摘要
海南岛火山海岸以沿小火山口形成的海蚀地貌和全新世火山爆发使局部海湾抬升为海岸阶地、河口堵流并形成深切海湾以及促进了珊瑚礁发育为特征。火山活动改变了海岸带的地势、坡度、动力条件、沉积特征以及海岸演变趋势,火山海岸发育受到构造内动力、波浪、潮流、风化作用等外动力以及生物作用的多重影响。火山岩岩性和时代反映出北部湾湾底的现代拉张构造活动。夏威夷火山海岸的环境效应以造陆和板块移动形成岛链、近期熔岩流喷溢改变地貌和大气质量等为特征。现代日本鹿儿岛火山碎屑喷发物掩埋道路和建筑物并促发泥石流灾害,改变着火山海岸作用过程。对比研究火山海岸及其环境效应,及时预报并进而制定有效的防灾、减灾对策。
Volcanic coast includes the coasts developed along the volcanic cone, volcanic crater or volcanic fissure eruption zone. It is different from the coast only formed by volcanic rocks. The land-ocean interactions in this special environment are characterized by the joint processes of the surfacial geologic processes and tectonic activities of the upper mantle. As a result, it not only affects on the local coast evolution, but also leads to a series effects on the regional environment. There are more than 2000 extinct with and about 500 active or dormant volcanoes scattered over the earth′s surface. These volcanoes are distributed in the three zonations: i. e. plates convergent boundaries, the mid-ocean ridges and the interior of the plates. Among them, more than 75 percent of the active and recently extinct volcanoes, i. e. 370 volcanoes, are located along the Pacific rim, which extents from the western side of the South and North America, Alaska Peninsula, Aleutian Islands, Pov Kamcatka, Japanese Islands, Taiwan Island, Philippines Islands to New Zealand. This volcanic belt is known as the fire ring of the Pacific, most of the volcanic coasts are developed accomplished with the fire ring. Three island volcanic coasts surveyed by the authors are selected as the cases studying for the volcanic coastal processes and environmental responses. These three volcanic coasts are: Mujishen and Longmen volcanic coasts of Hainan Island in China, discussed more detail, volcanic coasts of Hawaiian Islands of U. S. A., located in the interior of the Pacific Plates for comparing, and volcanic coasts of Sakura Volcano in Kagoshima of Japan, set at convergent plat boundaries(the circum-Pacific belt), the later two are still in the frequent eruption nowadays. Study on the environmental affection of the volcanic coast will improve the efforts on the environment protection. Volcanic coasts of Hainan Island have developed along a series of small craters with predominant marine erosional features. The volcanic eruption during Holocene has elevated the coastal bays to be terraces, blocked the river mouths, forced river channels migration and elevated the abundant river mouths to be deep erode-meandered bays, and volcanic rocky coast offered the basements for coral reef development. The volcanic activities have changed coastal landforms, slops, dynamic conditions, sedimentary characteristics and the trends of coastal evolution. The development of volcanic coast has shown a multi-affection of both inner and outer dynamic processes of tectonic, marine hydro-dynamics and biological factors. Comparatively, Hawaii volcanic coast is characterized by a volcanic-island chain formed by the lateral movement of the oceanic plate moving over a stationary hot spot. The ages of the islands increase toward the left, and new islands will continue to form over the hot spot. Recently, lava flows of Kauea eruption continue the island-building processes, produce a barren volcanic land scape of creator bay, lagoon etc., that served as a foundation for coral reefs and lives: plants, animals and humans. Also, the eruption has changed the local atmospheric environment. Plenty precipitation of the tropic islands develops fertilized soil, which produces favorable condition for luxury forests and bio-diversity. The Pacific volcanic islands are the precious location of tropic biological resources and ecological environment. Volcanic debris daily erupted by active volcano of Sakura Island have buried the island, highways, houses, temples, and have caused muddy flow disasters often, especially during thunder storm periods, as a result, they have changed the dynamic processes. Besides the effects on the coast geomorphology, volcanic activities change the dynamic processes of coastal zone, thus, they change the trend of coastal evolution. Furthermore, the environment responses to the volcanic activities have shown the long term climatical and ecological changes to the local or regional coastal area. What′s more important is that the volcanic activities might lead to a series of severe disasters. It should be paid special attention to study and predicate the volcanic hazards, to find the way for decreasing and preventing these kinds of natural disasters in the furore, and to maintain the sustainable development of the volcanic coasts.
出处
《第四纪研究》
CAS
CSCD
北大核心
1997年第4期333-343,共11页
Quaternary Sciences
关键词
火山活动
火山海岸
环境效应
灾害
海岛
volcanic activities, volcanic coast, environmental responses, hazards
