"Abnormal" Shore Platforms

Bartrum, J. A.

doi:10.1086/623367

Cited by 58 publications

(56 citation statements)

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“…Edwards (1941) discussed what he called "storm wave platforms" along the Victoria and Tasmania coasts of Australia. He considered these shore platforms to be identical in nature and mode of origin to those discussed by Bartrum (1924Bartrum ( , 1926. Like those described by Bartrum they occurred a few feet above high tide, although the Australian examples appear to have greater lateral extent, with Edwards reporting widths up to "300 feet".…”

Section: Weatheringmentioning

confidence: 87%

“…They noted that previously Bartrum (1916Bartrum ( , 1926Bartrum ( , 1935Bartrum ( , 1938 Bartrum (1916). This is clear, but they have added to Bartrum's theory by providing a detailed account of the processes implied by the term "subaerial" as used by Bartrum and many subsequent authors.…”

Section: Mass Movementmentioning

confidence: 90%

“…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%

“…They are less impeded [than waves washing over Old Hat type platforms discussed above], and therefore more effective erosive agents, when the tide is nearing flood, and for this reason one may well expect them under special circumstances to maintain a cut bench of the character described, above the level of the normal zone of wave-attack" (Bartrum 1924:495). Bartrum (1924Bartrum ( , 1926 proposed that shore platforms in the Whangaroa Harbour on the west coast of the North Island near Auckland, were also the result of storm waves and he subsequently referred to them as storm wave platforms. The best developed platforms appeared in the most exposed locations although there was no evidence to support a relationship between platform width and exposure to waves.…”

Section: Weatheringmentioning

confidence: 99%

“…He proposed that a sloping ramp develops because as waves shoal, energy is dissipated with maximum erosion occurring at the seaward edge of the platform and minimum erosion at the landward edge. Storm wave platforms as named by Bartrum (1924Bartrum ( , 1926 and Edwards (1941) were not a result of waves according to Hills (1949). He proposed that such shore platforms with a horizontal profile were in fact modified wave ramps.…”

Section: Marine and Weathering Processes Combinedmentioning

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: Weatheringmentioning

confidence: 87%

Section: Mass Movementmentioning

confidence: 90%

Section: The Thesis Problemmentioning

confidence: 99%

Section: Weatheringmentioning

confidence: 99%

Section: Marine and Weathering Processes Combinedmentioning

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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Patterns of surface downwearing on shore platforms in eastern Canada

Porter

Trenhaile

Prestanski

et al. 2010

Earth Surf Processes Landf

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Downwearing rates were measured on shore platforms at about 200 transverse micro-erosion meter (TMEM) stations, over periods ranging from 2 to 6 years. There were seven study areas in eastern Canada. The platforms were surveyed and a Schmidt Rock Test Hammer was used to measure rock hardness. More than 1200 rock samples from three of the study areas were also subjected each day, over a 3 year period, to two tidal cycles of immersion and exposure, which simulated the central intertidal zone. A further 840 samples were subjected to longer periods of exposure and immersion, over a 1 year period, which represented different elevations within the upper and lower intertidal zone, respectively. These experiments suggested that tidally generated weathering and debris removal is an effective erosional mechanism, particularly at the elevation of the lowest high tides. In the fi eld, mean rates of downwearing for each study area ranged from 0·24 mm yr −1 to more than 1·5 mm yr . Rates tended to increase with elevation in the fi eld, with maxima in the upper intertidal zone. This trend in the fi eld cannot be attributed entirely to the tidally induced weathering processes that were simulated in the laboratory, and must refl ect, in part, the effect of waves, frost, ice, and other mechanisms. It is concluded that there are no strong spatial downwearing patterns on shore platforms, and that downwearing rates in the intertidal zone are the result of a number of erosional mechanisms with different elevationeffi cacy characteristics. Furthermore, even if only one or two mechanisms were dominant in an area, any resulting relationship between downwearing rates and elevation would be obscured or eliminated by the effect of variations in the chemical and physical characteristics of the rocks.

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"Abnormal" Shore Platforms

Cited by 58 publications

References 0 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

Patterns of surface downwearing on shore platforms in eastern Canada

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