Ryan Hill
GEOS 401
11/26/02
Lesson: Rock Cycle-Focus on Metamorphic Rocks
I. Purpose
This lesson will introduce students to the metamorphic rock portion of the rock cycle. It will
allow students to learn how to identify metamorphic rocks based on its observable properties.
Metamorphic rocks are important to understand because their mode of formation is directly
related to the structure of the Earth, as certain temperature-pressure conditions found at different
regions beneath the Earth’s surface allow rock minerals to rearrange or change, depending on the
initial rock composition.
Standards
Content Standard D
1) Some changes in the solid earth cell can be described as the rock cycle. Old rocks at
the Earth’s surface weather, forming sediments that are buried, then compacted,
heated, and often recrystallized into new rock. Eventually, those rocks may be
brought to the surface by the forces that drive plate motions, and the rock cycle
continues.
2) Movement of matter between reservoirs is driven by Earth’s internal and external
sources of energy. These movements are often accompanied by a change in the
physical and chemical properties of the matter.
II. Big ideas
1) Metamorphic rocks are the result of rocks being altered by combinations of heat and
pressure.
2) Given the conditions under which they form, metamorphic rocks are commonly classified
based on their texture.
Prior Knowledge
1) Properties of Igneous Rocks
2) Properties of Sedimentary Rocks
III. Connections to the real world.
1) When placed in the oven, cookie dough expands from a ball and flattens out.
2) Under pressure, bread is compacted.
IV. Objectives
1) Students will identify properties such as texture and mineralogy of metamorphic rock
samples.
2) Students will identify the parent rocks of various metamorphic rocks when given both in
hand sample.
V. Assessment Instruments
Students will record their observations of different metamorphic rock samples and turn them
in for a grade. Also, they will have the task of comparing metamorphic and non-metamorphic
rock samples and determining which non-metamorphic rock is the parent rock of the
metamorphic rock.
VI. Activities
Spend a few minutes reviewing igneous and sedimentary rocks. Pass out samples of
metamorphic rocks (such as a gneiss). Ask the students what they observe about this particular
sample and ask them how it differs from the igneous or metamorphic rocks they have seen.
Observations could be things like “The crystals looked smushed, or stretched” or “It looks
banded.” Tell the students that this is the third type of rock, a metamorphic rock. Explain how
metamorphic rocks are rocks that have been altered under high temperatures and pressures where
minerals within the rock could reorient themselves. Explain that each metamorphic rock has a
parent rock. Tell students that they are going to first see a simple (and delicious!) form of
metamorphism and then try to match metamorphic samples to their parent rock samples.
Cookie baking activity: Divide that class into groups of 4 and give them each a workstation.
Have them follow the recipe to mix the ingredients for the cookie dough. Ask the students to
explain what they are doing and how it relates to rocks. Give them hints if needed, such as telling
them that each of the ingredients they are using represents sediments, or bits of rock. Ask them
what rock cycle process the mixing of the ingredients can be compared to. When the ingredients
are mixed together and the dough is formed, ask them for suggestions as to what type of rock(s)
it could be compared to.
Ask the students what is going to happen to the dough when it is placed in the oven. Explain how
the dough does not really melt, but the pieces that comprise it are able to reorient themselves
(just like a metamorphic rock). Put the cookies in the oven and take out when done.
Parent rock activity: While the cookies are in the oven, give each group sets of metamorphic
rocks and parent rocks. Ask each group to write down their observations of each of the
metamorphic rocks. Give them 5-10 minutes to do this. Then go over these observations as a
class and give them the proper terms of the properties and the names of the metamorphic rocks.
Now ask them to pair up each metamorphic with one of the “parent” rocks. Ask them to record
their reasoning. After they have done so, go over them as a class. Ask each group to share their
reasoning behind their matches. Lead the students to eventually make the correct matches as a
class.
Conclude the class by asking the students again what a metamorphic rock is and what are some
properties of metamorphic rocks that are useful for identifying them. Also be sure to eat the
cookies.
VII. Materials
1) Samples of metamorphic rocks: Gneiss, marble, quartzite, slate
2) Samples of parent rocks: Granite, limestone, sandstone, shale
3) Recipe for the cookies (attached)
Note: The cookie baking activity has been reformatted from a lesson written by Deborah
Hanuscin of the Indiana Geological Survey at Indiana University. The original lesson plan
can be found online at
http://igs.indiana.edu/geology/rocks/rockcycleactivities/metamorphmunchies.cfm