Which statement best describes igneous rocks?

Which statement best describes igneous rocks?

• A. Rocks formed by cooling of magma or lava
• B. Rocks formed by cementation of grains
• C. Rocks formed by metamorphism
• D. Rocks formed by deposition of organic material

Answer: (A)

Igneous rocks come from cooling and solidification of molten material. This molten material can be magma that cools underground, forming intrusive rocks with larger crystals, or lava that erupts onto the surface and cools rapidly to create fine-grained or glassy rocks. The rate of cooling determines the texture and mineral crystals you’d see in the rock. This is different from sedimentary rocks, which form by cementing together grains or by accumulating organic material, and from metamorphic rocks, which are existing rocks altered by heat and pressure without melting. Examples like granite or basalt illustrate igneous rocks formed from cooling magma or lava.

Igneous rocks come from cooling and solidification of molten material. This molten material can be magma that cools underground, forming intrusive rocks with larger crystals, or lava that erupts onto the surface and cools rapidly to create fine-grained or glassy rocks. The rate of cooling determines the texture and mineral crystals you’d see in the rock. This is different from sedimentary rocks, which form by cementing together grains or by accumulating organic material, and from metamorphic rocks, which are existing rocks altered by heat and pressure without melting. Examples like granite or basalt illustrate igneous rocks formed from cooling magma or lava.