Final answer:
A rock with many tiny air spaces is described as porous. These spaces can result from trapped gases during the rock formation process or from the shattering and fragmenting of sedimentary rocks over time.
Step-by-step explanation:
A rock that is full of tiny air spaces is said to be porous. This porosity comes from the rock's formation process. For example, when molten rock, or lava, cools and solidifies to form a type of rock known as basalt, gas bubbles that were in the lava can get trapped, leaving behind air spaces once the lava solidifies. This is frequently observed in lunar rocks, which often have visible holes from gas bubbles. Similarly, certain sedimentary rocks can contain small air spaces. Over time, impacts can shatter and fragment these rocks, leading to the formation of a fine-grained, porous material, like the dusty layer that covers the moon's surface.
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