Where do sedimentary rocks come from? � Physical weathering (wind, water, ice,
sunlight, and gravity) causes rock to break in to tiny fragments called sediments.
� Erosion causes these sediments to move
from place to place � Sediment in deposited in layers in low lying
areas (deposition) � Layer upon layer
� Older layers are on the bottom (Theory or
Original Horizontality) � Older layers become compressed and
compacted (squished) � Dissolved minerals (calcite and quartz)
seep through the compacted layers of rock and minerals and cement them together . . . forming a sedimentary rock!
Q: Where does sedimentary rock form? A: At or near the Earth’s surface. Q: Is heat and intense pressure involved? A: No, not like igneous or metamorphic rock formation. Strata = layers of rock, differ from one another depending on the kind, size, and color of their sediment Stratification = the process in which sedimentary rocks are arranged in layers
Q: How are sedimentary rocks classified? A: By their composition and how they were formed.
Three types of sedimentary rocks: � Clastic � Chemical � Organic
Clastic Sedimentary Rock
� Made from fragments of rock � Cemented together by a mineral such as
calcite or quartz � Classified according to the size of the
fragments Coarse Grained (conglomerate)
Medium Grained (sandstone)
Fine Grained (siltstone)
Very Fine Grained (shale)
Chemical Sedimentary Rock � Rainwater is naturally slightly acidic � It dissolves the rock material it passes over
and through � Forms from solutions of dissolved minerals
and water � Overtime, the solutions crystallize
Rock Salt (Halite)
Organic Sedimentary Rock
� Made from the remains of plants and animals
Limestone = remains, or fossils, of animals that once lived in the ocean Shells (clams, mollusks, oysters, and coral) are made of calcium carbonate . . . so is limestone Limestone is used for gravel, buildings, cement
Coal = made of the remains of decomposed plant material, takes millions of years to form Coal is used for fuel
Review: Where do sedimentary rocks come from?
Physical weathering causes fragments called sediments Erosion move sediments Sediment in deposited in layers Older layers are on the bottom Older layers become compressed and compacted Dissolved minerals cement layers together
How are Sedimentary Rocks Classified? Sedimentary rocks are classified by their composition and how they were formed. There are three types of sedimentary rocks: � Clastic � Chemical � Organic
Strata = layers of rock, differ from one another depending on the kind, size, and color of their sediment Stratification = the process in which sedimentary rocks are arranged in layers Theory or Original Horizontality = the oldest layers were originally formed on the bottom
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