1. Sedimentary Rocks

2. They are the largest group of rocks on the Earth’s surface.
Sedimentary rocks form from the breakdown of pre-existing rocks at Earth’s surface.
They are the largest group of rocks on the Earth’s surface.
Over 75% of all rock exposed at Earth’s surface is sedimentary rock.

3. Erosion (or transportation)
To form sedimentary rock a pre-existing rock must be subjected to the following four processes:
Weathering
Erosion (or transportation)
Deposition
Lithification

4. Weathering Weathering is the breaking down of rock.
This can occur through physical (or mechanical) processes in which the rock is broken into smaller pieces of the same rock, called sediment.
Or it can occur through a chemical process in which components of, or all of the rock is dissolved by water or reaction with air.
Weathering

5. This is the transportation of the sediment or dissolved materials, usually by water
Erosion

6. As the eroded material is transported it is subjected to hitting and scraping against each other.
This results in having sharp edges and corners ground away.
The particles edges take on a rounded shape.
This may take place in a distance of less than 2kms.
The rounder the material the further it has traveled from its source.
Rounding

7. The sediment or dissolved materials is eventually deposited in an environment where, given the proper condition the making of a rock occurs
Deposition

8. Sorting is the process by which sediment grains are selected and separated according to grain size (or grain shape or specific gravity).
This is usually the result of the moving water slowing down, losing energy and thus losing its capacity to carry sediment.
The larger, heavier particle settle out first as it takes more energy to transport them
Sorting

9. Lithification is the process that convert loose sediment into sedimentary rock.
It consist of two action
Compaction, and
Cementation
Lithification

10. Types of Sedimentary Rocks
Sedimentary rocks are classified as either
Clastic (detrital) or
derived from sediments
Chemical
derived from precipitation
Types of Sedimentary Rocks

11. Clastic Classification
Conglomerate – sediments of various sizes, with the majority of the sediments being larger than 2mm in length.
Sandstone – contains fragments or particles less than 2 mm in diameter but greater than 1/16 of a millimetre in diameter.
Siltstone and Shale – are much finer-grained and generally have a smooth texture. Particles are not visible to the naked eye.
Clastic Classification

12. Chemical Classification
Inorganic – sedimentary rock form from the evaporation of water. Materials often called evaporites.
Gypsum and Limestone are good examples.
Organic – are rocks formed by the action of plants (coal) or animals accumulated materials (shells)
Chemical Classification