**Sedimentary Rocks: Introduction**

Sedimentary rocks are one of the three main types of rocks found on Earth, alongside igneous and metamorphic rocks. They are formed through the process of sedimentation, which involves the accumulation and deposition of sediment particles over time. Sedimentary rocks are unique as they provide valuable insights into Earth's history, climate, and the environment in which they were formed.

**Stratification in Sedimentary Rocks**

One prominent characteristic of sedimentary rocks is their stratification, which refers to the layering or bedding pattern visible in these rocks. This stratification is a direct result of the deposition process and subsequent compaction and cementation of sediments. Sedimentary rocks are often referred to as stratified rocks due to this distinctive feature.

**Formation of Stratified Rocks**

The formation of stratified rocks involves several key processes:

1. **Weathering and Erosion:** Weathering breaks down rocks into smaller fragments, while erosion transports and relocates these fragments to new locations, usually by water, wind, or ice.

2. **Transportation:** Sediments are carried away from their original source by agents such as rivers, glaciers, or ocean currents. During transportation, sediments are sorted based on their size, shape, and density, leading to the formation of distinct layers.

3. **Deposition:** Once the transporting agent loses energy, it can no longer carry the sediments, resulting in their settling and deposition. This occurs in bodies of water, such as lakes, rivers, or oceans, or on land through wind deposition.

4. **Compaction and Cementation:** Over time, the weight of the overlying sediments and the pressure from the surrounding environment cause the sediments to compact. As compaction continues, the sediments become lithified, and mineral-rich groundwater seeps through the sediment layers, depositing minerals that act as cementing agents. This cementation binds the sediments together, forming solid rock.

**Significance of Stratified Rocks**

The stratification in sedimentary rocks provides valuable information about the past environments in which they were formed. The distinct layers can reveal changes in climate, fluctuations in sea levels, the presence of ancient ecosystems, and even evidence of geological events such as volcanic eruptions or meteorite impacts.

By studying the different layers and their composition, scientists can interpret the history of Earth's surface and gain insights into the evolution of landscapes, the movement of continents, and the occurrence of past geological events. Stratified rocks also serve as valuable reservoirs for natural resources like coal, petroleum, and groundwater.

In conclusion, sedimentary rocks are called stratified rocks due to their characteristic layering or stratification. This layering is a result of the deposition, compaction, and cementation processes that occur over time. Stratified rocks provide important clues about Earth's history and are significant in various scientific fields, including geology, paleontology, and environmental studies.

Answer and Explanation: Sedimentary rocks are also called secondary rocks because they are often formed from the accumulation of broken pieces of pre-existing rocks.