Hawaiian Ferruginous Laterite Crusts — SHERMAN 
317 
TABLE 1 
The Chemical Composition of a Typical Ferruginous Laterite Profile. This Profile is 
Located off the Kokee Road on Kauai 
HORIZON 
SiOo 
ALA, 
Fe 2 0 3 
Ti0 2 
inch el 
per cent 
per cent 
per cent 
per cent 
Surface 
0-3 
10.8 
10.7 
38.2 
19.4 
Ferruginous Crust 
3-11 
3.8 
9.9 
47.5 
25.1 
Friable Layer 
11-27 
5.5 
7.6 
78.5 
7.2 
Plastic Clay 
27~jj 
22.8 
21.7 
35.4 
3.3 
of the impervious horizon is very different 
from that of the other two horizons. The 
higher content of both silica and alumina in- 
dicates the presence of alumino-silicate clay 
minerals. 
Island of Molokai 
The hard, compacted, ferruginous laterite 
crusts are found on the westerly slopes of the 
mountain range. The areas of this soil are 
found in the zone of the open forest, just 
below the heavier canopy forest of the wet- 
ter, higher elevations. These areas are easy 
to observe because of their distinct purple 
color and shiny glazed surfaces. The hard 
surface layers of these laterite crusts are 
harder and more compacted than are those 
found on Kauai. The areas of this soil are 
limited to a very narrow belt on Molokai, 
whereas the laterite crusts are found over a 
much wider area on Kauai. The hard surface 
crust of these soils is very similar to those 
found on Kauai. The chief profile difference 
occurs in the friable layer. The friable layer 
below the hard surface horizon of the Molo- 
kai laterite crusts is very thin, ranging from 
4 to 8 inches. In every observed instance the 
friable layer lies over a solid rock formation. 
The physical and chemical compositions 
of the Molokai laterite crusts are very similar 
to those of the Kauai laterite crusts. The iron 
oxide content of the surface ranges from 48 
to 65 per cent and the titanium oxide from 
20 to 24 per cent. Likewise, the volatile mat- 
ter ranges from 3.2 to 4.2 per cent. The iron 
oxide content of the friable layer ranges from 
70 to 7 6 per cent. 
West Maui 
The ferruginous laterite crusts of West 
Maui occur as erosion remnants on the white 
trachyte cliffs. These areas are easily seen 
from an airplane. From the highway these 
areas can be seen as red caps on top of the 
grayish-white ridges running up the moun- 
tain slope. These areas are so badly eroded 
that in only a few locations does the profile 
remain intact. In one case the hard surface 
crust has slid away from its friable layer 
and the two now exist as separate erosion 
remnants. 
The hard surface horizon is a compacted, 
reddish silt loam having a high apparent spe- 
cific gravity but lower than that found for 
Kauai and Molokai laterite crusts. The sur- 
face of these crusts is hard but does not have 
the shiny glazed surface of the two other 
areas. The clay content of this horizon is 
higher, being more than 35 per cent. 
The friable layer of these soils has all the 
characteristics of the Kauai profile. It is very 
ferruginous and has a clay content exceeding 
65 per cent. The thickness of the friable 
layer has been found to range from 12 to 30 
inches. 
