Rocks, Rocks, and more Rocks -
Sedimentary
Sedimentary rocks are classified by
the types of sediments that make up
the rock
What are sediments?
• Definition:
–Small, solid pieces of material that
come from rocks or living things like
bones, leaves, stems, etc
Sizes of Sediments
Sediments will layer up over time, forming layered rocks
There are 4 main processes needed to
form sedimentary rock:
Step 1:
EROSION (wash away)
Forces of running water, wind, or ice that
loosen & carry away fragments of rock
Can you see the
sediment moving in
the water?
Have you ever seen
sediments being
moved during a hard
rain?
There are 4 main processes needed to
form sedimentary rock:
Step 2:
DEPOSITION
(drop down)
Sediments settle out of the water or wind
carrying them & settle to the bottom of a lake
or ocean.
Sediments move
down the sloped
land & settle at the
bottom.
Over time these
sediments layer up.
There are 4 main processes needed to
form sedimentary rock:
Step 3:
COMPACTION
(smashed together)
Process that presses
sediments together.
Thick layers of sediment
build up over time &
weigh down the layers
compacting them.
Those smashed sediments can form into layers like the ones
shown above.
There are 4 main processes needed to
form sedimentary rock:
Step 4:
CEMENTATION
(glued together)
Dissolved minerals
seep into spaces
between particles
(sediments) & then
crystallize as they
harden.
Examples of
cementation…
3 Types of Sedimentary Rocks
1. Clastic Sedimentary Rock
Made from fragments that are squeezed together
Comparing 2 Clastic Sedimentary Rocks:
Shale
Sandstone
Forms from mud - tiny clay
particles, quartz & calcite;
Forms from sand on beaches,
ocean floor, river beds, etc
Comparing 2 more…
Conglomerate
Breccia
From rounded sediments
From larger, sharp fragments
3 Types of Sedimentary Rocks
2. Organic Sedimentary Rock
Forms where the remains of plants & animals
are deposited in thick layers
Comparing 2 Organic Sedimentary Rocks
Coal
Limestone
From swamp plants buried
in water for millions of
years (plants  peat  coal)
Forms from hard shells w/calcite
from seashells, coral, clams,
oysters or skeletons that pile up on
the ocean floor for millions of
years slowly changing the
sediment to limestone
Use for coal & a location of limestone…
Coal
Plant Bowen is a power plant that uses
coal. Has anyone seen this before? It’s not
too far away!
Limestone
***
Limestone in England where there
was once H2O covering the land.
3 Types of Sedimentary Rock
3. Chemical Sedimentary Rock
Forms when minerals that have been dissolved
in a solution with water, crystallize
Examples of Chemical Sedimentary Rock
Limestone ***
Another form of limestone
forms from calcite in seas,
lakes & underground caves –
forms caverns & sinkholes in
the ground when it is eroded
by ground water
Rock Salt
Forms from halite when
evaporation leaves salt
behind
Comparing 2 Chemical Sedimentary Rocks
Limestone
***
Ruby Falls cave is made of limestone!
How did the cave form?
Rock Salt
600 million year old rock salt being mined in
the Himalayan Crystal Rock Mine.
Uses:
What things have been made from Sedimentary Rock?
• Flint: Arrowheads
• Sandstone: THE WHITE HOUSE
• Limestone: Blocks & slabs for building, making
cement & steel, flooring
Possibly the coolest thing about
Sedimentary Rock…
FOSSILS are
always found in
Sedimentary
Rock ONLY!
Why???
Fossils are the signs of the plants &
animals that have lived on Earth for
millions of years…
sometimes we see the whole creature
or actual parts of the plant…
sometimes we see evidence that a
creature lived…
One type of Fossil… Body Fossil
Another type of Fossil…Trace Fossil…
“Law of
Superposition”
states that new
sediment layers
are added on top
of older rock
layers on the
bottom
What is the correct order of the layers
from OLDEST to YOUNGEST?
Law of Superposition states
that older rock layers are at
the bottom.
If there is tectonic plate
movement or if an Igneous
rock intrusion breaks
through the rock layers,
then the order is disrupted.
Oldest: F
Next: E
What happened with
layer D?
Then: C, B, A
What is happening over
& on top of layer A?
How can fossils help us determine the
relative age of rocks?
Some great resources for Sedimentary Rocks & more:
Additional resources can be found on my webpage. You can also use the internet to
search the topic you are interest in. Lots of great stuff out there!
Geology
http://www.kidsgeo.com/geology-for-kids/0027-sedimentaryrocks.php
More Geology
http://www.rocksforkids.com/RFK/howrocks.html
Science Articles
http://www.buzzle.com/articles/rocks-and-minerals-for-kids.html
Sedimentary Rocks
http://www.rocksforkids.com/R&M/sedimentary.htm