1. Weathering:
* Physical Weathering: This involves the breakdown of existing rocks into smaller fragments by mechanical forces. Examples include:
* Frost Wedging: Water freezes in cracks, expands, and widens them.
* Abrasion: Rocks grind against each other (like in rivers or glaciers).
* Thermal Expansion/Contraction: Extreme temperature swings cause rocks to crack.
* Chemical Weathering: This involves the chemical alteration of rocks. Examples include:
* Dissolution: Acids in rain or groundwater dissolve minerals.
* Oxidation: Iron reacts with oxygen, forming rust (iron oxide).
* Hydrolysis: Water reacts with minerals, breaking them down.
2. Erosion and Transportation:
* Erosion: The weathered fragments are picked up and moved by forces like:
* Wind: Carries sand and dust.
* Water: Rivers, streams, and waves carry sediments.
* Glaciers: Powerful ice sheets transport massive amounts of debris.
* Transportation: Sediments are carried away from their source and deposited elsewhere.
3. Deposition:
* Sedimentary Basins: Areas where sediments accumulate, often low-lying areas like river valleys, lakes, or ocean floors.
* Sorting: Sediments are often sorted by size and density during transport. Larger, heavier fragments are deposited first, followed by smaller, lighter ones.
4. Compaction and Cementation:
* Compaction: As layers of sediment accumulate, the weight of the overlying layers squeezes out water and air, compacting the sediments.
* Cementation: Dissolved minerals in groundwater precipitate between sediment grains, binding them together. Common cementing agents include calcite, silica, and iron oxides.
5. Diagenesis:
* Changes After Burial: A series of physical and chemical processes that occur after deposition and burial. These can include:
* Recrystallization of minerals.
* Dissolution and reprecipitation of minerals.
* Formation of new minerals.
In Summary:
The formation of sedimentary rocks from fragments is a complex process that involves the breakdown of existing rocks, transport of the fragments, deposition, and the final cementation and hardening of the sediment into a solid rock.
