AFOQT Practice Test

What process transforms sediment into sedimentary rock?

1. Magma intrusions

2. Cementation and compaction

3. Crystallization

4. Metamorphosis

The correct answer is: Cementation and compaction

The transformation of sediment into sedimentary rock primarily involves the processes of cementation and compaction. When sediments—such as sand, silt, and clay—accumulate over time, they build up in layers. As additional layers are deposited on top, the weight of the overlying material exerts pressure on the lower layers. This pressure causes compaction, which reduces the volume of the sediment and aids in the density and structure of the resulting rock. Cementation is the next critical step, where minerals precipitate from groundwater and fill the spaces between sediment particles, effectively binding them together into a solid mass. This process is essential because without cementation, the compacted sediments would remain loose and not form cohesive rocks. In contrast, magma intrusions relate to igneous rock formation rather than sedimentary rocks. Crystallization involves the solidification of magma and is typical in the formation of igneous rocks. Metamorphosis, or metamorphism, describes the transformation of existing rocks (either igneous, sedimentary, or other metamorphic types) under heat and pressure, which does not apply to the direct process of sediment becoming sedimentary rock. Thus, cementation and compaction are key to understanding how sediments are converted