The development and evolution of sea bottom sand ridges and sand ripples are discussed.

讨论了海底沙脊和沙波发育演变问题。

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We put wet sand at the bottom, then feather moss, and into that I stuck the flowers.

我们在底部放上湿沙子，然后是羽毛苔藓，我把花插进去。

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The sand falls from the top of the sand glasses to the bottom.

沙子从沙漏的顶部落到底部。

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We paddle through a channel with a white sand bottom and walls of coral, spotting lobster antennae poking out from crevices.

WSJ: The Ultimate Breathtaking Dive

This was quite easy, because the sand at the bottom of the hole was very soft and fine and dry, like sea-sand.

NPR: Excerpt: 'Five Children and It'

So by taking a core from the bottom and looking for sand layers, Dr Liu was able to record the passage of ancient hurricanes over the pond.

ECONOMIST: Eye on the storm | The