Bellringer Complete #5 on page 70 in your book. You do not have to write the question.

Sedimentary Rocks Science 7 Study Pack #4

Today’s Goals… I can explain how sedimentary rocks form from sediments I can classify sedimentary rocks as detrital, chemical, or organic in origin.

Sedimentary Rocks 75% of rocks exposed at the surface of the earth are sedimentary Sediments are loose materials such as: rock fragments mineral grains remains of organisms bits of shell Carried to new locations by wind, water, ice, or gravity

Sedimentary Rocks Sediments come from already existing rocks that are weathered and eroded Rock forms when sediments are pressed and cemented together

Sedimentary Rocks Form as layers Older layers at the bottom They were deposited first

Sedimentary Rocks Classified by their composition and how they form Detrital Chemical Organic

Detrital Sedimentary Rocks Made from pieces of other rocks Rock is first weathered (broken up) and then eroded (carried away) Sediments are then deposited (laid down) Pressure from layers of rock cause the pieces to become stuck together or compacted

Detrital Sedimentary Rock Sometimes water and minerals flow between sediments and act as a natural cement to hold the sediments together Examples: Conglomerate: rounded sediments Breccia: sharp edged sediments

Conglomerate and Breccia Animation

Chemical Sedimentary Rocks Form when dissolved minerals come out of a solution Imagine a glass of salt water Examples: Limestone, rock salt (Halite) Many uses – page 75

Organic Sedimentary Rocks Made up of the remains of once living things May contain fossils Examples: chalk, coal, some limestone

Coal Forms when pieces of dead plants are buried under sediments in swamps Compacted for millions of years Most coal formed during the Carboniferous period