诸如砂岩这样的水成岩同样表明：昔日更短。
Sedimentary rocks such as sandstone also testify to the quicker days of yore.
它们是水成岩，是由海水作用沉至海底的。
They are sedimentary rocks, rocks which were laid down by the action of water on the bed of the ocean.
一种十分常见的水成岩叫油页岩，他是一种很软的岩石，很明显是因为被压积在海底而后形成的。
A very common sedimentary rock is called shale, which is a soft rock and was obviously formed by being deposited on the sea bed.
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