Geological Characteristics of the Cape and Bay of Coastal Zone from Jingshan to Wanli, Northern Taiwan
Date Issued
2007
Date
2007
Author(s)
Chang, Li-Shiu
DOI
zh-TW
Abstract
The coastal zone is the region of the highest density of global population presently. It is the narrow transition zone from land to sea. There is a close relation between the geological characteristics of landform and human activity. The coastal zone of this study is characterized by alternate headland and bay. This coastal zone consists of Jingshan bay, Jingshan headland, Kuosheng bay, Yeliu headland, and Wanli bay from west to east, respectively. This thesis discusses characteristcs of geology, landform and sediment of the coastal zone from Jingshan to Wanli and related geological process.
The upper boundary of this coastal zone is the first crest line from the average high-tide to inland, or the land region of obvious changes of vegetation. The lower boundary refers to the breaker zone at the shallow sea where is about 30m in depth. The length of coastal zones of these three bays ranges from 1.3 to 3.75km. The width ranges from 1680 to 2320m, of which land region is about between 100 and 250m in width. This characteristic landform reflects hilly and narrow hinterland. The average slope is between 0.80 and 1.17 degrees. The headlands are quite steep in rocky this coast. It becomes gentler far toward land. This is the small coastal zone characterized by alternating headland and bay. This landform was formed by differential erosion due to local structures.
The mineral composition of beach sediments of these three bays consists mainly of quartz, feldspar, and hornblende. Appearance of hornblende infers that the sediment comes from volcanic debris of Datun volcanos in the source area. These sediments are transported by the Malian stream, Yuantan stream, and Huang stream to the estuaries, and then redistributed by waves. The Montmorillonite distributes mainly in Malian stream, Wanli bay, and Kuosheng bay. Calcite is rarely found. This hints that biological remains are not widely distributed.
The direction of the northeast monsoon is perpendicular to the regional coastal line in northern Taiwan. The average tide range is between 0.6 and 1.7m. This coastal zone has been influenced by the wave of average height between 1.0 and 2.0m, characteristic of medium-high wave energy. The landform due to wave erosion in the marine cliffs at the present location was formed by the uplift movement of the crust there exist wave erosion grooves in rocky joint in headland and wave erosion caves at sea. This coastal zone can be considered as a primary coast because the influences of terrestrial processes are greater than that of marine processes.
The relationship between sorting and skewness of beach sediment in bays indicates that the nature of beach sediment is similar to that of river sands. This implies that source areas in land control the composition of the coastal sediment. The roundness of sediment is mainly subangular. The sphericity is generally not good. The transport distance of this coastal sandy sediment is not far. This coastal zone, including three bays, can be considered as the medium sandy coastal zone.
Subjects
海岸帶
沈積物
形貌特徵
coastal zone
sediment
topographical characteristics
north Taiwan
SDGs
Type
thesis
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