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Sedimentary Rock
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Title Slide: Sedimentary Rock
Slide 2: Sedimentary Rock
•Sedimentary rock forms at the surface of the Earth
•It forms in layers that are often visible
•They are created from particles deposited by water and wind
•Sediment is deposited then the processes of compaction and cementation change the sediment
into sedimentary rock.
Slide 3: Sediment
Sediment may include fragments of rock, shells, bones, leaves, stems, and other remains of
living things.
Over time, remains of living things in the sediment may slowly harden and form fossils in the
rock.
Slide 4: Formation of Sedimentary Rock
This is a four step process
•1st step : erosion
•2nd step : deposition
Lithification is the process by which sediment becomes sedimentary rock and includes
compaction and cementation
•3rd step : compaction
•4th step : cementation
This process can take millions of years
Slide 5: Sedimentary Rocks : Erosion
Erosion occurs when running water or wind loosens and carries away rock fragments.
The forces that are constantly breaking up and wearing away rocks include heat and cold, rain,
waves, and grinding ice.
Slide 6: Sedimentary Rocks: Deposition
Deposition is when sediment settles out of the water or wind carrying it.
Eventually, the moving water or wind slows and deposits the sediment.
Slide 7: Sedimentary Rock: Compaction
Compaction is the process that presses sediments together. At first, the layers fit together loosely.
Each year, more sediment falls on top, creating new layers.
The weight of the layers compacts the sediments, squeezing them tightly together.
Slide 8: Sedimentary Rocks: Cementation
Cementation is the process in which dissolved minerals crystallize and glue particles of sediment
together.
The minerals in the rock then slowly dissolve in the water.
Dissolved minerals eventually seep into the spaces between sediment particles.
Slide 9: Types of Sedimentary Rock
There are two types of sedimentary rock that are based on how they form and what they are
made of:
•Clastic sedimentary rock
•Chemical sedimentary rock
Slide 10: Clastic Sedimentary Rock
Clastic rocks are what we think of when we discuss sedimentary rocks. These are formed from
rocks that have been broken down into fragments by weathering, then have transported and
deposited elsewhere.
•Largely composed of quartz with other common minerals including feldspar, amphiboles, and
clay
•Examples include: conglomerate, breccia, sandstone, siltstone, and shale
Slide 11: Chemical Sedimentary Rock
•This type of sedimentary rock is not made from sediments
•Chemical sedimentary rock is created from mineral crystals made from elements that have
dissolved in water.
•Minerals in this rock type include: salt, calcite, and silica
•Examples include: halite, gypsum, limestone, and chert