end of the island chain, and the most 
recent is Hawaii at the southeastern end of the 
chain. The range of geological ages represented 
by the different islands affords excellent facilities 
for a study of age on soil development on rela- 
tively similar parent rocks having a low quartz 
content. The mountainous character of the 
islands provides a great variety of drainage con- 
ditions. Thus, soil sequences are developed 
which reflect the effect of age, rainfall, drainage 
or percolating water patterns, and parent ma- 
terial. 
SOIL SEQUENCE RELATED TO RAINFALL 
Tanada (1951) pointed out the relationship 
between rainfall and kaolin content of soils of 
the Hawaiian Islands. According to his results, 
it was concluded that where the rainfall was 
more than 30 inches per year, the kaolin content 
of the soil decreased with increasing annual 
rainfall. Cline et al. (1955) and Sherman 
(1949) have reported a sequence of soil devel- 
opment which was related to both the amount 
of annual rainfall and its monthly distribution. 
The former, in an indirect manner, described 
and classified soils by the association of increas- 
ing content of free oxides to increasing rainfall. 
Sherman (1949), having the benefit of a 
broader knowledge of chemical composition, 
was able to make more specific conclusions as 
to the type of oxides which would be concen- 
trated in the soil solum with the varying dis- 
tribution patterns of rainfall. He found that the 
soils developed under a climate having alternat- 
ing wet and dry seasons would show an increas- 
ing content of iron and titanium oxides and a 
corresponding loss of kaolin with increasing 
rainfall. Aluminum oxide would increase in the 
soils formed under a rainfall distribution which 
resulted in continuous moist conditions in the 
soil solum, and again with a loss of kaolin. In 
subsequent work, Sherman (1952) showed that 
these relationships would hold only under con- 
ditions of free internal drainage. If the internal 
drainage became restricted, resilication or kao- 
linization would occur in the soil. The data 
given in Table 1 show the mineral composition 
of a sequence of soils formed on a single basalt 
lava flow. As annual rainfall increases, the kaolin 
content decreases as long as the internal drain- 
age of the soil is good. The Koolau soils, which 
have poor internal drainage, have a high con- 
tent of kaolin. As rainfall increases, gibbsite in- 
creases in this soil sequence as long as internal 
drainage of the soils is good; again, this is 
shown by the Koolau soils. 
A sequence of soils will develop under very 
low rainfall conditions which do not provide 
sufficient leaching for the removal of the bases. 
Under these conditions, the content of the mont- 
morillonite type of clay minerals will increase 
with rainfall up to a point where the base re- 
moval has been sufficient to produce an acid 
condition resulting in an instabilty of the 2:1 
layered alumino-silicate crystal lattice structures. 
At this point, kaolinization will be initiated. 
From this point, the kaolin content will continue 
to increase until base removal in the leaching 
nears completion, creating a very acid condition 
in which kaolin becomes unstable and decom- 
poses, and further desiccation occurs. This will 
lead to the formation of free oxides. A sequence 
of soils having an increasing content of mont- 
morillonite minerals has not been observed in 
the Hawaiian Islands. Soils developed on vol- 
canic ash under an annual rainfall between 2 
and 20 inches will probably show this condition. 
Our preliminary examination would support 
this possible relationship. A sequence of soils 
showing increasing kaolin content has been 
found in the soils of the Low Humic Latosols 
