sedimentary rocks (7) Flashcards
Sedimentary Rock
Rock formed from the weathered products of preexisting rocks that have been transported, deposited, and lithified
Clastic Sedimentary Rock
Transported accumulations of rocks weathered by both mechanical and chemical processes
Chemical Sedimentary Rock
Sedimentary rock consisting of material that was precipitated from water by either inorganic or organic means
Organic Sedimentary Rock
Sedimentary rock composed of organic carbon from the remains of plants that died and accumulated on the floor of a swamp (COAL)
How does the volume of sedimentary rocks in Earth’s crust compare to the volume of igneous and metamorphic rocks?
Its a lot less
Only about 5% of rocks
List two ways in which sedimentary rocks are important.
They tell us about the past
Economically important for resources
Shale
The most common sedimentary rock, consisting of silt and clay size particles
Fissility
The property of splitting easily into thin layers along closely spaced, parallel surfaces, such as bedding planes in shale
Sandstone
An abundant, durable sedimentary rock primarily composed of sand-size grains
Sorting
The degree of similarity in particle size in sediment or sedimentary rock
Conglomerate
A sedimentary rock composed of rounded, gravel-size particles
Breccia
A sedimentary rock composed of angular fragments that were lithified
What minerals are most abundant in clastic sedimentary rocks? In which rocks do these minerals predominate?
Clay minerals and quartz
Shale and sandstone
What is the primary basis for distinguishing among clastic rocks?
Particle size
How do sediments become sorted?
Currents
Biochemical
A type of chemical sediment that forms when material dissolved in water is precipitated by water-dwelling organisms. Shells are common examples.
Limestone
A chemical sedimentary rock composed chiefly of calcite. Can form from biochemical processes or inorganically
Dolostone
A chemical sedimentary rock formed from dolomite, a calcium-magnesium carbonate mineral
Chert
A durable sedimentary rock formed of microcrystalline quartz
Evaporite
A sedimentary rock formed of material deposited from solution by evaporation of the water
Salt Flat
A white crust on the ground that is produced when water evaporates and leaves behind its dissolved materials
How do evaporites form?
When seawater evaporates
Coal
A sedimentary rock consisting primarily of organic matter, formed in stages from accumulations of large quantities of undecided land material. It is used as a fossil fuel.
What is the “raw material” for coal?
Dead plants (typically accumulated in still water)
What are the stages of the formation of coal?
Accumulation of large amounts of plant remains
Formation of peat and lignite
Formation of bituminous coal
Formation of anthracite coal
Diagenesis
A collective term for all the chemical, physical, and biological changes that take place after sediments are deposited and during and after lithification
Lithification
The process, generally involving cementation and/or computation, of converting sediments to solid rocks
Compaction
A type of lithification in which the weight of overlying material compresses more deeply buried sediment. It is most important in the fine-grained rocks such as shale
Cementation
One way in which sedimentary rocks are lithified. As a material precipitates from water that percolates through the sediments, open spaces are filled, and particles are joined into solid mass
Clastic
A sedimentary rock texture consisting of broken fragments of preexisting rock
Nonclastic/Crystalline
A term for the texture of sedimentary rocks in which the minerals form a pattern of interlocking crystals
What is the primary basis for distinguishing different chemical sedimentary rocks?
Chemical-composition
Clastic-particle size
Environment of Deposition
A geographic setting where sediment accumulates. Each site is characterized by a particular combination of geologic processes and environmental conditions
Facies
A portion of a rock unit that possesses a distinctive set of characteristics that distinguishes it from other parts of the same unit
Stata
Parallel layers of sedimentary rock
Bedding Plane
A nearly flat surface that separates two beds of sedimentary rock. Each bedding plane marks the end of one deposit and the beginning of another one that has different characteristics
Cross-Bedding
A structure in which relatively thin layers are inclined at an angle to the main bedding. Cross-bedding is formed by currents of wind or water
Graded Bed
A sediment layer characterized by a decrease in sediment size from bottom to top
Ripple Marks
Small waves of sand that develop on the surface of a sediment layer by the action of moving water or air
Mud Crack
A feature in some sedimentary rocks that forms when wet mud dries out, shrinks, and cracks
What are the 3 categories of sedimentary environments?
Continental- landslide
Marine-reef
Transitional-beach
Why might a single sedimentary layer be made up of different types of sedimentary rock?
Near shore to off shore sediments
What is the single most characteristic feature of sedimentary rocks?
Stratification
How might mud cracks and ripple marks be useful clues about the geologic past?
Show where water was
Carbon Cycle
An earth system in which carbon moves through the atmosphere, hydrosphere, biosphere, and geosphere, in different directions
Describe how chemical weathering and the formation of biochemical sediment remove carbon from the atmosphere and store it in the geosphere.
Carbonic acid helps break down (Granite) which produces ions of calcium
Example in which carbon moves from the geosphere to the atmosphere.
Eruption of volcanoes
