1 trilobite hunter, part 1 introduction to the grand canyon earth history, investigation 8

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Trilobite Hunter, Part 1

Introduction to the Grand CanyonEarth History, Investigation 8

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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.

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You bring back a grey rock with marks on it that look like a picture of a bug.

Your friend brings back a weird rock that hardly weighs anything and is full of tiny holes.

Two Rocks

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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?”

Trilobite Fossil

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.”

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Throughout this module, see if you can figure out the answers to these questions:

Questions

What kinds of rocks are likely to contain fossils?

Where should you look for trilobite fossils?

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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.

Where to Look

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Your friend's rock is called pumice.

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.

Compare Rock Types 8

Compare Rock Types

Contrasting Case Activity 1, Part 1Earth History, Investigation 8


Venn DiagramSimilarities. 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

These things

are only true

aboutthe

second rock


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?


List Observable Features

What do the rocks look like?

How do they feel?

Create a table in your lab notebook and list the features you can observe about the two igneous rock samples.

Igneous #11

Igneous #17


Which is Which?

Can you figure out which rock is granite and which is pumice?

11

17

11

17


What’s the same?

Look at the two cards.

Are any of the points exactly the same for both rocks?

How would you show this in the diagram?


Igneous

Granite OnlyBoth Granite &

PumicePumice Only

Formed when molten rock cools and hardens

11

17


What else is the same?

Are any of the points partly the same for both rocks?



Igneous

Granite Only Both Granite & Pumice

Pumice Only


Rough and dull


What is different?

Identify one thing that is true about granite but not about pumice.


11

17


Igneous


Pumice Only

Made of minerals


Rough and dull

It is hard and has shiny, smooth crystals

Most grains are coarse

Usually fairly light in color

Formed deep beneath Earth’s surface


What else is different?

Identify one thing that is true about pumice but not about granite.


11

17


Igneous


Pumice Only

Grain size is fine to medium

Contains a lot of small air pockets

Usually feels lighter than other rocks of its size

Formed on Earth’s surface from molten rock released by a volcano

Made of minerals


Rough and dull

It is hard and has shiny, smooth crystals

Most grains are coarse

Usually fairly light in color

Formed deep beneath Earth’s surface

Made of volcanic glass

1 trilobite hunter, part 1 introduction to the grand canyon earth history, investigation 8

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