LESSON 2- HOW ARE ROCKS FORMED?

AIMS:     1.  What are sedimentary rocks?

              2.  What are igneous rocks?

              3.  What are metamorphic rocks?      

MOTIVATION:  Now that we know what rocks are and how to identify some of their properties, who can tell us how they think the rocks formed?  Have students log on to http://fi.edu/tfi/units/rocks/rocks.html to find out what forms rocks. (Pressure, temperature, erosion and friction).  Show students pictures of each type of rock and ask them to identify their properties.  The sedimentary rock is sandstone from Utah.  It was taken from http://rocksforkids.com/howrocks.html#Sedimentary.  The igneous rock is granite.  The picture is from http://ivyhall.district96.k12.il.us/4th/kkhp/RocksandMinerals/granite.html.  The metamorphic rock is quartz.  The picture is from http://ivyhall.district96.k12.il.us/4th/kkhp/RocksandMinerals/metamorphic.html.

For a student database, click here.

Type of Rock

Description of Properties

Sedimentarysandstone You can see many layers. There are many colors.  You can tell they were made over a long period of time.
Igneous You can see many different colored large crystals in this rock.  You can tell it cooled slowly so the crystals could grow.
Metamorphic   The rock is very shiny or glassy.  You can tell it was made under great pressure and heat.

Procedure:

1.    Children are to log on to http://ivyhall.district96.k12.il.us/4th/kkhp/RocksandMinerals/granite.html and complete the following database to find out how each type of rock is formed.  For a blank student database, click here.

NAME

CAUSE

LOCATION

CHARACTERISTICS

Sedimentary

limestone; sandstone; chalk; coal; rock salt; shale; dolomite; conglomerate

 

created when layers of sediment (mud, sand, gravel and minerals) settle to the bottom of the ocean and then compacted (pressed together) over thousands of years

 

where oceans or bodies of water once existed or still exist

 

soft, layered, may contain fossils

 

Igneous

quartz; pumice; granite; basalt; obsidian

 

created when molten rock (lava) inside the Earth pushes through the crust (like in a volcanic eruption) and then cools

 

where volcanoes have or do exist

 

crystalline, glossy, coarse-grained

 

Metamorphic

marble; slate; gneiss; schist; quartzite; eclogite

 

created when sedimentary or igneous rocks undergo metamorphosis (change) caused by pressure, heat, and water acting on the rocks

 

deep within the earth (where pressure and heat have a very large affect)

hard, may contain bands or layers, may contain crystals

 

2.  Children can access the following animated graphics to show how sedimentary, igneous, and metamorphic rocks are formed.   This information is from the Rock Hound at http://fi.edu/fellows/payton/rocks/create/sediment.htm

SEDIANIM.GIF (205851 bytes)

SEDIMENTARY

 

IGNEOUSIGNANIM.GIF (230930 bytes)

 

METAMORPHIC

METAANIM.GIF (355469 bytes)

 

3.  Divide the class into two groups.  Have each group choose one of the following laboratory activities taken from Earth Science for Every Kid, by Janice VanCleave.

LAB ACTIVITIES:

Problem:  How can we demonstrate the formation of metamorphic rocks?

Hypothesis:  We think if we use a book to create pressure on some objects, then we can simulate the creation of metamorphic rocks.

Materials:  20 flat toothpicks, heavy book

Procedure: 1.  Snap the toothpicks in half, but leave them connected.  2.  Pile the toothpicks on a table.  3.  Place the book on top of the toothpick pile and press down.  4.  Remove the book.

Observations:  The students observe that the toothpicks are pressed into flat layers.

Conclusion:  The toothpicks flatten into layers under the pressure of the book.  in nature, the weight of rocks at the surface pushes down on rock and dirt beneath, forcing them to flatten into layers.  Rocks formed by great pressure are called metamorphic rocks.

Problem:  How can we demonstrate a sedimentary rock formation?

Hypothesis:  We think if we can layer various substances then we can show the formation of sedimentary rocks.

Materials:  2 slices of bread, crunchy peanut butter, jelly, knife, (for spreading), and plate

Procedure:  1.  Lay one slice of bread on a plate.  2.  Use the knife to spread a layer of peanut butter on the slice of bread.  3.  Add a layer of jelly on top of the peanut butter layer.  4.Place the second slice of bread on top of the jelly layer.  5.  Eat the sandwich!

Observations:  The students observe a series of layers that can be differentiated by color and texture.

Conclusion:  Sedimentary rocks are formed from loose particles that have been carried from one place to another and redeposited.  These rocks are usually deposited in a series of layers similar to the layers in the sandwich.  Each layer can be distinguished by differences in color, texture, and composition.  The oldest layer and lowest bed is deposited first and the youngest layer is at the top.  The layers over a period of time become compacted and cemented together to form solid rock.

INTERNET ACTIVITIES:

Become a rock expert!  Take the rock quiz on how different rocks are formed.  Log on to the Rock Hound here:  http://fi.edu/fellows/payton/rocks/quiz/index.html

FOLLOW-UP:    This lesson will lead to Lesson 3- "What is the Rock Cycle?"

 

 

 

OVERVIEW

ASSESSMENTS

RUBRICS

STUDENT SAMPLES

 

Rocks and Minerals

LESSON 1- WHAT ARE ROCKS AND MINERALS?

ROCKMAP.GIF (8575 bytes)

 

LESSON 2- HOW ARE ROCKS FORMED?

LESSON 3- WHAT IS THE ROCK CYCLE?

LESSON 4- HOW CAN WE TELL THE HARDNESS OF ROCKS?