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