What type of rock forms when lava cools quickly on the Earth's surface?

When lava cools quickly on the Earth's surface, it solidifies to form extrusive rock. This rapid cooling occurs because the lava is exposed to the much cooler temperatures of the atmosphere or water, leading to the formation of fine-grained textures or even glassy surfaces due to the quick crystallization of minerals. Extrusive rocks, such as basalt and pumice, are typically characterized by their small crystal sizes, as the minerals do not have sufficient time to grow large before the rock solidifies.

In contrast, intrusive rocks form when magma cools slowly beneath the Earth's surface, resulting in larger crystals due to the extended cooling period. Metamorphic rocks arise from existing rocks that undergo transformation due to heat, pressure, or chemically active fluids, while sedimentary rocks form from the accumulation of sediments over time, often through processes involving compaction and cementation. Thus, the properties and formation processes of extrusive rocks make them distinct in comparison to the other types mentioned.