Sedimentary Rocks

Formation of Sedimentary Rocks

Sedimentary rock forms at or near the surface, when sediments are pressed and cemented together, or when minerals form from solutions.

Sedimentary rocks often form as layers, strata.

The process by which sediment becomes sedimentary rock is known as lithification.

What is sediment? Sediments are loose

materials such as rock fragments, mineral grains, and remains of some organisms caused from

Sediments come from weathered and eroded igneous, metamorphic, and sedimentary rocks.

Classifying Sedimentary Rocks

Sedimentary rocks are classified by their composition and by the manner in which they formed.

The three types of sedimentary rocks are:– Clastic– Chemical– Organic

Clastic Sedimentary Rocks

Clastic sedimentary rocks are made from the broken fragments of other rocks cemented together by a mineral.

Clastic sedimentary rocks can have coarse-grained, medium-grained, or fine-grained textures

Ex. Sandstone, breccia, conglomerate, shale

Sandstone = formed where sand is laid and buried – beaches, dunes, and seafloors

Shale = forms from the compaction of silt and clay-size mineral particles

Monument Valley in Arizona

Processes that help form sedimentary rocks:

Weathering = Breaking down of material by wind, water, ice, sunlight, & gravity

Erosion = Movement of sediments Deposition = The process by which

sediment is dropped or settles in new locations.

Compacted = Smaller sediments pushed together

Cemented = Dissolved minerals such as quartz or calcite act as a natural glue cementing larger sediments together

Clastic Sedimentary Rock

Chemical Sedimentary Rocks Chemical sedimentary rocks form from

solutions of dissolved minerals and water. Minerals crystallizes out of solution Ex. Halite, limestone, gypsum

Organic Sedimentary Rock

• Rocks made of the remains of once-living things are called organic sedimentary rocks.

• One of the most common organic sedimentary rocks is fossil-rich limestone.

• Coal- forms underground from plant material buried under sediment & changed to coal over millions of years

Example of Organic Sedimentary Rock

• Chalk is another organic sedimentary rock that is made of microscopic shells.

• When you write withnaturally occurringchalk, you’re crushingand smearing the calcite-shell remains of once-living ocean organisms.

already-existing already-existing rocks that are rocks that are weathered and weathered and

erodederoded

forms when sediments are forms when sediments are pressed and cemented pressed and cemented

together, or when together, or when minerals form from minerals form from

solutionssolutions

ClasticClastic ChemicalChemical OrganicOrganic

Broken Broken fragments of fragments of other rocksother rocks

weatheringweathering

erosionerosion

compactioncompaction

cementationcementation

Dissolved minerals come out Dissolved minerals come out of solutionof solution

limestone HaliteHalite

Made of the Made of the remains of once remains of once

living thingsliving things

chalkchalk coalcoal