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Trilobite Hunter, Part 1
Introduction to the Grand Canyon
Earth History, Investigation 8
1
Rock Hunt
Imagine you are on a field trip to a local
quarry with your school. The teacher asks
everybody to find the coolest rock they can
and bring it back to her.
You and your friend go to opposite sides of
the quarry. You both find rocks at the same
time and you wave to each other.
2
Two Rocks
Your friend brings back a weird
rock that hardly weighs
anything and is full of tiny
holes.
You bring back a grey rock
with marks on it that look
like a picture of a bug.
3
Trilobite Fossil
Your teacher says,“That’s a
trilobite fossil. You can sell
that on the internet for a lot
of money.”
Your friend says, “I want one
too. Where should I look?”
The teacher answers, “If you want to find
fossils, you have to know how rocks form and
what kinds of rock have fossils in them.”
4
Questions
Throughout this module, see if you can
figure out the answers to these questions:
What kinds of rocks are likely to
contain fossils?
Where should you look for trilobite
fossils?
5
Where to Look
There are some places where it's easy to
find lots of different kinds of rocks.
The tallest mountains and deepest canyons
are both great places to look.
The Grand Canyon is a really great place to
look, because you can see rock layers
there that represent millions of years of
Earth's history.
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Pumice
Your friend's rock is called
pumice.
Let’s go find some pumice in the Grand
Canyon and see if we can figure out
why your friend's rock doesn't have a
trilobite fossil.
7
Compare Rock Types
Contrasting Case Activity 1, Part 1
Earth History, Investigation 8
Compare Rock Types
8
Venn Diagram
Similarities. Rocks of the same type have
some things in common.
Differences. Rocks of the same type can also
be different from each other.
These
things
are only
true
about
the first
rock
These
things
are true
about
both
rocks
Compare Rock Types
These
things
are only
true
about
the
second
rock
9
How to use a Hand Lens
Hold the hand lens so the big circle is very
close to your eye. Bring the rock closer and
closer to the lens until it pops into focus.
Try the same thing with the smaller circles. The
magnification is stronger, but you can only see
part of the rock at a time.
Holding the lens close to your eye will take full
advantage of its magnifying power.
What does this word mean?
Compare Rock Types
10
List Observable Features
Igneous #11
What do the rocks
look like?
How do they feel?
Igneous #17
Create a table in your
lab notebook and list
the features you can
observe about the two
igneous rock samples.
Compare Rock Types
11
Which is Which?
11
17
Can you figure out
which rock is granite
and which is pumice?
Compare Rock Types
12
What’s the same?
11
Look at the two cards.
17
Are any of the
points exactly the
same for both
rocks?
How would you show
this in the diagram?
Compare Rock Types
13
Igneous
Granite Only
Both Granite &
Pumice
Pumice Only
Formed when molten rock
cools and hardens
Compare Rock Types
14
What else is the same?
11
Are any of the points
partly the same for both
rocks?
17
How would you show
this in the diagram?
Compare Rock Types
15
Igneous
Granite Only
Both Granite &
Pumice
Pumice Only
Formed when molten rock
cools and hardens
Rough and dull
Compare Rock Types
16
What is different?
11
Identify one thing that
is true about granite
but not about pumice.
17
How would you show
this in the diagram?
Compare Rock Types
17
Igneous
Granite Only
It is hard and has
shiny, smooth
crystals
Most grains are coarse
Usually fairly light in
color
Both Granite &
Pumice
Pumice Only
Formed when molten rock
cools and hardens
Rough and dull
Made of minerals
Formed deep beneath
Earth’s surface
Compare Rock Types
18
What else is different?
11
Identify one thing that
is true about pumice
but not about granite.
17
How would you show
this in the diagram?
Compare Rock Types
19
Igneous
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
20