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Grade Level: 3 - 4
Purpose and Goals:
In this lesson, students are introduced to the three types of
rocks: igneous, sedimentary, and metamorphic. After receiving background
information on the processes by which these rocks are formed, students
are allowed to perform activities which will help them understand the
conditions leading to rock formation.
Targeted Objective:
Explain the three ways rocks are formed.
Background:
Igneous rocks are made from cooled and hardened magma. Magma is the hot
molten rock from deep inside the earth. Igneous rocks which formed inside
the earth, like granite, are intrusive igneous rocks. They were pushed
(intruded) into other rocks. They cool slowly and have crystals. Mountain
ranges are often made of these kinds of rock. Other igneous rocks are
called extrusive igneous rocks, or volcanic rocks. They were formed when
magma came to the surface (lava) and cooled. Extrusive rocks cool rapidly
and have fine grains. Basalt and obsidian (volcanic glass) are extrusive
igneous rocks.
Sedimentary rocks are the bits and pieces of rocks that were eroded,
or worn away and carried by wind, water, and ice large distances. These
bits and pieces are deposited and form layers. Over many years, these
layers become cemented together and become sedimentary rock. The type
of sedimentary rock depends on the kind of material in its layers. Fine
sediment (clay) forms shale, sand forms sandstone, pebbles make conglomerate,
while seashells form limestone.
Metamorphic, or changed rocks, start as sedimentary or igneous rocks,
then are remade into new forms by extreme heat and pressure. An example
of metamorphic rock is slate, formed when shale is exposed to great heat
and pressure. Other examples are gneiss (pronounced nice), formed from
granite, and marble, formed from limestone.
(The above information has been copied as a student handout – Appendix
1)
Materials/Preparation:
For each student:
- A rock (from the classroom collection)
- Science notebook
- Hand lens
- Types of Rock information sheet (Appendix 1)
- Copy of the Rock Cycle (Appendix 2)
- Copy of the Rock Cycle Song (Appendix 3)
For each group of 4 students:
- One half-cup peanut butter
- 12 crackers
- Plastic knife and spoon
- 12 pieces of saltwater taffy in three different colors
- 8 pieces of waxed paper
- 4 candy molds
For the class:
- Chart tablet
- Marker
- Samples igneous, sedimentary, metamorphic rocks
- Hot plate
- Equivalent of 2 cups of almond bark (to melt)
- Large spoon
Procedure:
- Distribute Science notebooks, Types of Rock information sheets, and
Rock Cycle diagrams. Ask the students to turn to a clean page in their
Science notebooks and write today’s date. Discuss with the students
the concept that rocks vary in appearance according to how they are
formed. Go over the information on the three kinds of rocks and how
they are formed. Make a class chart with the names and definitions of
the three types of rock and examples of each. Have the students copy
the information into their Science notebooks. Look at the Rock Cycle
diagram. Talk about what a “cycle” is, and how one kind
of rock can become another kind of rock.
- Have each student get his or her rock from the class collection and
examine it with a hand lens. Ask them to think about which of the three
types of rocks they have. Visit the ISM Geology Online GeoGallery and
look at the rocks. Ask: “Is your rock shown on the Web site? What
is your rock’s name?” (this could have already been determined
if you also did the Exploring Rocks lesson), “What type of rock
is your rock?” (The rocks on the Web site are listed according
to type.). NOTE: It is good to have some books that also explore rock
types. The best for identification purposes is: Mottant, A., R. Crispi,
and G. Liborio. 1978. Simon & Schuster's Guide to Rocks &
Minerals. New York: Simon & Schuster, Inc. (there is undoubtedly
a new edition available). Have the students put the rocks back in the
classroom collection. Pass around samples of the three types of rocks
and allow the students to examine them. If possible, have samples of
slate, marble, and gneiss.
- Edible Rocks Activity:
Tell the class they are going to do an activity showing how the three
types of rock are formed. Put the students in groups of four. Give four
candy molds sprayed with cooking oil and a plastic spoon to each group.
For the first part of the activity, allow the class to gather around
the table as you melt the almond bark in a pan on the hot plate. Tell
the students that the melted chocolate represents magma. Have them return
to their groups, and take the container of “magma” to each
group. Allow the students to spoon the melted mixture into their candy
molds. While their “igneous rocks” cool, distribute the
materials to make sedimentary rocks (peanut butter, crackers, knives),
and metamorphic rocks (taffy, waxed paper). The students make cracker
and peanut butter stacks to illustrate the layers in their “sedimentary
rocks”. Each student should then take three pieces of different
colored taffy, unwrap them, and stack them on a piece of waxed paper.
The student then places the other piece of waxed paper on top of the
stack and presses down hard to make “metamorphic rock”.
To end the activity, call out the name of a rock type and have the students
hold up the correct rock model they have made. They can then eat their
rock creations.
Questions:
Ask the students to write the answers to these questions in their
Science notebooks:
- How can an old rock become a new rock?
- How is metamorphic rock formed?
Extensions:
- Allow special needs students to orally answer questions or dictate
their answers to other students who can scribe for them.
- Do additional activities on the three types of rocks from these Web
sites:
- Language Arts: Write a narrative story about how a rock is formed.
Describe what happens to the rock as it goes through the processes that
change it from one type of rock into another type. Throughout the story,
describe how the rock feels as the changes are occurring. Use the following
questions to help you write your story:
Did you start as magma? (igneous rock). Are you on the surface (lava),
near the surface, or deep beneath it? Do you cool fast or slowly? Do
you have crystals? What do you look like?
Or—Are you sedimentary rock? You are being broken into smaller
pieces and carried away. What is this called? What is causing it? What
is carrying you away? Where are you going? Where do you end up? You
are surrounded by other rock fragments. Are they the same type and size?
Are more piling up above you? You are now sedimentary rock. What changed
you? What do you look like now?
Or—Are you changing? (metamorphic). What kind of rock are you
at first? What changes must happen to you to turn you into metamorphic
rock? Where will this change occur? How do you get there? What do you
look like when you have changed?
Assessment:
- Science notebooks: Were questions answered thoroughly and did the
answers show an understanding of the rock formation processes?
- Observation checklist for collaborative group work (Appendix 4).
- Edible rocks: Did the students show an understanding of rock formation
as they made their edible rocks? Did they hold up the correct rocks
when you called out the names?
- Culminating: Ask the students to make a drawing of the rock cycle,
using arrows and these terms: sedimentary rock, igneous rock, metamorphic
rock, heat and pressure, erosion.
- Optional: Have the students learn and perform the Rock Cycle song
(Appendix 3).
Resources:
Lesson Specifics:
- Skills: Exploring, observing, making a model, analyzing, communicating.
- Duration: Two or three class periods.
- Group size: Any.
- Setting: Classroom.
Illinois State Board of Education Goals and Standards:
- 11A: Know and apply the concepts, principles, and processes
of scientific inquiry.
- 11B: Know and apply the concepts, principles, and processes
of technological design.
- 12E: Know and apply concepts that describe the features and
processes of the Earth and its resources.
- 13A: Know and apply the accepted practices of science.
Additional Online Resources:
Appendices:
Appendices for this lesson are available in the downloadable PDF. Click
here to download. |
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