AFOQT Practice Test

What is sedimentary rock primarily formed from?

1. Molten materials that have solidified

2. Particles that are pressed and cemented together

3. Existing rocks that undergo significant pressure

4. Large igneous formations that have eroded

The correct answer is: Particles that are pressed and cemented together

Sedimentary rock is primarily formed from particles that are pressed and cemented together. This process occurs over time as sediments, which can include fragments of other rocks, minerals, and organic materials, accumulate in layers. As additional layers build over them, the weight and pressure compact the lower layers, while minerals precipitate from water and act as a cement, binding the sediments together. This method of formation distinguishes sedimentary rocks from other types such as igneous or metamorphic rocks. Igneous rocks are formed from cooled and solidified molten materials, while metamorphic rocks originate from existing rocks that have been altered by heat and pressure. Additionally, the erosion of large igneous formations may contribute to the sediment that forms sedimentary rocks, but they do not directly participate in the formation process. Thus, the formation of sedimentary rock is specifically tied to the compaction and cementation of particles rather than molten materials, existing rocks undergoing pressure, or large igneous formations.