Page number 110 and 111.

Sedimentary rocks are formed from the accumulation and cementation of sediments, which are particles of minerals or organic matter. These sediments, often the result of weathering and erosion, are transported by water, wind, or ice and then deposited in layers. Over time, these layers are compacted and cemented together, transforming the loose sediments into solid sedimentary rock. 

Key characteristics of sedimentary rocks:

• Formation:

  Sedimentary rocks form at or near the Earth's surface from pre-existing rocks or organic matter. 

  
  

• Sediment Origin:

  The sediments that make up these rocks come from various sources, including:

  • Clastic: Fragments of other rocks and minerals. 

  • Biochemical: The remains of living organisms (like shells). 

  • Chemical: Minerals that precipitate from water solutions. 

    
    

• Layering:

  Sedimentary rocks often exhibit distinctive layering or bedding patterns. 

  
  

• Lithification:

  The process of converting loose sediment into solid rock through compaction and cementation. 

  
  

• Porosity:

  Sedimentary rocks tend to be porous, meaning they have spaces between the grains, which allows for water and other fluids to flow through them. 

  
  

• Strength:

  Compared to igneous and metamorphic rocks, sedimentary rocks are generally weaker and more susceptible to erosion. 

  
  

• Fossils:

  Sedimentary rocks often contain fossils, making them valuable for studying Earth's history and past life forms. 

Examples of sedimentary rocks:

• Sandstone: Composed of sand-sized grains.

• Limestone: Primarily composed of calcium carbonate, often formed from the remains of marine organisms.

• Shale: Fine-grained sedimentary rock, often formed from mud and clay.

• Conglomerate: Made up of rounded gravel-sized particles.

• Siltstone: Composed of silt-sized particles. 

Importance of sedimentary rocks:

• Fossil record: They provide valuable information about past life and environments. 

  
  

• Earth's history: They help geologists understand the geological history of the Earth, including changes in climate,

  tectonic activity, and the evolution of organisms. 

  
  

• Economic resources: Sedimentary rocks contain valuable resources such as coal, oil, gas, and various minerals.