GED Science TestEarth and Space ScienceEasy
A scientist is studying a rock sample found deep within the Earth's crust. The rock exhibits distinct layers, with evidence of fossilized marine organisms. Which of the following processes is most likely responsible for the formation of this rock?
- ADeposition of sediments and compaction over time
- BIntense heat and pressure transforming existing rock
- CVolcanic eruption and rapid cooling of magma
- DErosion by wind and water, then recrystallization
Show answer & explanationAnswer & explanation
Correct answer: A. Deposition of sediments and compaction over time
Sedimentary rocks are formed from the accumulation and compaction of sediments, often containing fossils. The presence of layers and marine fossils strongly indicates a sedimentary origin.
Why the other options are wrong
- B. Intense heat and pressure form metamorphic rocks, which may have layers but generally do not contain intact fossils.
- C. Volcanic eruptions form igneous rocks, which typically lack layers and fossils.
- D. Erosion breaks down rocks; recrystallization is a metamorphic process, not primary formation for fossilized sedimentary rock.
Sedimentary Rock Formation
Sedimentary rocks are formed from the accumulation, compaction, and cementation of sediments, often containing fossils and showing distinct layers.
- Formed from weathered rock, organic matter, or chemical precipitates.
- Characterized by layers (bedding) and often contain fossils.
- Examples include sandstone, shale, limestone.
Memory trick: Sediments Settle Slowly, forming Solid Structures.