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Day 3
What’s the same and different about sand,
silt, and clay?
They are all made up of a lot of small
grains, but the size of the grains is
different. Silt has much finer grains than
sand, and clay’s are very, very fine.
Daily Warm-Up Exercises
1
Wentworth Scale
Compare Rock Formation, Part 1
2
Compare Rock Types
Contrasting Case Activity 1, Part 3
Earth History, Investigation 8
Compare Rock Types
3
Conclusions about Igneous Rocks
What features are shared by both igneous rocks?
Granite Only
It is hard and has
shiny, smooth
crystals
Most grains are
coarse
Usually fairly light
in color
Both Granite &
Pumice
Formed when molten rock
cools and hardens
Rough and dull
Pumice Only
Usually feels
lighter than other
rocks of its size
Grain size is fine
to medium
Contains a lot of
small air pockets
Made of volcanic
glass
Made of minerals
Formed on Earth’s
surface from molten
rock released by a
volcano
Formed deep
beneath Earth’s
surface
Compare Rock Types
4
Conclusions about Metamorphic Rocks
What features are shared by both metamorphic rocks?
Schist Only
Both Schist & Quartzite
Fairly shiny
Rough
Medium to coarse
grain size
Crystals are flat and
arranged in layers
Formed from slate, a
metamorphic rock
Made of minerals
Formed when a rock
changes due to heat
and/or pressure
Formed deep beneath
Earth’s surface
Compare Rock Types
Quartzite Only
Dull, and hard
Fine grain size
Grains appear to
be fused
together
Formed from
sandstone, a
sedimentary rock
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Conclusions about Sedimentary Rocks
What features are shared by both sedimentary rocks?
Shale Only
Smooth
Both Shale & Sandstone
Dull and hard
Sandstone Only
Rough
May contain fossils
Very fine grain size
Made of minerals
Grains are arranged in
layers
Formed when something
gets compacted and
cemented together
Formed from particles
of silt or clay
May form on or below
Earth’s surface
Compare Rock Types
Medium to coarse
grain size
Formed from grains
of sand
6
Compare Rock Types
Look at the center sections of all three
diagrams. Is there anything that all three
rock types have in common?
no
Is there anything that two of the three rock
types have in common?
Metamorphic and sedimentary
rocks are both made of minerals.
Compare Rock Types
7
Compare Rock Types
Look at the igneous diagram. Is either of
these rocks made of minerals?
granite is; pumice is not
What can we conclude from this?
Most rocks are made of minerals.
Look at the last Venn diagram. This one
has three circles, one for each rock type.
How would you show that most rocks are
made of minerals?
Compare Rock Types
8
Rock Types
Igneous
Most rocks
are made
of
minerals
Metamorphic
Sedimentary
Compare Rock Types
9
Compare Rock Types
Is there anything else that is true about two
rock types but not true about the third?
Igneous and sedimentary rocks may form
on or below Earth’s surface.
Metamorphic rocks only form below
the surface.
How would you show this in the diagram?
Compare Rock Types
10
Rock Types
Igneous
Only form below
Earth’s surface
Most rocks
are made
of
minerals
Metamorphic
May form on
or below
Earth’s
surface
Sedimentary
Compare Rock Types
11
Compare Rock Types
Fill in the diagram by entering at least one
feature that is true about igneous rocks only.
Do the same for metamorphic and
sedimentary rocks.
Compare Rock Types
12
Rock Types
Igneous
Form when molten rock cools & hardens
Only form
below Earth’s
surface
Most rocks
are made
of
minerals
May form on
or below
Earth’s
surface
Form when
something gets
compacted &
cemented
together
Sedimentary
Metamorphic
Form when a rock
changes due to heat
and/or pressure
May contain fossils
13
Compare Rock Types
Concluding Discussion
Based on your diagram, what do most rocks
have in common?
They are made of minerals.
Suppose a previously unknown rock is
discovered, and scientists categorize it as
sedimentary. What can you say about this rock?
It probably formed when something got
compacted and cemented together. It could
have formed on or below Earth’s surface. It
may contain fossils.
Compare Rock Types
14
Concluding Discussion
Suppose they categorize the unknown rock as
metamorphic. What can you say about it then?
It probably formed deep beneath Earth’s
surface, when a rock changed because of
heat and/or pressure.
What if they categorize it as igneous? What can
you say about it then?
It probably formed when molten rock cooled
and hardened. It could have formed on or
below Earth’s surface.
Compare Rock Types
15