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PACIFIC SCIENCE, Vol. 1 , April, 1947 
the shore line on the right, or downthrown, 
side. The accompanying maps of the Wai- 
mea, Oahu, region (Fig. 2 and 5) show 
that the shore line has a general trend from 
northeast to southwest, but that the part 
northeast of the bay, if continued southwest- 
ward, would lie about two thirds of a mile 
seaward of the southwestern part of the 
shore line. A fault at Waimea would result 
in this sort of offsetting of the shore line. 
OFFSETTING OF RESTORED 
CONTOUR LINES 
The volcanic domes sketched in Figure 1 
have topographic contour lines drawn on 
them, and it will be noted that on the faulted 
Fig. 1. Diagram to explain offsetting of a shore 
line by a fault. 
dome the lower contour lines are offset like 
the shore line, but to a lesser distance. The 
shore line, of course, may be thought of as 
the contour line of zero altitude. If a fault 
cut the Waimea Bay region, we should be 
able to find traces of offsetting of some of 
the contour lines. 
Figure 2 was prepared by tracing as light 
lines the 500-, 1,000-, 1,500-, and 2,000-foot 
contour lines from a topographic map of 
Oahu (U. S. Geol. Survey, 1938) as the first 
step. The contour lines of the original map 
were slightly smoothed and generalized in 
tracing. Next, smoothly sweeping, curved, 
heavy lines were drawn so as to be tangent 
Fig. 2. Generalized contour map of the Wai¬ 
mea, Oahu, region. The light lines are the present- 
day contour lines; the heavy, smoothly curving 
lines are restored contour lines; the heavy, broken 
line shows a reasonable course of the fault, with 
spurs extending toward the downthrown side; and 
the straight, heavy line is the line of the profile 
of Figure 6. 
to the seaward salients of the actual contour 
lines, and thus to form "envelopes” around 
the present-day contour lines. These smooth, 
restored contour lines show approximately 
the shape of this part of the Koolau volcanic 
dome as it was before dissection by stream 
erosion had roughened it. The restored con¬ 
tour lines at 500, 1,000, and 1,500 feet have 
their northeastern parts offset seaward with 
respect to their southwestern parts in the 
same way that the shore line is offset, and, 
presumably, for the same reason. 
The precise course of the fault is obscured, 
but the heavy, broken line of Figure 2 shows 
a reasonable approximate position. The short 
lines perpendicular to the several segments 
indicate the downthrown side of the fault. 
HEIGHTS OF WAVE-CUT CLIFFS 
Volcanic domes are subject to erosion by 
streams and by waves. If we neglect the 
work of streams for the moment, and con¬ 
sider only the work of waves, we realize that 
the sloping shores would become cliffed, as 
is suggested in the upper sketch of Figure 3. 
The sketch cannot show it, but the cliff would 
