Praxis Pennsylvania Grades 4–8 Core Assessment (5152) Practice Exam

Rocks formed directly from the cooling of magma are known as igneous rocks. This process occurs when magma, which is molten rock beneath the Earth's surface, cools and solidifies either beneath the surface, forming intrusive igneous rocks, or after it reaches the surface during a volcanic eruption, resulting in extrusive igneous rocks.

The key factor in the classification of igneous rocks is their origin from magma. This distinction sets them apart from other types of rocks. For instance, metamorphic rocks arise from the transformation of existing rocks through heat and pressure, while sedimentary rocks are formed from the accumulation and compression of mineral and organic particles over time. Organic rocks, a subset of sedimentary rocks, are specifically composed of materials derived from living organisms. Therefore, igneous rocks represent a fundamental category of rock formed by the cooling of magma, making them unique in the rock cycle.