Question

How do sedimentary rocks show the Earth’s history?

Answer 1

Hint: Sedimentary rocks are formed by the weathering of pre-existing rocks, transportation and deposition of the formed sediments and its lithification over time to form solid compressed rock. This process leads to stratification of such rocks, which then, becomes an indicator of the Earth’s timeline.

Complete answer: The sedimentary rocks form over thousands of years, through the process of lithification and the environment, major events, etc., that are witnessed by the process, are reflected in the rock structure after its formation is complete. The gravel, sand and mud sediments slide to the bottom of water bodies, where they might trap living and dead animals and plants, causing these to fossilise. When these rocks are studied years later, they reveal the kind of living beings that a particular environment habituated at a particular time.

Also, sedimentary rocks are formed layer by layer, one forming above another. This law of superposition is very integral to the understanding of the Earth’s history, because at a particular location, it indicates the age and fossils of the rocks. Sedimentary rocks are characterised by rock strata (or layers) and the study of the strata, which is known as stratigraphy, relates to the study of time and helps in showing the Earth’s history.

Note: Sedimentary rocks are the most common rocks exposed on the Earth’s surface. However, it only constitutes a small portion of the Earth’s crust. Yet, studying it helps in understanding the timeline of a particular place the most.