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Lower Hutt Past and Present (1941)


A Brief Geological Survey

"In the beginning God created the heaven and the earth."
The Hutt Valley has never been the scene of volcanic activity. The Wellington district thus offers a contrast to the localities of other large towns of New Zealand. Those rigid hill ramparts which form the handsome and impressive boundaries of the Valley are actually composed of sands, deposited countless ages ago on the shore of our ancient land, which was probably an island even then; though with a coastline which was very different from that of the present time.
Millions of years have gone by since these ancient beds of sand were deposited. They have been compressed, hardened, and raised from their low and level state into mountain structures.
These changes have been due to the action of the huge forces which result from the gradual shrinkage of the earth as it slowly cools. This shrinkage causes wrinkles, which in a little sphere or globe would seem trifling, but which, in a sphere of the size of the earth, become structures that have the dimensions of mountains. Each of the hills around us could be considered in terms such as those.
But even while these wrinkles or mountain ranges were being gradually elevated they were also being sculptured by the wearing action of the streams that carried the abundant rainfall from their surfaces. It is in this way that the varied tracery of the surface, the sharp contours and rugged spurs of our majestic hills, have been developed.
The Hutt Valley itself, however, requires rather further consideration. In its lower course at least this Valley contrasts strongly with those of the Waikanae and Otaki. They run at right angles to the mountain structures, while the Hutt Valley is parallel to them. They are simply enlarged stream channels which carry the rainfall outward from the central ranges.
The Hutt Valley, on the other hand, is longitudinal, and flows along a trough which lies perhaps between two original wrinkles. The Hutt Valley, however, is deeper than seems proper and natural to a structure of this kind, and its development required further action.
Any observer sees at once that the western wall of the Hutt Valley is a direct continuation of the western shore of the Wellington Harbour. The eastern wall is nearly parallel to that on the west for much of its length.
This has suggested to many that during the stress of mountain forming this strip of country—the Hutt Valley—had insufficient support and subsided or was faulted down, as the phrase goes.
Others think that during the folding of the rocks, or subsequently, earth shrinkage has caused such stress that huge thrust movements of rock masses took place from west to east, parallel to the wrinkles or folds. Those who hold this view would regard the Hutt Valley as the unmoved strip between two large thrust masses of rock.
Whichever view is correct, it is certain that the formation of the Hutt Valley has been associated with the actions of those earth forces by which the ranges of the Orongorongo, Wainui, Belmont and Rimutaka were formed.
More things have happened since the formation of the Valley. Originally far deeper, it has been shallowed by the depositions of gravels and sands that have been carried into it by the streams, large and small, which rush down its steep sides. Material derived in this way forms the flat area on which Lower Hutt has been built. In these beds of sand percolates that well-filtered and clear water—the source of that artesian supply that is so valuable to the residents of the Valley.
Slowly this deposit of sand continues, and gradually the beach of Petone is advancing into Port Nicholson. The rate of advance is so leisurely that little or no progress can be traced since first the settlers' ships anchored near its attractive surface.
It is possible that the earth pressures to which the hills and the Hutt Valley are due still act and are still adding to their stature and dignity. The earthquakes which are occasionally felt are probably evidence of this. In actual fact elevation of a large area took place when the earthquake of 1855 occurred. Evidence of an earlier movement is seen in the natural ramp of Petone, about a quarter of a mile distant from the beach.
What a lapse of years has been necessary to effect all this! The end is not yet. In the lapse of hundreds of years we see only one short stage of its progress.

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