Here's why:
* Extrusive Igneous Rocks: These rocks form when magma (molten rock) erupts onto the Earth's surface as lava and cools rapidly. The rapid cooling results in small crystals or even a glassy texture.
* Basalt: This is a very common extrusive igneous rock formed from the cooling of mafic lava (lava rich in magnesium and iron). It's often found in volcanic areas and has a dark color and fine-grained texture.
While other extrusive igneous rocks exist (like rhyolite, andesite), basalt is the most likely due to its common occurrence and formation directly from lava flows.
