What characterizes extrusive rock?

Extrusive rock is characterized by its formation from magma that cools very quickly on the Earth's surface after being expelled during volcanic activity. This rapid cooling can occur when lava is erupted during a volcanic eruption and comes into contact with the atmosphere or water, resulting in the formation of fine-grained rocks such as basalt or pumice.

In contrast, options that relate to cooling slowly underground pertain to intrusive rocks, which form from magma that cools slowly within the Earth’s crust, allowing larger crystals to develop. The formation of rocks from compressed layers of sediment describes sedimentary rocks, while the creation of rocks through extreme heat and pressure aligns with metamorphic rocks. Therefore, the correct answer clearly highlights the rapid cooling process that defines extrusive rock.