ASBOG Practice Exam

Sedimentary rock predominantly forms from organic materials because it often originates from the accumulation and compaction of organic debris and sediments over time. These materials can include plant debris, shells, and other organic remains. An example of this is coal, which is formed from the remains of prehistoric plants that accumulated in swampy environments and were subjected to heat and pressure over millions of years.

In contrast, igneous rock forms from the cooling and solidification of molten magma or lava and does not contain organic material as part of its formation process. Metamorphic rock arises from the alteration of existing rock types under heat and pressure, which can change pre-existing sedimentary or igneous rocks but does not create new rocks from organic material. Volcanic rock, a subset of igneous rock, specifically relates to rocks formed from volcanic eruptions and, like other igneous rocks, does not involve the direct influence of organic matter in its formation.