Download Sedimentary Rocks - Frost Middle School

 Most
sedimentary rock forms this way
 Sediment is material that settles out of water
or air
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Sand at the beach
Mud in the bottom of a lake
Pebbles in a river
Dirt in your yard
Dust on furniture
 Rock
develops when layers of sediment
build up on land or water and get cemented
together
 Rain
• Washes away rock particles as it runs down slopes
 Water
• Streams can move sediment that ends up in lakes or
the ocean
 Wind
• Strong wind can pick up sand and rock dust and
carry it to distant places
 As
this sediment is transported it gets laid
down in layers
 As
layers of sediment layer on top of
each other the pressure causes the layers
to form into rock
• Silt and clay
 Other
times minerals need to crystallize
between sediment acting as cement.
 Made
mainly of sand-size weathered
debris (1/16 – 2 millimeters in diameter)
 Forms mostly where large amounts of
sand accumulate
• Beaches
• Deserts
• Flood plains
• Deltas
 Fine-grained
 Formed
from silt and clay-size minerals
• Otherwise known as mud
 Made
of thin layers
 Does
not contain any minerals
 Made from the remains of plants and
animals
 Takes millions of year to form
 Conditions must be right
• Forms from ancient swamps
 Made
of carbonate minerals like calcite
 Shells and skeletons of ocean organisms
have these minerals
 Ocean organisms die and their remains
go to the bottom of the ocean
• Over time the shells/skeletons get cemented
together because their minerals dissolve and reform
 Coral reefs also consist of limestone
• As the coral grows its old shells die
 Minerals
are dissolved in water
 When water evaporates it leaves the
minerals behind
 These minerals then recrystalize to form
rock
 Rock salt or halite is an example
• Detroit has a huge deposit of this under the city
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The only type of rock that fossils can be found in
• Tell us about plants and animals that lived in the past
Crossbeds
• Show the direction wind was blowing over sand
dunes
Ripples
• Show the direction water was traveling over the sand
Mud Cracks
• Show periods of wet followed by dry periods
Floods
• Shown when sediment size is layered large up to
small