Since the rocks cool very quickly, they are fine grained.

Also, the rock may slowly cool down under the surface.

Our arrival here was understood before the rock beneath us cooled.

The normal rule just about everywhere is, the slower rock cools, the larger the crystals.

As the scientists reconstructed events, the rock underwent its last heating and cooling four billion years ago.

So the halite crystals probably formed after this, when the rock was cooling.

It took millions of years before the rocks had cooled enough for liquid water to gather once more.

The rock gradually cooled, and moisture began collecting in the bottom of the six-decimeter-deep trench.

If molten rock cools slowly, then large crystals can form.

Then, as the rock cools, they stay aligned.