Shore Platforms

Hills, E. Sherbon

doi:10.1017/s0016756800074501

Cited by 56 publications

(40 citation statements)

References 6 publications

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“…Even though a large body of literature has arisen, a satisfactory explanation of how shore platforms develop has not been forthcoming because different processes leading to development have been identified. It was argued by Dana (1849), Bartrum (1924Bartrum ( , 1926, Edwards (1941Edwards ( , 1951, Sunamura (1978aSunamura ( , 1992, and Trenhaile (1987), that the primary agent of shore platform development is the erosive force of waves while Bartrum (1916Bartrum ( , 1938, Wentworth (1938Wentworth ( , 1939, and Hills (1949), identified subaerial weathering as the formative process. This difference of views, led to a "wave versus weathering" debate.…”

Section: The Thesis Problemmentioning

confidence: 99%

“…Studies that have recognised both weathering and wave erosion as having a role in platform development have tended to emphasise one over the other, assigning either weathering to a secondary role (Bartrum and Turner 1928;and Bartrum 1935) or waves to a secondary role (Hills 1949;andWentworth 1938, 1939). Few studies have suggested that both processes are of equal importance.…”

Section: The Thesis Problemmentioning

confidence: 99%

“…Such terms include: shore platform (Dana 1849;Bartrum 1935Bartrum , 1938Jutson 1939;Wentworth 1938Wentworth , 1939Wentworth , 1940Hills 1949;Edwards 1951;Cotton 1963;Mil 1962;Bird and Dent 1966;McLean and Davidson 1968;Healy 1968a, Hills 1971Trenhaile 1971Trenhaile , 1972Trenhaile , 1974aTrenhaile , 1974bTrenhaile , 1978Trenhaile , 1980Trenhaile , 1983aTrenhaile , 1983bAbrahams and Oak 1975;Takahashi 1975Takahashi , 1977Robinson 1977aSunamura 1978aSunamura , 1983Sunamura , 1990Sunamura , 1991Sunamura , 1992Layzell1980, 1981;Hansom 1983;Trenhaile and Bryne 1986;Tsujimoto 1987;Lawrie 1993;Griggs and Trenhaile 1994), rock bench (Bell and Clarke 1909), high water rock platform and Old Hat Type platform (Bartrum 1916), abrasion platform (Johnson 1919;Cinque et al 1995), shore bench …”

Section: Thesis Aimsmentioning

confidence: 99%

“…The degree of interaction depends on environmental conditions. The two most commonly described weathering processes on shore platforms are salt weathering and water layer weathering (Bartrum 1935;Wentworth 1938;Hills 1949;Sanders 1968aSanders , 1970Sunamura 1978a;andTrenhaile 1980, 1987). A distinction has been made between the two by many authors as a matter of convenience for discussion but in reality the two processes are closely related.…”

Section: ) Unloadingmentioning

confidence: 99%

“…Johnson (1938) was critical of the term water level weathering because it could be construed to mean weathering in relation to mean water level and hence sea level. Hills (1949) suggested that the term "water level weathering" should be replaced with the "term water layer weathering", since the pools of 20 water occurred in layers. The term "water layer weathering" has been used widely and is used subsequently in this study.…”

Section: ) Unloadingmentioning

confidence: 99%

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Development of shore platforms on Kaikoura Peninsula, South Island, New Zealand

2000

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Shore platforms on the Kaikoura Peninsula have been examined to determine the roles of marine and subaerial weathering processes in platform evolution. Erosion was measured to assess rates of development and processes of erosion. Lowering rates on platforms are presented from two years of monitoring using a traversing micro-erosion meter. Cliff retreats were calculated using aerial photographic interpretation. Marine processes were investigated by using deep water wave data, by measuring waves on shore platforms and by analysing measured tidal data. Weathering processes were investigated using tidal data, climate data, the Schmidt Hammer test, and a laboratory experiment on wetting and drying.Lowering rates over two years ranged from 0.07 to 19.80mm, and annual rates ranged from 0.154 to 9.194mm/yr. Rates of erosion varied with lithology and the type of platform.Erosion on Type A mudstone platforms was 1.98mm/yr; on Type B mudstone platforms erosion was 0.733mm/yr; and on limestone platforms it was 0.88mm/yr. The grand mean lowering rate for all shore platforms was 1. 13mm/yr . These rates fall in the middle of the range of published rates from previous studies at Kaikoura and at locations around the world. For the fITst time, erosion data from a traversing micro-erosion meter were presented as volumes of material eroded.The total volume of rock eroded from study sites having, each with an area of 45.4cm 2 , ranged from 1.20 to 92.50cm 3 • A significant finding was that rock surfaces swell up as indicated by a rise in surface level rather than lowering from erosion. The maximum measured swelling was 8.90mm. At some measurement sites as much as 90 per cent of measurements showed swelling over a period of 98 days. Values for erosion and swelling were higher during summer months.Both erosion and swelling were shown to be statistically related to season, suggesting that weathering is the group of processes causing both erosion and swelling. Summer provides better conditions for wetting and drying, which is thought to be the most important weathering process on shore platforms. Horizontal retreat rates were calculated over 52 years for cliffs, beaches and lagoon deposits backing shore platforms at Kaikoura, these ranged from 0.05 to 0.91mJyr.Investigation of marine processes showed that the deep water wave environment off the Kaikoura Peninsula is very energetic, but the amount of wave energy delivered to platforms is very low. A comparison of deep water wave energy flux with wave energy flux at the landward cliff of platforms, showed that there was a reduction by as much as five orders of magnitude. An analysis of the role of breaking waves revealed that these were ineffective as an erosional agent ii because the depth of water offshore causes breaking well before waves arrive on platform surfaces. Shear stresses and dynamic forces under waves were calculated from waves measured on shore platforms. TIus showed that these forces never exceeded the compressive strength the platform rocks at Kaikoura. It was co...

