陨击坑

海南岛白沙陨击坑是一个直径约3.5km的环形镶边坳陷，组成陨击坑边缘的环形山连续性好，并具二元结构；

The Baisha meteorite-impacted crater is a circular rimmed depression with about 3 . 5km in diameter in Hainan Island . The mountain range surrounding the crater is obviously continuous with a binary configuration composed of the lower and upper parts .

特别是关于异常铱的来源、陨击坑的确定、撞击作用对地球环境的影响以及生物绝灭的机制等方面还存在着不少疑问。

The origin of anomalous iridium , confirmation of craters , effect of an impact event on the earth 's environment and mechanism of mass extinction .

自80年代初新突变学说兴起以来，陨击坑及冲击变质作用研究，已成为国际地学界的重大课题之一。

Since the neocatastrophism has rapidly developed from the beginning of 1980 's , the study of meteorite crater and shock metamorphism has become one of the most important topics in the earth sciences all over the world .