Transcript Sedimentary Rocks

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