Which type of rock forms from lava that cools on the Earth's surface?

Lava that cools on the Earth's surface forms extrusive rock. When lava erupts from a volcano and comes into contact with the cooler temperatures of the atmosphere or water, it rapidly cools and solidifies. This process results in the formation of igneous rocks that are characterized by their fine-grained texture, as the rapid cooling does not allow large crystals to form. Common examples of extrusive rock include basalt and pumice, which are often found in volcanic regions.

In contrast, intrusive rocks, like granites, form from magma that cools slowly beneath the Earth's surface, allowing larger crystals to form. Peridotite is a specific type of intrusive rock primarily composed of olivine and is found deep within the Earth’s mantle. Sedimentary rock, on the other hand, is formed through the accumulation and compaction of sediments over time rather than from the cooling of lava or magma. Understanding the distinctions between these types of rocks helps clarify why the cooling of lava specifically leads to the formation of extrusive rock.