People didn't understand continental drift because they didn't understand seafloor spreading.

人们不相信大陆漂移说是因为他们不了解海底扩张学说。

This continuous process, known as seafloor spreading, results in a ridge with a central rift valley.

这种连续的过程被称为海底扩张，形成了带有中央裂谷的海脊。