Less dense substances move upwards to form a crust.

密度小的物质向上浮动并形成一层皮。

《牛津词典》

As the water evaporates, a crust of salt is left on the surface of the soil.

水蒸发后，土壤表面留下一层盐。

《柯林斯英汉双解大词典》

Earth's surface is not made up of a single sheet of rock that forms a crust but rather a number of "tectonic plates" that fit closely, like the pieces of a giant jigsaw puzzle.

地球表面并不是由构成地壳的单块岩石构成，而是许多紧密相连的“构造板块”，像一块巨大的拼图。

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Alexander chronicles those experiences in his book,"52 Loaves: One Man's Relentless Pursuit of Truth, Meaning and a Perfect Crust."

VOA: standard.2010.07.16

"It's a horizontal motion of two pieces of the Earth's crust on either side of a vertical crack in the Earth,"

VOA: standard.2010.01.13

The changes in the weather create a crust of hard ice over the lichen, preventing the reindeer from eating.

UNESCO: On the frontlines of climate change: Sami reindeer herders

For those who wonder how Scotland earns a crust in the new global economic order, here's a compelling part of an answer.

BBC: Aberdeen's pipeline of solutions

The surface cooled, a crust formed, and oceans condensed upon it.

NEWYORKER: The Martian Chroniclers