316 IOWA STUDIES IN NATURAL HISTORY 
has been aggraded by the slow encroachment of the Hutt delta. 
A considerable amount of sediment doubtless covers the entire 
floor of the harbor mantling and smoothing the warped-down 
surface, which is thought to have had considerable relief. <A 
contour map of the bottom shows a rapid drop to deep water 
along the escarpment of the northwest shore, and as a rule a 
much more gently sloping floor elsewhere. 
Evidences of tilting into the depression are many and interest- 
ing. The general structure of the Wellington peninsula runs 
north-northeast, and the major streams are adjusted to it. Asa 
result, the streams east of the Port Nicholson depression lie in 
valleys which are more or less parallel to the axis of movement. 
However, the headwater tributaries which enter the Wainui-o-mata 
from the west and northwest show remarkable aggradational ef- 
fects due to headward tilting. Moreover, the streams entering the 
sea between Cape Turakirae and the harbor entrance are progres- 
sively more and more drowned at their mouths as the harbor 
region is approached. Indeed, there is a small lake at the mouth 
of each of the two major streams nearest the entrance. The head- 
lands on this strip of coast retain a series of benches which are 
the remnants of elevated wave-cut rock platforms. These benches 
tilt toward the Port Nicholson depression at the rate of about 
175 feet per mile. If this endwise tilt is a measure of the amount 
of warping, and if the area involved extends from the fault searp 
across Port Nicholson to the valley of the Orongorongo river—a 
distance of ten miles—then the maximum downwarp should be in 
the neighborhood of 1750 feet. Doctor Cotton has placed it at 
fully fifteen hundred feet. 
In 1855, there occurred a remarkable uplift in the Wellington 
area. It was accompanied by a severe earthquake such as would. 
be highly disastrous were it to occur in the same region now. 
While the amount of uplift was not sufficient to change the shore- 
lines materially, minor effects and the subsequent changes they 
have suffered due to the various agents of erosion can be accur- 
ately studied under conditions where the time element is known. 
A few of the more obvious ones studied during the brief time 
available to us may be mentioned. The shores south and south- 
west of Wellington previous to the uplift were cliffed, and broad 
wave-cut platforms had been developed. The latter are now ex- 
posed; on them are several stacks out of reach of the present 
