Sedimentary Rock
Formation
When loose fragments of rock, minerals, and organic material, known as sediments, are compacted or cemented together, it forms sedimentary rock.
The Classes of Sedimentary Rock
Chemical Sedimentary Rock-It forms when the ions of dissolved minerals precipitate out of water due to changing concentrations ofchemicals. An example of this type of rock is gypsum or halite.
Organic Sedimentary Rock- It forms from the remains of living things. Coal and some limestones are an example of this class of rock.
Clastic Sedimentary Rock- Sedimentary rocks that form when fragments of preexisting rocks are cemented together form Clastic rock.Some types of this rock are sandstone and breccia.
Organic Sedimentary Rock- It forms from the remains of living things. Coal and some limestones are an example of this class of rock.
Clastic Sedimentary Rock- Sedimentary rocks that form when fragments of preexisting rocks are cemented together form Clastic rock.Some types of this rock are sandstone and breccia.
Features of Sedimentary Rock
Stratification-It occurs when the conditions of sediment deposistion change. It is the layering of sedimentary rock. Stratified layers vary in thickness because of the legnth of time during which sediment is deposited and how much is deposited.
Cross-Beds- They are the slanting layers that some sedimentary rocks are classified by. They generally form in sand dunes or river beds.
Graded Bedding-It is when varioussizes and kinds of materialsare deposited withih one layer. They transistion from largest grains on the bottom to smalleat grains in the top.
Reverse Grading- It is caused by mudflows, which cause the smallest grains to go to the bottom and the largest grains to go to the top.
Cross-Beds- They are the slanting layers that some sedimentary rocks are classified by. They generally form in sand dunes or river beds.
Graded Bedding-It is when varioussizes and kinds of materialsare deposited withih one layer. They transistion from largest grains on the bottom to smalleat grains in the top.
Reverse Grading- It is caused by mudflows, which cause the smallest grains to go to the bottom and the largest grains to go to the top.
Formation of Limestione
Limestone forms when animals die and their shell and skeletal debris accumulate as a sediment that might be lithified into limestone. Their waste products can also contribute to the sediment mass. Their biological origin is often revealed in the rock by the presence of fossils.