Transcript Day 19

Day 19
What is ice wedging (or frost wedging)?
Ice wedging is a physical weathering
process. It happens when water seeps into
cracks, then freezes and expands, pushing
outward and breaking the rock apart.
What is the difference between weathering
and transport?
Weathering is when rocks break apart.
Transport is when rock pieces are carried
from one place to another.
Daily Warm-Up Exercises
1
Make Sandstone
(Part 5)
Investigation 4
My Sediments Exactly
2
Compare Sand & Sandstone
What's the same about sand and sandstone?
They're both made up of small particles of
rock.
What's different about them?
The sandstone is glued together. The sand
is loose.
3
Matrix
The material that glues the sand together in
sandstone is called a matrix. A matrix is a
chemical that glues a rock together.
Several materials can act as the matrix in
sandstone.
Today, you will make sandstone using a matrix
called sodium silicate.
4
Sodium Silicate
• Silicate minerals are found in many kinds of
rocks.
• These minerals may be chemically weathered
& dissolved in water.
• Our solution is a mixture of sodium silicate
and water.
– similar to the the solution found in nature
5
Basin
In the stream table, what happened to the
eroded material?
The water carried it downhill and deposited
it in a lower area.
Low areas are called basins. You will use a
plastic container as your model basin.
Follow the recipe on page 33 to make
sandstone.
6
Compare Model to Reality
Where would we find large collections of
sand?
beaches, sand dunes
How could sodium silicate get between the
sand grains?
Water with a lot of dissolved sodium
silicate could seep into the sand.
7
Sequence of Events
Just after
deposition,
sand is
loosely
packed
(lots of space)
Sand is
compacted
over an
extended
period of time
(very little
space)
Water
carrying
dissolved
matrix seeps
into the sand
Sand is
cemented
together by
matrix as
water
evaporates
8
Questions
How can acid or water soak into
sandstone?
There are spaces between grains that can
hold liquid.
What type of rock is sandstone?
sedimentary
9
Examine & Compare
• Use a hand lens to examine your model sandstone.
• Compare your model to Coconino Sandstone.
Record similarities and differences. Think about:
–
–
–
–
the origin of the sand
the matrix that holds the sandstone together
the size and compactness of the sand grains
evidence for your conclusions
10