Question

Concerning the formation and types of sedimentary rocks:Which of the statements is/are correct?

1. Rock salt is a type of chemical sedimentary rock.
2. Sandstone and Shale are examples of biochemical rocks.
3. Natural forces like flowing water contribute to sediment accumulation.

• A. All
• B. 3 only
• C. 1, 3
• D. 1 only

Answer 1

Answer:

C. 1, 3

Sedimentary Rocks: Formation and Types

Formation of Sedimentary Rocks:

• Sedimentary rocks are formed from the accumulation and cementation of sediments derived from pre-existing rocks, organic matter, or chemical precipitation.

• Natural forces such as flowing water, wind, glaciers, and gravity play a crucial role in the transportation and deposition of these sediments.

• Over geological time, these deposited sediments are compacted by the weight of overlying layers and cemented together by minerals dissolved in groundwater, transforming them into solid rock.

Types of Sedimentary Rocks:

• Clastic Sedimentary Rocks: Formed from fragments (clasts) of pre-existing rocks and minerals. Examples include sandstone, shale, conglomerate, and breccia.

• Chemical Sedimentary Rocks: Formed when dissolved minerals precipitate out of a solution (like water).

  • Rock salt (Halite) is a prime example, formed by the evaporation of saline water bodies. Other examples include gypsum and some limestones.

• Biochemical (or Organic) Sedimentary Rocks: Formed from the accumulation of organic debris or by the activities of organisms.

  • Examples include coal (from plant matter) and some limestones (formed by shell-secreting organisms like corals and mollusks).

  • Sandstone and Shale are classified as clastic sedimentary rocks, not biochemical.