Final answer:
Igneous rocks form when magma or lava cools and solidifies, with extrusive rocks like basalt forming at the surface and cooling rapidly, while intrusive rocks like granite form beneath the Earth's surface and cool more slowly.
Step-by-step explanation:
Igneous rocks form in settings where magma or lava cools and solidifies. Extrusive igneous rocks, like basalt, are created when lava erupts from a volcano and cools rapidly at the Earth's surface, leading to fine-grained textures or a lack of visible crystal growth. Conversely, intrusive igneous rocks, such as granite, form as magma cools slowly beneath the Earth's surface, resulting in a coarse-grained structure due to the longer time available for crystal growth.
Different tectonic environments will yield different types of igneous rocks. For example, granite is often associated with continental crust environments where subduction or continental collision takes place, allowing for the slow cooling of intrusive rocks. Basalt, on the other hand, is typically found at mid-ocean ridges or hotspots where faster cooling rates are prevalent.
Considering the diversity of igneous rocks, it's clear that factors such as cooling rate, chemical composition, and tectonic setting all contribute to the unique characteristics of each rock type. Learning about igneous rock formation helps us understand not only the nature of the rocks but also the geological processes that shape our planet.