The crust is the outermost concentric layer of the earth. It has an average thickness of thirty kilometers and is the thin, rocky veneer that constitutes the continents and the floors of the oceans.是什么意思_The crust is the outermost concentric layer of the earth. It has an average thickness of thirty kilometers and is the thin, rocky veneer that constitutes the continents and the floors of the oceans.在線(xiàn)翻譯_英語(yǔ)_讀音_用法_例句