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Section: The Thesis Problemmentioning

confidence: 99%

Section: The Thesis Problemmentioning

confidence: 99%

Section: Thesis Aimsmentioning

confidence: 99%

Section: ) Unloadingmentioning

confidence: 99%

Section: ) Unloadingmentioning

confidence: 99%

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Development of shore platforms on Kaikoura Peninsula, South Island, New Zealand

2000

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Rates and patterns of erosion on inter-tidal shore platforms, Kaikoura Peninsula, South Island, New Zealand

Stephenson

Kirk

1998

Earth Surf. Process. Landforms

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This paper presents measured rates of erosion on shore platforms at Kaikoura Peninsula, South Island, New Zealand. Surface lowering rates were measured with a micro-erosion meter and traversing micro-erosion meter. The mean lowering rate for all shore platforms was 1·130 mm a −1 . Differences in lowering rates were found between different platform types and lithologies. The rate of surface lowering on Type A (sloping) mudstone platforms was 1·983 mm a −1 , and 0·733 mm a −1 on Type B mudstone platforms (subhorizontal). On limestone platforms the lowering rate was 0·875 mm a −1 . A previously reported cross-shore pattern of surface lowering rates from Kaikoura was not found. Rates were generally higher on the landward margins and decreased in a seaward direction. Season is shown statistically to influence erosion rates, with higher rates during summer than winter. The interpretation given to this is that the erosive process is subaerial weathering in the form of wetting and drying and salt weathering. This is contrary to views of shore platform development that have favoured marine processes over subaerial weathering.

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Modelling the effect of waves, weathering and beach development on shore platform development

Trenhaile

2005

Earth Surf Processes Landf

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A mathematical model was used to study shore platform development. Mechanical wave erosion was dependent on such variables as tidal range, wave height and period, breaker height and depth, breaker type, surf zone width and bottom roughness, submarine gradient, rock resistance and the elevational frequency of wave action within the intertidal zone. Also included were the effects of sand and pebble accumulation, cliff height and debris mobility, and downwearing associated with tidal wetting and drying. The occurrence, location and thickness of beaches often depended on initially quite minor variations in platform morphology, but owing to their abrasive or protective effect on underlying rock surfaces, they were able to produce marked differences in platform morphology. Generalizations are difficult, but the model suggests that platform gradient increases with tidal range. Platform width also increases with tidal range with slow downwearing but it decreases with fast downwearing. Platform gradient decreases and width increases with wave energy, and decreasing rock resistance and platform roughness. With low tidal range, platform gradient is generally lower and platform width greater with beaches of fine sand than with gravel, but the relationship is more variable with a high tidal range. Platform width increases and platform gradient decreases with the rate of downwearing on bare surfaces, particularly in low tidal range environments, but the pattern is less clear on beach-covered platforms. Platforms with large amounts of beach sediment tend to be narrower and steeper than bare platform surfaces. Platform gradient increases and platform width decreases with increasing cliff height and with decreasing cliff debris mobility.

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Shore Platforms

Cited by 56 publications

References 6 publications

Development of shore platforms on Kaikoura Peninsula, South Island, New Zealand

Development of shore platforms on Kaikoura Peninsula, South Island, New Zealand

Rates and patterns of erosion on inter-tidal shore platforms, Kaikoura Peninsula, South Island, New Zealand

Modelling the effect of waves, weathering and beach development on shore platform development

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