VOLCANIC COASTS AND ENVIRONMENTAL RESPONSES: ISLAND VOLCANIC COASTS AS THE EXAMPLES
火山海岸与环境反馈——以海岛火山海岸为例

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 o