关于中生代末期(白垩系和老第三系界线)发生生物群大量灭绝的事实,过去曾有人认为是由于小行星撞击地球,使地球环境发生突变造成的,最近有许多文章支持这种观点.本文根据北海道所发现的这一界线层,讨论了依靠ODP(国际深海钻探计划)探索小行星撞击地点的重要意义. The fact that a large extinction of biota occurred in the late Mesozoic (the Cretaceous and the Tertiary boundary) occurred in the past as a result of asteroid impact on the earth and mutation of the Earth’s environment, and many articles support this view recently. Based on this boundary layer found in Hokkaido, the importance of exploring an asteroid impact location relying on the ODP (International Deepwater Drilling Program) is discussed.