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A model for wave abrasion on underwater bedrock, with an application to rapidly downwearing tephra cones adjacent to Surtsey Island in Iceland
Earth Surface Processes and Landforms ( IF 2.8 ) Pub Date : 2021-04-09 , DOI: 10.1002/esp.5128
Tsuguo Sunamura 1
Affiliation  

Wave abrasion is a major erosional process shaping shallow-water coastal bedrock morphologies. In spite of various erosion studies having been conducted on underwater bedrock features, modelling research for wave-induced abrasion is limited. Based on an existing formula for bedrock abrasion by fluid flows, this study obtains a predictive equation for the rate of wave abrasion, which is given by a function of a shear stress of wave-induced, oscillatory bottom flow and the resistivity of bedrock. A model is derived from this equation to describe temporal change in abrasion depth of subaqueous bedrock. The model is applied to rapidly abrading summits of two submarine tephra cones, Jólnir and Syrtlingur, both residing adjacent to the Surtsey volcanic island in Iceland. Nearly horizontal platforms develop as a result of abrasion. Jólnir is a site exposed to storm-wave attack, while Syrtlingur is a sheltered site. The modelling based on design storm waves is found to well describe temporal change in erosion depth in the middle to late stage of the platform evolution at the two sites. The result of model calculations indicates that: (1) deep-water wave energy of waves causing abrasion at Syrtlingur is 33% that of waves responsible for abrasion at Jólnir; (2) the efficacy of abrasion occurring at Syrtlingur is about four times higher than that at Jólnir; and (3) the wave base (i.e. the maximum water depth for bedrock erosion) is 51.5 m for Jólnir and 34.4 m for Syrtlingur.

中文翻译:

水下基岩上的波浪磨损模型,适用于冰岛苏尔特西岛附近快速磨损的火山锥

波浪磨损是塑造浅水海岸基岩形态的主要侵蚀过程。尽管已经对水下基岩特征进行了各种侵蚀研究,但波浪诱发磨损的建模研究仍然有限。本研究基于现有的流体流动对基岩磨损的公式,获得了波浪磨损速率的预测方程,该方程由波浪引起的振荡底部流的剪切应力和基岩电阻率的函数给出。从这个方程推导出一个模型来描述水下基岩磨损深度的时间变化。该模型应用于两个海底火山锥(Jólnir 和 Syrtlingur)的快速磨损峰顶,这两个锥体都位于冰岛的 Surtsey 火山岛附近。由于磨损而形成近乎水平的平台。Jólnir 是一个易受风暴波袭击的地点,而 Syrtlingur 是一个庇护地点。发现基于设计风暴波的建模可以很好地描述两个站点平台演化中后期阶段侵蚀深度的时间变化。模型计算结果表明:(1)在Syrtlingur引起磨损的波浪的深水波能是在Jólnir引起磨损的波浪的33%;(2) Syrtlingur 发生的磨损效率大约是 Jólnir 的 4 倍;(3) Jólnir 的波基(即基岩侵蚀的最大水深)为 51.5 m,Syrtlingur 为 34.4 m。发现基于设计风暴波的建模可以很好地描述两个站点平台演化中后期阶段侵蚀深度的时间变化。模型计算结果表明:(1)在Syrtlingur引起磨损的波浪的深水波能是在Jólnir引起磨损的波浪的33%;(2) Syrtlingur 发生的磨损效率大约是 Jólnir 的 4 倍;(3) Jólnir 的波基(即基岩侵蚀的最大水深)为 51.5 m,Syrtlingur 为 34.4 m。发现基于设计风暴波的建模可以很好地描述两个站点平台演化中后期阶段侵蚀深度的时间变化。模型计算结果表明:(1)在Syrtlingur引起磨损的波浪的深水波能是在Jólnir引起磨损的波浪的33%;(2) Syrtlingur 发生的磨损效率比 Jólnir 高 4 倍左右;(3) Jólnir 的波基(即基岩侵蚀的最大水深)为 51.5 m,Syrtlingur 为 34.4 m。(2) Syrtlingur 发生的磨损效率大约是 Jólnir 的 4 倍;(3) Jólnir 的波基(即基岩侵蚀的最大水深)为 51.5 m,Syrtlingur 为 34.4 m。(2) Syrtlingur 发生的磨损效率大约是 Jólnir 的 4 倍;(3) Jólnir 的波基(即基岩侵蚀的最大水深)为 51.5 m,Syrtlingur 为 34.4 m。
更新日期:2021-06-17
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