Volume 4, Number 1, 1970

This collection contains all the articles from Volume 4, Number 1, 1970 of the Earth Science Journal.

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    Coverpage and Contents
    (Journal Article, Waikato Geological Society, The University of Waikato, 1970) Waikato Geological Society
    Coverpage and Contents from Volume 4, Number 1, 1970 of Earth Science Journal.
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    An appraisal of nutrient supplies available for tree growth in a pumice soil
    (Journal Article, Waikato Geological Society, The University of Waikato, 1970) Knight, P.J.; Will, G.M.
    Chemical analyses have confirmed and explained the results of an earlier pot trial in which the availability of major nutrients in six pumice ash layers of Kaingaroa silty sand was assessed by the growth of radiata pine seedlings. Almost all of the tree-available P is found in the present topsoil: the quantities-of P that occur in two buried soils (Waimihia and Rotoma ashes) are almost entirely in the form of organic P which is apparently very resistant to breakdown due to complexing with allophane. The N in these layers is similarly unavailable. The mineral layers, about 4 ft in thickness (Taupo pumice and lapilli), which lie between the present topsoil and the uppermost buried soil, are very low in total N and P and exchangeable Mg, but relatively high in exchangeable K. Only the lower buried soil contains a reasonable quantity of exchangeable Mg and has a Mg : K ratio in favour of Mg.
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    The movement of sediment in a channel in relation to magnitude and frequency concepts- a New Zealand example
    (Journal Article, Waikato Geological Society, The University of Waikato, 1970) Pain, C.F.; Hosking, Peter L.
    In areas where surface wash contributes most of the debris to a channel network, the effect of events of moderate magnitude and frequency appear to be more important than catastrophic events for land form development. In previous studies this idea has been emphasised, largely as a result of the fact that the contribution of bedload to sediment yield has rarely been considered. Examination of these ideas under certain New Zealand conditions would seem to present a somewhat different picture. Where rapid mass movement is the main contributor of sediment to the channel, both the development of hill-slope form and the movement of sediment in channels must be related to the frequency of occurrence of mass movements. The evidence seems to suggest that most major mass movements are triggered during high-intensity, low-frequency storms. The Orere River catchment in the Hunua greywacke block of South Auckland, New Zealand, is examined to test these ideas. Although historical data are limited, the character of the sediments in the lower catchment would suggest a succession of major periods of deposition. High-intensity storms of 1966 and 1967 resulted in the deposition of large amounts of material in the channels throughout the catchment, with a gradual removal of material mainly from the upper catchment since that time. From the limited evidence that is available, a simple model of sediment movement through the catchment is presented.
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    Measurement of tide induced changes to water table profiles in coarse and fine sand beaches along Pegasus Bay, Canterbury
    (Journal Article, Waikato Geological Society, The University of Waikato, 1970) Ericksen, Neil
    Measurements of changing water table profiles in beaches along Pegasus Bay, Canterbury, show an interchange of water between the sea and beach sand pores throughout a single semi-diurnal tidal cycle. The velocity of water escaping from the water table in response to an ebbing tide does not appear sufficient to elutriate material of silt size or larger from the beach. The low computed velocity is thought to be due to hydrostatic control, by sand dunes at the back of the beach, on water table amplitude. Fresh water and wave wash are considered important supplementary sources to that of tidal water in influencing water table profiles.
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    A flume for studying the relative erodibility of soils and sediments
    (Journal Article, Waikato Geological Society, The University of Waikato, 1970) Selby, Michael J.
    A flume has been built for studying the erodibility of soils and sediments by gullying. It consists of two boxes containing undisturbed soil samples. One box is set above the other and water from a stilling tank passes over the soil of the upper box and falls onto the soil of the lower box causing lip and channel scour and plunge-pool erosion. The sediment is collected and measured, and a measure of erodibility related to discharge, length of test and sediment yield is thus available.
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