Geology—mode of formation: Rocks that are formed by the gradual deposition, compaction, and cementation of sediments are known by which fundamental class name?

Introduction / Context:

Understanding rock formation processes helps civil and mining engineers anticipate ground behavior, permeability, and durability. Among the three major rock classes, sedimentary rocks are uniquely tied to depositional environments such as rivers, lakes, and seas, and they host many construction materials (sandstones, limestones) and aquifers.

Given Data / Assumptions:

• ‘‘Gradual deposition’’ refers to the settling of particles or chemical precipitates over time.
• Subsequent compaction and cementation transform sediments into rock.
• Common examples: shale, sandstone, limestone.

Concept / Approach:

Sedimentary rocks form from deposited sediments (clastic or chemical/biochemical) that are compacted and cemented (lithified). This process contrasts with igneous rocks, which crystallize from molten magma/lava, and metamorphic rocks, which are transformed by heat/pressure from pre-existing rocks.

Step-by-Step Solution:

Verification / Alternative check:

Introductory geology references define sedimentary processes exactly in these terms, listing diagnostic features such as bedding, fossils, and clastic textures.

Why Other Options Are Wrong:

• Igneous: crystallization from melt; not depositional.
• Metamorphic: solid-state recrystallization under heat/pressure.
• None of these: incorrect because a standard class name exists.
• Pyroclastic only: pyroclastics are volcaniclastic deposits but ‘‘sedimentary’’ is the broader correct class.

Common Pitfalls:

• Confusing chemical sedimentary rocks (e.g., limestone) with igneous due to crystalline appearance.

Final Answer:

sedimentary rocks